Important Questions for Class 10 Science Chapter 9 – Heredity and Evolution

Below are some important questions for class 10 science chapter 9 – Heredity and Evolution students must study thoroughly.Heredity and Evolution are the two most important and fundamental branches of biology, and they are linked by inheritable traits. Both terms are interconnected, and there can be no evolution without heredity. Heredity refers to the biological processes by which certain traits are passed down from parents to their offspring. Evolution, on the other hand, is a slower process that is dependent on the offspring’s ancestors. The theory of Evolution, one of the fundamental pillars of modern biological theory, explores how such changes occur.

Some of the important questions topics for class 10 science chapter 9 – Heredity and Evolution are:

• The mechanism by which variations are created.
• Rules of heredity determine the pattern of inheritance.
• How Accumulation of Variations leads to Evolution.

Below are some of the important questions for class 10 science chapter 9 – Heredity and Evolution from an examination point of view.

Class 10 Science Important Questions Chapter 9 – Heredity and Evolution

Q1. Name the information source for making proteins in the cells.

Solution:

Deoxyribonucleic acid (DNA) present in the chromosomes of cell nucleus is the information source for making proteins.

Q2. Why is the progeny always tall when a tall pea plant is crossed with a short pea plant? 

Solution:

When a tall pea plant is crossed with a short pea plant, the resultant progeny is always tall because tall is dominant trait and short is recessive trait. Therefore, dominant trait expresses itself in the progeny.

Q3. Write a difference between inherited traits and acquired traits giving one example of each. 

Solution:

A trait (or characteristic) of an organism which is ‘not inherited’ but develops in response to the environment is called an acquired trait. For example, if a group of mice are normally bred, all their progeny will have tails. Now, if the tails of these mice are cut by surgery in each generation, tailless mice will not be produced. This is so because removal of the tail is an acquired character.

A trait (or characteristic) of an organism which is caused by a change in its genes (or DNA) is called an inherited trait. Inherited traits can be passed on to the progeny of the organism because they have produced changes in the genes (or DNA) of the organism. For example, skin colour in human beings.

Q4. How is the sex of the child fixed during the fertilisation, step in human beings? Explain.

Solution:

Human beings have 23 pairs chromosomes (22 pairs of autosomes +1 pair of sex chromosome). A male has one X chromosome and one Y chromosome whereas a female has two X chromosomes. Sex of a child depends on the two conditions which takes place during fertilisation. The two conditions are given below:

• If a sperm carrying X chromosome fertilises an ovum which carries X chromosome, then the child born will be girl.
• If a sperm carrying Y chromosome fertilises an ovum which carries X chromosome, then the child born will be a boy.

Q5. Give the respective scientific terms used for studying:

(a) the mechanism by which variations are created and inherited and

(b) the development of new type of organisms from the existing ones.

Solution:

(a) Heredity is the mechanism by which variations are created and inherited.

(b) Evolution is the process in which development of new type of organisms takes place from the existing ones.

Q6. Write the contribution of Charles Darwin in the field of evolution.

Solution:

The contribution of Charles Darwin in the field of evolution is that only the organism which can adapt; to the changing environmental conditions can survive and he also stated that the natural selection is a process which plays an important role in evolution of plants and animals by selecting the organisms with traits favourable to the environment.

Q7. “An individual cannot pass on to its progeny the experiences of its life-time”. Justify the statement with the help of an example and also give reason for the same.

Solution:

If we breed a group of mice, all the progeny of mice will have tails just like their parents. Now, if we remove the tails surgically and again breed them, we still get new mice with tails. This is because cutting the tails of mice does not change the genes of their reproductive cells (or gametes). And since the acquired trait of “cut tails” does not bring about a change in the genes of mice, this trait cannot be passed on to their next generations. From this we conclude that the experiences acquired by an individual during his lifetime (called acquired traits) cannot be passed on to its progeny, and hence cannot lead to evolution because they are not caused by the change in genes.

Q8. Explain the terms:

(i) Speciation;

(ii) Natural selection.

Solution:

(i) Speciation: The process by which new species develop from the existing species is known as speciation. The important factors which could lead to the formation of new species are:

Geographical isolation of a population caused by various types of barriers like mountain ranges, rivers, sea etc. The geographical isolation leads to reproductive isolation due to which there is no flow of genes between separated groups of population.

Genetic drift caused by drastic changes in the frequencies of particular genes by chance alone.

Variations caused in individuals due to natural selection.

(ii) Natural Selection: Natural selection is the process of evolution of a species whereby characteristics which help individual organisms to survive and reproduce are passed on to their offsprings and those characteristics which do not help are not passed on.

Q9. What is meant by the term speciation? List four factors which could lead to speciation.

Solution:

The process by which new species develop from the existing species is known as speciation. Important factors which could lead to the formation of a new species are as follows:

Genetic drift caused by drastic changes in the frequencies of particular genes by chance alone.

Geographical isolation of a population caused by various types of barriers like mountain ranges, river, sea etc. The geographical isolation leads to reproductive isolation due to which there is no flow of genes between separated groups of population.

Variation caused in individuals due to natural selection.

Sometimes the sub-population becomes reproductively isolated by ecological barriers. Therefore it occurs within the same geographical area and within the original population.

Q10. (i) Classify the following as homologous or analogous pairs:

(i) Broccoli and cabbage

(ii) Ginger and radish

(iii) Forelimbs of birds and lizard

(iv) Wings of a bat and wings of a bird

(v) State the main feature that categorizes a given pair of organs as homologous or analogous. 

Solution:

(i) Broccoli and cabbage – Homologous organs

(ii) Ginger and radish – Analogous organs

(iii) Forelimbs of birds and lizard – Homologous organs

(iv) Wings of bat and wings of a bird – Analogous organs

(v) Homologous organs have the same fundamental structure but different in function, while analogous organs have different internal structure but similar functions.