These NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.
Heredity and Evolution NCERT Solutions for Class 10 Science Chapter 9
Class 10 Science Chapter 9 Heredity and Evolution InText Questions and Answers
In-text Questions (Page 143)
Question 1.
If a trait A exits in 10% of a population of an asexually reproducing specie’s and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier ?
Answer:
Both the traits arise in the same position, trait A will exist 10% and trait B will be exist in 60% ratio at the same time. For the segeregation of traits sexual reproduction (crossing of) is essential without sexual reproduction traits will not be segregated.
Question 2.
How does the creation of variations in a species ensure survival ?
Answer:
Creation of variations in a species survive by the synthetic theory of Evolution in which organ origin of species is based on the interaction of genetic variation and natural selection
In-text Questions (Page 147)
Question 1.
How do Mendel’s experiments show that traits may be dominant or recessive ?
Answer:
When plants which are dissimilar in given character (such as flower colour) are crossed; the two characters thus brought together differ markedly in ability to express themselves in the resulting hybrid plant.
When the pure red flowered plant is crossed with a pure white flowered plant; all the offspring of F1 generation resemble the red parent. Such a character which appears (as a red flower colour) was termed by Mendel as ‘dominent’ whereas the other character which fails to appear in offspring (as the white flower colour) was termed ‘recessive’.
Question 2.
How do Mendel’s experiments show that traits are inherited independently ?
Answer:
According the Mendel’s Law of segregation traits are inherited independently, When two of the red flowered plants of F1 generation are crossed; both red flowered and white flowered plants appear in the off spring of the F2 generation.
Question 3.
A man with blood group ‘A’ marries a woman with Blood group ‘O’ and their daughter has blood group ‘O’. Is this information enough to tell you which of the traits-blood group A or O is dominant? Why or why not?
Answer:
Blood group ‘O’ is dominant because in F1 generation only dominant traits appear.
Question 4.
How is the sex of the child determined in human beings?
Answer:
Sex determination takes place in human being as follows:
The human male has one x chromosome and oney chromosome. That half the sperms will have x chromosomes and the other half sperms will have y chromosomes. A human female has two x chromosomes (but no y chromosomes) That, is; all the ova (or eggs) will have only x chromosomes. The sex of a child depends on what happens at fertilization.
(a) If sperm carrying x chromosome fertilizes an ovum (or egg) which carries x chromosome; then the child born will be a girl (or female). This is because the child will have xx combination of sex chromosome.
(b) If a sperm carrying y chromosome fertilizes an ovum (or egg) which carries x chromosomes then the child born will be a boy (or male) this is because the child will have xy combination of chromosomes.
In-text Questions (Page 150)
Question 1.
What are the different ways in which individuals with a particular trait may increase in a population?
Answer:
Different ways in which individuals with a particular trait may increase in a population:
- They can increase by hybridisation.
- They can increase by natural selection.
- They can increase by struggle for existence.
- They can increase by adaptation or survival of fittest.
Question 2.
Why are traits acquired during the lifetime of an individual not inherited ?
Answer:
Traits acquired during lifetime are not inherited because these changes are somatic changes means there do not have any influence of changes in the genes, genetic (D.N.A.) changes are only inherited changes. Somatic (changes in body) are not at all e.g.
A rat whose tail has been cut does not give rise to a rat without tail.
Question 3.
Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics ?
Answer:
Small numbers of tigers a cause of worry from the point of view of genetics because it the variety of tigers are less than the recombination of genes will be in less quantity, then there are no chances for the new varieties. Number of individual’s should be more for the new varieties.
In-text Questions (Page 151)
Question 1.
What factors could lead to the rise of a new species ?
Answer:
Following factors could lead to rise a new species.
- It should be some changes in genes (D.N.A) (mutation)
- Change in chromosome structure and number.
- Genetic recombination.
- Natural selection.
- Reproductive isolation.
Question 2.
Will geographical isolation be a major factor in the separation of a self pollinating plant species ? Why or why not?
Answer:
Yes, because the plant needs some organism for Pollination.
Question 3.
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually ? Why or Why not ?
Answer:
Geographical isolation is not a major actor in the speciation of an organism that reproduces asexually because only those changes are inherited which are in the ‘genes’ (D.N.A.), isomatic changes are not inherited to the next generation. Asexual reproduction is totally somatic, there is no any crossing over at the time of asexual reproduction. Thus it will not be any speciation during a sexual reproduction.
In-text Questions (Page 156)
Question 1.
Give an example of characteristics being used to determine how close two species are in evolutionary terms.
Answer:
Way of tracing evolutionary relationships depends on the original idea that changes in D.N.A. during reproduction are the basic events in reproduction. If that is the case then comparing the D.N.A. of different species should give us a direct estimate of how much the D.N.A. has changed during the formation of these species.
