CBSE Class 7

These NCERT Solutions for Class 7 Science Chapter 13 Motion and Time Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Motion and Time NCERT Solutions for Class 7 Science Chapter 13

Class 7 Science Chapter 13 Motion and Time Textbook Exercise Questions and Answers

Question 1.
Classify the following as motion along a straight line, circular or oscillatory motion:
a. Motion of your hands while running.
b. Motion of a horse pulling a cart on a straight road.
c. Motion of a child in a merry-go-round.
d. Motion of a child on a see-saw.
e. Motion of the hammer of an electric bell.
f. Motion of a train on a straight bridge.
Answer:
a. Oscillatory motion
b. Along a straight line (rectilinear motion)
c. Circular motion
d. Oscillatory motion
e. Oscillatory motion
f. Rectilinear motion

Question 2.
Which of the following are not correct?
a. The basic unit of time is second.
b. Every object moves with a constant speed.
c. Distances between two cities are measured in kilometres.
d. The time period of a given pendulum is not constant.
e. The speed of a train is expressed in m/h.
Answer:
b., d. and e.

Question 3.
A simple pendulum takes 32 s to complete 20 oscillations. What is the time period of the pendulum?
Answer:
Number of oscillations = 20
Total time taken to complete 20 oscillations = 32 s
Time period = \(\frac{\text { Total time taken }}{\text { Number of oscillations }}\)
= \(\frac {32}{20}\) = 1.6 s

Question 4.
The distance between two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the speed of the train.
Answer:
Distance between two stations = 240 km
Time taken = 4 h
Speed = \(\frac{\text { Distance }}{\text { Time taken }}\) = \(\frac {240}{4}\) = 60 km/h

Question 5.
The odometer of a car reads 57321.0 km when the clock shows the time 08:30 AM. What is the distance moved by the car, if at 08:50 AM, the odometer reading has changed to 57336.0 km? Calculate the speed of the car in km/min during this time. Express the speed in km/h also.
Answer:
Initial reading of the odometer of the car = 57321.0 km
Final reading of the odometer of the car = 57336.0 km
Distance covered by the car = Final reading of the odometer – Initial reading of the odometer
= 57336.0 – 57321.0 km = 15 km
The given car starts at 8:30 AM and stops at 8:50 AM.
Therefore, time taken by the car to cover the distance is (8:50 – 8:30) min = 20 min
Distance covered by the car = 15 km
Time taken by the car = 20 min
Speed = \(\frac{\text { Distance covered }}{\text { Time taken }}\)
= \(\frac{15 \mathrm{~km}}{20 \mathrm{~min}}\)
= 0.75 km/min
Again,
60 min = 1 h
20 min = \(\frac {1}{60}\) × 20 = \(\frac {1}{3}\)h
Time taken by the car = \(\frac {1}{3}\)h
Speed = \(\frac{\text { Distance covered }}{\text { Time taken }}\)
= \(\frac{15 \mathrm{~km}}{\left(\frac{1}{3}\right) \mathrm{h}}\)
= 45 km/h

Question 6.
Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/s, calculate the distance between her house and the school.
Answer:
Time taken by Salma to reach her school from her home = 15 min
= 15 × 60 = 900 s
Speed of her bicycle = 2 m/s
Distance covered = Speed × Time taken = 2 × 900= 1800 m
1000 m = 1 km
∴ Distance = \(\frac {1}{1000}\) × 1800 = 1.8 km

Question 7.
Show the shape of the distance-time graph for the motion in the following cases:
a. A car moving with a constant speed.
b. A car parked on a side road.
Answer:
a. A car moving with a constant speed covers equal distances in equal intervals of time. Such motion of car is represented by the given distance-time graph.

b. The distance-time graph of a car parked on a road side is such that with the increase in time, there is no change in distance, as shown in the given figure.

Question 8.
Which of the following relations is correct?
a. Speed = Distance × Time
b. Speed = Distance/Time
c. Speed = Time/Distance
d. Speed = 1/Distance Time
Answer:
b. Speed = Distance × Time

Question 9.
The basic unit of speed is
a. km/min
b. m/min
c. km/h
d. m/s
Answer:
d. m/s

Question 10.
A car moves with a speed of 40 km/h for 15 minutes and then with a speed of 60 km/h for the next 15 minutes. The total distance covered by the car is:
a. 100 km
b. 25 km
c. 15 km
d. 10 km
Answer:
b. 25 km
First, the car is moving with 40km/h for 15 minutes.
15 minutes = 15/60 h = 1/4 h
Distance covered = 40 × 1/4 = 10 km
Second, the car is moving with 60 km/h for 15 minutes.
Distance covered = 60 × 1/4 = 15 km
Total distance covered = 10 km + 15 km = 25 km

Question 11.
Suppose the two photographs, shown below, had been taken at an interval of 10 seconds. If a distance of 100 meters is shown by 1 cm in these photographs, calculate the speed of the blue car (circled).


Answer:
First, measure the distance moved by the car with the help of scale and then proceed as given below.
Suppose the distance measured by the scale is 2 cm.
Multiply 2 with 100 to get the actual distance = 2 × 100 = 200 m.
(given, 1cm = 100 m)
Interval of time between the photos taken = 10 s.
Speed of the blue car = 200/10 = 20 m/s

Question 12.
Figure given here shows the distance-time graph for the motion of two vehicles A and B. Which one of them is moving faster?

Distance-time graph for the motion of two cars
Answer:
Vehicle A is moving faster which is evident from the higher slope for distance-time graph of this vehicle compared to that of the other vehicle.

Question 13.
Which of the following distance-time graphs shows a truck moving with speed which is not constant?

Answer:
(c) The slope of the graph in this option is not a straight line and hence it does not show a uniform motion.

NCERT Extended Learning Activities and Projects

Question 1.
You can make your own sundial and use it to mark the time of the day at your place. First of all find the latitude of your city with the help of an atlas. Cut out a triangular piece of a cardboard such that its one angle is equal to the latitude of your place and the angle opposite to it is a right angle. Fix this piece, called gnomon, vertically along a diameter of a circular board a shown in the figure. One way to fix the gnomon could be to make a groove along a diameter on the circular board.

Next, select an open space, which receives sunlight for most of the day. Mark a line on the ground along the North-South direction. Place the sundial in the sun as shown in the figure. Mark the position of the tip of the shadow of the gnomon on the circular board as early in the day as possible, say 8:00 AM. Mark the position of the tip of the shadow every hour throughout the day. Draw lines to connect each point marked by you with the centre of the base of the gnomon as shown in the figure. Extend the lines on the circular board up to its periphery. You can use this sundial to read the time of the day at your place. Remember that the gnomon should always be placed in the North-South direction as shown in the figure.
Hint:
Do it yourself.

Question 2.
Collect information about time-measuring devices that were used in the ancient times in different parts of the world. Prepare a brief write up on each one of them. The write up may include the name of the device, the place of its origin, the period when it was used, the unit in which the time was measured by it and a drawing or a photograph of the device, if available.
Hint:
a. Sundials and Obelisks: In 1500 B.C. simple sundials were used to divide the time interval between sunrise and sunset in 12 different parts. The Ancient Egyptian Obelisk, constructed about 3500 B.C. was the oldest shadow clock used to measure time. The shadows that move to different marks enabled the Egyptians to calculate time which helped to divide the day into two parts.

b. Sand-glass: It is also called an hourglass, made up of two conical glasses connected vertically by the narrow neck, came into being in the 14th Century. It could measure passage of specific time period depending upon the size and width of the glass and the quantity of sand in it.

c. Water clock: It was known to have existed in Babylon in Egypt around 16th Century. It was used to measure time observing steady flow of water from or into a container. Measurements were marked on the container but there were variations due to the pressure of water flow.

d. Candle clock: The candle was marked with numbers and the burning of wax indicated a specific period of time. It is unknown where the candle clocks were used although it was first referred by a Chinese poet called You Jiangu in 520 A.D.

e. Pendulum: A scientific study was done around 1602 by an Italian astronomer Galileo Galilei on pendulum where its motion was used to keep a track of time. It was considered to be the the world’s most accurate time-keeping invention until 1930. The pendulum clock was invented by Christian Huygens in the year 1658 which was used till 270 years.

f. The Quartz: In early 20th Century, Albert Einstein proposed theories of relativity and defined time as the fourth dimension. The quartz clocks were developed in 1930 which were far more improvised version of a pendulum clock. The quartz crystal has to be placed in the suitable circuit in a way that creates vibrations in the crystal to generate a constant frequency. This is used to operate electronic clock display.

g. Last, the atomic and laser invention in 1960’s has changed the measurement of time forever. These are the most accurate clocks so far.

Question 3.
Make a model of a sand clock which can measure a time interval of 2 minutes.

Hint:
Do it yourself.

Question 4.
You can perform an interesting activity when you visit a park to ride a swing. You will require a watch. Make the swing oscillate without anyone sitting on it. Find its time period in the same way as you did for the pendulum. Make sure that there are no jerks in the motion of the swing. Ask one of your friends to sit on the swing. Push it once and let it swing naturally. Again measure its time period. Repeat the activity with different persons sitting on the swing. Compare the time period of the swing measured in different cases. What conclusions do you draw from this activity?
Hint:
We can conclude that the time period of a pendulum depends on the acceleration due to gravity and the length of the suspension. So keeping those constant, the time period of the simple pendulum will remain constant. It will not change with changing mass or weight of bob (people sifting on the swing).

Activity 1

Objective: To show that some objects moves fast and some objects move slow.
Material Required: Pen and paper.
Procedure:

• Find the distance covered by four different modes of transport.
• Also, record the time taken by each of them to cover a certain distance.

Observations:

Conclusion: In this observation, car has the fastest speed while walking has the slowest speed.

Measuring Time: There are many events in nature that repeat after a certain time interval:

• Morning marks the rising of the sun and time taken by earth to complete one rotation.
• Day and Night mark the time between the sunrise and sunset.
• Month marks the time between two new moons.
• Year marks the time the earth takes to complete its one revolution around the sun.

Time Measuring Devices or Clocks:
Clocks use the concept of periodic motion to measure time. It means that it uses motion that repeats itself in equal intervals of time. There are different types of time measuring devices. Some ancient devices are:
i. Sundial: A sundial measures time by the position of the shadow cast by the sun during different times of the day.

ii. Sand clock: The sand clock uses the flow of sand (from one glass bulb to another) to measure time. The length of time taken by the sand to pass from one bulb of the sand clock to the other, gives a constant time interval.

iii. Water clock: A water clock uses the rate at which water drops from one vessel to another to measure time intervals. Water is allowed to drip from one vessel to another vessel kept at a lower level. The time taken by the entire water to drop from the upper vessel to the lower vessel is used for measuring time intervals. Every time the upper vessel is filled with water, its water takes exactly the same time to drip into the lower vessel.

The latest trends in measurement of time: The clocks and watches which use quartz crystals for their working are called quartz clocks and quartz watches. The time measured by quartz clocks and watches is much more accurate than that measured by clocks and watches available earlier.

Periodic Motion of a Simple Pendulum:
One of the most well-known periodic motions is that of a simple pendulum. A simple pendulum consists of a small metallic ball or a piece of stone suspended from a rigid stand by a thread. The metallic ball is called the bob of the pendulum. When the bob of the pendulum is released after taking it slightly to one side, it begins to move to and fro. The to and fro motion of a simple pendulum is an example of a periodic or an oscillatory motion. The pendulum is said to have completed one oscillation when its bob, starting from its mean position O, moves to A, then to B and back to O. The pendulum also completes one oscillation when its bob moves from one extreme position A to the other extreme position B and comes back to A. The time taken by the pendulum to complete one oscillation is called its time period.

Activity 2

Objective: To determine the time-period of a simple pendulum.
Materials Required: Metallic bob, string (thread), stop watch and meter scale.
Procedure:

• To set the pendulum in motion, hold the bob gently and move it slowly to one side (say, right side).
• Now release the bob from its displaced position gently.
• Start a stop watch when the bob is at one of the extreme positions. Keep on counting the number of oscillations made by the pendulum bob.
• Measure the time which the pendulum bob takes to make 20 complete oscillations.

Divide the time taken for 20 oscillations by 20. This will give the time taken by pendulum for making one oscillation. It is the time-period of the pendulum.
Observations:

Conclusion: The time period of the pendulum calculated is seconds. The time period of a given pendulum remains constant.

Units of Time and Speed: Unit of distance is metre (m) or kilometre (km) and that of ‘ time is second (s) or hour (h). Common units of speed are therefore metre/second (m/s) or kilometre/hour (km/h) Units are always written in singular, that is, km and not kms.

If a car takes 30 min to travel a distance of 20 km, speed will be:
Speed = Distance/Time
Speed = 20 km/30 min = 20 km/ (30/60) h
Speed = 40 km/h
Minute : 1 minute has 60 seconds in it.
Hour : 1 hour has 60 minutes in it.
Day : 1 day has 24 hours in it.
Month : 1 month has 30 or 31 days in it.
Year : 1 year has 365 days in it (366 days during a leap year).

Speedometer: An instrument on a vehicle’s dashboard which indicates the speed of the vehicle when it is running is called speedometer. The speedometer has the symbol ‘km/h’ written on its dial. Speedometer tells us the speed of a running vehicle at that instant of time in kilometres per hour.

Odometer: It is a device used to measure the distance covered by a vehicle. Odometer records the total distance travelled by a vehicle in kilometres.

Distance-Time Graph: A graph which represents the distance travelled by an object with respect to time is called a distance-time graph. If a vehicle covers a distance of 5 km every hour and travels for 5 hours, the distance-time graph for the given vehicle can be plotted as follows using the table given below:

Distance time graph of a vehicle moving with a constant speed is a straight slanting line. More the slope of this graph, more is the speed of the object.

Types of Graphs: We can represent the data in pictorial form by three ways:
i. Bar graph: A bar graph consists of horizontal or vertical bars that show the values of one quantity against another.

ii. Pie chart: A pie chart is a circular graph used to present relative percentages or shares of a total. It looks like a pie cut into several slices, and hence the name pie chart.

iii. Line chart: A line that joins dots plotted on a graph paper is called a line graph. It is used to show the variation of one quantity with respect to another.

Advantages of Graphs:

• The inter-dependence of two variables can be established easily using graphs, e.g, if the graph is a straight line, it indicates direct proportionality between the variables.
• The mean value of the ratio of two variables can be accurately obtained using graphs without rigorous mathematical calculations.
• The probable value of variables can be calculated with the help of graph within or beyond the observed values from the mean value without lengthy numerical computations.
• An important advantage of graphs is that some of the salient features of a given experimental data can be seen visually, which cannot be easily concluded by simply looking at the experimental data. For example, the point of maximum, minimum or inflexion can be easily identified by careful observation of the graph representing the experimental data.

Class 7 Science Chapter 13 Motion and Time Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is motion?
Answer:
Motion is a change in the position of an object with time.

Question 2.
What is the S.I unit of distance?
Answer:
Metre.

Question 3.
Name an object that shows oscillatory motion.
Answer:
Pendulum.

Question 4.
What is circular motion?
Answer:
Motion of an object in a circular path is called circular motion.

Question 5.
Name the device on vehicles to track the distance covered.
Answer:
Odometer.

Question 6.
What type of graph is used to represent motion of an object?
Answer:
Distance-time graph.

Question 7.
What is the basic unit of time?
Answer:
The basic unit of time is a second. Its symbol is ‘s’.

Question 8.
What is speedometer?
Answer:
Speedometer is an instrument that indicates the speed of a vehicle.

Question 9.
What is speed?
Answer:
The distance moved by an object in a unit time is called its speed.

Question 10.
What is oscillatory motion?
Answer:
The to and fro motion of an object is called oscillatory motion.

Question 11.
What is non-uniform motion?
Answer:
If the speed of an object moving along a straight line keeps changing, its motion is said to be non-uniform.

Question 12.
What is uniform motion?
Answer:
An object moving along a straight line with a constant speed is said to be in uniform motion.

Question 13.
What is the smallest time interval that can be measured with commonly available clocks and watches?
Answer:
The smallest time interval that can be measured with commonly available clocks and watches is one second.

Question 14.
What is bob?
Answer:
The metallic ball in a simple pendulum is called bob.

Question 15.
How many types of graphs are there?
Answer:
(a) Bar graph, (b) Line graph and (c) Pie chart.

Question 16.
What are X and Y-axis in a graph?
Answer:
The horizontal line in a graph is called the X-axis and the vertical line is called the Y-axis.

Question 17.
How did our ancestors find out the time of the day?
Answer:
Our ancestors could tell the approximate time of the day by looking at shadows.

Question 18.
Name some units of measuring time.
Answer:
Second, minute, hour, etc.

Question 19.
Name some devices which are used to measure time.
Answer:
Quartz clock, sundial and sand clock.

Question 20.
What is a distance-time graph?
Answer:
A graph representing the motion of an object in pictorial form by plotting its distance travelled and time taken, is called a distance-time graph.

Short Answer Type Questions

Question 1.
What are the characteristics of the distance-time graph for an object moving at a uniform speed?
Answer:
The characteristics of distance-time graph for an object moving with uniform speed are:
a. It is always a straight line.
b. The uniform speed of the moving object is equal to the slope of the straight line plotted.

Question 2.
State the factors on which the time period of a simple pendulum depends.
Answer:
Factors affecting the time period of a simple pendulum are:

• The time period of oscillation is directly proportional to square root of the effective length.
• The time period of oscillation is inversely proportional to the square root of acceleration due to gravity.

