Heredity & Evolution Important Questions Class 10 2026

The chapter Heredity and Evolution is one of the most interesting and thought-provoking topics in Class 10 Biology.and also connects the principles of genetics with the broader concept of evolution and gives students a scientific understanding of variation, heredity, and natural selection.

By studying this topic, students understand how genes determine characteristics, how dominant and recessive traits work, and how evolution provides evidence of life’s continuity on Earth. It forms the foundation for advanced topics in genetics, biotechnology, and evolution in higher classes.

The Heredity and Evolution Important Questions for Class 10 are compiled to help you:

• Strengthen conceptual understanding of inheritance and variation.
• Revise key experiments, definitions, and reasoning-based questions.

Here is a detailed blog post on mastering this chapter and important questions to aid in your preparation.

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In the table below, we have provided the links to downloadable Heredity And Evolution Class 10 Most Important Questions With Answers PDFs. Now you can download them without requiring a login.

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Chapter 8 Heredity And Evolution: Important Questions Answers

Q1. Evolution in living organisms can be understood by studying the characteristics of different species. These characteristics can be different or similar based on their ancestors.

Given below are pictures of two sets P and Q, of organs of different species. Each set is grouped based on the evolution of these organs in different species.

(a) Name the scientific terms that describe the evolutionary relationship of the organs in sets P and Q.

(b) What are the differences between the two sets of organs?

Answer:

(a) Set P (Frog, Lizard, Human limbs): The organs in this set are homologous organs.

Set Q (Butterfly wing, Bat wing): The organs in this set are analogous organs.

(b)

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Q2. As part of a theatrical presentation on tracing evolutionary evidences, two teams of class 10 dressed up as the following:

Team P: One person each dressed as a cat and a dolphin to show the cat's leg and a dolphin's flippers as homologous organs.

Team R: One person each dressed as an insect and a bird to show the insect's wings and the bird's wings as homologous organs.

(a) Define homologous organs.

(b) Which of the two teams should win the presentation for correct depiction?

(c) What is incorrect about the losing team's presentation?

(d) Apart from such anatomical connections, name TWO other sources of evidence of evolution used by us.

Answer:

1. Homologous organs are structures in different species that have a similar underlying anatomy due to a common evolutionary ancestor but perform different functions. For example, a cat's leg and a dolphin's flipper are homologous because they have a similar bone structure but serve different purposes (walking vs. swimming).
2. Team P should win the presentation.

The cat's leg and the dolphin's flippers are homologous organs because they have a similar structure (e.g., bones like humerus, radius, and ulna) inherited from a common ancestor, even though they perform different functions.

3. Team R incorrectly presented the insect's wings and the bird's wings as homologous organs.

These are not homologous but analogous organs, meaning they perform a similar function (flying) but have different structural origins:

• Bird wings are modified forelimbs with bones.
• Insect wings are extensions of the exoskeleton and lack bones.

They evolved independently due to convergent evolution, not a common ancestor.

4. Fossil Evidence: Fossils show the gradual changes in species over time and transitional forms, such as Archaeopteryx (a link between reptiles and birds).

Molecular Evidence: Similarities in DNA sequences, proteins, and genetic material across different species indicate shared ancestry. For example, humans and chimpanzees share approximately 98–99% of their DNA.

Q3. Sex determination in humans happens through sex chromosomes. Along with other parameters, such processes often help in forensic studies in crime investigation and/ or identification of accidents and natural calamities,

In order to determine whether an accident victim is male or female, which cells can be used and why?

Answer:

To determine whether an accident victim is male or female, any nucleated cell from the victim's body can be used because these cells contain the sex chromosomes in their nuclei.

Commonly Used Cells:

Blood cells (White Blood Cells):

Red blood cells lack nuclei, but white blood cells (WBCs) are nucleated and contain DNA.

Skin cells:

Found on the body surface or in tissue samples.

Bone cells:

Bone tissue often survives accidents and natural calamities, making it a reliable source of DNA.

Hair follicle cells:

The base of hair strands contains nucleated cells.

Soft tissue cells:

If available, muscle or organ tissues can also be used.

Why These Cells?

The sex chromosomes in the cells (XX for females, XY for males) determine the sex:

• Females have two X chromosomes in their cells.
• Males have one X and one Y chromosome in their cells.

By analyzing the chromosomes through techniques like karyotyping, polymerase chain reaction (PCR), or fluorescence in situ hybridization (FISH), forensic experts can determine the victim's sex accurately.

Q4. Before the Industrial Revolution, the black peppered moth was rare. During the early decades of the Industrial Revolution in England, the countryside between London and Manchester became blanketed with soot from the new coal-burning factories. Many of the light-bodied lichens died from sulphur dioxide emissions, and the trees became darkened.

