NCERT Solutions for Class 10 Science Chapter 8 Heredity

Heredity is the transfer of traits from parents to offspring through genes present on chromosomes. NCERT Solutions for Class 10 Science Chapter 8 connect this topic with variation, Mendel’s experiments, dominant traits and sex determination.

Class 10 Science Chapter 8 explains why children resemble parents but are never exact copies. The chapter begins with variation during reproduction, then moves to inherited traits, Mendel’s pea plant experiments, gene expression and sex determination in humans. 

NCERT Solutions for Class 10 Science Chapter 8 - All Exercise Questions

Heredity and Evolution
Difficult
Q.
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
Heredity and Evolution
Medium
Q.
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.
Heredity and Evolution
Easy
Q.
In evolutionary terms, we have more in common with
(a) a Chinese school-boy.
(b) a chimpanzee.
(c) a spider.
(d) a bacterium.
Heredity and Evolution
Medium
Q.
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?
Heredity and Evolution
Difficult
Q.
How are the areas of study – evolution and classification – interlinked?
Heredity and Evolution
Medium
Q.
Explain the terms analogous and homologous organs with examples.
Heredity and Evolution
Difficult
Q.
Outline a project which aims to find the dominant coat colour in dogs.
Heredity and Evolution
Medium
Q.
Explain the importance of fossils in deciding evolutionary relationships.
Heredity and Evolution
Medium
Q.
What evidence do we have for the origin of life from inanimate matter?
Heredity and Evolution
Difficult
Q.
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?
Heredity and Evolution
Difficult
Q.
How is the equal genetic contribution of male and female parents ensured in the progeny?
Heredity and Evolution
Medium
Q.
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?

For CBSE 2026-27 board preparation, this chapter is important because questions often test crosses, ratios and reasoning. Students must understand why tallness can dominate shortness, how traits recombine independently and why the father determines the sex of a child. These NCERT Solutions for Class 10 Science Chapter 8 give direct answers with the exact logic needed for school exams.

Key Takeaways

  • Variation: Reproduction creates small differences that can help survival.
  • Dominant trait: A trait expressed with one gene copy is called dominant.
  • Mendelian ratio: A monohybrid F2 cross gives a 3:1 visible trait ratio.
  • Sex determination: A father’s X or Y chromosome decides the child’s sex.

NCERT Solutions for Class 10 Science Chapter 8 Structure 2026-27

Exercise No. Topic Question Count
Intext Questions 8.1 Variation during reproduction 2
Intext Questions 8.2 Mendel’s rules and sex determination 4
Exercises Heredity and genetic contribution 4

NCERT Solutions for Class 10 Science Chapter 8 Exercise Answers

The NCERT 2026-27 Heredity chapter has 10 textbook questions across intext and exercise sections. These class 10 heredity ncert solutions follow the textbook order and explain each answer through genes, traits and chromosome logic.

Q1. If a trait A exists in 10% of a population of an asexually reproducing species and trait B exists in 60% of the same population, which trait is likely to have arisen earlier?

Trait B is likely to have arisen earlier.

In an asexually reproducing species, variations appear through small changes during DNA copying. A trait found in 60% of the population has had more time to spread.

Trait A is present in only 10% of the population. It is more likely to be a newer variation.

Q2. How does the creation of variations in a species promote survival?

Variations promote survival by giving some individuals an advantage in a changing environment.

For example, if a heat wave occurs, bacteria that can tolerate heat will survive better. Those bacteria can reproduce and pass the useful variation to the next generation.

Environmental selection acts on these variations. This makes variation important for long-term survival.

Q3. How do Mendel’s experiments show that traits may be dominant or recessive?

Mendel’s monohybrid cross showed dominance when all F1 pea plants became tall after crossing tall and short plants.

The short trait did not appear in F1, but it reappeared in one-fourth of the F2 plants. This showed that the short trait was present but hidden in F1.

Tallness is dominant because one copy of the tall gene is enough to show tallness. Shortness is recessive because both gene copies must be recessive.

The cross can be shown as:

Parents: TT × tt
Gametes: T and t
F1: Tt, Tt, Tt, Tt

All F1 plants are tall.

F1 self-cross:

Tt × Tt

F2 combinations:

TT, Tt, Tt, tt

Visible ratio:

Tall : Short = 3 : 1

Q4. How do Mendel’s experiments show that traits are inherited independently?

Mendel’s dihybrid cross showed that two traits can be inherited independently.

He crossed pea plants with round yellow seeds and wrinkled green seeds. All F1 seeds were round and yellow because round shape and yellow colour were dominant.