Question 3.
How do we know an object is moving faster as compared to another object?
Answer:
By finding the distance travel by a moving body in unit time, say 1 h or 1 s, we know the speed of an object that helps us to know which one is moving faster, i.e., having greater speed.

Question 4.
A simple pendulum takes 15 seconds to complete 5 oscillations. What is the time period of the pendulum?
Answer:
The time taken by pendulum to complete 1 oscillation is called the time period.
The time taken by pendulum to complete 5 oscillation = 15 s
The time taken by pendulum to complete 1 oscillation = 15/5 = 3 s
So, time period is 3 seconds.

Question 5.
Give the difference between uniform speed and non-uniform speed.
Answer:

Question 6.
What are the points that should be considered while choosing the most suitable scale for drawing a graph?
Answer:
Some of the points to be kept in mind while choosing the most suitable scale for drawing a graph are:
a. The difference between the highest and the lowest values of each quantity.
b. The intermediate values of each quantity, so that with the scale chosen it is convenient to mark the values on the graph.
c. To utilise the maximum part of the paper on which the graph is to be drawn.

Question 7.
Define units of speed.
Answer:
In the S.I system, the unit of speed is m s^-1 (m/s). If the distances covered are very small, then the speed is expressed in cm/s or cm s^-1. For example, if we want to know the speed at which an ant or an earthworm is moving, we will express it in cm s^-1.

On the other hand if the distance covered is fairly large, the speed is expressed in km/h or km h^-1, such as the speed of a train.

Question 8.
What is simple pendulum? How does it perform an oscillatory motion?
Answer:
A simple pendulum consists of a small metallic ball suspended from a rigid stand by a thread. The metallic ball is called the bob of pendulum. When the bob of a pendulum is released after taking it slightly to one side, it begins to move to and fro. The to and fro motion of simple pendulum is an example of oscillatory motion.

Question 9.
A train is running at a speed of 50 km h^-1. How long will it take to cover a distance of 250 km?
Answer:
Speed = 50 km h^-1
Distance = 250 km
Speed = \(\frac{\text { Distance }}{\text { Time }}\) or Time = \(\frac{\text { Distance }}{\text { Speed }}\)
Time = 250 km/50 km h^-1
= 5 h

Question 10.
Find the speed of a car that travels 300 km in 6 hours.
Answer:
Time = 6 hours
Distance = 300 km, Speed =?
Speed = Distance covered/Time taken
= 300 km/6 h
= 50 km/h

Question 11.
A car travels a distance of 200 km at the speed of 50 km/h. Calculate the time taken to cover the distance.
Answer:
Distance = 200 km
Speed = 50 km/h
Time = Distance/Speed
= 200/50 = 4 h

Question 12.
What does the path of an object look like when it is in non-uniform motion?
Answer:
In non-uniform motion, the path of an object can be a curved line, zig-zag line or even a circle. It can have any shape. This is because in non-uniform motion, speed is not constant. The direction of motion may change.

Question 13.
Why do we need to measure time?
Answer:
We measure time for different reasons:

• Farmers need to measure the time between sowing and harvesting of crop.
• Students need to measure time to complete an examination.
• A traveller needs to measure the time of his journey.
• A sportsman needs to measure the time he might take to complete an event.
• Doctors need to measure the number of times the heart beats in one minute for a patient.

Long Answer Type Questions

Question 1.
Explain how in ancient times a day, a month and a year were measured?
Answer:
Our ancestors noticed that many events in nature repeat themselves after definite intervals of time. For example, they found that the sun rises every day in the morning. The time between one sunrise and the next was called a day. Similarly, a month was measured from one new moon to the next. A year was fixed as the time taken by the earth to complete one revolution of the sun.

Question 2.
Explain how we can plot a graph.
Answer:
To plot a graph, take a graph paper. At the centre of the paper, draw two lines perpendicular to each other. Mark the point of intersection of the lines as ‘O’. The horizontal line is called the X-axis, while the vertical line is called the Y-axis. The point of intersection of the two axes is called the origin, ‘O’. Take one quantity along the X-axis and the other along the Y-axis, after choosing suitable scales for both. For every value along one axis, mark a point matching the related value on the other axis. Join the point, and your graph is ready.

Question 3.
Complete the data of the table given below with the help of the distance-time graph given in the figure.

Answer:
The graph given above represents a case of uniform motion. Hence, from the graph;

Question 4.
Given below is the distance-time graph of the motion of an object.
a. What will be the position of the object at 20 s?
b. What will be the distance travelled by the object in 12 s?
c. What is the average speed of the object?

Answer:
a. From the graph, it is clear that the position at 20 s is 8 m.
b. Distance travelled by the object in 12 s is 6 m.
c. Average speed = \(\frac{\text { Total distance }}{\text { Total time }}\)
= \(\frac {8}{20}\) = 0.4 m/s

Question 5.
What are the advantages of graph?
Answer:
Advantages of graphs are:
a. The inter-dependence of two variables can be established easily, e.g, if the graph is a straight line, it indicates direct proportionality between the variables.

b. The mean value of ratio of two variables can be accurately obtained without rigorous mathematical calculations.

c. The probable value of variables can be calculated with the help of graph within or beyond the observed values from the mean value without lengthy numerical computations.

d. An important advantage of graphs is that some of the salient features of a given experimental data can be seen visually, which cannot be easily concluded by simply looking at the experimental data. For example, the point of maximum, minimum or inflexion can be easily identified by careful observation of the graph representing the experimental data.

Picture-Based Questions

Question 1.
a. Observe the following figure and identify it.

b. What type of motion does it undergo?
c. Name the devices used by our ancestors to measure the time.
Answer:
a. The above figure is of a pendulum clock.
b. It undergoes periodic or oscillatory motion.
c. Sundials, water clocks, sand clocks, etc.

Question 2.
Observe the following figures and identify them:

Answer:
a. Sundial at Jantar-Mantar in Delhi
b. Sand clock
c. Water clock

Question 3.
a. Observe the following figure and identify it.

b. State the function of the device shown above.
Answer:
a. Speedometer.
b. It measures the speed of a vehicle.

NCERT Solutions for Class 7 Science

• Class 7 Science Chapter 1 Nutrition in Plants
• Class 7 Science Chapter 2 Nutrition in Animals
• Class 7 Science Chapter 3 Fibre to Fabric
• Class 7 Science Chapter 4 Heat
• Class 7 Science Chapter 5 Acids, Bases and Salts
• Class 7 Science Chapter 6 Physical and Chemical Changes
• Class 7 Science Chapter 7 Weather, Climate and Adaptations of Animals of Climate
• Class 7 Science Chapter 8 Winds, Storms and Cyclones
• Class 7 Science Chapter 9 Soil
• Class 7 Science Chapter 10 Respiration in Organisms
• Class 7 Science Chapter 11 Transportation in Animals and Plants
• Class 7 Science Chapter 12 Reproduction in Plants
• Class 7 Science Chapter 13 Motion and Time
• Class 7 Science Chapter 14 Electric Current and its Effects
• Class 7 Science Chapter 15 Light
• Class 7 Science Chapter 16 Water: A Precious Resource
• Class 7 Science Chapter 17 Forests: Our Lifeline
• Class 7 Science Chapter 18 Wastewater Story

These NCERT Solutions for Class 7 Science Chapter 12 Reproduction in Plants Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Reproduction in Plants NCERT Solutions for Class 7 Science Chapter 12

Class 7 Science Chapter 12 Reproduction in Plants Textbook Exercise Questions and Answers

Question 1.
Fill in the blanks:
a. Production of new individuals from the vegetative part of parent is called ………………
b. A flower may have either male or female reproductive parts. Such a flower is called ………………
c. The transfer of pollen grains from the anther to the stigma of the same or of another flower of the same kind is known as ………………
d. The fusion of male and female gametes is termed as ………………
e. Seed dispersal takes place by means of ………………, ……………… and ………………
Answer:
a. vegetative propagation
b. unisexual flower
c. pollination
d. fertilisation
e. wind, water, animals

Question 2.
Describe the different methods of asexual reproduction. Give examples.
Answer:
There are following methods of asexual reproduction:
a. Vegetative propagation: In this asexual reproduction, new plants are produced from roots, stems, leaves and buds of individual plant. For example: stem cutting in champa, eye growth in potatoes, leaf bud in case of Bryophyllum, etc.

b. Budding: The bud is a small projection which gradually grows and gets detached from the parent cell and forms a new cell. The new cell grows, matures and produces more cells. For example, in yeast and Hydra.

c. Fragmentation: In this mode of reproduction, the growth and multiplication is done by rapidly breaking down into two or more fragments. Each piece grows into new individual when water and nutrients are available. For example, algae.

d. Spore formation: This reproduction is done by spores, which germinate under favourable conditions and develop into a new individual. For examples, mosses and ferns.

Question 3.
Explain what you understand by sexual reproduction.
Answer:
When two parents are involved in reproduction, it is called sexual reproduction. Formation of male and female gametes is the first step of sexual reproduction. The male and female gametes fuse during fertilisation to produce zygote. The zygote subsequently develops into an embryo which further develops into a new individual.

Question 4.
State the main differences between asexual and sexual reproduction.
Answer:

Question 5.
Sketch the reproductive parts of a flower.
Answer:
Stamen is the male while pistil is the female reproductive part of a flower.

Question 6.
Explain the difference between self-pollination and cross-pollination.
Answer:

Question 7.
How does the process of fertilisation take place in flowers?
Answer:
When ripe pollen from an anther lands on the stigma of the same kind of flower, each pollen grain sends out a tiny thread-like tube. The tube grows down through the style and pierces one of the ovules in the ovary. This pollen tube carries a male gamete to meet the female gamete in the ovule. Two gametes fuse together to form zygote. The process of fusion of male and female gametes (to form a zygote) is called fertilisation. The zygote develops into an embryo.

Question 8.
Describe the various ways by which seeds are dispersed.
Answer:
Following are the various methods of seed dispersal:
a. Dispersal by Wind: Seeds of some plants are light-weight or have hair-like or wing-like structures present on them. Such seeds float in air and are thus dispersed by wind. For example: Dandelion, maple, drumstick, etc.

b. Dispersal by Water: Dispersal by water takes place in some aquatic plants and in some which grow near a water body. Seeds of water lily float and thus are dispersed by water. The coconut seed has a tough fibrous covering which has plenty of air inside. This helps the coconut seeds in floating on water.

c. Dispersal by Animals: Some seeds have spine-like structures on them. They get stuck to the fur of animals and thus get spread to different places. For example: Beggar tick, Xanthium, Urena, etc. Some seeds are swallowed by birds and animals along with fruits. These seeds get dispersed with bird or animal droppings.

d. Dispersal by Bursting: Some fruits burst open when they mature. The force of bursting is enough to spread the seeds. For example: ladyfinger, castor, balsam, etc.

e. Dispersal by Humans: Human beings also help in dispersal of seeds, especially during farming.

Question 9.
Match the items in column I with those of column II

Answer:
1. (c),
2. (e),
3. (b),
4. (a),
5. (d)

Question 10.
Tick the correct answer:
a. The reproductive part of a plant is the
(i) leaf
(ii) stem
(iii) root
(iv) flower
Answer:
(iv) flower

b. The process of fusion of the male and the female gametes is called
(i) fertilisation
(ii) pollination
(iii) reproduction
(iv) seed formation
Answer:
(i) fertilisation

c. Mature ovary forms the
(i) seed
(ii) stamen
(iii) pistil
(iv) fruit
Answer:
(iv) fruit

d. A spore producing plant is
(i) rose
(ii) bread mould
(iii) potato
(iv) ginger
Answer:
(ii) bread mould

e. Bryophyllum can reproduce by its
(i) stem
(ii) leaves
(iii) roots
(iv) flower
Answer:
(ii) leaves

NCERT Extended Learning Activities and Projects

Question 1.
Make your own garden by collecting pieces cut from different kinds of cacti. Grow the variety in one single flat container or in separate pots.
Hint:
Cactus can grow in scarcity of water and can withstand the absence of water for a long time. That is why, it can grow easily in the deserts. Thus, cactus can be grown quite easily in pots in home in single container or in separate pots.

Question 2.
Visit a fruit market and collect as many local fruits as possible. If many fruits are not available, you can collect tomatoes and cucumber (these are fruits, though we use them as vegetables). Make drawings of the different fruits. Split the fruits and examine the seeds within. Look for any special characteristics in the fruit and their seeds. You can visit a library also to learn about this.
Hint:
Collect the fruits and study the characteristics of fruits and seeds on your own.

Question 3.
Think of ten different fruit-bearing plants. Remember that many vegetables are also fruits of the plants. Discuss with your teacher, parents, farmers, fruit growers and agricultural experts (if available nearby) and find out the manner of their dispersal. Present your data in the form of a table as shown below.

Hint:

Question 4.
Suppose there is one member of a particular kind of organism in a culture dish, which doubles itself in one hour through asexual reproduction. Work out the number of members of that kind of organism which will be present in the culture dish after ten hours. Such a colony of individuals arising from one parent is called a “clone”.
Hint:
The answer will be 2¹⁰, i.e., 1024. Hence, new colony will have 1024 members after 10 hours.

Activity 1

Objective: To observe tuber of a potato and grow new plants from potato tubers.
Materials Required: A potato with buds or eyes and pot with soil in it.
Procedure:

• Plant the parts of the potato with eyes or buds in the soil.
• Water the soil regularly.
• Observe over a week.

Observation: After a week, new shoots and roots emerge out from the potato.
Conclusion: The conclusion of this activity is that the new plants can be grown from the tubers of potato.

ii. Budding: This method is used by unicellular plants like yeast. Yeast is a fungus and fungi are also known as non-green plants. The yeast cell produces a bulb-like projection coming out of the parent cell, called a bud, which gets its own nucleus. The bud develops to certain size and detaches from the mother cell to produce the new yeast cell. Sometimes another bud arises from a bud before it gets detached, forming a chain of buds.

Activity 2
Objective: To observe budding in yeast.
Materials Required: A petri dish, yeast (dry), sugar solution and a magnifying glass.
Procedure:

• Add some yeast into the petri dish containing sugar solution.
• Keep it undisturbed for 30 minutes.
• Observe the yeast cells under a magnifying glass.

Observation: We can see the bubbles with foam in the petri dish.
Conclusion: Due to the budding process, the yeast cells divide and increase the volume of the solution while releasing gases.

iii. Fragmentation: Algae, likeSpirogyra, generally reproduces by the process of fragmentation in which they divide themselves into multiple parts. As soon as the plant finds enough water and nutrients, it fragments and each fragment then grows into a new individual. This process continues and algae multiply quickly in a short period of time.

iv. Spore Formation: Spores are special asexual reproductive structures covered by a hard protective coat. They can withstand unfavourable conditions, such as high temperature, with the help of protective coat. They can germinate under favourable conditions and can develop into a new individual. Spores can float in the air and cover long distances. For example, ferns, mosses, lichens and fungi reproduce by spore formation.

Sexual Reproduction in Flowering Plants: Flower is the reproductive part of a plant. A complete flower is made up of four whorls on it. From outside inwards, these are sepals, petals, stamens and pistil. These four whorls are attached to a flattened tip of the flower called as receptacle.

i. Sepals collectively form calyx. These are green in colour and protect the inner parts of the flower in its bud condition.

ii. Petals collectively form corolla. These are the coloured structures which attract insects and birds for pollination.

iii. Stamens are the male reproductive parts of a flower. Stamen is made up of two structures namely, a filament and an anther. Filament is a tubular structure. Anther is a knob-like structure containing pollen sacs filled with pollen grains. Pollen grains produce the male gametes or the male reproductive cells.

iv. Pistil is the centrally located female reproductive part of a flower. It is made up of stigma, style and ovary. The stigma is a flattened structure which receives the pollen grains. It is sticky in nature. The style is a long tubular structure which conveys pollen to the ovary. The ovary contains numerous ovules. Each ovule contains a female gamete or egg cell.

Activity 3

Objective: To dissect a flower and observe its reproductive parts.
Materials Required: A mustard/china rose/ petunia flower, needle, a blade and hand lens.
Procedure

• Observe the flower using a hand lens and examine the parts.
• Carefully remove its stamen and pistil.
• Study the various parts of a stamen and pistil.

Observation: Stamen is the male reproductive part of the flower. Stamen consists of two parts anther and filament. Pistil is the female reproductive part of the flower. It is comprised of the stigma, style and the ovary.
Conclusion: Stamen and pistil are the reproductive parts of the flower.

Types of Flowers: Flowers, based on the reproductive whorls they carry, can be classified into unisexual flowers and bisexual flowers.
i. A unisexual flower is the flower which consists of either stamens or pistil. A flower with a whorl of stamens is called as male flower. A flower with just a pistil is called as a female flower. Eg., papaya, watermelon, cucumber, coconut, etc.

ii. A bisexual flower is the flower which consists of both the whorls of stamens and pistil, i.e., both male and female reproductive structures. Eg., lily, rose, brinjal, Hibiscus, Petunia, mustard, etc.

Pollination: The transfer of pollen grains from anthers to the stigma of a flower is called pollination. Pollination is of two types, viz., self pollination and cross pollination.
i. Self Pollination: If the pollens are transferred from the anthers to the stigma of the same flower, it is called self pollination.

ii. Cross Pollination: If the pollens are transferred from the anthers to the stigma of different flowers of the same plant or flowers of a different plant of the same kind, it is called cross pollination. Plants need help ftom various agents of pollination to carry out cross pollination. Wind, water, insects, birds and other animals play the role of pollination agents.