This led to an increase in bird predation for light-coloured moths, as they no longer blended in a well in their polluted ecosystem.(Source: Wikipedia:- https://en.wikipedia.org/wiki/Peppered_moth_evolution)

4.1 What would have happened to the population of light-coloured moth over time and why?

4.2 What could be an external factor that determines the return of the light-coloured moths?

Answer:

4.1 The population of light-coloured moths would have decreased over time.

• This is because the soot-darkened environment made light-coloured moths more visible to predators, such as birds.
• As a result, more light-coloured moths were preyed upon, reducing their survival and reproductive success.
• The process of natural selection favored the darker (melanistic) moths, as they were better camouflaged and less likely to be eaten, leading to an increase in their population.

4.2 An external factor that could determine the return of light-coloured moths is a reduction in pollution.

• With cleaner air and the removal of soot from trees (due to stricter pollution control measures, like those in the late 20th century), the trees could regain their lighter, lichen-covered appearance.
• This would once again provide camouflage for light-coloured moths, increasing their survival and allowing their population to recover.

5. The farmer crosses two heterozygous green seeded plants and obtains 100 plants in the F1 generation.

What would be the number of green and yellow seeds respectively in the F1 generation?

Answer:

To solve this, we use a Punnett square and Mendel's principles of inheritance:

Green seed color (G) is dominant.

Yellow seed color (g) is recessive.

Both parent plants are heterozygous (Gg).

Punnett Square:

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Genotype Ratios:

• GG: 1
• Gg: 2
• gg: 1

Phenotype Ratios:

• Green seeds (GG + Gg): 3
• Yellow seeds (gg): 1

Total Offspring: 100

• Green seeds: 3/4×100=75
• Yellow seeds: 1/4×100=25

Green seeds: 75

Yellow seeds: 25

Q6. Coelacanth is a deep sea dwelling fish that was believed to be extinct 66 million years ago, around the same time the dinosaurs went extinct. However, in 1938 a specimen of the fish was discovered near the shores of South Africa. Scientists also believe that this fish may be the member of species of fish that crawled onto land to evolve into animals with legs. Upon investigation of the specimen by marine biologists certain features of the fish was discovered.

Some of them are listed below:

(i) It has paired lobe-shaped fins that move in an alternating pattern similar to the limbs of a four-legged animal. 

(ii) It has a lung in its body but carries out exchange of gases through gills.

6.1 The lobed fin of the fish and limbs of a terrestrial animal have similar structure but different function. What are such organs called?

6.2 A vestigial organ is an organ that is carried forward to progeny by evolution but serves no specific purpose in the body of the individual. What organ in the fish can be called a vestigial organ?

6.3 How can scientists so accurately determine the apparent time of extinction of the fish?

Answer:

6.1 These are called homologous organs.

Homologous organs have a similar structure due to a common evolutionary ancestor but may perform different functions in different species.

6.2 The lung in the coelacanth can be considered a vestigial organ.

• While the lung exists in the fish's body, it does not perform gas exchange, as the coelacanth relies on its gills for respiration.
• This lung may be a remnant from its evolutionary ancestors, which possibly used it for breathing air.

6.3  Scientists use fossil records to determine the apparent time of extinction.

• Fossils provide evidence of when the species last existed and can be dated using methods like radiometric dating, which calculates the age of rock layers containing the fossils.
• The coelacanth's fossils were last found in rock layers dated to about 66 million years ago, coinciding with the mass extinction event that wiped out the dinosaurs.

Q7. Plants that reproduce through asexual reproduction give rise to similar and not identical offsprings.

What could be the most likely reason for the above statement to be true?

Answer:

The most likely reason for the statement to be true is:

"Mutations in the genetic material during DNA replication."

In asexual reproduction, offspring are produced from a single parent without the involvement of gametes. The process usually involves mitotic cell division, resulting in offspring that are genetically identical to the parent.

However, errors during DNA replication (mutations) can introduce slight genetic differences, leading to offspring that are similar but not identical to the parent.

These mutations are rare but are the primary source of genetic variation in organisms that reproduce asexually.

Q8. Consider a pea plant that is recessive for plant height. Its 'genotype' is tt and 'phenotype' is dwarf.

(a) Assuming that the gene for plant height obeys the Mendel's laws of inheritance, indicate the genotypes and phenotypes of ALL the possible parent pairs that could have dwarf offspring.

(b) Using any of the parent pairs mentioned by you in (a), perform a cross to show the genotypes of the offspring that might arise in the next generation.

Answer:

1. The recessive trait for plant height (dwarf) is expressed when both alleles are recessive (tt). For offspring to have the tt genotype, each parent must contribute a t allele. The possible parent combinations are:

tt × tt

Both parents are homozygous recessive.

All offspring will be dwarf (tt).

Tt × tt

One parent is heterozygous (Tt), and the other is homozygous recessive (tt).

50% of the offspring will be dwarf (tt), and 50% will be tall (Tt, but phenotypically tall).

Tt × Tt

Both parents are heterozygous (Tt).