Question 2.
Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not ?
Answer:
Wings of a butterfly and the wings of a bat cannot be considered homologous organs because the origin of these wing are different and the function of these wings are same.
Homologous organs : Those organs which have same origin and different function are called as homologous organs e.g., arm of man of mar and wing of a bird.
Question 3.
What are fossils ? What do they tell us about the Process of evolution ?
Answer:
Fossils : The remains (or impressions) of dead animals or plants lived in the remote past are known as fossils. Fossils provide evidence for evolution; a fossil bird called Archaeopteryx look like a bird but it has many other features which are found in reptiles. This is because Archaeopteryx has feathered wings like those of birds but teeth and tail like those of reptiles.
Archaeopteryx 1s, therefore, a connecting link between the reptiles and birds; and hence suggest that the birds have evolved from the reptiles. Thus fossils provide the evidence that the present animals (plants) have originated from the pre existing ones through the process of continous evolution.
In-text Questions (Page 158)
Question 1.
Why are human beings who look so different from each other in terms of size, colour and looks said to belong to the same species ?
Answer:
All human beings who look so different from each other in terms of size; colour and looks said to by products of the same species because all human beings contain same number of chromosomes and their genetic cells (sperm and ova) and somatic cells, there are some somatic differences in the human beings but the genetic structure is same in all the human beings.
Question 2.
In evolutionary terms, can we say which among bacteria, Spiders, fish and chimpanzees have a better body design ? Why or why not ?
Answer:
In evolutionary terms we can say that chimpanzees have a better body design. Among all of above, chimpanzees have better by design because it has more complex body and it has more sensitive organs in order of evolution.
Class 10 Science Chapter 9 Heredity and Evolution Textbook Questions and Answers
Page no. 159
Question 1.
Medelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progenies all bore violet flowers, but almost half were short. This suggests that the genetic make up of the tall parent can be depicted as
(a) TTWWT
(b) TTww
(c) TtWW
(d) TtWw
Answer:
(b) TTww.
Question 2.
An example of homologous organs is
(a) our arm and a dog’s fore-leg,
(b) our teeth and elephant’s tusks,
(c) Potata and runners of grass.
(d) All of the above.
Answer:
(d) All of the above.
Question 3.
In evolutionary terms, we have more in common with
(a) a Chinese school-boy
(b) a chimpanzee
(c) a spider
(d) a bacterium
Answer:
(b) A chimpanzee.
Question 4.
A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive ? Why or why not ?
Answer:
The light coloured eyes of the children is due to dominant genetic character. Because in first generation according to the Menden’s Law of dominance only dominant characters appeared.
Question 5.
How are the areas of study-evolution and classification-interlinkerd ?
Answer:
Evolution of the organisms and classification of the organisms are interlinked because both the processes are in same direction. Both the processes move from simpler one to complex ones. Evolution and classification of organisms never move backwardly.
Question 6.
Explain the terms analogous and homologous organs with examples
Answer:
Analogous organs : Analogous organs are those organs whose structure (origin) is different and function same eg wings of insects, birds etc.
Homologous organs : Those organs whose origin are same and function different called as homologous organs, eg Forelimbs of a frog bird and a man show the same basic design (or basic structure) of bones but they work differently. Such organs are called as homologous organs.
Question 7.
Outline a project which aims to find the dominant coat colour in dogs.
Answer:
To find the dominant coat colour in dogs the DNA Sequence has to be checked.
Question 8.
Explain the importance of fossils in deciding evolutionary relationships.
Answer:
Fossils provide the evidence that present animals (and plants) have originated from the previously existing ones. Turough the process. Of continously evolution fossils are the connecting links between many species and phylums.
Question 9.
What evidence do we have for the origin of life from inanimate matter ?
Answer:
For the origin of life from inanimate matter are amino acids. From simple elements, amino acids are formed. These amino acids part in the formation of genes. These genes like chemicals are suppose to be ancient living beings. So the amino acids are important for the origin of life.
Question 10.
Explain how sexual reproduction gives rise to more variable variation than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually ?
Answer:
In sexual reproduction two individuals are involved, one Male and the other female. Both may have different blood groups and the off springs produced may also vary in blood group. This way sexual reproduction gives rise to more variable variation. Change in DNA sequence and blood group can affect the evolution of their organism that produce sexually. For example, if any partner Suffering from an infection diseases, the off spring might also be affected by this disease.
Question 11.
How is the equal genetic contribution of male and female parents ensured in the progeny?
Answer:
Equal contribution of male and female parents is ensured in the progeny because both parents are involved in the formation of the zygote which leads to the formation of the of spring.
Question 12.
Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement ? Why or why not.
Answer:
No, evolution cannot be said to progress from lower form to higher forms. Rather, evolution seems to have given rise to more complete body designs even while the simple body designs continue to flourish.