Fertilisation: When pollen settles on top of the stigma, it germinates to produce a pollen tube. The pollen tube enters the ovary through the style. Male nuclei are transferred to the ovary through the pollen tube. Inside the ovary, male gamete fuses with the egg cell present inside the ovule. The cell formed, just after fertilisation, is called zygote. Zygote develops into embryo. Each embryo develops into a seed. This process of fusion of male gamete with that of the egg nucleus is called fertilisation.

Fruits and Seeds: After fertilisation, ovary develops into fruit and ovules develop into seeds. Other flower parts fall off. The seed is an embryo enclosed in a protective coat. Some fruits are fleshy and juicy, such as mango and orange, while some are dry and hard, such as almonds and walnuts.

Dispersal of Seeds: The transportation of seeds from the parent plant to different places is called seed dispersal. Seed dispersal allows growth of the same kind of plants in different regions. This is helpful because it minimises the competition for food, sunlight, water and minerals among the plants of the same kind in the same area. It also allows them to grow in different habitats.

Seed dispersal is carried out by agencies like air, water, birds and other animals including man.

• Seeds dispersed by wind can have wings, such as in drumstick and maple, can be light-weighted as in grasses or can be hairy as in aak and sunflower (hairy fruit).
• Seeds dispersed by water have spongy or fibrous outer coat that helps in floating, such as in coconut.
• Seeds dispersed by animals are spiny and hooked so that they can get attached to the animal body and carted to different places. For example, Xanthium and Urena.
• Some seeds, such as in castor and balsam are dispersed by the bursting of fruit with sudden jerks.

Advantages of seed dispersal:

• Seed dispersal prevents competition between the plant and its own seedlings for sunlight, water and nutrients.
• Plants can acquire new habitats by seed dispersal and distribute widely.
• It avoids overcrowding of young plants around their parent plants. Overcrowding could lead to severe competition for sunlight, water, minerals and space. As a result, seedlings would not grow into healthy plants.

Class 7 Science Chapter 12 Reproduction in Plants Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is meant by reproduction?
Answer:
The process of producing new individuals of the same kind of the same species is called reproduction.

Question 2.
Why is reproduction an essential life process?
Answer:
Reproduction is essential for continuation of the species from generation to generation.

Question 3.
What do you mean by vegetative propagation?
Answer:
Vegetative propagation is the ability of plants to reproduce by using vegetative parts like root, stem and leaves.

Question 4.
Define fertilisation.
Answer:
The process of fusion of male and female gametes to form a zygote is called fertilisation.

Question 5.
Define fragmentation.
Answer:
The process of asexual reproduction in which an organism breaks up into two or more fragments is called fragmentation. These fragments grow into new individuals.

Question 6.
What is meant by a unisexual flower?
Answer:
A flower having either pistil or only the stamens is called a unisexual flower.

Question 7.
What is zygote?
Answer:
The cell which results after the fusion of gametes during fertilisation is called a zygote.

Question 8.
Which pat of flower gives rise to fruit?
Answer:
After fertilisation, the ovary grows into a fruit and other parts of the flower fall off. The fruit is the ripened ovary.

Question 9.
Name the reproductive organ of a flowering plant.
Answer:
The flower is a reproductive organ of a flowering plant.

Question 10.
What is the role of pollen grains in flowering plants?
Answer:
Male gametes are produced inside pollen grains.

Question 11.
Give an example of an organism which reproduces by budding.
Answer:
Yeast.

Question 12.
How many parents are involved in asexual reproduction?
Answer:
Only one.

Question 13.
What is the benefit of colourful petals for plants?
Answer:
Colourful petals attract insects, birds and other animals. It helps in cross pollination and seed dispersal.

Question 14.
Give two examples of seeds which are dispersed by wind.
Answer:
Dandelion and maple.

Question 15.
Name the male reproductive part of the flower.
Answer:
Stamen.

Question 16.
Name the female reproductive part of the flower.
Answer:
Pistil.

Question 17.
Name the various modes of asexual reproduction in plants.
Answer:
Vegetative propagation, budding, fragmentation and spore formation.

Short Answer Type Questions

Question 1.
Explain the two types of reproduction in plants.
Answer:
The two types of reproduction in plants are:
a. Asexual reproduction: plants give rise to new plants without the formation of seeds. The reproductive organs are not required. New plants grow by means of:

• vegetative propagation,
• budding,
• fragmentation, or
• spore formation.

b. Sexual reproduction: In this, new plants are produced through the formation of seeds. Male and female gametes fuse to form a zygote which later on develops into a seed. For example: Petunia and mango.

Question 2.
How plants such as mosses and ferns reproduce?
Answer:
Plants such as mosses and ferns reproduce by means of spores. Spores are asexual reproductive bodies. Each spore is covered by a hard protective coat to withstand unfavourable conditions such as high temperature and low humidity. Hence, spores can survive for a long time. Under favourable conditions, a spore germinates and develops into a new individual.

Question 3.
How does reproduction take place in yeast cells?
Answer:
Yeast is a single-celled organism. The small bulb-like projection coming out from the yeast cell is called a bud. The bud gradually grows and gets detached from the parent cell and forms a new yeast cell. The new yeast cell grows, matures and produces more yeast cells. Sometimes, another bud arises from the bud forming a chain of buds. If this process continues, a large number of yeast cells are produced in a short time.

Question 4.
Write the advantages of vegetative propagation.
Answer:

• New plants can be produced quickly.
• The plants so produced are exact copies of parent plants.
• Seedless plants can be easily propagated.

Question 5.
What types of seeds are dispersed by animals?
Answer:
Some seeds are dispersed by animals, especially spiny seeds with hooks which get attached to the bodies of animals and are carried to distant places. Examples are Xanthium and Urena.

Question 6.
How do potatoes reproduce?
Answer:
Potatoes can be grown asexually by vegetative reproduction. This can be done by planting a part of potato with an eye into the soil and watering it regularly for a few days. The new stem starts arising on the eyes of the potato and a potato plant will develop.

Question 7.
How do algae reproduce?
Answer:
Slimy green patches seen in ponds or in other stagnant water bodies are the algae. When water and nutrients are available, algae grow and multiply rapidly by fragmentation. An alga breaks up into two or more fragments. These fragments or pieces grow into new individuals. This process continues and they cover a large area in a short period of time.

Question 8.
What is the difference between cutting and grafting?
Answer:
Cutting is a process in which a piece of vegetative part (root, stem or leaf) of a plant is selected and is rooted in the soil whereas grafting is practised in those plants which do not produced roots readily. In this process, cutting of a plant is attached to the piece of another rooted plant. The cutting is called a scion while the rooted plant is called a stock.

Question 9.
What are fruits? What are fleshy and dry fruits?
Answer:
Ripened ovary after fertilisation is called fruit. There are two types of fruits:

• Fleshy fruits: The fruits which are fleshy and juicy like mango, apple and orange are called fleshy fruits.
• Dry fruits: The hard and dry fruits like almonds and walnuts are called dry fruits.

Long Answer Type Questions

Question 1.
What is pollination? Explain various types of pollination.
Answer:
Pollination: The transfer of pollen grains from anthers to the stigma of a flower is called pollination. There are following two types of pollination:

a. Self Pollination: When pollen gains are transferred from the anthers of a flower to the stigma of the same flower or another flower of the same plant, it is called self pollination.

b. Cross Pollination: When pollen grains from the anthers of a flower are transferred to the stigma, of the flowers on different plants, it is called cross pollination. Cross pollination is the norm in most of the plants. Plants need help from various agents of pollination to carry out cross pollination. Wind, water, insects, birds and other animals play the role of agents of pollination.

Question 2.
Describe the structure of a typical flower.
Answer:
Flowers are the reproductive parts of the plant. A typical flower consists of the following parts:
a. Sepals: These are green leaf like structures which help in the preparation of food.
b. Petals: These are coloured big leaf-like structures in the flower which help in the pollination.
c. Stamens: Stamens are the male reproductive parts of the flowers. There are two parts of each stamen: (i) anther and (ii) filament. Anther contains pollen grains which have male gametes.
d. Pistil: Pistil is the female reproductive part of the flowers. There are three main parts of a pistil: (i) stigma, (ii) style and (iii) ovary. The ovary contains one or more ovules. The female gametes or the eggs are formed in an ovule.

Question 3.
How the male gamete in the pollen grain reaches the female gamete present in the ovule?
Answer:
Generally, pollen grains have a tough protective coat which prevents them from drying up. Since pollen grains are light, they can be carried by wind or water. Insects visit flowers and carry along pollen on their bodies. Some of the pollens land on the stigma of a flower of the same kind. Pollen grains on the stigma grow a tiny tube, all the way down the style to the ovary. This pollen tube carries a male gamete to meet a female gamete in an ovule.

Question 4.
Describe various steps involved in the formation of a plant seed starting from pollination.
Answer:
The transfer of pollen grains from another to the stigma of a flower is called pollination. Now the male gamete enters into the ovary where fusion of male and female gametes takes place. This process is called fertilisation.

After fertilisation of ovules, various changes take place. The petals, sepals and stamens are dried and destroyed. Only ovary remains. The ovary contains fertilised ovule. After fertilisation, ovary containing a number of fertilised ovules is called fruit. The fertilised and developed ovule is called seed.

Picture-Based Questions

Question 1.
Draw a diagram to show:
a. Cross-pollination
b. Self-pollination
Answer:

Question 2.
a. Identify the following fruits (i) and (ii).
b. Which of these is a fleshy fruit?
c. Which of these is a dry fruit?

Answer:
a. (i) Apple, (ii) Walnuts
b. Apple
c. Walnut

Question 3.
Draw a diagram to show reproduction in fungus by spore formation. Label the following parts: hypha, sporangium and spores.
Answer:

Question 4.
Observe the following figure. Identify it and write how its dispersal take place.

Answer:
It is a seed of Xanthium. Seeds of Xanthium have numerous spines on them which get attached to the fur of animals. Hence, these are dispersal by animals.

NCERT Solutions for Class 7 Science

• Class 7 Science Chapter 1 Nutrition in Plants
• Class 7 Science Chapter 2 Nutrition in Animals
• Class 7 Science Chapter 3 Fibre to Fabric
• Class 7 Science Chapter 4 Heat
• Class 7 Science Chapter 5 Acids, Bases and Salts
• Class 7 Science Chapter 6 Physical and Chemical Changes
• Class 7 Science Chapter 7 Weather, Climate and Adaptations of Animals of Climate
• Class 7 Science Chapter 8 Winds, Storms and Cyclones
• Class 7 Science Chapter 9 Soil
• Class 7 Science Chapter 10 Respiration in Organisms
• Class 7 Science Chapter 11 Transportation in Animals and Plants
• Class 7 Science Chapter 12 Reproduction in Plants
• Class 7 Science Chapter 13 Motion and Time
• Class 7 Science Chapter 14 Electric Current and its Effects
• Class 7 Science Chapter 15 Light
• Class 7 Science Chapter 16 Water: A Precious Resource
• Class 7 Science Chapter 17 Forests: Our Lifeline
• Class 7 Science Chapter 18 Wastewater Story

These NCERT Solutions for Class 7 Science Chapter 11 Transportation in Animals and Plants Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Transportation in Animals and Plants NCERT Solutions for Class 7 Science Chapter 11

Class 7 Science Chapter 11 Transportation in Animals and Plants Textbook Exercise Questions and Answers

Question 1.
Match structures given in Column I with functions given in Column II.

Answer:
1. (b),
2. (d),
3. (a),
4. (c)

Question 2.
Fill in the blanks.
a. The blood from the heart is transported to all parts of the body by the ……………….
b. Haemoglobin is present in ………………. cells.
c. Arteries and veins are joined by a network of ……………….
d. The rhythmic expansion and contraction of the heart is called ……………….
e. The main excretory product in human beings is ……………….
f. Sweat contains water and ……………….
g. Kidneys eliminate the waste materials in the liquid form called ……………….
h. Water reaches great heights in the trees because of suction pull caused by ……………….
Answer:
a. arteries,
b. red blood,
c. capillaries,
d. heartbeat,
e. urea,
f. salts
g. urine,
h. transpiration

Question 3.
Choose the correct options:
a. In plants, water is transported through
(i) xylem
(ii) phloem
(iii) stomata
(iv) root hair
Answer:
(i) Xylem

b. Water absorption through roots can be increased by keeping the plants
(i) in the shade
(ii) in dim light
(iii) under the fan
(iv) covered with a polythene bag
Answer:
(iii) under the fan

Question 4.
Why is transport of materials necessary in a plant or in an animal? Explain.
Answer:
Every cell of plants and animals needs nutrients and oxygen for performing various metabolic activities. Different types of waste products are created during these metabolic activities. Transport of materials is necessary to supply the required substances and to remove the waste products from the cells.

Question 5.
What will happen if there are no platelets in the blood?
Answer:
The blood platelets are responsible for clotting of blood in case of an injury or a scratch. As we know, when an injury occurs the blood starts flowing for a while and then it clots on its own. If in any case, there are no platelets, the blood will not be able to clot and keeps on flowing. Huge loss of blood will ultimately lead to death.

Question 6.
What are stomata? Give two functions of stomata.
Answer:
The lower surface of the leaves have small openings. These openings or pores are called stomata. These pores are surrounded by guard cells.

Functions of stomata:

• It helps to eliminate excess water from the plant, i.e, transpiration.
• The process of loss of water from stomata will cause an upward pull, i.e., suction pull which in turn helps in absorption of water from the roots.
• They are responsible for the exchange of gases for respiration.

Question 7.
Does transpiration serve any useful function in the plants? Explain.
Answer:

• By creating a suction pull, it enhances the absorption of dissolved minerals and water in the plants.
• It helps in getting rid of the excess water in plants.
• It transports minerals and water to the leaves. The leaves use the water to carry out photosynthesis.
• It creates a cooling effect in plants.

Question 8.
What are the components of blood?
Answer:
Blood is composed of four main components:

• Plasma: It is the liquid part of the blood which is yellowish in colour and contains 90% water. It also contains enzymes, food, proteins and other wastes.
• Red Blood Cells: They are disc-shaped cells containing a red-coloured pigment called haemoglobin in it. Haemoglobin helps in transportation of oxygen.
• White Blood Cells: These are the fighting cells and are also called as warrior cells which protect us from infections caused by bacteria and foreign materials.
• Platelets: The platelets help in clotting of the blood.

Question 9.
Why is blood needed by all the parts of a body?
Answer:
All the parts of the body need food and oxygen, which is carried to them by blood. They also release their wastes into the blood which is then transported to those parts from where they can easily be removed. Hence, blood is needed by all parts of the body.

Question 10.
What makes the blood look red?
Answer:
Haemoglobin present in blood is a red pigment. This pigment is responsible for carrying oxygen to various parts of the body through blood and makes it appear red.

Question 11.
Describe the function of the heart.
Answer:
The human heart is divided into four chambers. The upper two chambers are called right and left atria and the lower two chambers are called the right and left ventricles. Right atrium receives carbon dioxide-rich blood from the body. Blood from right atrium enters the right ventricle, which contracts and pumps the blood to the lungs for purification.

On the other hand, oxygen rich blood from the lungs returns to the left atrium. From the left atrium, blood enters left ventricle. Left ventricle contracts and pumps the blood to all parts of the body. Hence, the rhythmic contraction and expansion of various chambers of the heart maintains the transport of blood and oxygen to all parts of the body.

Question 12.
Why is it necessary to excrete waste products?
Answer:
All cells of our body produce waste products. These waste products are toxic to the body and therefore need to be excreted out. This process of removing waste products produced in the cells of living organisms is called excretion.

Question 13.
Draw a diagram of the human excretory system and label the various parts.
Answer:

NCERT Extended Learning Activities And Projects

Question 1.
Find out about blood groups and their importance.
Hint:
The best-known way of grouping of blood types is the ABO system, although there are other groups too. Within the ABO group, four major categories are divided into eight common blood types: A, B, O and AB. Here, alphabets A and B refer to certain substances which are present in the Red Blood Cells. The blood group AB contains both A and B substances in the RBCs whereas, both these substances are absent in the blood group O.

The grouping is very important when it comes to having a blood transfusion. If blood is given to a patient that has a blood type that is incompatible with the blood type of the blood that the patient receives, it can cause intravenous clumping in the patient’s blood which can be fatal.

Question 2.
When a person suffers from chest pain, the doctor immediately takes an ECG. Visit a doctor and get information about ECG. You may even look up an encyclopaedia or the internet.
Hint:
An electrocardiogram (ECG) is a medical test that detects cardiac (heart) abnormalities by measuring the electrical activity generated by the heart as it contracts. The machine that records the patient’s ECG is called an electrocardiograph. The electrocardiograph records the electrical activity of the heart muscle and displays this data as a trace on a screen or on paper. This data is then interpreted by a medical practitioner. ECGs from healthy hearts have a characteristic shape. Any irregularity in the heart rhythm or damage to the heart muscle can change the electrical activity of the heart so that the shape of the ECG is changed.

A doctor may recommend an ECG for people who may be at risk of a heart disease because there is a family history of heart disease or because they smoke, are overweight, or have diabetes, high cholesterol or high blood pressure.