In F2, new combinations appeared. Some seeds were round green, and some were wrinkled yellow.

The F2 ratio was:

Round yellow : Round green : Wrinkled yellow : Wrinkled green = 9 : 3 : 3 : 1

This proved that seed shape and seed colour were inherited independently.

Q5. A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell whether blood group A or O is dominant? Why or why not?

No, this information is not enough by itself to prove which trait is dominant.

The daughter has blood group O, so she must have received an O gene from both parents. The mother with blood group O can give only an O gene.

The father has blood group A but must also carry an O gene. His genetic combination can be AO.

This case shows that O can remain hidden in a person with blood group A. More family data is needed to confirm dominance.

Q6. How is the sex of the child determined in human beings?

The sex of a child is determined by the chromosome inherited from the father.

Human females have XX sex chromosomes. Human males have XY sex chromosomes.

The mother always contributes an X chromosome. The father contributes either X or Y.

If the child receives X from the father:

XX = Girl

If the child receives Y from the father:

XY = Boy

So, the father’s sperm determines the sex of the child.

Q7. 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 which option?

The correct answer is (c) TtWW.

All progeny bore violet flowers, so the violet flower trait must be dominant. The tall parent must have WW for flower colour if the other parent has white flowers.

Almost half the progeny were short. This means the tall parent must carry one tall gene and one short gene.

The tall parent’s genetic make-up is:

TtWW

Cross for height:

Tt × tt

Offspring:

Tt, Tt, tt, tt

Visible ratio:

Tall : Short = 1 : 1

This matches the question.

Q8. A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. Can we say whether light eye colour is dominant or recessive? Why or why not?

No, this information is not enough to decide whether light eye colour is dominant or recessive.

The study only shows that eye colour is inherited. It does not show the trait ratio across generations.

To identify dominance, we need controlled data from parents and children. We must know whether the trait disappears in one generation and reappears later.

Mendel used counted ratios to identify dominant and recessive traits. A simple observation of similarity is not enough.

Q9. Outline a project which aims to find the dominant coat colour in dogs.

A project can study coat colour inheritance by tracking dog parents and their puppies over several generations.

  1. Select one dog breed to reduce unrelated differences.
  2. Record coat colours of male and female parents.
  3. Record coat colours of all puppies in each litter.
  4. Repeat the study across many families.
  5. Compare how often each coat colour appears in offspring.
  6. Check whether any coat colour appears even when only one parent shows it.

The coat colour that appears more often in mixed-parent crosses may be dominant. A larger sample gives a more reliable result.

Q10. How is the equal genetic contribution of male and female parents ensured in the progeny?

Equal genetic contribution is ensured because male and female gametes carry one set of chromosomes each.

Body cells contain two sets of chromosomes. Gametes contain only one set because chromosome number is halved during gamete formation.

During fertilisation, the male gamete and female gamete fuse. This restores the normal chromosome number in the zygote.

So, the child receives one set of chromosomes from the father and one set from the mother.

Class 10 Science Chapter 8 Concepts Behind the NCERT Solutions

Class 10 Science Chapter 8 Heredity uses crosses, ratios and chromosome movement to explain inheritance. These concepts help students write stronger heredity class 10 questions and answers in CBSE exams.

Variation During Reproduction

Variation means small differences among individuals of the same species. These differences appear because DNA copying is not perfectly identical.

In asexual reproduction, variations are fewer because only one parent is involved. In sexual reproduction, variations are greater because genes from two parents combine.

Useful variations can help survival. This is why heredity and variation class 10 questions often use bacteria, heat waves and environmental change.

Inherited Traits

Inherited traits are characteristics passed from parents to offspring through genes. Examples include earlobe type, plant height and seed shape.

A child gets genetic material from both parents. So, each trait can be influenced by paternal and maternal DNA.

Inherited traits class 10 answers should mention genes. Genes carry information for proteins that control traits.

Mendel Experiment Class 10

Mendel studied pea plants because they had clear contrasting traits. Examples include tall or short plants and round or wrinkled seeds.

In a monohybrid cross class 10 question, one pair of contrasting traits is studied. Mendel’s tall and short pea plant cross gave a 3:1 F2 ratio.

In a dihybrid cross class 10 question, two pairs of contrasting traits are studied. Mendel’s seed shape and seed colour cross gave a 9:3:3:1 F2 ratio.

Dominant and Recessive Traits Class 10

A dominant trait appears even when only one copy of its gene is present. Tallness in pea plants is dominant.

