Important Questions of Class 10 Science Chapter 8 Heredity and Evolution

Heredity and Evolution Class 10 Important Questions: Heredity is the biological process through which parents pass on their traits to their offspring. In Class 10 Science, Chapter 8 explains how characteristics are inherited, the role of genes and chromosomes, and how variation arises in living organisms.

Understanding these concepts is essential for answering Heredity Class 10 Important Questions and important questions of Heredity Class 10, as it helps explain inheritance patterns, dominance, and recessiveness of traits, and the genetic basis of variation in plants and animals.

Heredity and Evolution Class 10 Important Questions with Answers

Strengthen your understanding of Class 10 Science Chapter 8: Heredity and Evolution with these high-yield questions and answers.

Practice concepts like inheritance of traits, Mendelian laws, genetic variations, evolution, and natural selection. Solving heredity and evolution class 10 important questions helps you revise effectively, understand key mechanisms of inheritance and evolution in living organisms, and improve accuracy in exams.

Heredity Class 10 Important Questions MCQ

1. Two pea plants, one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds produce F1 progeny having round, yellow (RrYy) seeds. When F1 plants are selfed, the F2 progeny will have the following combination of characters:
   (A) 15:1 (B) 9:3:3:1
   (C) 9:3:4 (D) 12:3:1
   Ans. (B) 9:3:3:1

2. Assertion (A): The sex of a child in human beings will be determined by the type of chromosome he/she inherits from the father.
   Reason (R): A child who inherits „X‟ chromosome from his father would be a girl (XX), while a child who inherits a „Y‟ chromosome from the father would be a boy (XY).
   (A) Both (A) and (R) are true and (R) is the correct explanation of the assertion (A).
   (B) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion (A).
   (C) (A) is true, but (R) is false.
   (D) (A) is false, but (R) is true.
   Ans. (A) Both (A) and (R) are true and (R) is the correct explanation of the assertion (A).

3. Which of the following scientist gave the principles of inheritance?
   (A) Mendel (B) Griffin
   (C) Johanssen (D) Watson and Crick
   Ans. (A) Mendel

4. Which of the following is not correct?
   (A) For every hormone there is a gene.
   (B) For every protein there is a gene.
   (C) For production of every enzyme there is a gene.
   (D) For every molecule of fat there is a gene.
   Ans. (D) For every protein there is a gene.

5. A crossing between the tall plant (TT) and the short pea plant (tt) resulted in a progeny that was all tall plants because:
   (A) tallness is the dominant trait.
   (B) height of the pea plant is not governed by the gene „T‟ or „t‟.
   (C) tallness is the recessive trait.
   (D) shortness is the dominant trait.
   Ans. (A) tallness is the dominant trait.

Heredity and Evolution Very Short Answer Type Question

6. What are dominant genes?
   Ans. A dominant gene is one which expresses itself in homozygous as well as heterozygous condition.

7. All the variations in a species do not have equal chances of survival. Why?
   Ans. In the habitat they live in, not all varieties have an equal chance of surviving. Depending on the type of adaptations, individuals may benefit in different ways. The organisms that are best suited to their surroundings will endure.

8. Name the information source for making proteins in the cells.
   Ans. The information needed to make proteins comes from the deoxyribonucleic acid (DNA) found in the chromosomes of the cell nucleus.

9. What is a gene?
   Ans. A gene is a piece of DNA located on a chromosome that directs the production of a certain protein that controls a particular trait (or set of characteristics) in an organism.

10. What is heredity?
    Ans. The inheritance of characters (or traits) from the parents to their offspring is called heredity.

11. Write one difference between heredity and variation.
    Ans. Heredity is the transmission of genetic traits from parents to offspring, resulting in similarities, while variation refers to the differences in traits among individuals within a species, leading to diversity.

12. A normal pea plant bearing coloured flowers suddenly starts producing white flowers. What could be the possible cause?
    Ans. Mutation is responsible for the appearance of white flowers as change in a plant's genetic material can lead to new plant varieties, including different flower colors.

13. Mention any two recessive traits of garden pea.
    Ans. Dwarf (height of plant) and wrinkled seed.

14. The progeny always tall when a tall pea plant is crossed with a short pea plant? Why is it so?
    Ans. Because tall is the dominant trait and short is the recessive trait. When a tall pea plant crosses with a short pea plant, the offspring is always tall. As a result, the children display the dominant trait.

15. What will be the percentage of ab gametes produced by AaBb parent?
    Ans. 25 percent

Short Answer Type Question [2 Marks]

16. Why acquired traits are not inherited?
    Ans. Acquired traits are those that organisms develop over the course of their lives. These characteristics are not inherited because they're caused by nonreproductive tissue.

17. What are autosomes and sex chromosomes?
    Ans. There are 23 pairs of chromosomes in a human cell. 22 pairs are termed autosomes, while the remaining 1 pair, which determines a child's sex, is called sex chromosome.

18. Do genetic combination of mothers play a significant role in determining the sex of a newborn?
    Ans. No, genetic combinations of mothers do not determine the sex of a newborn. The sex of a newborn is primarily determined by the sperm cell that fertilizes the egg. Sperm cells carry either an X or a Y chromosome, while egg cells carry only an X chromosome. If a sperm with an X chromosome fertilizes the egg, the resulting embryo will be female (XX), and if a sperm with a Y chromosome fertilizes the egg, the resulting embryo will be male (XY).