Activity 1

Objective: To prepare a simple stethoscope of your own.
Materials Required: A glass funnel, rubber tubes and a piece of rubber sheet
Procedure:

• Take a small funnel of 6-7 cm in diameter.
• Fix a rubber tube (50 cm long) tightly on the stem of the funnel.
• Stretch a rubber sheet or a balloon on the mouth of the funnel and fix it tightly with a rubber band.
• Put the open end of the tube on one of your ears.
• Place the mouth of the funnel on your chest near the heart.
• Listen carefully to the thumping sound. The thumping sound is the heart beat.
• Count the heartbeats per minute.
• Now run for 4-5 minutes and again count your heart beats.
• Your stethoscope is ready.

Observations: It can be observed that the heartbeat increases after running. Also, at rest, heartbeats around 72 times per minute.
Conclusion: The pulse rate of an adult person while resting is 72 to 80 beats per minute. A physical activity demands more oxygen, hence, heart beats faster.

Excretion: As our body carries out its daily activities it produces waste materials. These waste materials have to be removed from the body, otherwise they become harmful. The process by which the organisms remove waste products from their body is called excretion. The organ system involved in this process constitutes the excretory system.

Human Excretory System: It consists of kidneys, ureters, urinary bladder and urethra.
i. Kidneys: Kidneys are bean-shaped. They work like filters. They filter only unwanted substances from the blood. There are two kidneys in the human body, one each on the right and left side of the abdomen. These are located on either side of the vertebral column, just below the level of the stomach. They filter the blood and the useful substances are absorbed back into the blood white unwanted waste is dissolved in water and removed as urine.

ii. Ureter: The tube through which urine travels through the kidneys and get stored in the bladder is called ureter Human body has a pair of ureters, one attached to each kidney.
iii. Urinary bladder: The two ureters carry urine from both the kidneys to a bladder called the urinary bladder. In the urinary bladder, urine is temporarily stored.
iv. urethra. Finally, the urine is ejected through a urinary passage called urethra. It is a muscular tube with urinary opening at the end.

Excretion of Urine: Urine contains 95% water, 2.5% urea and 2.5% other wastes. Protein is made up of nitrogen. Metabolism of proteins creates nitrogenous wastes in the body. The nitrogenous wastes are formed by the breakdown of proteins into products such as ammonia. Ammonia is later on converted into urea. In this process, a small amount of uric acid is also formed. Urea is less harmful as compared to ammonia. Accumulation of urea in blood may even cause death. This urea is removed from the blood by filtration through kidneys in the form of urine. Urine is expelled out from time to time. An adult human being normally passes 1-1.8 L of urine in 24 hours.

Sweat: It is the moisture exuded through the pores of the skin. Sweat is produced by sweat glands in the skin. It removes water and salts from the body. When we sweat, it helps to cool our body. It is also an excretory mechanism to get rid of unwanted wastes such as excess water and some salts.

Dialysis: Sometimes a person’s kidneys may stop working due to infection or injury. As a result of kidney failure, waste products start accumulating in the blood. Such persons cannot survive unless their blood is filtered periodically through an artificial kidney. This process is called dialysis.

Mode of Excretion in Other Animals: The way in which waste chemicals are removed from the body of the animal depends on the availability of water.

• Aquatic animals like fishes, excrete cell waste as ammonia which directly dissolves in water.
• Some land animals like birds, lizards, snakes excrete a semi-solid, white coloured compound (uric acid).
• The major excretory product in humans is urea.
• In unicellular organisms like Amoeba and Paramecium, excretory products are removed by diffusion from the body of the organism into the surrounding water.

Transportation is Plants: In plants, water and minerals are absorbed by the roots. Roots have hair, known as root hair which increase the surface area of root for the absorption of water and mineral nutrients dissolved in water. This needs to be transported to the leaves so that they can prepare food. Also, the food prepared by leaves needs to be transported to rest parts of the plant.

Vascular Tissues: Plants have pipe-like vessels to transport water, nutrients and foods which are called vascular tissues. A tissue is a group of cells that perform specialised functions in an organism. They can be seen forming a fine network in a leaf. This network in a leaf is called venation. Plants have two main types of vascular tissues:

• Xylem: It is the vascular tissue for the transport of water and minerals. The xylem forms a continuous network of channels that connects roots to the leaves through the stem and branches and thus transports water to the entire plant.
• Phloem: The phloem consists of vessels, called sieve tubes. It is the vascular tissue that transports the food synthesised in the leaves to all parts of the plant.

Activity 2

Objective: To demonstrate transportation of water through the cells.
Materials Required: A large potato, sugar solution, pin, a petri dish and water.
Procedure:

• Take a large raw potato and cut it into two halves.
• Now take one cut potato piece and peel off its outer skin.
• Cut its round end slightly to make its base flat.
• Make a deep cavity in the centre of the potato piece.
• Fill half of the cavity of potato piece with sugar solution and mark the level of sugar solution in it by inserting a pin through the potato wall as shown the figure.
• Place this potato piece (with sugar solution in it) in a petri-dish containing small amount of pure water.
• The level of water in the petri-dish should be below the level of pin inserted in the potato.
• Allow the apparatus to stand for a few hours.

Observation: After a few hours, the level of sugar solution in the potato piece rises above the level of pin marks. This means that there is an increase in the level of sugar solution inside the potato cavity.
Conclusion: Water can move from cell to cell in the potato wall and reach inside the cavity. In the same way, water reaches xylem vessels of the root from the soil.

Transpiration: In plants, the excess water evaporates through the stomata present on the surface of the leaves by the process of transpiration. The evaporation of water from leaves generates a suction pull (the same that you produce when you suck water through a straw) which can pull water to great heights in the tall trees.

Benefits of Transpiration: It helps in the transport of water and minerals from the soil to the leaves. Also, the water evaporated due to transpiration produces a cooling effect which helps to protect delicate cells of plants from being destroyed by the sunlight.

Class 7 Science Chapter 11 Transportation in Animals and Plants Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is removed along with water as sweat?
Answer:
Extra salts are removed along with water as sweat.

Question 2.
What is the function of stethoscope?
Answer:
Stethoscope is used by doctors to amplify heartbeat so that it can be analysed properly.

Question 3.
What is pulse?
Answer:
Throbbing sensation that occurs in arteries due to flowing of blood is called pulse.

Question 4.
How is a clot formed?
Answer:
Clot is produced as an action of platelets during any external injury to prevent excessive loss of blood.

Question 5.
What is meant by excretion?
Answer:
It is the process of removal of toxic substances from the body.

Question 6.
Name the two main types of blood vessels.
Answer:
Arteries and veins.

Question 7.
Where is heart located in human body?
Answer:
Heart is located in the chest cavity with its lower part slightly tilted towards the left.

Question 8.
What is heartbeat?
Answer:
The muscles of the heart contract and relax, constituting a heartbeat.

Question 9.
Name the various waste products formed in the body.
Answer:
Urea, uric acid and excess water.

Question 10.
Why is urine yellow in colour?
Answer:
Urine is yellow-coloured due to the presence of urochrome pigment.

Question 11.
What is urine?
Answer:
The mixture of various wastes with water filtered from the blood is called urine.

Question 12.
What is vascular tissue?
Answer:
Plants have pipe-like cells to transport water, nutrients and food which are called vascular tissues.

Question 13.
What is Xylem?
Answer:
The vascular tissue which is used to transport water and nutrients in the plants is called xylem.

Question 14.
What is Phloem?
Answer:
The vascular tissue which is used to transport food to all parts of the plant is called phloem.

Question 15.
Why are valves present in veins?
Answer:
Valves are present in veins to prevent backflow of blood in them.

Question 16.
What is sweat?
Answer:
Salts and urea are removed along with water from the skin as sweat.

Question 17.
What are capillaries?
Answer:
Arteries divide into smaller vessels. On reaching the tissues, they divide further into extremely thin tubes called capillaries.

Short Answer Type Questions

Question 1.
What is the main function of the kidneys?
Answer:
The kidneys perform the essential function of removing waste products from the blood and produce urine which is composed of wastes and extra fluid. It helps in regulating the water-fluid levels in the body.

Question 2.
How do plant roots absorb water and minerals from the soil?
Answer:
Plants absorb water and minerals by the roots. The roots have root hair, that increase the surface area of the root for the absorption of water and mineral nutrients dissolved in water. The root hair is in contact with the water present between the soil particles.

Question 3.
What is transpiration? How is it useful to the plants?
Answer:
It is the process of removal of extra water in the form of water vapours through stomata in plants. This process helps in eliminating extra water from the plant body and keeping the plant cool.

Question 4.
What are the three types of cells present in the blood of humans?
Answer:
The three types of cells present in human blood are:

• Red blood cells (RBCs) which contain a red pigment called haemoglobin.
• White blood cells (WBCs) which fight against germs that may enter our body.
• Platelet cells which helps in the clotting of the blood.

Question 5.
Write the functions of blood?
Answer:
Functions of blood:

• It carries oxygen from lungs to body cells.
• It removes waste from the cells.
• It regulate body temperature.
• It protects the body against infections.
• It transports nutrients to all body cells.

Question 6.
What is meant by translocation? Where does it take place?
Answer:
The transport of soluble products of photosynthesis from leaves (where they are formed) to other parts of the plant is called translocation. It occurs in the part of the vascular tissue known as phloem.

Question 7.
Write differences between arteries and veins.
Answer:

Question 8.
What is dialysis? Explain.
Answer:
Dialysis is the artificial process of getting rid of waste and unwanted water from the blood by machines. Dialysis machines contain a tank with solution of water, glucose and salt. Patient’s blood is allowed to pass through the solution for the removal of waste. The cleaned blood is pumped back to a vein. The dialysis continues till entire blood has been purified.

Question 9.
Write the differences between RBCs and WBCs.
Answer:

Question 10.
Why is heart known as the pumping organ of the human body?
Answer:
Heart is the pumping organ of the human body as it continuously acts as a pump for transporting blood to all body parts. Heart pumps carbon dioxide-rich blood to lungs and oxygen-rich blood to the rest of the body.

Question 11.
What is the significance of dividing heart into different chambers?
Answer:
The division of heart into different chambers ensures that there is no intermixing of oxygenated and deoxygenated blood. This ensures a better efficiency of circulation and transportation of oxygen.

Question 12.
Why is haemoglobin important for the human body?
Answer:
Haemoglobin binds with oxygen and transports it to all the parts of the body and ultimately to all the cells. It will be difficult to provide oxygen efficiently to all the cells of the body without haemoglobin.

Long Answer Type Questions

Question 1.
Describe the circulation of blood across the heart and the body.
Answer:

a. Blood circulation starts when the heart relaxes between two heartbeats. Blood goes from both the atria into the ventricles which then expand. The following phase is called ejection period, which is when both ventricles pump the blood into the large arteries.

b. In the systemic circulation, the left ventricle pumps oxygen-rich blood into the main artery (aorta). The blood travels from the main artery to larger and smaller arteries and into the capillary networks. There the blood releases oxygen, nutrients and other important substances and takes up carbon dioxide and waste substances. The blood, which is now low in oxygen, is collected in veins and travels to the right atrium from where it goes into the right ventricle.

c. Now pulmonary circulation starts. The right ventricle pumps blood that carries little oxygen into the pulmonary artery, which transports this blood to the lungs. This is where carbon dioxide is released from the blood into the air contained in the lungs and fresh oxygen enters the bloodstream. When we breathe out, carbon dioxide leaves our body. Oxygen-rich blood travels through the pulmonary vein into the left atrium from where it goes into the left ventricle. The next heartbeat starts a new cycle of the systemic circulation.

Question 2.
Describe the structure of the human heart.
Answer:
The human heart is of the size of a fist.

• Heart is a triangular shaped organ. It is made up of cardiac muscles and is located between the lungs inside chest cavity. Its lower tip is slightly tilted towards left.
• It beats 72 to 80 times per minute throughout life. It pumps blood to all parts of the body.
• The heart has four chambers. The upper chambers are called auricles (or atria) and the lower two chambers are called ventricles.
• The left chambers are completely separated from right side by a partition called septum to avoid mixing of pure and impure blood. The chambers contain valves which ensure the flow of blood in one direction only.
• The right auricle receives carbon-dioxide rich blood from various parts of the body. The right ventricle pumps the blood to the lungs. Inside lungs, carbon-dioxide is exchanged with oxygen.
• The left auricle receives oxygen-rich blood from the lungs. The left ventricle pumps this blood to the rest of the body.

Question 3.
Explain the excretory system in human beings.
Answer:
The waste present in the blood has to be removed from the body. A system to filter the waste is required. This is done by the blood capillaries in the kidneys. When blood reaches the two kidneys, it contains both useful and harmful substances.

The useful substances are absorbed back into the blood after filtration in kidneys. The waste dissolved in water is removed as urine. From the kidneys, the urine goes into the urinary bladder through tubes called ureters. It is stored in the bladder and is passed out through the muscular tube called urethra. The kidneys, ureters, urinary bladder and urethra form the excretory system in humans.

Question 4.
What are the methods used by plants to get rid of excretory products?
Answer:
To get rid of excretory products, plants use the following ways:

• Excess water is lost by transpiration.
• Many plants store waste products in vacuoles of the cells.
• Some waste products are stored in the leaves. They are removed as the leaves fall off.
• Some waste products such as resins and gums are stored, especially in non-functional old xylem.
• Some waste products such as tannins, resins, gums, etc., are stored in bark, thereby removed as it peels off.
• Plants also excrete some waste substances through roots into the soil around them.
• Oxygen is lost while the stomata open for taking in carbon-dioxide.

Picture-Based Questions

Question 1.
Sketch a human heart and label the pulmonary artery, right and left atria, right and left ventricles, septa, pulmonary vein and aorta.
Answer:

Question 2.
Look at the figure given below and answer the following questions.

a. Name the process depicted.
b. Where is this process used in plants?
Answer:
a. Osmosis.
b. Osmosis is used by plant roots to absorb water and minerals from the soil.

Question 3.
Observe the given figure and write its use.

Answer:
The above picture is of a stethoscope and it is used by a doctor as a device to amplify the sound of heartbeat.

NCERT Solutions for Class 7 Science

• Class 7 Science Chapter 1 Nutrition in Plants
• Class 7 Science Chapter 2 Nutrition in Animals
• Class 7 Science Chapter 3 Fibre to Fabric
• Class 7 Science Chapter 4 Heat
• Class 7 Science Chapter 5 Acids, Bases and Salts
• Class 7 Science Chapter 6 Physical and Chemical Changes
• Class 7 Science Chapter 7 Weather, Climate and Adaptations of Animals of Climate
• Class 7 Science Chapter 8 Winds, Storms and Cyclones
• Class 7 Science Chapter 9 Soil
• Class 7 Science Chapter 10 Respiration in Organisms
• Class 7 Science Chapter 11 Transportation in Animals and Plants
• Class 7 Science Chapter 12 Reproduction in Plants
• Class 7 Science Chapter 13 Motion and Time
• Class 7 Science Chapter 14 Electric Current and its Effects
• Class 7 Science Chapter 15 Light
• Class 7 Science Chapter 16 Water: A Precious Resource
• Class 7 Science Chapter 17 Forests: Our Lifeline
• Class 7 Science Chapter 18 Wastewater Story

These NCERT Solutions for Class 7 Science Chapter 10 Respiration in Organisms Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Respiration in Organisms NCERT Solutions for Class 7 Science Chapter 10

Class 7 Science Chapter 10 Respiration in Organisms Textbook Exercise Questions and Answers

Question 1.
Why does an athlete breathe faster and deeper than usual after finishing the race?
Answer:
During the run, the demand of energy is high but the supply of oxygen to produce energy is limited. Therefore, anaerobic respiration takes places in the muscle cells to fulfil the demand of energy. After finishing the race, an athlete breathes faster and deeper than usual so that more oxygen is supplied to the cells to resume aerobic respiration.

Question 2.
List the similarities and differences between aerobic and anaerobic respiration.
Answer:
Similarities:

• In both the aerobic and the anaerobic respiration, food is broken down to release energy.
• Both takes place inside the cells.
• Both produce by products.

Differences:

Question 3.
Why do we often sneeze when we inhale a lot of dust-laden air?
Answer:
We often sneeze when we inhale a lot of dust-laden air to expel out these foreign particles. These particles get past the hair in the nasal cavity and irritate the lining of the cavity which results in sneezing reflex.

Question 4.
Take three test-tubes. Fill each of them with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of CO₂?
Answer:
Test-tube A will have the highest concentration of CO₂ because snail will take in oxygen dissolved in water and gives out CO₂. In test tube B, plant will release oxygen while in test tube C, the level of oxygen and carbon dioxide will remain stable due to gaseous cycle between the plant and the animal. The oxygen released by plant will be taken up by the animal while the carbon dioxide released by the animal will be taken up by the plant. Also, in test-tubes B and C, the CO₂ will be utilised by the water plant for synthesising food and hence there will be less concentration of CO₂ in these tubes.

