9. Heredity and Evolution Science class 10 in English Medium ncert book solutions Exercise

Exercise

Q1. 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

Ans: (c) TtWW   

Q2. 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 the above.

Ans: (d) all of the above.

Q3. In evolutionary terms, we have more in common with

(a) a Chinese school-boy.

(b) a chimpanzee.

(c) a spider.

(d) a bacterium.

Ans: (a) a Chinese school-boy. 

Q4. 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?

Ans: On this basis it can be eaten. that the symptom of light colored eyes is dominant. Since the parents also have light colored eyes, we would call the dominant trait light coloured, although the dark colored trait is recessive.

Q5. How are the areas of study – evolution and classification – interlinked?

Ans: The ancestors of humans were the same. Gradually the organisms evolved and due to this development, the organisms easily progressed towards complexity and were classified into different categories. Thus, biological evolution is the ladder of classification

Q6. Explain the terms analogous and homologous organs with examples.

Ans: Those organs which are similar in basic structure but perform different functions, are called homologous organs, for example - birds, water - land, others have four legs but everyone's functions are different. On the contrary, those organs whose basic structure is not the same but perform the same functions in different organisms are called homologous organs. Example - Wings of bats and birds. The wings of a bat are formed by the expansion of the skin between the extended fingers, but the spread of the skin of the entire forearm of the bird.

Q7. Outline a project which aims to find the dominant coat colour in dogs.

Ans: For this purpose we have to take one black dog and one white colored dog. If after crossbreeding between the two, all the children are born of black color, then we can say that black color is dominant and white color is recessive.

Q8. Explain the importance of fossils in deciding evolutionary relationships.

Ans: Fossils are the remains of those organisms which are now extinct. When we compare the structure of the fossils of those organisms with the present organisms, then we get to know how the organisms evolved and also explain the evolutionary order system.

Q9. What evidence do we have for the origin of life from inanimate matter?

Ans: In 1929, British scientist J.B.S. Haldane suggested that perhaps some complex organic molecules were synthesized which were essential for living things. Elementary organisms may have arisen by other chemical synthesis. It had molecules of ammonia, methane, and hydrogen sulfide but no oxygen. After a week, 15 percent of the carbon was converted into simple organic compounds when sparks were created in a mixture of gases at temperatures below 1000 C. They also synthesized the amino acids that make up protein molecules. In this way living beings arose from inorganic substances.

Q10. Explain how sexual reproduction gives rise to more viable variations than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually?

Ans: Asexual reproduction variations are very less because DNA replication is almost the same, so there is a lot of similarity in the offspring. In this process, the variations of DNA are permanent and are also beneficial for the survival of the species.

Q11. How is the equal genetic contribution of male and female parents ensured in the progeny?

Ans: In sexual reproduction, the gin set is not in the form of only one DNA chain. Two independent molecules of DNA consist of two chromosomes. In sexual reproduction, the offspring receives two chromosomes - one from the pupa and one from the mother. The symptom which is effective is visible in the child.

Q12. 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? 

Ans: Yes, it is true. Nature selects the particles of the living beings. Those organisms which show diversity and adapt themselves to the environment are able to survive. On the contrary, those that do not show variation, get extinct. Example - A decrease in the number of tigers due to the unfavorable environment.