Very Short Answer -Class 10 -Science-Biology-Chapter 8 :Heredity and Evolution

Class 10 -Science-Very Short Answer -Biology-Chapter 8 :Heredity and Evolution

Q1. Why did Mendel choose pea plant for his experiments?

Ans:

Mendel chose pea plants for his experiments because they had easily observable traits, could be easily controlled in breeding, had a short generation time, produced a large number of offspring, and exhibited variability in traits.

Q2. Give reasons for the appearance of new combinations of characters in F2 generation

Ans: New combinations of characters in the F2 generation arise due to independent assortment of alleles during gamete formation and random fertilization, as genes for different traits are located on different chromosomes.

Q3. How many pairs of chromosomes are present in human beings?

Ans: Human beings typically have 23 pairs of chromosomes, for a total of 46 chromosomes. This includes 22 pairs of autosomes (non-sex chromosomes) and one pair of sex chromosomes, which determine an individual’s biological sex (XX for females and XY for males).

Q4. A group of grasshoppers — some green and some brown lived in a grassland having dry bushes and dry grass.

a. Which one would normally be picked up by predatory birds and why?

b. Population of which grasshopper will increase?

 c. Name this phenomenon.

 Ans :  a. Green grass hopper, because they stand out, against brown background of dry bushes.

b. Brown

c. Natural selection.

Q5. Explain why the wing of a bat and the wing of bird are considered to be analogous organs.

(b) List two factors that lead to the formation of a new species.

 Ans :  a. Design, structure and components are different. Origins are not common.

b. Genetic drift and natural selection.

Q6. Differentiate between: 1. Homologous organs and Analogous organs. 2. Pollination and Fertilization

(b) What do fossils tell us about the process of evolution?

Ans :  a. (i) Organs in different organisms with same origin with different function different origin, same function.

 (ii) Transfer of pollen from the stamen to the pistil of the flower/fusion of male and female gametes.

b. Help in establishing links and act as evidence of evolution.

Q7. What function is performed by human arms, forelimbs of dog and forelimbs of whales?

b. Which type of organs are these?

 c. Why do we call them so?

Ans : a. Human arm : holding things Forelimbs of dog : running Forelimbs of whales : paddles b. Homologous, c. Same origin, different functions.

Q8. If a population of red beetles, living on green bushes, is being eaten by crows. During sexual reproduction, a green beetle is found in progeny:

a. What is the future of new trait?

b. Will it survive in the new habitat?

 Ans :  a. Among progeny, when green beetle is found, it escaped attack of crows as it merged with green colour. Green beetles increased, red decreased.

 b. New trait will survive.

Q9.  An angiosperm plant having red coloured flowers when crossed with the other having the same colour produced 40 progenies, out of which 30 plants were with red coloured flowers, 10 plants were with white coloured flowers. Find out:

a. What is the possible genotype of parent plants?

 b. Which trait is dominant and recessive?

c. What is this cross called as and what is its phenotypic ratio?

Ans : 

a. Rr and Rr.

b. Red colour of flowers is the dominant trait while white colour is the recessive trait.

c. Monohybrid cross, phenotypic ratio is 3 : 1.

Q10. In a pea plant, find the contrasting trait if:

a. the position of flower is terminal.

b. the flower is white in colour.

c. shape of pod is constricted.

Ans :  a. Axial position of flower.

b. Purple colour of flower.

c. Inflated shape.

Q10. What are chromosomes ? Explain how in sexually reproducing organisms the number of chromosomes in the progeny is maintained.

Ans :  Chromosomes – Thread like structures made up of DNA found in the nucleus. The original number of chromosomes becomes half during gamete formation. Hence, when the gametes combine, the original number of chromosomes gets restored in the progeny. (or same thing explained in the form of a flow chart).

Q11. a.“Chromosomes are heredity carriers.” Why do we say so?

 b. Which vital function is not controlled by autosomes?

Ans :  a. Chromosomes are made-up of DNA. Genes are located on the chromosomes. It is the DNA copy which transfers from both the parents to their offspring. Therefore, chromosomes made-up of DNA and containing genes are said to be the heredity carriers.

b.Sex of the child is not controlled by autosomes.

Q12. List three main factors responsible for the speciation and briefly describe each one of them.

 Ans :  Genetic Drift: Random change in the frequency of genes. Natural Selection: Nature selects the fittest individual in a population. Reproductive Isolation: When two individuals are geographically isolated and natural selection operates upon them differently leading to inability of the individuals to interbreed.

Q13. Each organism has its own identity”. Explain. (b) What is speciation?

Ans a. (i) The DNA of each organism is different from others

(ii)The DNA of each organism is specific within the same species with specific number of chromosomes/genes.

b. Emergence of new species from pre-existing forms through natural selection/artificial selection/ genetic drift/evolution, etc.

Q14. An organ like a wing in birds are an advantage to an organism. Did they appear in different stages or were formed due to a single sudden change in them.

Ans :  Feathers in dinosaur were long and they could not fly using feathers. It gave them protection from cold weather and warmth. Birds seem to have later adapted the feathers to flight.

Q15. In an area A, the leaf materials available to beetles were very less. What are the two consequences seen in case of beetles?

 Ans : 

a. Due to poor nutrition, the average weight of adult beetles decreases.

b. The number of beetles (population) decreases due to starvation.