Question 5.
Tick the correct answer:
a. In cockroaches, air enters the body through
(i) lungs
(ii) gills
(iii) spiracles
(iv) skin
Answer:
(iii) spiracles

b. During heavy exercise, we get cramps in the legs due to the accumulation of
(i) carbon dioxide
(ii) lactic acid
(iii) alcohol
(iv) water
Answer:
(ii) lactic acid

c. Normal range of breathing rate per minute in an average adult person at rest is
(i) 9-12
(ii) 15-18
(iii) 21-24
(iv) 30 – 33
Answer:
(ii) 15-18

d. During exhalation, the ribs
(i) move outwards
(ii) move downwards
(iii) move upwards
(iv) do not move at all
Answer:
(ii) move downwards

Question 6.
Match the items in Column I with those in Column II:

Answer:
1. (c)
2. (d)
3. (a)
4. (e)
5. (b)
6. (f)
7. (g)

Question 7.
Mark T if the statement is true and F if it is false:
a. During heavy exercise the breathing rate of a person slows down. (TV F)
b. Plants carry out photosynthesis only during the day and respiration only at night. (T/ F)
c. Frogs breathe through their skins as well as their lungs. (T/ F)
d. The fishes have lungs for respiration. (T/ F)
e. The size of the chest cavity increases during inhalation. (T/ F)
Answer:
a. F,
b. F,
c. T,
d. F,
e. T

Question 8.
Given below is a square of letters in which are hidden different words related to respiration in organisms. These words may be present in any direction – upwards, downwards or along the diagonals. Find the words for your respiratory system. Clues about those words are given below the square.

a. The air tubes of insects
b. Skeletal structures surrounding chest cavity
c. Muscular floor of chest cavity
d. Tiny pores on the surface of leaf
e. Siriaii openings on the sides of the body of an insect
f. The respiratory organs of human beings
g. The openings through which we inhale
h. An anaerobic organism
i. An organism with tracheal system
Answer:

a. Trachea
b. Ribs
c. Diaphragm
d. Stomata
e. Spiracles
f. Lungs
g. Nostrils
h. Yeast
i. Ant

Question 9.
The mountaineers carry oxygen with them because:
(a) At an altitude of more than 5 km there is no air.
(b) The amount of air available to a person is less than that available on the ground.
(c) The temperature of air is higher than that on the ground.
(d) The pressure of air is higher than that on the ground.
Answer:
(b) The amount of air available to a person is less than that available on the ground.

Extended Learning Activities and Projects

Question 1.
Observe fish in an aquarium. You will find flap like structures on both sides of their heads. These are flaps which cover the gills. These flaps open and close alternately. On the basis of these observations, explain the process of respiration in the fish.
Hint:
Respiration in fish takes place with the help of gills. Most fish possess gills on either sides of their head. Gills are the tissues made up of feathery structures that provide a large surface area for gaseous exchange. A large surface area is crucial for gaseous exchange in aquatic organisms as water contains very little amount of dissolved oxygen. Fish take in oxygen-rich water through their mouths and pump it over their gills. As water passes over the gill filaments, blood inside the capillary network picks up the dissolved oxygen. The circulatory system then transports the oxygen to all body tissues and ultimately to the cell, while picking up carbon dioxide, which is also removed from the body through the gills. After the water flows through the gills, it exits the body of the fish through the openings in the sides of the throat or through the operculum, a flap, usually found in bony fish, that covers and protects the fish gills.

Question 2.
Visit a local doctor. Learn about the harmful effects of smoking. You can also collect material on this topic from other sources. You can seek help of your teacher or parents. Find out the percentage of people of your area who smoke. If you have a smoker in your family, confront him with the material that you have collected.
Hint:
As this is an activity, the students are expected to do them on their own. Some harmful effects of smoking on our body are:
a. Smoking paves the way to hard drugs. Tobacco has been used by human beings for more than 400 years. It is smoked, chewed or used as a snuff.
b. Smoking is associated with increased incidents of cancer of lungs, urinary bladder and throat, bronchitis, emphysema, coronary heart disease, gastric ulcer, etc.
c. Tobacco chewing is associated with increased risk of cancer of the oral cavity.
d. Also, depression has been found to have a strong association with cigarette smoking. Adults who are depressed are 40% -50% more likely to smoke than adults who are not depressed.

Question 3.
Visit a doctor. Find out about artificial respiration. Ask the doctor:
a. When does a person need artificial respiration?
b. Does the person need to be kept on artificial respiration temporarily or permanently?
c. From where can the person get supply of oxygen for artificial respiration?
Hint:
a. Artificial respiration is needed by an individual at the time of acute breathing problems. It is an artificial method of breathing required when the person is unable to breathe normally.
b. Artificial respiration is not provided permanently to every person. It is given temporarily to person suffering from breathing problems. But artificial respiration can also be provided permanently to those who are in coma or unable to breathe on his or her own.
c. During artificial respiration, a cylinder filled with oxygen is attached to a machine which provides oxygen for artificial respiration.

Question 4.
Measure the breathing rate of the members of your family and some of your friends. Investigate:
a. if the breathing rate of children is different from that of adults.
b. if the breathing rate of males is different from that of females.
If there is a difference in any of these cases, try to find the reason.
Hint:
a. Children have faster respiratory rates than adults and the ‘normal’ respiratory rate can vary significantly by age.
b. Male heart rates are slower on average. Given these facts, it seems counterintuitive, but women have lower metabolic rates than men.

Activity 1

Objective: To show the variation in breathing rate during different activities.
Procedure: Perform the various activities as shown in the figure during a normal day and keenly observe your breathing rate.

Observation: When we do different activities, the rate of breathing increase or decrease depending on the activity. During sleeping and sitting, the breathing rate is slow while when we are doing physical activities like running, jumping, etc., the rate of breathing is fast.
Conclusion: Breathing rate depends upon the activity we do. Breathing rate of a person is not constant and it keeps changing.

Mechanism of Breathing in Humans:
In human beings, breathing occurs in the following way:

i. We take in the air present in the environment through our nostrils which travels through the nasal cavity. The mucous present here moistens and warms the air. The hair in the nasal cavity traps the dust and germs, thereby filtering the air.

ii. Then the air moves through the windpipe or trachea and reaches the lungs. The trachea divides into right and left primary bronchi that enters their respective lungs. Bronchi further divide and subdivide into bronchioles inside the lungs.

iii. The lungs are located in the chest cavity which is surrounded by the ribs.

iv. On the floor of the chest cavity lays a muscle sheet called diaphragm.

v. During the breathing process, the movement of the ribs and diaphragm takes place. This is so because the lungs expand and contract during breathing.

vi. As we take in the air, it fills up the lungs. This moves the diaphragm downwards and the ribs outwards and upwards. This increase space of chest cavity so that maximum air can be inhaled.

vii. When the lungs release out air from the body, it brings back the diaphragm and the ribs to their original positions, i.e., the ribs move downwards and inwards and the diaphragm moves upwards. This reduces the space in our chest cavity and pushes the air out.

Activity 2

Objective: To measure the change in size of the chest cavity during breathing.
Materials Required: Measuring tape.
Procedure:

• Take a deep breath.
• Measure the size of your chest with a measuring tape and record your observations.
• Do the same process with your classmates and record your observations.
• Now exhale complete air and measure the size again.

Observations:

Conclusion: The chest expands during inhalation and contracts during exhalation.

Activity 3

Objective: To demonstrate how diaphragm in the body helps in the process of breathing in and out of the air.
Materials Required: Two glass bell jars, two Y-shaped glass tubes, two balloons, two rubber corks, two thin rubber sheets and a piece of string.
Procedure:

• Take a wide plastic bottle and remove is bottom.
• Get a Y-shaped glass or plastic tube.
• Make a hole in the lid of the bottle so that the tube may pass through it.
• To the forked end of the tube, fix two deflated balloons.
• Introduce the tube into the bottle.
• Now cap the bottle. Seal it to make it airtight.
• To the open base of the bottle, tie a thin rubber or plastic sheet using a large rubber band.
• To understand the expansion of the lungs, pull the rubber sheet from the base downwards.
• The volume of the cavity increases. This causes the pressure to decrease.
• Air rushes in to equalise the pressure, causing the balloons to inflate.
• Next, push the rubber/plastic sheet up. The volume of the cavity decreases. This causes an increase in pressure within the bottle and the air rushes out of the balloons causing them to deflate.

Observation: When space in the jar is increased, balloons get inflated while when space in the jar is decreased, balloons get deflated.
Conclusion: When the lungs are filled with air, the diaphragm moves downward and when we exhale, the diaphragm moves upward.

Gases involved in Breathing: We inhale 21% oxygen and 0.04% carbon dioxide. Apart from this, small amounts of other gases present in the atmosphere are also involved in breathing. The exhaled air primarily contains large amount of carbon dioxide gas. This can be tested by blowing air into lime water. Lime water turns milky indicating presence of carbon dioxide gas.

Why Do We Sneeze?
As we inhale the air present in the surroundings, sometimes various unwanted elements such as smoke and dust are also included in it. However, they get stuck in the hair in our nostrils but some of them can get through the nasal cavity. They thus cause irritation in the nasal cavity which makes us sneeze. This helps in getting rid of the unwanted particles out of the nasal cavity.

Smoking damages lungs and can also cause cancer. Hence, it must be avoided. We should do regular breathing exercises (pranayam) as they increase our inhaling capacity, thereby bringing more energy to the body.

Breathing in Other Animals: Many animals have lungs in the bodies just like human beings, for example, lions, elephants, goats, cows, snakes and birds. However some animals have a different mechanism.
i. Breathing in Cockroach: Many insects like cockroaches have small openings called spiracles present on the sides of the bodies. Also, they have a network of air tube-like structures called the tracheae that allow the exchange of gases in these insects. The air enters the body through the spiracles into the tracheae and diffuses in the cells of the body. Similarly, the air from the cells enters the tracheal tubes and moves out of the body through spiracles.

ii. Breathing in Earthworm: Earthworms have a soft, slimy and moist skin. Hence, the gases can easily pass in and out of the earthworm’s body through its skin. Similarly, frogs also have a slippery and moist skin that can help in breathing. However, frogs possess lungs too. These animals, called the amphibians, can breathe on land by lungs and through moist skin under water. For example: frogs and toads.

iii. Breathing in Aquatic Animals:
Animals that live under water have special respiratory organs called gills. They are a comb-like structures present on the skin of these animals. Gills are richly supplied with blood vessels and allow the exchange of gases between animals and the water easily.

Respiration in Plants: Plants too require the phenomenon of respiration for survival. They also take in oxygen from the air and give out carbon dioxide. During this process, most of the plants use atmospheric oxygen to breakdown glucose into carbon dioxide and water with the release of energy.

In plants, breathing takes place through tiny holes or openings called stomata. Stomata trap the air and the exchange of carbon dioxide and oxygen takes places by the process called diffusion.

Root hair, lenticels and stomata are some of the parts present in plants for gaseous exchange. The roots of plants too respire to generate energy but they follow a different method. They take up air rich in oxygen from air spaces between the soil particles. Lenticels are the pores or cracks in the woody stems of plants that help in gaseous exchange.

Class 7 Science Chapter 10 Respiration in Organisms Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is respiration?
Answer:
Respiration is a biological process in which food is utilised to produce energy.

Question 2.
What is the end product of respiration in most of the organisms?
Answer:
Carbon dioxide, water and energy.

Question 3.
What is the end product of anaerobic respiration in muscle cells of humans?
Answer:
Lactic acid.

Question 4.
What is breathing?
Answer:
Breathing means taking in air rich in oxygen and giving out air rich in carbon dioxide with the help of respiratory organs.

Question 5.
What is inhalation?
Answer:
The taking in of air rich in oxygen into the body is called inhalation.

Question 6.
What is exhalation?
Answer:
Giving air rich in carbon dioxide out of the body is called exhalation.

Question 7.
What is the primary respiratory organ in humans?
Answer:
Lungs.

Question 8.
Which membrane controls the movement of lungs?
Answer:
Diaphragm.

Question 9.
What is the respiratory organ in fish?
Answer:
Gills.

Question 10.
What is the respiratory organ in a cockroach?
Answer:
Spiracles and tracheae.

Question 11.
How do birds breathe?
Answer:
Birds have lungs for breathing.

Question 12.
Why should we eat regularly?
Answer:
The food has stored energy which is released during respiration, thus we should eat regularly.

Question 13.
What forms the floor of the chest cavity?
Answer:
A large muscular sheet called diaphragm forms the floor of the chest cavity.

Question 14.
Why smoking should be avoided?
Answer:
Smoking damages lungs. Smoking is also linked to cancer. So, it must be avoided.

Question 15.
Give the general equation for aerobic respiration?
Answer:

Question 16.
Do we exhale only carbon dioxide or a mixture of gases along with it?
Answer:
No, some amount of moisture (water vapour) is also exhaled.

Question 17.
Which gas is released during exhalation?
Answer:
Mainly, carbon dioxide gas is released during exhalation.

Question 18.
Name an organism that can survive in the absence of air.
Answer:
Yeast can survive in the absence of air.

Question 19.
What does a breath mean?
Answer:
A breath means one inhalation plus one exhalation.

Question 20.
What are anaerobes?
Answer:
Some organisms, such as yeast, that can survive in the absence of air or oxygen are called anaerobes.

Short Answer Type Questions

Question 1.
What is aerobic respiration?
Answer:
The process of respiration which takes place in presence of oxygen is called aerobic respiration. In this process, breakdown of glucose (food) takes place into carbon dioxide and water with the help of oxygen.
Glucose (presence of oxygen) → Carbon dioxide + Water + Energy

Question 2.
What is anaerobic respiration?
Answer:
The process of respiration which takes place in the absence of oxygen is called anaerobic respiration. In this process, food is broken down without using oxygen into alcohol or lactic acid, carbon dioxide and energy.
Glucose (absence of oxygen) → Alcohol + Carbon dioxide + Energy

Question 3.
Do the plants also respire?
Answer:
Like other living organisms, plants also respire for their survival. They also take in oxygen from the air and give out carbon dioxide. In the cells, oxygen is used to break down glucose into carbon dioxide and water as in other organisms.

Question 4.
Why do we feel hungry after a physical activity?
Answer:
When we need extra energy, we breathe faster. As a result more oxygen is supplied to our cells. It speeds up the breakdown of food and more energy is released. Due to rapid breakdown of food, we feel hungry.

Question 5.
Give any two characteristics of all respiratory organs.
Answer:
Some characteristics of respiratory organs are:

1. Large surface area to get more oxygen.
2. Thin walls for easy diffusion and exchange of respiratory gases.
3. Rich blood supply for the transport of gases (except tracheal system).

Question 6.
How does exchange of gases take place in insects?
Or
Explain respiration in cockroach.
Answer:
The respiratory organs of insects include air tubes or trachea. They have small openings on the sides of their body which are called spiracles. Insects have a network of air tubes called tracheae for gaseous exchange. Oxygen-rich air enters through spiracles into the tracheal tubes and from here the air diffuses into the body tissues and reaches every cell of the body through finer branching of tracheal tubes called tracheoles. Thus, every cell gets oxygen directly. Similarly, carbon dioxide released by the cells, moves out through the spiracles.

Question 7.
What are the stages of respiration?
Answer:
Respiration takes place in the following stages:
a. External respiration or gaseous exchange: The exchange of gases between the environment and the body is called external respiration or gaseous exchange. This is also called breathing.

b. Internal respiration: It is a bio-chemical processes involved in respiration which breaks down the food using inhaled oxygen to release energy and takes place in the tissues within the cells of an organism. Thus, this is also called the cellular or tissue respiration.

Question 8.
What are gills? Where can they be seen?
Answer:
Gills in fish help them to use oxygen dissolved in water. Gills are the projections of the skin and are well supplied with blood vessels for exchange of gases. These gills can be seen in most of the aquatic animals like fish, prawns and mussels where they function as their respiratory organs.

Question 9.
Explain anaerobic respiration in yeast cells and in our muscles.
Answer:
Anaerobic respiration in yeast cells: Yeast gets energy through anaerobic respiration. In the absence of oxygen, yeast respires and breaks down glucose into alcohol and carbon dioxide. Following reaction takes place without the use of oxygen:
Glucose (without oxygen) → Alcohol + Carbon dioxide + Energy

Anaerobic respiration in Muscles: Our muscles can also respire anaerobically, but only for a short time. During heavy exercise, anaerobic respiration takes place in which glucose is broken into lactic acid and energy. Following reaction takes place in absence of oxygen:
Glucose (in muscles) → Lactic acid + Energy

Question 10.
What is the function of large intercellular spaces in plants?
Answer:
The large inter-cellular spaces ensure that all cells are in contact with air. Both CO₂ and O₂ are exchanged by diffusion in the intercellular spaces. These gases can either go into the cells or away from them or out into the air.

Question 11.
Explain respiration in earthworm.
Answer:
Earthworm breathes through its moist skin. The skin of an earthworm feels moist and slimy on touching and gases can pass easily through them.

Question 12.
What is the importance of breathing?
Answer:
All the organisms need energy for their various functions. This energy is released from the breakdown of the food (glucose) with the help of oxygen. The breathing ensures the continuous supply of oxygen to different body cells for this process.

Long Answer Type Questions

Question 1.
Describe the respiratory system in humans.
Answer:
When we breathe in, the air enters through our nostrils. Hair and the moist inner lining of the nose prevent the dust and germs from entering the respiratory system. The air passing the nasal passage gets warm and moist and enters the lungs through trachea and bronchi. In lungs, each bronchus divides into smaller tubes called bronchioles.

At the other end of these bronchioles, there are very small air sacs called alveoli. These air sacs are surrounded by blood vessels. These blood vessels absorb oxygen present in the air we breathe in. Carbon dioxide present in the blood is released into the air sacs and is expelled out of our body when we breathe out. Thus during breathing, exchange of oxygen and carbon dioxide takes place in the lungs.