Class 10 Science Chapter 9 Heredity and Evolution Textbook Activities
Activity 9.1 (Page 143)
Question 1.
Observe the ears of all students in the class. Prepare a list of students having free or attached ear lobes and calculate the percentage of students having each (Fig.) Find out about the earlobes of the parents of each student in the class. Correlate the earlobe type of each student with that of their parents. Based on this evidence, suggest possible rule for the inheritance of earlobes types.
Answer:
There are forty students in the class. Out of forty 12 students have attached earlobes and 28 have free earlobes. It means 30% of the students have attached and 70% students have free earlobes.
Fig. : (A) free and (B) attached earlobes. The lowest parts of the ear. called the earlobe. Is closely attached to the side of the head in some of us, and not in other. Free and attached earlobes are two variants found in human populations.
Activity 9.2 (Page 144)
Question 1.
In Fig, what experiment would we do to confirm that the F2 generation did in fact have a 1 : 2 : 1 ratio of TT, Tt and tt trait combinations ?
Answer:
In this explanation, both TT and Tt are tali plants, while only tt is a short plant. In other words, a single copy of ‘T’ is enough to make the plant tail, while both copies have to be ‘t’ for the plant to be short. Traits like ‘T’ are called dominant traits, while those that behave like ‘t’ are called recessive traits.
Class 10 Science Chapter 9 Heredity and Evolution Additional Important Questions and Answers
Very Short Answer Type Questions
Question 1.
What is Heredity ?
Answer:
Heredity means the continuity of features from one generation to another. In other words, heredity can be defined as the resemblances among individuals related by descent.
Question 2.
Name the plant on which Mendel performed his experiment.
Answer:
Mendel performed his experiments on garden pea.
Question 3.
Define variation.
Answer:
Variation can be defined as the occurrence of differences among the individuals.
Question 4.
Define a gene.
Answer:
A gene is a segment of D.N.A. on a chromosome occupying specific position and performs specific functions.
Question 5.
Write the expanded form of D.N.A.
Answer:
The expanded form of D.N.A. is De-oxyribo nucleic Acid.
Short Answer Type Questions
Question 1.
What is a sex chromosome ?
Answer:
The pair of chromosomes which determines the sex of an individual is called sex chromosomes. In males, the sex chromosome are xy and the gametes they produced are the two types: x and y bearing. On the other hand, in females the sex chromos are xx and the gametes they produce are the only one type : X bearing
Question 2.
How sex is determined in human beings ?
Answer:
In male individuals, one x-sex chromosome and one y sex chromosomes are present. In female individuals, the part of X sex chromosome is present.
Question 3.
Define homologous organs?
Answer:
Homologous organs are those organs which are formed on the same fundamental and structural plan but they differ in their shape because they have to function differently.
Long Answer Type Question
Question 1.
Describe the principle of inheritance as explained by Mendel.
Answer:
The principle of inheritance was first of all explained by scientist named Mendel studied the inheritance of contrasting characters (or traits) like tallness, dwarfness etc. of the garden pea plant (Pisumsatum) in various generations of garden pea and came to the conclusion that the various contrasting characters or traits of the pea plant (like tallness; dwarfness etc.) are controlled by certain factors. Mendel considered these factors as the carriers of hereditary information from one generation of the pea plants to the next. We now know that the Mendel’s factors which were considered to be the carriers of hereditary information are actually genes. The term ‘gene’ was coined by a scientist named Johnson in 1909.
Multiple Choice Questions
Question 1.
Laws of inheritance were formulated by
(a) Strass Burger
(b) Mendel
(c) Watson and Crick
(d) Darwin
Answer:
(b) Mendel
Question 2.
Which was the material for Mendel’s work ?
(a) Drosophila
(b) Neuropteran
(c) Pea plants
(d) None of these
Answer:
(c) Pea plants
Question 3.
A tall pea plant when crossed with a dwarf pea plant it produces tall offspring. This proves that tallness is:
(a) Dominant factor
(b) Recessive factor
(c) Hybrid factor
(d) Non-genetic factor
Answer:
(a) Dominant factor
Question 4.
What is the name of discipline which deals with studies about inheritance of characters?
(a) Cylology
(b) Evolution
(c) Genetics
(d) Embryology
Answer:
(c) Genetics
Question 5.
According to Mendels law of independent assortment in a dihybrid cross:
(a) It is possible to calculate the rate of reproduction in animals.
(b) The F generation contains 16 phenotypes.
(c) Only one among 16 offsprings of F, generation exhibit both recessive characters.
(d) F2 generation contains 4 genotypes in the ratio of 9 : 3 : 3 : 1.
Answer:
(c) Only one among 16 offsprings of F, generation exhibit both recessive characters.