19. A very small population of a species faces a greater threat of extinction than a larger population. Provide a suitable genetic explanation.
    Ans. A very small population of a species faces a greater threat of extinction due to genetic factors such as inbreeding depression, loss of genetic diversity, and increased susceptibility to genetic disorders. In small populations, there is a higher chance of harmful genetic mutations becoming fixed, leading to decreased fitness and viability of individuals within the population.

20. Give the pair of contrasting traits of the following characters in pea plant and mention which is dominant and recessive?
    (i) yellow seed
    (ii) round seed
    Ans. In pea plants, the pair of contrasting traits for seed color are yellow seed (dominant) and green seed (recessive), while for seed shape, the pair of contrasting traits are round seed (dominant) and wrinkled seed (recessive).

21. Why did Mendel choose pea plant for his experiments?
    Ans. Mendel chose pea plants for his experiments because they possess several advantageous characteristics for genetic studies, such as easy cultivation, short generation time, large number of offspring, distinct and easily observable traits, ability to self-fertilize or cross-fertilize, and existence of pure breeding lines. These features allowed Mendel to conduct controlled breeding experiments and accurately track the inheritance patterns of traits.

22. What is phenotypic ratio obtained by Mendel by monohybrid cross? Answer with the help of diagram.
    Ans. 3:1 (Phenotypic ratio of dominant to recessive traits in F2 generation).
    
    

23. Write 3 differences between Autosomes and Allosomes.

24. List two differences in tabular form between dominant trait and recessive traits. What percentage/proportion of the plants in the F2 generation/progeny were round, in Mendel's cross between round and wrinkled pea plants

Proportion of round plants in F2 generation: 75% (3:1 ratio of round to wrinkled seeds)

25. Explain Mendel’s three laws of inheritance in detail

Ans. (i) Law of Dominance:

1. Characters are controlled by discrete units called factors.

2. Factors occur in pairs.

3. In a dissimilar pair of factors, one member of the pair dominates (dominant) over the other (recessive).

• The law of dominance is used to explain the expression of only one of the parental characters in a monohybrid cross in the F1 and the expression of both in the F2. It also explains the proportion of 3:1 obtained in the F2.

• Alleles do not show blending. Both parental traits are recovered in the F2 generation, even though one may not be seen in the F1 generation.

• During gamete formation, the two alleles for each trait segregate from each other so that each gamete receives only one allele from the pair.

• A homozygous parent will produce gametes with the same allele, while a heterozygous parent will produce two kinds of gametes in equal proportions, each carrying one of the alleles.

26. Differentiate between inherited traits and acquired traits

27. Answer the following questions:

(a) Why did Mendel carry out an experiment to study inheritance of two traits in garden pea?
Ans. Mendel carried out experiments with two traits to study how they were inherited together and whether their inheritance was independent of each other. He conducted a dihybrid cross to observe the interaction between two different traits. In this experiment, Mendel found that when two pairs of characters were considered, each trait was inherited independently of the other. This led to the formulation of Mendel's Law of Independent Assortment.

(b) What were his findings with respect to inheritance of traits in F1 and F2 generation and state the ratio obtained in the F2 generation in the above mentioned experiment.
Ans. For example, a cross between round yellow and wrinkled green parents.

In F1 generation, all plants have round-yellow seeds. But in F2 generation, all types of plants appear:

• Round-yellow = 9

• Round-green = 3

• Wrinkled-yellow = 3

• Wrinkled-green = 1

28. How do Mendel’s experiments show that:
(a) the traits may be dominant or recessive?
(b) inheritance of the two traits is independent of each other?

Ans.
(a) Mendel discovered that only tall pea plants were created in the F1 generation when he crossed pure-bred tall pea plants with pure-bred dwarf pea plants. In the F2 generation, tall and dwarf plants appeared in a 3:1 ratio. He explained that the dwarfness of one parent was suppressed in F1 but reappeared in F2. Tallness is the dominant trait, while dwarfism is recessive.

(b) In Mendel's dihybrid cross, he studied two traits simultaneously (seed colour and seed shape). Crossing pure-bred round-yellow (RRYY) with wrinkled-green (rryy) produced F1 plants that were all round-yellow (RrYy) because round and yellow are dominant traits.

When F1 plants self-pollinated, the F2 generation produced four combinations in a 9:3:3:1 ratio:

• 9 round-yellow

• 3 round-green

• 3 wrinkled-yellow

• 1 wrinkled-green

The appearance of round-green and wrinkled-yellow seeds shows that inheritance of one trait does not affect the other, demonstrating Mendel’s Law of Independent Assortment.

29. A blue-flowering plant (BB) is cross-bred with a white-flowering plant (bb)

(a) Colour of F1 generation: All plants will have blue flowers because the blue allele (B) is dominant. The genotype of F1 plants will be Bb.

(b) Percentage of white flower plants in F2 generation if F1 (Bb) are self-pollinated: 25%.

• Punnett square for Bb × Bb:
  
  

• BB (blue)

• Bb (blue)

• bb (white)
  
  

(c) Expected ratio of genotypes BB and Bb in F2 progeny: 1:2

• BB = 1/4
  
  

• Bb = 2/4 (or 1/2)

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