Question 2.
What is meant by breathing rate? Explain the mechanism of inhalation and exhalation which are responsible for breathing rate?
Answer:
The number of times a person breathes in a minute is termed as the breathing rate. During breathing, inhalation and exhalation take place alternately. A breathe means one inhalation plus one exhalation. During inhalation, ribs move up and outwards and diaphragm moves down. This movement increases space in our chest cavity and air mshes into the lungs. The lungs get filled with air. During exhalation, ribs move down and inwards, while diaphragm moves up to its original position. This reduces the size of the chest cavity and air is pushed out of the lungs.

Question 3.
Explain the mechanism of respiration in plants?
Answer:
Plants can be of various sizes. Developing respiratory organs could not be a fruitful solution for plants because of their unlimited growth. Each plant part breathes through its external layer of cells. Roots breathe through root hair by taking air from spaces between soil particles. Stems breathe through lenticels and epidermis. Leaves have numerous small pores or openings called stomata. Stomata trap air and the exchange of carbon dioxide and oxygen takes places by a process called diffusion.

Question 4.
Differentiate between cellular respiration and breathing.
Answer:

Question 5.
Write some differences between respiration and combustion.
Answer:

Picture-Based Questions

Question 1.
Draw a diagram of open and closed stomata.
Answer:

Question 2.
Draw a diagram of a fish and label the position of gills in it.
Answer:

Question 3.
a. Observe the given picture. What does it show?
b. Label the parts of the body marked as A, B and C.
c. Identify the structure D and state its function.

Answer:
a. The given picture shows the human respiratory system.
b. A-Nostril; B-Trachea; C-Lung
c. D is the diaphragm. It moves up and down to increase and decrease the space of chest cavity during inhalation and exhalation, respectively.

NCERT Solutions for Class 7 Science

• Class 7 Science Chapter 1 Nutrition in Plants
• Class 7 Science Chapter 2 Nutrition in Animals
• Class 7 Science Chapter 3 Fibre to Fabric
• Class 7 Science Chapter 4 Heat
• Class 7 Science Chapter 5 Acids, Bases and Salts
• Class 7 Science Chapter 6 Physical and Chemical Changes
• Class 7 Science Chapter 7 Weather, Climate and Adaptations of Animals of Climate
• Class 7 Science Chapter 8 Winds, Storms and Cyclones
• Class 7 Science Chapter 9 Soil
• Class 7 Science Chapter 10 Respiration in Organisms
• Class 7 Science Chapter 11 Transportation in Animals and Plants
• Class 7 Science Chapter 12 Reproduction in Plants
• Class 7 Science Chapter 13 Motion and Time
• Class 7 Science Chapter 14 Electric Current and its Effects
• Class 7 Science Chapter 15 Light
• Class 7 Science Chapter 16 Water: A Precious Resource
• Class 7 Science Chapter 17 Forests: Our Lifeline
• Class 7 Science Chapter 18 Wastewater Story

These NCERT Solutions for Class 7 Science Chapter 9 Soil Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Soil NCERT Solutions for Class 7 Science Chapter 9

Class 7 Science Chapter 9 Soil Textbook Exercise Questions and Answers

Question 1.
In addition to the rock particles, the soil contains
a. air and water
b. water and plants
c. minerals, organic matter, air and water
d. water, air and plants
Answer:
c. minerals, organic matter, air and water

Question 2.
The water holding capacity is the highest in
a. sandy soil
b. clayey soil
c. loamy soil
d. mixture of sand and loam
Answer:
b. Clayey soil

Question 3.
Match the items in Column I with those in Column II:

Answer:
1. (b)
2. (c)
3. (a)
4. (e)
5. (d)

Question 4.
Explain how soil is formed.
Answer:
Soil is formed through the process of weathering. Weathering is a process of physical breakdown and chemical decomposition of rocks and minerals near or at the surface of the earth. This physical and chemical decomposition is primarily done by wind, water and climate. As a result of these processes, large rock pieces are converted into smaller pieces and eventually to soil.

Question 5.
How is clayey soil useful for crops?
Answer:
Clayey soil can retain much water and consequently contains a lot of moisture even in summer. That’s why it is the most useful for crops like paddy which requires lot of water. Clayey soil is useful for wheat also.

Question 6.
List the differences between clayey soil and sandy soil.
Answer:

Question 7.
Sketch the cross section of soil and label the various layers.
Answer:

Question 8.
Razia conducted an experiment in the field related to the rate of percolation. She observed that it took 40 min for 200 mL of water to percolate through the soil sample. Calculate the rate of percolation.
Answer:
Given amount of water = 200 mL
Percolation time = 40 min
Therefore, percolation rate = \(\frac{\text { Amount of water (mL) }}{\text { Percolation time (min) }}\)
= \(\frac{200 \mathrm{~mL}}{40 \mathrm{~min}}\) = 5 mL/min

Question 9.
Explain how soil pollution and soil erosion could be prevented.
Answer:
The persistent build-up of toxic compounds in the soil is defined as soil pollution. To prevent soil pollution, its causes must be controlled.

• Reduce the use of plastics: Plastics and polythene bags destroy the fertility of soil. Hence, these should be disposed off properly and if possible, their use should be avoided.
• Industrial pollutants: Some waste products from industries and homes pollute soil. These pollutants should be treated chemically to make them harmless before they are disposed off.
• Insecticides: Other pollutants of soil include pesticides and insecticides. Therefore, excessive use of these chemicals should be avoided.

Soil Erosion: Removal of topsoil by weathering agents, such as wind and water is known as soil erosion.

Causes of soil erosion:

• The cutting of down of forests whether for agriculture, construction of buildings, roads or dams often leads to soil erosion.
• The excessive use of chemical fertilisers and disposal of waste materials pollutes the soil, increasing the risk of erosion.
• The floods and overgrazing by animals also result in erosion of nutrient materials from the soil, making it infertile and unproductive.

Preventive measures for soil erosion: Soil erosion can be prevented to great extent by planting of trees and protecting forests. Government has started programmes like wasteland development, control and reclamation of ravines to prevent soil erosion.

Question 10.
Solve the following crossword puzzle with the clues given:
Across:
2. Plantation prevents it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organism in the soil.
Down:
1. In desert soil erosion occurs through
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil.

Answer:
Across:
2. Erosion
5. Polythene
6. Clay
7. Earthworm

Down:
1. Wind
3. Wheat
4. Sandy
5. Profile

Extended Learning Activities and Projects

Question 1.
Boojho would like to know the difference between raw and baked soil? Investigate how the soil from which matkas are made is different from the soil used to make statues.
Hint:

• Raw Soil: This type of soil contains many microorganisms in it like bacteria, fungi, etc., which are very useful for the growth of plants.
• Baked Soil: This soil is devoid of any living organisms because it is heated to a very high temperature as a result of which the microorganisms are killed.

Matkas are made from loamy soil as it is porous with large sized particles. Statues are made from clayey soil as it is smooth and moist.

Question 2.
Paheli is worried. She could see a brick kiln from her house. Bricks were being made there. There was so much smoke coming out of the kiln. She was told that the best quality of clay is required for making pottery, statues and bricks. She has seen truck loads of bricks being taken away for construction of buildings. At this rate, she fears, no soil will be left. Are her fears justified? Discuss this problem with your parents, teachers and other experts of your area and prepare a report.
Hint:
No, her fear is not to be justified because bricks and pots are only made by clayey soil and loamy soil is used for irrigation. Also, soil is a renewable resource.

Question 3.
Try to find out the moisture content of a soil sample. One method is given here.
Activity: Take 100 g soil. (Take help from any shopkeepers to weigh the soil). Place it on a newspaper in the sun and allow it to dry for two hours. This activity is best done in the afternoon. Take care that the soil does not spill outside the newspaper. After drying it, weigh the soil again. The difference in the weight of the soil before and after drying and is called the percentage moisture content.
Suppose your sample of soil loses 10 g on drying. Then percent of moisture in soil
= \(\frac{\text { wt. of moisture }(\mathrm{g})}{\text { Original wt. of soil sample (g) }} \times 100\)
In this example,
Percent of moisture in soil = \(\frac{10 \times 100}{100}\) = 10%
Hint:
Do it yourself according to the activity.

Activity 1

Objective: To identify the various layers of the soil.
Materials Required: A glass tumbler, a sample of soil from your garden.
Procedure:

• Put some soil sample from your garden and place it in a glass tumbler.
• Fill the jar up to two-third of its height with water.
• Stir the mixture with the help of a spoon and allow it to stand for a few hours.
• Observe the contents of the tumbler.

Observations: Different layers appear in the tumbler. Gravel particles are the biggest and weigh more than sand, so the bottom layer will be the gravel part of the soil. Next up is the sand layer. Silt particles are smaller than sand and weigh less so they appear over the sand. Next up is the clay layer. Next up you will have the water. This is likely to be discoloured. Humus will be present on the topmost layer.

Conclusion: In this activity, we conclude that soil has different layers which include gravel, sand, silt, clay, water and humus.

Horizons: Layers of soil are referred to as horizons. Horizons of soil are categorised into four types: A-horizon, B-horizon. C-horizon and Bedrock.

• A-horizon: It is the topmost soil which is dark in colour and rich in humus. It is soft, porous and has the ability to retain water. It contains many organisms and plant roots.
• B-horizon: It is the middle next layer of the soil profile. It has lesser humus and more minerals. This layer is harder and more compact.
• C-horizon: The third layer of soil is known as C-horizon. C-horizon is made of small lumps of rocks with cracks and crevices.
• Bedrock: The layer below the C-horizon is known as bedrock. Bedrock is composed of rocks and is hard to dig with spades.

Types of Soil: The size of particles of the soil is very important for determining the properties of soil. Hence, soils are categorised mainly in three types based on the proportion of size of particles. These are sandy soil, clayey soil and loamy soil.
i. Sandy soil: It contains soil particles with a diameter of 0.2 to 2.0 mm. It comprises of around 60% sand along with some clay. It has very low water retention capacity. It is not rich in humus.
ii. Clayey soil: It contains soil particles with a diameter of less than 0.2 mm. It has an excellent water retention capacity and little space for air.
iii. Loamy soil: It is the most suitable soil for plant growth as it contains some large particles to keep the soil porous and some smaller particles for increasing its water holding capacity. This soil is a mixture of sand, silt and day. Silt occurs as a deposit in riverbeds and has particle size intermediate between sand and clay. Loamy soil is also rich in humus.

Important Uses of Soil: The soil is our most important natural resource. It is useful to us in many ways:

• Soil is used for growing food crops (like grains, pulses, fruits, vegetables, etc.).
• Soil is used to grow trees for obtaining wood for building purposes (timber), for burning as fuel (firewood) and for making paper.
• Soil is used to grow cotton plants which give us cotton clothes. Soil is also used to grow mulberry trees for rearing silkworms which provide us silk for making silk clothes.
• Soil is used to make bricks and mortar for building houses.
• Soil is used to make earthenware or pottery (such as matkas, surahis, etc.), crockery (cups and plates), toys, statues, etc.

Properties of Soil:
i. Percolation Rate of Water: Amount of water drained through the soil in unit time is known as percolation rate of water in that soil. Percolation rate of water can be calculated using the formula given below:
= \(\frac{\text { Amount of water (in mL) }}{\text { Time taken to percolate }}\)
Time taken to percolate The percolation rate of water in sandy soil is the fastest and in clayey soil is the slowest.

Activity 2

Objective: To determine the percolation rate of water in a soil sample.
Materials Required: PVC pipe (diameter 5 cm, length 20 cm) open from both ends.
Procedure:

• Fix one end of the pipe into the soil up to a depth of 2-3 cm.
• Pour 100 mL or 200 mL of water into the pipe and immediately note the time in your watch.
• Note the time when whole of the water has percolated down, i.e., there is no water left in the pipe.

Observation: Volume of water poured in the pipe, (say) V = 200 mL
Time taken by water to percolate down, (say) t = 40 min
Percolation rate of water in the soil = \(\frac{\text { Volume of water percolated }}{\text { Time taken for percolation }}\)
= V/t = 200 mL/40 min
= 5 mL/min

Conclusion: The percolation rate of water in the given soil sample is 5 mL per min.

ii. Moisture Content in Soil: Amount of water present in the soil naturally between the particles is called moisture present in soil. The amount of moisture present in clayey soil is the highest and that in the sandy soil is the lowest.

Activity 3

Objective: To find the moisture content of a soil sample.
Materials Required: A plastic funnel, filter paper, dry powdered soil, measuring cylinder and a dropper.
Procedure:

• Take a plastic funnel.
• Take a filter paper (or a piece of newspaper sheet), fold and place it in the funnel as shown in the figure.
• Weigh 50 g of dry, powdered soil and pour it into the funnel.
• Measure a certain amount of water in a measuring cylinder and pour it drop by drop on the soil. You can use a dropper for this purpose.
• Do not let all the water fall at one spot.
• Pour water all over the soil. Keep pouring water till it starts dripping.

Observations: Subtract the amount of water left in the measuring cylinder from the amount you started with. This is the amount of water retained by the soil. Record your results in the following manner:
Weight of soil = 50 g
Initial volume of water in the measuring cylinder = UmL
Final volume of water in the measuring cylinder = VmL
Volume of water absorbed by the soil = (U – V) mL
Weight of water absorbed by the soil = (U – V)g
(1 mL of water has weight equal to 1 g)
Percentage of water absorbed = \(\frac{(\mathrm{U}-\mathrm{V})}{50}\) × 100
Conclusion: The given sample of soil contains _________ % (by mass) of moisture.

iii. Absorption of Water: Different soils absorb or hold different amounts of water. Clayey soil holds the highest amount of water because of its higher water retention capacity. On the other hand, sandy soil absorbs the least amount of water because of its lower water retention capacity.

Soil and Crops: The climatic factors as well as the composition of soil, determine the various types of vegetation and crops that might grow in any region.

• Clayey and loamy soils are both suitable for growing cereals like wheat and gram. Such soils are good at retaining water.
• For paddy, soils rich in clay and organic matter and having a good capacity to retain water are ideal.
• For lentils (Masoor) and other pulses, loamy soil, which drain water easily, are required.
• For cotton, sandy loam or loam, which drain water easily and can hold plenty of air are more suitable.
• Crops such as wheat are grown in the fine clayey soils because they are rich in humus and are very fertile.

Soil Pollution: Soil gets polluted by plastics and polythene bags thrown into it. They also kill the organisms living in the soil. Hence, we should ban the use of plastics and polythene bags. Pesticides sprayed on the crops in excess also pollute the soil. Waste products and chemicals released from factories also pollute the soil. They should be properly treated before their disposal.

Soil Erosion: Removal of topsoil by weathering agents, such as wind and water is known as soil erosion.
Causes of soil erosion:

• The cutting down of forests, whether for agriculture, construction of buildings, roads or dams, often leads to soil erosion.
• The excessive use of chemical fertilisers and disposal of waste materials pollutes the soil, increasing the risk of erosion.
• The floods and overgrazing by animals also result in erosion of nutrient materials from the soil, making it infertile and unproductive.

Preventive Measures for Soil Erosion: Soil erosion can be prevented to great extent by planting of trees and protecting forests. Government has started programmes like wasteland development, control and reclamation of ravines to prevent soil erosion.

Class 7 Science Chapter 9 Soil Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is soil?
Answer:
Mixture of rock particles, sand and humus is known as soil.

Question 2.
What is soil profile?
Answer:
A vertical section through different layers of soil is known as soil profile.

Question 3.
What is soil erosion?
Answer:
Removal of topsoil by weathering agents such as wind, water and ice is known as soil erosion.

Question 4.
What are horizons?
Answer:
Layers of soil are called horizons. Horizons of soil are categorised into four types: A-horizon, B-horizon, C-horizon and Bedrock.

Question 5.
Define soil texture.
Answer:
The soil texture is determined by the relative proportion of particles of different sizes. Soils of different textures feel different when rubbed between fingers.

Question 6.
What is bedrock?
Answer:
The layer below the C-horizon is known as bedrock. Bedrock is composed of rocks and is hard to dig with spades.

Question 7.
Define weathering.
Answer:
Soil is formed by the breakdown of the parent rock material by a very slow and gradual process called weathering.

Question 8.
Which absorbs more water-sandy soil or clay?
Answer:
Clay absorbs more water.

Question 9.
Which is the layer of soil that contains the largest rock pieces?
Answer:
Gravel or bedrock contains the largest rock pieces.

Question 10.
What is the role of plants in the formation of soil?
Answer:
The roots of plants penetrate into the rocks and break them. In this way, plants help in the formation of soil.

Question 11.
How many layers are there in the soil profile?
Answer:
There are four layers in the soil profile.

Question 12.
What is humus?
Answer:
The rotting dead organic matter in the soil is called humans.

Question 13.
Name three different types of soils.
Answer:
Sandy soil, Clayey soil, Loamy soil.

Question 14.
Which layer of soil contains humus.
Answer:
The topsoil or A-horizon contains humus.

Question 15.
Which type of soil has the highest percolation rate of water?
Answer:
Sandy soil.

Question 16.
Which type of soil would be the best for making pots, toys and statues?
Answer:
Clayey soil.

Question 17.
What is C-horizon made up of?
Answer:
It is made up of small lumps of rocks with cracks and crevices.

Question 18.
Define percolation rate.
Answer:
It is the ratio of the amount of water percolated through the soil to the percolation time. It indicates the water holding capacity of the soil.

Question 19.
Name the five factors controlling soil formation.
Answer:
Soil formation is controlled by five factors namely, nature of parent rock, the topography, the climate, the organisms in the soil and time.