A recessive trait appears only when both gene copies are recessive. Shortness in pea plants is recessive.

The basic combinations are:

TT = Tall
Tt = Tall
tt = Short

This explains why the short trait disappears in F1 but returns in F2.

Genes and Chromosomes

A gene is a section of DNA that gives information for making a protein. Proteins help control traits.

Chromosomes are thread-like structures made of DNA. Each cell has two copies of each chromosome, one from each parent.

Gametes carry only one set of chromosomes. Fertilisation restores the normal chromosome number.

Sex Determination Class 10

Sex determination in humans depends on sex chromosomes. Females have XX chromosomes, while males have XY chromosomes.

The mother always gives an X chromosome. The father gives either X or Y.

The sex determination pattern is:

Mother: XX
Father: XY

Possible children:

XX = Girl
XY = Boy

This shows why the father determines the sex of the child.

NCERT Solutions for Class 10 Science Chapter 8 Important Terms

Heredity chapter class 10 answers become easier when students use key terms accurately. These terms are also important for one-mark, two-mark and reasoning-based board questions.

NCERT Solutions for Class 10 Science Chapter 8 Key Terms

Term Meaning Chapter Link
Heredity Transfer of traits from parents to offspring Inheritance
Gene DNA segment that controls a trait Trait expression
Sex Chromosomes X and Y chromosomes that determine sex Human inheritance

Heredity

Heredity is the transfer of characters from one generation to the next. It explains why offspring resemble their parents.

In Class 10 Science Chapter 8, heredity is explained through genes, chromosomes and Mendel’s experiments.

Variation

Variation means differences among individuals of the same species. These differences arise during reproduction.

Some variations improve survival in changing environments. This connects heredity with natural selection.

Gene

A gene is a section of DNA that gives information for a protein. Proteins help produce visible traits.

For example, plant height can depend on a hormone-making enzyme. The gene controls the enzyme’s efficiency.

Chromosome

A chromosome is an independent DNA-containing structure inside the cell. Genes are present on chromosomes.

Humans have 22 pairs of regular chromosomes and one pair of sex chromosomes. The sex chromosome pair is XX in females and XY in males.

Dominant Trait

A dominant trait is expressed even when one copy of its gene is present. In Mendel’s pea plant experiment, tallness is dominant.

A plant with TT or Tt will be tall. This makes T the dominant factor.

Recessive Trait

A recessive trait appears only when both gene copies are recessive. In pea plants, shortness is recessive.

A plant with tt will be short. One dominant T can hide the recessive t.

Monohybrid Cross

A monohybrid cross studies one pair of contrasting traits. Mendel’s tall and short pea plant cross is one example.

The F2 visible ratio in a monohybrid cross is 3:1. This ratio shows dominance and recessiveness.

Dihybrid Cross

A dihybrid cross studies two pairs of contrasting traits. Mendel’s seed shape and seed colour experiment is one example.

The F2 ratio is 9:3:3:1. This ratio shows independent inheritance of traits.

Sex Chromosomes

Sex chromosomes determine the sex of a child in humans. Females have XX chromosomes, while males have XY chromosomes.

A child receiving X from the father becomes a girl. A child receiving Y from the father becomes a boy.

Q.1 Asexual reproduction takes place through budding in

1. amoeba.
2. yeast.
3. plasmodium.
4. leishmania.

b. Yeast

Explanation: Out of the four organisms mentioned, only in yeast asexual reproduction takes place though budding. Asexually Amoeba and Leishmania reproduce through binary fission and Plasmodium reproduces by multiple fission method.

Q.2 Which of the following is not a part of the female reproductive system in human beings?

1. Ovary
2. Uterus
3. Vas deferens
4. Fallopian tube

Vas deferens

Explanation: Ovary, uterus and fallopian tube are the parts of the female reproductive system in human beings whereas vas deferens is the part of male reproductive system in human beings.

Q.3 The anther contains

1. sepals.
2. ovules.
3. carpel.
4. pollen grains.

d) Pollen grains

Explanation: The anther contains pollen grains. Sepals are generally green in colour and protect flower in bud stage. Ovules are present in ovary of the carpel (female reproductive organ of plant).

Q.4 What are the advantages of sexual reproduction over asexual reproduction?

Advantages of sexual reproduction over asexual reproduction are:

1. Sexual reproduction is responsible for variations in a population.
2. Variations in individuals are responsible for survival of a species in an ecosystem.
3. Sexual reproduction plays an important role in origin of new species and is a beginning for evolution.
4. Sexual reproduction helps in providing stability to populations of species.

