NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution
NCERT Solutions for Class 10 Science Chapter 9 Heredity and Evolution are available for free on Gkrankers, and they can be a great resource for students who are struggling to understand the concepts in their textbooks. The students can use these solutions to improve their grades in the examinations.
The Chapter 9 Class 10 Science NCERT Solutions will also provide a better understanding of the exam pattern and the type of questions asked in exams. The questions at the end of each chapter will test your knowledge and help improve your problem-solving skills.
Chapter 9 Heredity and Evolution Class 10 Science NCERT Solutions
In Text Questions
1. If a trait A exists in 10% of population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Solution
In asexually reproducing organism, trait B has originated earlier. The variations in a population are only due to inaccuracies of DNA copying.
2. How does the creation of variations in a species promote survival?
Solution
The useful variations in individuals of a species enable them to adapt according to the changes and new needs. Thus variations promote survival of species.
1. How do Mendel’s experiments show that gene may be dominant or recessive?
Solution
Mendel conducted experiments on garden pea plant selecting seven visible contrasting characters. He selected and crossed homozygous tall pea plant having the genotype TT with a homozygous dwarf pea plant having the genotype tt. F1 generation consists only of tall plants, having genotype Tt. Since they have an allele for dwarfness also, they are all hybrids. The expressed allele T for tallness dominated over the unexpressed allele t for dwarfness. The fact that the allele for dwarfness is present in the F1 plants can be verified by self pollinating them when F2 progeny will consist of both tall and dwarf plants in the ratio of 3: 1. On this basis he proposed “Law of Dominance.”
2. How do Mendel’s experiments show that traits are inherited independently?
Solution
When plants with two contrasting traits are crossed, the dominant traits express themselves in F1 generation. When the progeny or F1 are self-crossed, traits separate in F2 generation in 9:3:3:1 ratio. It suggests that the traits are inherited independently.
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?
Solution
Though the blood O is dominant, but the information regarding blood group is not given.
4. How is the sex of the child determined in human beings?
Solution
A human’s sex is determined by their chromosomes. For males, there are 44 + XY chromosomes, while for females, there are 44 + XX chromosomes. In this case, X and Y chromosomes determine sex.
In males, two types of gametes form, one with an X-chromosome and one with a Y-chromosome. Both are produced in a ratio of 1: 1. In females, gametes only have one type with an X-chromosome.
It is true that females are homogametic. If male gametes with Y-chromosomes fuse with female gametes that have X-chromosomes, the zygote will have XY chromosomes, and that will give rise to a male child.
In the case of a fusion of an X-chromosome male gamete with an X-chromosome female gamete, the zygote will have the XX-chromosome, giving rise to a female child.
1. What are the different ways in which individuals with a particular trait may increase in a population?
Solution
The individuals may increase in a population due to Natural selection and genetic drift.
2. Why are traits acquired during the lifetime of an individual not inherited?
Solution
As changes in non-reproductive tissue cannot be passed on to germ cells, the acquired trait will disappear with the death of the individual. It is not inheritable and cannot be passed down from generation to generation.
3. Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?
Solution
The small numbers of surviving tigers is a cause of worry because once the tigers are lost the genes also will be lost.
1. What factors could lead to the rise of new species?
Solution
(i) Genetic variations
(ii) Natural selection
(iii) Reproductive isolation
(iv) Origin of new species
2. Will geographical isolation be a major factor in the speciation by a self-pollinating plant species? Why or why not?
Solution
No, in self-pollinating species geographical isolation will not play any role for speciation because the self-pollination occurs on the same plant.
3. Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually? Why or why not?
Solution
No, neither genetic drift nor gene flow play any role during speciation. Moreover asexual reproduction involves single parent and natural geographical barrier can occur between different organisms.
1. Give an example of characteristics being used to determine how close two species are in evolutionary terms.
Solution
Homologous organs.
2. Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not?
Solution
No. These are analogous organs. These have different structural plan. They are only used for flying.
3. What are fossils? What do they tell us about the process of evolution?
Solution
Fossils are impressions on rocks of dead organisms that got buried in earth millions of years ago. They give us information about the type of organisms that existed at that time and provide evolutionary relationship with present-day animals.
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?
Solution
The DNA studies have shown that they belong to the same species, Homo sapiens. They interbreed among themselves to produce fertile young ones of their own kind.
2. In evolutionary terms can we say that which among bacteria, spider, fish and chimpanzee have a better body design? Why or why not?
Solution
The chimpanzee has the most complex body design, but it is incorrect to say they are the best because all organisms are very well adapted to their environments, and their body designs have evolved accordingly.
Exercises
1. A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as
(a) TTWW
(b) TTww
(c) TtWW
(d) TtWw
Solution
(c) TtWW
2. An example of homologous organs is
(a) our arm and a dog’s fore-leg
(b) our teeth and an elephant’s tusks
(c) potato and runners of grass
(d) All of these
Solution
(d) All of these
3. In evolutionary terms, we have more in common with
(a) a Chinese school-boy
(b) a chimpanzee
(c) a spider
(d) a bacterium
Solution
(a) a Chinese school-boy
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?
Solution
The dominant or recessive nature of light eye colour cannot be determined until a cross is made between a parent who has light eye colour and another who has dark eye colour. Only then can the dominant or recessive nature of light eye color be determined.
5. How are areas of study of evolution and classification interlinked?
Solution
(i) Characteristics are shared by most of the organisms. The characteristic in the next level of classification will be shared by most and not by all.
(ii) Cell designs also indicate this relationship.
(iii) Groups formed during classification are related to their similarities.
6. Explain the terms analogous and homologous organs with examples.
Solution
(i) Homologous Organs. Organs that have similar origin and structural plan but perform different functions are called homologous organs. For example: Inheritance pattern of limbs in amphibians (frog), reptiles (lizard), birds (sparrow) and mammal (human) is same. The limbs in above organisms perform different functions.
(ii) Analogous Organs. Organs that have dissimilar origin and structural plan but perform similar function are called analogous organs. For example: Wings of birds (sparrow), bat (a mammal), insects (cockroach), etc., have the same use flying, but are structurally different. Wings of birds have feathers, wing of bat is a skin fold between the fingers, wings of insects are membranous without bones.
7. Outline a project which aims to find the dominant coat colour in dogs.
Solution
Male Dog with white colour WW
Female Dog with black colour ww
8. Explain the importance of fossils in deciding evolutionary relationships.
Solution
Different fossils of different organisms are studied. For example, studying the origin and evolution of feathers in dinosaurs. It demonstrates that dinosaurs also had them but didn’t use them. Birds used feathers for flight. In light of the fact that birds are reptiles, they are related to dinosaurs.
9. What evidence do we have for origin of life from inanimate matter?
Solution
Urey and Miller provided experimental evidence regarding origin of life from inanimate matters. They assembled an atmosphere similar to that, thought to exist on early Earth.
10. Explain how sexual reproduction gives rise to more viable variation than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually?
Solution
Following mechanism during sexual reproduction gives rise to more viable variation and are raw materials of evolution:
(i) Crossing over during gamete formation.
(ii) Random segregation of chromosomes during meiosis at the time of gamete formation.
(iii) Random rejoining of gametes having different genetic set up in the chromosomes during fertilisation.
11. How is the equal genetic contribution of male and female parents ensured in the progeny?
Solution
By sexual reproduction. The formation of germ cells carry genetic material from each parent. When the germ cells unites to form the zygote they contribute equal genetic material.
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?
Solution
Yes. Because those individuals that do not show variations will die due to environmental factors such as natural selecting as in case of red and green beetles where the crow is predator.