Question 20.
What are natural resources?
Answer:
Natural resources are the resources which are provided by nature to support life. For example, water, air, minerals, sunlight and various life forms.

Short Answer Type Questions

Question 1.
Which soil will hold more water-sandy soil or clayey soil? Why?
Answer:
Clayey soil will hold more water. Clayey soil mostly contains clay. Water drains through it very slowly since the particles are very small and tightly packed.

Question 2.
What is humus?
Answer:
Humus is dark brown in colour and consists of decaying remains of plants and animals. A variety of dead and decaying organisms contribute to the formation of humus. Humus makes the soil fertile by providing organic nutrients. It also provides food to earthworms and other animals living in the soil.

Question 3.
Explain which horizon of soil is most suitable to grow plants and why?
Answer:
Top layer of soil, i.e., A-horizon is the most suitable for this. A-horizon is generally dark in colour. It is rich in humus and is hence fertile. A-horizon is generally soft and porous. It retains more water. Roots of small plants are entirely embedded in topsoil. Topsoil also provides shelter to many living organisms, such as worms, insects, moles, rats, snakes, etc., which all enhance soil fertility.

Question 4.
How is loamy soil very useful for the crops?
Answer:
Particles of loamy soil are smaller than sand and larger than clay. Loamy soil is the mixture of sandy soil, clayey soil and silt. Silt is the deposit in riverbeds. Loamy soil has right water holding capacity and is well aerated. Hence, this is considered as the best soil for the growth of plants.

Question 5.
What makes soil a shelter for many living organisms?
Answer:
Soil contains organic materials, such as starch, sugar, cellulose, fats, proteins and remains of dead organisms. These give energy to living organisms. Air, water and minerals present in soil also give enough energy to living organisms to sustain themselves.

Question 6.
List the different processes that help to produce soil.
Answer:
There are four processes responsible to produce soil:

1. Weathering of rocks
2. Earthquakes or volcanic eruptions
3. Corrosion or decomposition of rocks by chemical processes
4. Addition of humus

Question 7.
How is soil erosion harmful for the soil?
Answer:

• It is leads to the loss of soil fertility,
• It results in the formation of gullies by flowing water.
• The soil taken away by wind or flood often gets deposited which is bad for aquatic life.

Question 8.
What factors affect the soil profile and bring changes in the soil structure?
Answer:
Soil is affected by wind, rainfall, temperature, light and humidity. These are some important climatic factors which affect the soil profile and bring changes in the soil structure.

Question 9.
Why is there a demand to ban the use of polythene bags and plastics?
Answer:
Polythene bags and plastics pollute the soil. They also kill the organisms living in the soil. That is why there is a demand to ban the use of polythene bags and plastics.

Question 10.
What are the properties of loamy soil?
Answer:

• The best topsoil for growing plants is loam. Loamy soil is a mixture of sand, clay and another type of soil particle known as silt.
• The loamy soil also has humus in it.
• It has the right water holding capacity for the growth of plants.
• It’s particle size is in between those of clay and sand.

Question 11.
What are the properties of clayey soil?
Answer:

• Clay particles, being much smaller, pack tightly together leaving little space for air.
• Water can be held in the tiny gaps between the particles of clay. So clay soils have little air.
• They are heavy as they hold more water than the sandy soils.

Question 12.
Why is soil regarded as one of the most important natural resources?
Or
Why is soil an inseparable part of our life?
Answer:
Soil is one of the most important natural resources. It supports the growth of plants by holding their roots firmly and supplying water and nutrients to them. It is the home for many organisms. Soil is essential for agriculture. Agriculture provides food, clothing and shelter for all. Soil is thus an inseparable part of our life.

Question 13.
What are the properties of sandy soil?
Answer:

• Sand particles are quite large.
• Sand particles cannot fit closely together, so there are large spaces between them. These spaces are filled with air. So, the sand is well aerated.
• Water can drain quickly through the spaces between the sand particles. So, sandy soils tend to be light and dry.

Question 14.
Is it a good practice to remove grass and small plants that are growing in an open, unused field? Give reasons for your answer.
Answer:
No, it is not a good practice. Plants cover the soil surface and their roots bind the soil particles and hold them in place. During strong winds and rains they prevent soil erosion and thereby protect the topsoil. Hence, we should not remove them.

Long Answer Type Questions

Question 1.
What is soil erosion? What are the preventive measures for soil erosion.
Answer:
Soil Erosion: Removal of topsoil by weathering agents, such as wind, water and ice is known as soil erosion. Soil erosion affects the fertility of soil, as humus present in the soil is eroded along with the soil. Hence, it is important to prevent soil erosion.

Preventive measures for soil erosion:

• Deforestation should be prevented at all costs to prevent soil erosion.
• Shelterbelt plantation of trees is good for preventing soil erosion.
• Terrace farming in hilly areas is effective in preventing soil erosion.

Question 2.
What is soil? Discuss its properties?
Answer:
Soil: Mixture of rocks particles, sand and humus is known as soil. Soil supports the growth of plants by holding their roots and supplying water to them.

Properties of soil are:
a. Percolation Rate of Water: The Amount of water drained through the soil in unit time is known as percolation rate of water in that soil. Percolation rate of water can be calculated using the formula given here.
Percolation rate (mL/min) = \(\frac{\text { Amount of water in } \mathrm{mL}}{\text { Time taken to percolate }}\)
The percolation rate of water in sandy soil is the highest and in clayey soil is the lowest.

b. Moisture in Soil: Amount of water present naturally between the particles in soil is called moisture present in soil. The amount of moisture present in clayey soil is the highest and that in sandy soil is the lowest.

c. Absorption of Water: Different soils absorb different amounts of water. Clayey soil holds the highest amount of water because of its higher water retention capacity. On the other hand, sandy soil absorbs the least amount of water because of its lower water retention capacity.

Question 3.
Distinguish between clay, silt and sand.
Answer:
a. Clay has the smallest size of particles. In fact, you cannot see a single clay particle. Clay feels smooth because of its small particle size. It has highest water holding capacity and least air spaces.

b. Silt has particles larger than clay (diameter between 0.002 mm and 0. 2 mm). Therefore, it is not so smooth. For example, it can be found in a river bed. It has intermediate air spaces and water holding capacity as compared to clay and sand.

c. Sand has the largest-sized particles, which can easily be seen (diameter greater than 0.2 mm). They are coarse to touch. It has highest air spaces and least water holding capacity.

Question 4.
Describe the different layers of soil profile.
Answer:
Different layers of soil profile are as follows:
a. The uppermost horizon is generally dark in colour as it is rich in humus and minerals. The humus makes the soil fertile and provides nutrients to growing plants. This layer is generally soft, porous and can retain more water. It is called the topsoil or the A-horizon. This provides shelter for many living organisms such as worms, rodents, moles and beetles. The roots of small plants are embedded entirely in the topsoil.

b. The next layer has a lesser amount of humus but more of minerals. This layer is generally harder and more compact and is called the B-horizon or the middle layer.

c. The third layer is the C-horizon, which is made up of small lumps of rocks with cracks and crevices.

d. Below this layer is the bedrock, which is hard and difficult to dig with a spade.

Question 5.
How does absorption of water by the soil differ from percolation of water through the soil?
Answer:
Water absorption capacity of a soil is described in terms of the amount of water absorbed by a particular type of soil. High water absorption means higher water retention capacity of the soil. Percolation property of any material is linked to its porosity. Different soils have different porosity. Therefore, water percolates differently through different soils. Higher the percolation rate through a soil, lower is its water retention capacity.

Percolation rate of water in the soil = \(\frac{\text { Volume of water percolated (mL) }}{\text { Time taken for percolation (min) }}\)

Picture-Based Questions

Question 1.
Observe the given picture and answer the following questions.

a. Some people are doing work in the given picture. Guess and tell what are they doing?
b. Which type of soil is used to do this?
c. What is the main property of such type of soil?
Answer:
a. In the above picture, people are making pots.
b. Clayey soil is used for making pots.
c. The water holding capacity of this soil is the highest among all soils and the particles are compactly held.

Question 2.
Observe the given picture and answer the following questions.

a. Which is the heaviest rock material?
b. Which is the lightest soil component?
c. Why different layers of soil components are formed?
Answer:
a. Gravel is the heaviest rock material.
b. Humus is the lightest soil component which floats on water surface.
c. The soil component forms various layers one above the other according to the size and weight of particles.

NCERT Solutions for Class 7 Science

• Class 7 Science Chapter 1 Nutrition in Plants
• Class 7 Science Chapter 2 Nutrition in Animals
• Class 7 Science Chapter 3 Fibre to Fabric
• Class 7 Science Chapter 4 Heat
• Class 7 Science Chapter 5 Acids, Bases and Salts
• Class 7 Science Chapter 6 Physical and Chemical Changes
• Class 7 Science Chapter 7 Weather, Climate and Adaptations of Animals of Climate
• Class 7 Science Chapter 8 Winds, Storms and Cyclones
• Class 7 Science Chapter 9 Soil
• Class 7 Science Chapter 10 Respiration in Organisms
• Class 7 Science Chapter 11 Transportation in Animals and Plants
• Class 7 Science Chapter 12 Reproduction in Plants
• Class 7 Science Chapter 13 Motion and Time
• Class 7 Science Chapter 14 Electric Current and its Effects
• Class 7 Science Chapter 15 Light
• Class 7 Science Chapter 16 Water: A Precious Resource
• Class 7 Science Chapter 17 Forests: Our Lifeline
• Class 7 Science Chapter 18 Wastewater Story

These NCERT Solutions for Class 7 Science Chapter 8 Winds, Storms and Cyclones Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Winds, Storms and Cyclones NCERT Solutions for Class 7 Science Chapter 8

Class 7 Science Chapter 8 Winds, Storms and Cyclones Textbook Exercise Questions and Answers

Question 1.
Fill the missing word in the blank spaces in the following statements:
a. Wind is ……………… air.
b. Winds are generated due to ……………… heating on the earth.
c. Near the earth’s surface ……………… air rises up whereas ……………… air comes down.
d. Air moves from a region of ……………… pressure to a region of ……………… pressure.
Answer:
a. moving
b. uneven
c. warm, cooler
d. high, low

Question 2.
Suggest two methods to find out wind direction at a given place.
Answer:
Two methods to find the direction of wind are:

1. Take a handful of sand or dust. Release it slowly from a height and observe the direction in which the falling sand is moving. This will show the direction of wind.
2. Tie a thin plastic sheet or cloth with a stick. Keep the stick at a place which is as high as possible. The direction in which the cloth sways shows the direction of wind.

Question 3.
State two experiences that made you think that air exerts pressure (other than those given in the text).
Answer:

1. A parachute helps the people in reaching the ground safely. The air pressure reduces the speed of the parachute and the paratrooper lands without getting injured.
2. Ink can be filled in a fountain pen with the help of atmospheric pressure. When the tube of the pen is squeezed, the air in it rushes out so that the pressure in the tube decreases. The air pressure outside the tube now pushes the ink into the pen.

Question 4.
You want to buy a house. Would you like to buy a house having windows but no ventilators? Explain your answer.
Answer:
No, a house should have ventilators along with windows. This is because the warm air would rise up and exit from the ventilators. The cooler air would rush in through the windows. This will help in making the rooms comfortable. A room without ventilators shall not be cooled as efficiently as the one with ventilators.

Question 5.
Explain why holes are made in hanging banners and hoardings.
Answer:
Banners and hoardings are usually very large. The air pressure because of the moving air can blow away the banners. Holes are made in banners and hoardings so that the wind can move through them. This helps in reducing the impact of air pressure on the hoardings and thus they are not blown away.

Question 6.
How will you help your neighbours in case cyclone approaches your village/ town?
Answer:
We will take following steps to help our neighbours in case of cyclone:

• We will help them to shift to a safer place.
• We will organise a community kitchen during the stress period.
• We will provide first aid to injured people.
• We will also arrange for safe drinking water for the people.
• We will built temporary safe shelter for them.

Question 7.
What planning is required in advance to deal with the situation created by a cyclone?
Answer:
Following planning is required to deal with the situation created by a cyclone:

• Proper shelters should be built by the government agencies so that people can be accommodated in them.
• Alternate arrangements of seamless communication among rescue agencies should be made.
• Proper stock of emergency medicines should be kept.
• Proper arrangements of safe drinking water should be made.
• Government should chalk out a rehabilitation plan for those affected by cyclone.

Question 8.
Which one of the following place is unlikely to be affected by a cyclone?
(a) Chennai
(b) Mangaluru (Mangalore)
(c) Amritsar
(d) Puri
Answer:
(c) Amritsar

Question 9.
Which of the statements given below is correct?
a. In winter the winds flow from the land to the ocean.
b. In summer the winds flow from the land towards the ocean.
c. A cyclone is formed by a very high-pressure system with very highspeed winds revolving around it.
d. The coastline of India is not vulnerable to cyclones.
Answer:
a. In winter the winds flow from the land to the ocean.

NCERT Extended Learning Activities and Projects

Question 1.
You can perform the Activity 8.5 (of NCERT textbook) in the chapter slight differently at home. Use two plastic bottles of the same size. Stretch one balloon on the neck of each bottle. Keep one bottle in the sun and the other in the shade. Record your observations. Compare these observations and the result with those of Activity 8.5 (of NCERT textbook).

Hint:
The balloon kept in the sun will become slightly inflated as the air is hot in sun. However, the balloon in shade will contract as the air is cooler.

Question 2.
You can make your own anemometer. Collect the following items: 4 small paper cups (used ice cream cups), 2 strips of cardboard (20 cm long and 2 cm wide), gum, stapler, a sketch pen and a sharpened pencil with eraser at one end.

Take a scale; draw cross on the cardboard strips as shown in the figure. This will give you the centres of the strip.

Fix the strip at the centre, putting one over the other so that they make a plus (+) sign. Now fix the cup at the end of the strips. Colour the outer surface of one cup with a marker or a sketch pen. All the four cups should face in the same direction.

Push a pin through the centre of the strips and attach the strips and the cup to the eraser of the pencil. Check that strips rotate freely when you blow air on the cups. Your anemometer is ready. Counting the number of rotations per minute will give you an estimate of the speed of the wind. To observe the changes in the wind speed, use it at different places and at different times of the day. If you do not have a pencil with attached eraser you can use the tip of a ball pen. The only condition is that the strips should rotate freely.
Remember that this anemometer will indicate only speed changes. It will not give you the actual wind speed.
Hint:
Do it yourself with the help of the process suggested in the question.

Question 3.
Collect articles and photographs from newspapers and magazines about storm and cyclone. Make a story on the basis of what you learnt in this chapter and the matter collected by you.
Hint:
Do it yourself.

Question 4.
Suppose you are a member of a committee, which is responsible for creating development plan of a costal state. Prepare a short speech indicating the measures to be taken to reduce the suffering of the people caused by cyclones.
Hint:
As concerned members of a development plan committee, it is important that we must take proper precautions in advance to reduce the suffering and devastation to a great limit. The warning must be issued in advance and people must stay away from the sea. They must keep essential commodities with them and must move to safer places in advance. Water, medicines, food, etc., must be kept in handy to handle the difficult situation in future. They should be requested to keep ready the phone number of emergency services like police, fire brigade and medical centres, etc.

Question 5.
Interview eyewitness to collect the actual experience of people affected by a cyclone.
Hint:
Do it yourself.

Question 6.
Take an aluminium tube about 15 cm long and 1 to 1.5 cm in diameter. Cut slice of a medium-sized potato about 2 cm thick. Insert the tube in the slice, press it, and rotate it 2-3 times. Remove the tube. You will find a piece of potato fixed in the tube like a piston head. Repeat the same process with the other end of the tube. Now you have the tube with both ends closed by potato pieces with an air column in between. Take a pencil with one end unsharpened. Place this end at one of the pieces of potato. Press it suddenly to push the potato piece in the tube. Observe what happens. The activity shows rather dramatically how increased air pressure can push things.
Caution: When you perform this activity, make sure that nobody is standing in front of the tube.

Hint:
You will observe that the potato piece on the other side of the tube is blown away. This happens because the air inside the tube exerted pressure on the potato piece.

Activity 1

Objective: To show that high speed winds are accompanied by reduced pressure.
Materials Required: An empty bottle and a piece of paper.
Procedure:

• Crumble a small piece of paper into a ball of size smaller than the mouth of an empty bottle.
• Hold the empty bottle on its side and place the paper ball just inside its mouth.
• Now try to blow on the ball to force it into the bottle.
• Now repeat the activity with bottles of different sizes.

Observation: It is very difficult to force the paper ball into the bottle. In most cases, the ball falls out of the bottle.
Conclusion: Since the pressure inside the bottle become higher than that outside the bottle when air is blown, the paper ball doesn’t go inside. In fact, the ball comes out of the bottle.

Activity 2

Objective: To show that high speed wind causes low pressure.
Materials Required: Two balloons of approximately equal size, water, a rod and a string.
Procedure:

• Take two balloons of approximately equal size.
• Put a little water in the balloons.
• Blow up both the balloons and tie each one to a string.
• Hang the balloons 8-10 cm apart on a cycle spoke or a stick.
• Blow in the space between the balloons.

Observation: The balloons move inwards towards each other when air is blown between them.
Conclusion: Since the pressure at the outer parts of the balloons is higher than in between them, the balloons move towards each other.

