CBSE Class 10 Science Important Questions Chapter 9 Heredity and Evolution Part 4

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

Ans. Analogous organs: Such organs which perform similar function but are different in structure and origin. Example- Wings of birds and wings of insects. Homologous organs: Such organs which may have different functions but similar structure and origin. Example- fore arm of frog, lizard and bird.

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

Ans. The evidence was given by Stanley L. Miller and Harold C. Urey in 1953. They assembled an atmosphere similar to that thought to exist on early earth over water. This was maintained by them at a temperature just below 100 degree Celcious and sparks were passed through the mixture of gases to stimulus lightening. At the end of week, they found that 15% of the carbon had been converted to simple compounds of carbon including amino acids which make up protein molecules.

33. 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. Variations arise either because of errors in DNA copying or as a result of sexual reproduction. Due to sexual reproduction genetic variability increases in the population from one generation to another. This happens due to the fact that sexually reproducing organism inherits half the genes from each parent. These variations are very important for the process of evolution.

34. 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. No, depending on the nature of variations different individuals have been different kinds of advantages. However, when a drastic change occurs in environment only those organisms in the population will survive which have an advantageous variation in that population to survive in changed environment.

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

Ans. Equal contribution of male and female parents is ensured in progeny during sexual reproduction. Each trait of progeny is determined by a pair of alleles and gametes of male and female contain one allele. Each allele pairs during fertilisation combine together to determine traits. Thus, the traits of progeny are determined by equal genes from male and female.

36. Is it true that when a new species is emerged, the old species is eliminated and why?

Ans. No, it is not true that when a new species is emerged, the old species is eliminated. Because when there is a change in any species, the change is only in a part or a few members of the species population. If the newly generated species after genetic change is better in any way, it will get more opportunity to survive and if the genetic change is against the environment, it will die. Thus, unchanged members of other species may also remain and tend to live in changed environment.

37. Why are traits acquired during life-time of an individual not inherited?

Ans. Traits acquired during life-time of an individual not inherited because change in non-reproductive tissue or somatic cells cannot be passed on to the DNA of germ cells. Thus, the acquired trait will die with the death of the individual. It is therefore non-heritable and cannot be passed on to its progeny.

38. The gene type of green stemmed tomato plants is denoted as GG and that of purple stemmed tomato plants as GG when these two are crossed.

i. What colour of stem would you expect in progeny?

ii. Give the percentage of purple stemmed plants if F are self-pollinated.

iii. In what ratio would you find the gene types CG and Gg in the F progeny?

Ans. i. Colour of progeny — Green

ii. Percentage of purple stemmed plants in generation ¼ or 25%.

iii. Ratio of genotypes GO and Ug 1:2

39. What are the causes of variations in clones?

Ans. i. inaccuracies during DNA copying

ii. Effect of environment termed acquired variation.

iii. Mutations are sudden stable changes which are discontinuous inheritable as produced due to changes in genetic make-up.

40. Only variation that confer and advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?

Ans. We agree with the statement. All the variation do not have an equal chance of surviving in the environment in which they find themselves. The chances of surviving depend on the nature of variation. Different individuals have different kind of advantages. A bacteria that can withstand heat will survive better in heat wave.

41. Study the given data and answer the questions following the data: Parental plants cross fertilised and seeds collected First Generation offsprings Of Thprings of self pollination of Male parents always bare red flowers, Female parent always had white flowers, 330 seeds sown and observed, All 330 gave red flowers, Out of 44 seeds 33 seeds gave plants with red flowers and 11 seeds gave plants with white flowers.

i. What is the term for this type of cross?

i What does the data of the column marked F indicate?

iii. Express the gene type of the (a) parents (b) progeny and (c) progeny

Ans. i. Monohybrid cross

ii. Red colour of flower dominant over white flower

iii. a. Parents – (RR) and (rr)

b. progeny – Rr

c. progeny – RR, Rr and rr

42. Wild cabbage was converted into number of variants like cauliflower, broccoli and cabbage by man. What is this process known as? Does it play an important role in organic evolution?

Ans. This process is known as artificial selection. It plays a important role in organic evolution because it is parallel to natural selection. It helps to produce new species having useful traits in less time.

43. How are variant genotypes produced?

Ans. Variant genotypes can be produced by:

1. Mutation in genes and chromosomes.

2. Recombination of genes.

3. Hybridization of genes.

44. Can geographical isolation lead to speciation? How?

Ans. Yes, geographical isolation can lead to speciation. Due to geographical isolation, the members of two sub groups may not be able to interbreed as a result of genetic drift. Natural selection also operates diffetently in these subgroups. This leads to speciation.

5 Marks Questions

1. (i) Who provided the evidence of DNA as genetic material?

(ii) Why DNA is called polynucleotide?

(iii) List three important features of double helical model of DNA.

Ans. (i) Mendel.

(ii) DNA is made up many units of nucleotides.

(iii) Important features-

(a) Both the chains in helical runs anti-parallel.

(b) There two nitrogenous base Purine (A, G) and pyrimidine (T, C).

(c) A always bind with T and C always binds with G.

2. Give the basic features of the mechanism of inheritance.

Ans. Basic features of mechanism of inheritance-

(a) Each character is controlled by a pair of factors. The factors may be similar or dissimilar.

(b) When two dissimilar factors of a character are present in an organism, only one expresses itself while other remains unexpressed.

(c) Two factors of a character are separated at the time of gamete formation and get only one factor for that character.

(d) Inheritance of two or more pairs of contrasting traits in such a way that one pair of contrasting traits is independent of the other pairs of contrasting traits.

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

Dominant coat colour in dogs

Dominant Coat Colour in Dogs

Dominant coat colour in dogs

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