Q.5 What are the functions performed by the testis in human beings?

Testes are the male reproductive organs in human beings. Functions of testis are:

1. It produces male gametes i.e., sperms.
2. It also produces male hormone called testosterone that regulates the formation of sperms and is responsible for secondary sexual characters in human males at the time of puberty.

Q.6 Why does menstruation occur?

Menstruation is a process in which blood and mucosal tissues are discharged periodically from the inner lining of uterus through the vagina. In human female, every month one egg is released from one ovary. Simultaneously the uterus prepares itself for pregnancy. During this phase, the inner lining of the uterus gets thickened and new blood vessels are formed that will nourish the future embryo. If pregnancy does not occur, then the lining of the uterus breaks down slowly and the content is released in the form of blood and mucus through the vagina and the process is known as menstruation.

Q.7 Draw a lebelled diagram of the longitudinal section of a flower.

Q.8 What are the different methods of contraception?

The different methods of contraception are:

1. Barrier method: In this method, the meeting of ovum with sperm is checked with the help of a mechanical barrier. Mechanical barrier such as condoms are made of thin and flexible rubber. The mechanical barrier is available for both males and females. These are used to cover penis in males and vagina in females and prevent sperms from entering the uterus during sexual intercourse to avoid pregnancy.
2. Oral contraceptive: This is method in which hormones are introduced in the female partner to prevent the release of egg to avoid pregnancy. The hormones are taken orally in the form of tablets or pills.
3. Intrauterine devices (IUDs): Contraceptive devices such as the loop or Copper T are placed in the uterus that prevent sperms from reaching the egg and prevent pregnancy to occur.
4. Surgical methods: Transfer of gametes can be blocked by using surgical methods. Surgical method is an irreversible method of contraception. Surgically, in males, vas deferens is blocked to stop the sperm transfer. This process is known as vasectomy. In females, surgically fallopian tubes are blocked to carry the eggs to the uterus. This surgical procedure in females is called tubectomy.

Q.9 How are the modes for reproduction different in unicellular and multicellular organisms?

Unicellular organisms have single cell. Generally, unicellular organisms reproduce by asexual methods like binary fission, multiple fission, budding, etc. For example, Amoeba reproduces by binary fission, yeast reproduces by budding, and Plasmodium reproduces by multiple fission method. Multicellular organisms are made up of either simple cells or complex tissues and organs. Some of their cells are specialised to perform the function of reproduction. Multicellular organisms can employ the asexual methods of reproduction as well as sexual methods of reproduction. Asexual methods include budding, fragmentation, spore formation and vegetative propagation. Complex multicellular organisms possess a well developed reproductive system having specialised reproductive organs.

Q.10 How does reproduction help in providing stability to populations of species?

In an ecosystem, organisms of different species use their ability of reproduction to survive and maintain their populations in their niches.

In an ecosystem, every individual of a species struggle for food, shelter and protection for their survival and existence. Factors like death at the end of natural life cycle, competition, predation, migration and sudden environmental changes keep on reducing population of species on a regular basis. The process of reproduction is the only way to overcome this continuous depletion of individuals from the populations of diverse species. Therefore, reproduction helps in providing stability to populations of species.

Q.11 What could be the reason for adopting contraceptive methods?

Contraceptive methods are mainly adopted because of the following reasons:

1. These devices prevent unwanted pregnancies to occur.
2. These devices not only help in restricting the number of children but also help in maintaining age gap between children. The age gap between children help parents in good bringing up of their children and less number of children ensures the improved living standards of a family.
3. These devices also prevent the spread of sexually transmitted diseases (STDs).
4. These devices play a role in controlling increase in human population and help in reducing pressure on life supporting natural resources such as food, air, water, fuel, etc.

Please register to view this section

FAQs (Frequently Asked Questions)

Heredity is the transfer of traits from parents to offspring through genes. It explains why children resemble their parents in body features, blood group, eye colour and other inherited characters.

Heredity passes traits from parents to offspring, while variation creates differences among individuals of the same species. Heredity keeps basic body design similar, and variation helps survival in changing environments.

Mendel explained inheritance by crossing pea plants with contrasting traits. His tall and short plant cross showed dominant and recessive traits, while his two-trait cross showed independent inheritance.

A recessive trait reappears in F2 because it remains hidden in the F1 generation. When two recessive gene copies come together in F2, the recessive trait becomes visible.

The father determines the gender of a child in humans. The mother always gives an X chromosome, while the father gives either X for a girl or Y for a boy.