Activity 3

Objective: To show that moving air can provide lift.
Materials Required: A strip of paper.
Procedure:

• Take a strip of paper. Hold one end of it. The other end drops down due to gravity.
• Now place it close to your mouth and blow on top of it.

Observation: The paper is pushed up.
Conclusion: High speed air reduces pressure above paper strip, so the strip moves up from high pressure area to low pressure area. Hence, moving air can provide lift.

Hot Air and Cold Air: When the air is heated, it expands. As a result, it occupies more space and becomes lighter in weight. Therefore, we can say that warm air is lighter in weight and cold air is heavier.

Activity 4

Objective: To demonstrate that warm air is lighter than cold air.
Materials Required: Two paper cups of same size, a metal or a wooden stick, a piece of thread and a candle.
Procedure:

• Take two paper cups of the same size.
• Hang the two cups in the inverted position at the two ends of a metal or a wooden stick.
• Tie a piece of thread in the middle of the stick.
• Hold the stick by the thread.
• Put a burning candle below one of the cups as shown in the figure and observe.

Observation: Hot air from candle goes inside one of the paper bags. The other bag has normal air. The bag above the candle flame rises higher.
Conclusion: Hot air, being lighter than normal air, moves up and takes the paper bag up with it. The other bag has cooler air, hence it goes down.

Warm air rises up, whereas comparatively cooler air tends to move towards the earth’s surface. When warm air rises up, air pressure at that place is reduced and the cooler air moves in to that place.

Generation of Wind Currents Due to Uneven Heating on the Earth: There are two situations where winds are generated on the earth:
i. Uneven heating between the equator and poles causes the north-south winds. The equatorial regions receive maximum sunlight and are hence warm. The hot air from equator rises up and a cooler air from 0°-30° latitude on either sides of the equator moves in. Similarly, polar air is cooler than air in about 60° latitude. Hence, cool air moves from poles towards warmer latitudes. These air currents tend to change direction because of the rotation of the earth.

ii. Uneven heating of land and water causes monsoon winds on the earth which bring rainfall. Land gets heated up and cooled down faster than water. Hence, air over the land gets heated in summer and rises while cold air from oceans rushes towards land. These are monsoon winds.

Monsoon Winds: The flow of moist air from oceans towards land in summer is called monsoon or monsoon wind. The term ‘Monsoon’ had traditionally been used to describe the typical climate of the Indian Peninsula during the rainy season. Nowadays, the term ‘Monsoon’ is also being used to describe the similar climate in other parts of the world. Monsoon winds carry water vapour which falls over the land in the form of rain after cooling down. In India, the harvest depends on the monsoon wind because it is the major factor for bringing rainfall in India.

Thunderstorm: Thunderstorm occurs frequently in hot and humid tropical areas, such as India. In summer, the air rises up along with lot of moisture. After rising up to a certain height, water vapour cools down and starts coming down in the form of water droplets. The swift drifting of water droplets along with rising air creates electric charge among clouds. This manifests in the form of lightning and sound. This is known as thunderstorm.

Precautions during a thunderstorm:

• Do not lie on the ground or take shelter under a tall tree.
• Do not carry umbrella with metallic end.
• Do not sit near a window.
• Do not stay inside water bodies.
• Do not take shelter in open garages, storage sheds, metal sheds, etc.

Cyclone: Fast moving air towards a centre, usually with heavy rain, is known as cyclone. Wind direction, wind speed, humidity and temperature together create cyclone. When water vapour in the clouds cools down, it releases heat. This heat warms the air around the clouds. The warm air rises up and creates a low pressure zone. This low pressure zone is quickly filled in by cooler air from the surrounding. This creates a system in which the centre is having very low pressure and is surrounded by high speed winds moving around it. The wind from the surroundings moves in a circular fashion towards the centre and gives rise to cyclone. In this way, a thunderstorm can manifest itself into a cyclone.

Structure of a cyclone: Cyclone is about 10-15 km high. Its centre is a calm area and is called the eye. The diameter of the eye varies from 10-30 km and it is free of clouds with light winds. Around eye, there is a cloud region of 150 km having high speed winds, thick clouds and heavy rain. Wind speed gradually decreases away from this region.

The formation of a cyclone depends upon different factors:

• The temperature of the place
• The wind speed
• The direction of the winds
• The humidity of the place

Tropical cyclones are also called Hurricane in USA and Typhoon in Japan and Philippines.

Destruction caused by Cyclones: It pushes huge water waves towards the land, as high as 3-12 m. Hence, sea water floods the coastal areas causing loss of life and property. Soil also becomes infertile due to seawater. Houses are damaged and communication systems are destructed.

Tornado: A tornado is a violently rotating dark funnel shaped cloud that reaches from the sky towards the ground. Diameter of a tornado ranges from few metres to a km. It grows bigger by taking dust and anything else near its base because of low pressure. Smaller tornadoes can only make dust rotate with itself whereas a bigger tornado can take vehicles or even houses. Precautions: During tornado, shut all windows, take shelter under a table, bench, etc. Take safety position by bowing down on knee and protecting head and neck. A tornado shelter is an underground room with no windows.

Precautions: During tornado, shut all windows, take shelter under a table, bench, etc. Take safety position by bowing down on knee and protecting head and neck. A tornado shelter is an underground room with no windows.

Effective Safety Measures: Following safety measures should be adopted in case of a thunderstorm or cyclone.
i. On part of the government:

• With help of satellites and radars, a cyclone alert or cyclone watch is issued 48 hours in advance of any storm.
• A cyclone warming is issued 24 hours in advance.
• Rapid communication of warnings is done to the government agencies, ports, fishermen, ships and general public.
• Cyclone shelters are constructed in cyclone-prone areas.

ii. On part of the people:

• Avoid driving on roads through standing water.
• Keep the phone numbers of all emergency services like police, fire brigade, etc., ready.
• Do not drink water that could be contaminated.
• Do not touch wet switches and fallen power lines.
• Cooperate with your neighbours, friends and rescue force.

Class 7 Science Chapter 8 Winds, Storms and Cyclones Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is wind?
Answer:
The moving air is called wind.

Question 2.
Does air exert pressure?
Answer:
Yes, air exerts pressure.

Question 3.
Name the instrument which measures the wind velocity.
Answer:
Anemometer.

Question 4.
From which word is the term monsoon derived?
Answer:
The word monsoon is derived from the Arabic word mausam which means season.

Question 5.
What are the other names of cyclones?
Answer:
Hurricane and Typhoon.

Question 6.
What is tornado?
Answer:
A dark funnel shaped cloud that reaches from the sky to the ground is called tornado.

Question 7.
What is a wind storm?
Answer:
A wind storm is just a storm with high speed violent winds but with little or no rain.

Question 8.
What is hurricane?
Answer:
Tropical cyclones are also called Hurricane in USA.

Question 9.
What is air?
Answer:
Air is a mixture of gases.

Question 10.
What is thunderstorm?
Answer:
Many a times, rain is associated with lightning and roaring sound. Rain with lightning is called thunderstorm.

Question 11.
What are cyclones?
Answer:
The weather condition of formation of a very low pressure system with very high speed winds revolving around it, accompanied by heavy rain is called a cyclone.

Question 12.
What are the two technologies which help in making the forecast of a cyclone?
Answer:
Satellites and radars.

Question 13.
Which factor increases the speed of wind?
Answer:
Reduction of air pressure increases wind speed.

Question 14.
What is wind vane?
Answer:
An instrument used to find the direction of the wind is called wind vane.

Question 15.
Which area of a cyclone is calm, free of clouds and has only light winds?
Answer:
Centre of the cyclone called the eye of cyclone.

Question 16.
In which direction does air exert maximum pressure?
Answer:
Air exerts pressure equally in all directions.

Question 17.
What happens to the air, when temperature is increased?
Answer:
On heating, the air expands and becomes lighter.

Question 18.
What are the factors which contribute to the development of cyclones?
Answer:
Wind speed, wind direction, temperature and humidity contribute to the development of cyclones.

Question 19.
Why is warm air lighter than cold air?
Answer:
Air expands on heating. Due to expansion, air occupies more space (volume). As a result, density decreases and it becomes lighter. Thus warm air is lighter than the cold air.

Short Answer Type Questions

Question 1.
What causes lightning during a thunderstorm?
Answer:
Static electricity or charge is produced due to the collisions between water droplets and ice crystals in the atmosphere. This causes huge sparks between clouds or between a cloud and the ground in the form of lightning during a thunderstorm.

Question 2.
Describe the ‘eye of a cyclone’.
Answer:
At the centre of the cyclonic storm is a calm, cloudless area. This is called the eye. Its diameter may vary from 10 km to 30 km. There is no rain here and the winds are fairly light.

Question 3.
Explain why a rubber sucker pressed on a smooth surface gets stuck to it.
Answer:
Rubber sucker when pressed against a flat smooth surface, forces air between the smooth surface and the sucker out. This reduces air pressure in the space between the sucker and the smooth surface. There is greater air pressure outside. Hence, this outside air pressure firmly presses the rubber sucker to the smooth surface and it gets stuck.

Question 4.
A child blows air with a straw near the opening of another straw which has its other end in a soft drink bottle. What do you think will happen and why?
Answer:
The level of soft drink will rise in the bottle. This will happen because the air pressure is reduced above the straw and hence the drink will rise in it due to a greater air pressure inside.

Question 5.
Explain why smoke and hot air balloon always rises up.
Answer:
Smoke goes up because it is lighter than air. In the case of smoke, it’s density is less than that of the surrounding air and thus it rises. The same goes for a hot air balloon. The density of the hot air trapped inside a balloon is less than that of the surrounding cooler air and hence it makes the balloon rise.

Question 6.
What is thunderstorm? How does it develop?
Answer:
In summer, the air rises up along with lot of moisture. After rising up to a certain height, water vapour cools down and starts coming down in the form of water droplets. The swift drifting of water droplets and rising air creates electricity among clouds. This manifests in the form of lightning and sound. This is known as thunderstorm.

Question 7.
Which regions of India are vulnerable to cyclones?
Answer:
The whole coastline of India is vulnerable to cyclones, particularly the eastern coast. The west coast of India is less vulnerable to cyclonic storms both in terms of intensity and frequency of the cyclones.

Question 8.
How does air move?
Answer:
Air moves because of difference in air pressure. Air moves from the region where the air pressure is high to the region where the pressure is low. The greater the difference in pressure, the faster the air moves. Also, pressure variation occurs in air due to uneven heating in different regions.

Question 9.
List some effective safety measures that should be taken by the government for dealing with cyclone.
Answer:
Some effective safety measures are:

• A cyclone forecast and warning service.
• Rapid communication of warnings to the government agencies, the ports, fishermen, ships and to the general public.
• Construction of cyclone shelters and administrative arrangements for moving people to safer places.

Question 10.
What are the destructions caused by cyclones?
Answer:
As a result of cyclone, the seawater enters the low-lying coastal areas, causing severe loss of life and property. It also reduces the fertility of the soil. Continuous heavy rainfall may further worsen the flood situation. High-speed winds accompanying a cyclone can damage houses, telephones and other communication systems, trees, etc., causing tremendous loss of life and property.

Question 11.
List some actions on the part of people in case of a cyclone.
Answer:
Actions on the part of people in case of cyclone are:

• We should not ignore the warnings issued by the meteorological department through TV, radio or newspapers.
• We should make necessary arrangements to shift the essential household goods, domestic animals and vehicles, etc., to safer places.
• We should avoid driving on roads through standing water, as floods may have damaged the roads.
• We should keep ready the phone numbers of all emergency services like police, fire brigade and medical centres.

Question 12.
What precautions should we take if a storm is accompanied by lightning?
Answer:
If a storm is accompanied by lightning, we must take the following precautions:

• Do not take shelter under an isolated tree. If you are in a forest, take shelter under a small tree. Do not lie on the ground.
• Do not take shelter under an umbrella with a metallic end.
• Do not sit near a window. Open garages, storage sheds, metal sheds are not safe places to take shelter.
• A car or a bus is a safe place to take shelter.
• If you are in water, get out and go inside a building.

Question 13.
What is an anemometer? Explain its construction and working.
Answer:
An anemometer is used to measure the wind speed at a particular place. Anemometers come in a variety of forms but the simplest type is the cup anemometer. It consists of vertical pole with four horizontal cups attached to the ends of the four arms. Wind causes the cups to rotate the arms around the vertical pole. If wind is blowing very fast, then the speed with which the cups rotate will increase. This can give a relative estimate of wind speed.

Long Answer Type Questions

Question 1.
How are wind currents generated? Explain.
Answer:
Depending on the locations involved, two situations are possible:
a. Regions close to the equator get maximum heat from the Sun. The air in these regions gets warm. The warm air rises and the cooler air from the regions in the 0-30 degrees latitude belt on either sides of the equator moves in. These winds blow from the north and the south towards the equator. At the poles, the air is colder than that at latitudes about 60 degrees. The warm air at these latitudes rises up and the cold wind from the polar regions rushes in to take its place. In this way, wind circulation is set up from the poles to the warmer latitudes.

b. Uneven heating of the land and water on the earth also causes wind currents. Land gets heated up and cooled down faster than water. Hence, air over the land gets heated in summer and rises while cold air from oceans rushes towards land. These are monsoon winds.

Question 2.
Explain the formation of a cyclone?
Answer:
Fast moving winds towards a centre, usually with heavy rain, is known as cyclone. Wind direction, wind speed, humidity and temperature together create cyclone. When water vapour in the clouds cools down, it releases heat. This heat warms the air around the clouds. The warm air rises up and creates a low pressure zone. This low pressure zone is quickly filled in by cooler air from the surrounding. This creates a system in which the centre is having very low pressure and is surrounded by high speed winds moving around it. The wind from the surroundings moves in a circular fashion towards the centre and gives rise to cyclone.

Question 3.
Explain with the help of an activity that an increase in the speed of air results in the drop of pressure.
Answer:
Take two balloons of approximately equal size. Put a little water into the balloons. Blow up both the balloons and tie each one to a string. Hang the balloons 8-10 cm apart on a cycle spoke or a stick. Blow in the space between the balloons. We will observe that the freely suspended balloons move towards each other. The reason is, when high speed air moves through the gap in between the balloons, the pressure of air falls in the gap. Thus, air at high pressure on the sides of balloons forces them inwards.

Question 4.
Write an experiment to show that on heating, the air expands and occupies more space.
Answer:
Take two paper bags or empty paper cups of the same size. Hang the two bags in the inverted position on the two ends of a metal or wooden stick. Tie a piece of thread in the middle of the stick. Hold the stick by the thread as in a balance. Put a burning candle below one of the bags. We will see that the balance of the bags gets disturbed. This happen because as the warm air rises up, it pushes the bag above the candle higher.

Question 5.
How does modern technology help us to predict cyclones in advance?
Answer:
Modem technology helps us in fol lowing ways:

• Satellites and radars helps in forecasting cyclones.
• Cyclone alert or cyclone watch is issued 48 hours in advance of any expected storm.
• Cyclone warning is issued 24 hours in advance.
• The message is broadcasted every hour or half an hour when cyclone is near the coast.
• Several national and international organisations cooperate to monitor the cyclone related disaster.

Question 6.
Describe the formation of a tornado.
Answer:
A tornado is a weather condition when a cloud having a dark funnel-shape reaches from the sky to the ground. The diameter of a tornado can range from one metre to several kilometres. The tornadoes can be formed within cyclones as well. In a tornado, winds blow at high speed of 300 km per hour.

The funnel-like shape of a tornado sucks everything that comes near it at the base because of the low pressure exerted by the winds. It then throws the things upwards. Hence, tornados can be devastating.

Picture-Based Questions

Question 1.
Figure shows a diagrammatic representation of trees in the afternoon along a sea coast. State on which side A or B is the sea located. Give reason for your choice.

Answer:
In the afternoon, the wind blows from sea to land as air pressure on the land is less than the pressure above the sea. Hence, the sea is on B side.

Question 2.
Look at the picture of a cyclone approaching the coast of Orissa. Write the dates of the cyclones.

Answer:
a. Date of first cyclone: 18 October 1999.
b. Date of second cyclone: 29 October 1999.

Question 3.
Look at the following diagram and answer the following questions:

a. Which bag (1) or (2) contains hot air?
b. What does this activity show?
Answer:
a. Bag (1) contains hot air.
b. This activity shows that hot air is lighter and rises up.

NCERT Solutions for Class 7 Science

• Class 7 Science Chapter 1 Nutrition in Plants
• Class 7 Science Chapter 2 Nutrition in Animals
• Class 7 Science Chapter 3 Fibre to Fabric
• Class 7 Science Chapter 4 Heat
• Class 7 Science Chapter 5 Acids, Bases and Salts
• Class 7 Science Chapter 6 Physical and Chemical Changes
• Class 7 Science Chapter 7 Weather, Climate and Adaptations of Animals of Climate
• Class 7 Science Chapter 8 Winds, Storms and Cyclones
• Class 7 Science Chapter 9 Soil
• Class 7 Science Chapter 10 Respiration in Organisms
• Class 7 Science Chapter 11 Transportation in Animals and Plants
• Class 7 Science Chapter 12 Reproduction in Plants
• Class 7 Science Chapter 13 Motion and Time
• Class 7 Science Chapter 14 Electric Current and its Effects
• Class 7 Science Chapter 15 Light
• Class 7 Science Chapter 16 Water: A Precious Resource
• Class 7 Science Chapter 17 Forests: Our Lifeline
• Class 7 Science Chapter 18 Wastewater Story