25% of the offspring will be dwarf (tt), and 75% will be tall (25% TT and 50% Tt).

2. Let's use the Tt × tt parent pair for this demonstration.

Parent Genotypes:

• Parent 1: Tt (heterozygous, tall phenotype)
• Parent 2: tt (homozygous recessive, dwarf phenotype)

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Genotypes of Offspring:

• 50% Tt (heterozygous, tall phenotype)
• 50% tt (homozygous recessive, dwarf phenotype)

Phenotypes of Offspring:

• 50% Tall
• 50% Dwarf

This demonstrates Mendel's laws of segregation and dominance.

Q9. Select the option that correctly summarises the given observations in the passage.

a. Majority of the peppered moths changed their appearances to become melanistic moths so that they could survive.

b. The predator birds help in controlling the number of any given type of moth so that neither one gets an undue advantage of survival.

c. Different types of moths had to continuously make efforts to adapt themselves in order to survive in the changing environmental conditions.

d. It is by chance that different types of moths were present at any given point of time and the environmental factors determined which type got a survival benefit.

Answer:

(d) It is by chance that different types of moths were present at any given point of time and the environmental factors determined which type got a survival benefit.

Explanation: 

• The passage likely refers to the classic example of natural selection in peppered moths during the Industrial Revolution. The melanistic moths did not "choose" to change their appearance; rather, the environmental conditions (pollution darkening the environment) favored those with darker coloration, which provided better camouflage. This survival advantage increased their population.
• The presence of different moth types is due to genetic variation, and environmental factors (e.g., pollution, predation) determined which type had a better chance of survival.

This aligns with the principles of natural selection.

Q10. Attached earlobes in humans is an inherited condition. The allele for attached earlobes is recessive.

What are the chances of parents, both having attached earlobes, to have a child with attached earlobes?

a. 0%

b. 25%

c. 75%

d. 100%

Answer:

(d) 100%

Explanation: 

If both parents have attached earlobes, their genotype must be homozygous recessive (aa) since the allele for attached earlobes is recessive.

• Genotype of both parents: aa
• A child inherits one allele from each parent.
• Since both parents can only pass on the recessive allele (a), all offspring will inherit aa.

The chances of the child having attached earlobes are 100%.

Some More Important Question Answers of class 10 Heredity & Evolution

Q1. What is heredity? Why is it important?

Answer:

• Heredity - process by which traits (characteristics) are passed from parents to offspring through genes.
• Importance:
  
  1. Ensures continuity of species (offspring resemble parents).
  2. Preserves basic body design (e.g., humans always give birth to humans, not dogs).
  3. Introduces variations through gene combination, useful for adaptation and evolution.

Q2. Define variation. How does it occur?

Answer:

• Variation: Differences in traits among individuals of the same species.
• Causes:
  
  • Sexual reproduction: Mixing of genes from two parents.
  • Errors during DNA replication (mutations).
  • Environmental factors: temperature, nutrition, etc.
• Example: In humans, siblings may differ in height, skin color, or ability to resist disease.

Q3. State Mendel’s laws of inheritance.

Answer: Mendel, “Father of Genetics,” performed pea plant experiments and proposed 3 laws:

1. Law of Dominance: In hybrids, one trait (dominant) is expressed, while the other (recessive) remains hidden.
2. Law of Segregation: Pair of alleles separate during gamete formation, so each gamete gets only one allele.
3. Law of Independent Assortment: Genes for different traits are inherited independently.

Q4. Why did Mendel choose pea plants for his experiments?
Answer:

• Short life cycle → many generations in a short time.
• Produced many seeds.
• Had easily observable contrasting traits (tall/dwarf, round/wrinkled seeds, etc.).
• Could be self-pollinated or cross-pollinated easily.
• Pure breeding lines were available.

Q5. In Mendel’s monohybrid cross, a tall pea plant (TT) was crossed with dwarf pea plant (tt). Show results with Punnett square.
Answer:

• F1 generation: All plants = Tt (tall, since T dominant).
• Conclusion: Only dominant trait expressed in F1.

Q6. Explain Mendel’s dihybrid cross with an example.

Answer: Cross between plants with two contrasting traits:

• Parent: Round yellow seeds (RRYY) × Wrinkled green seeds (rryy).
• F1: All Round yellow (RrYy).
• F2: Phenotypic ratio 9:3:3:1.
  
• 9 Round yellow, 3 Round green, 3 Wrinkled yellow, 1 Wrinkled green.

Conclusion: Traits are inherited independently (Law of Independent Assortment).

Q7. Differentiate between genotype and phenotype with examples.

Answer:

• Genotype: Genetic constitution (alleles present). Eg: Tt = heterozygous tall.
• Phenotype: Observable trait (appearance). Eg: plant looks tall.
• Genotype Tt and TT → same phenotype (tall) but different genotypes.

Q8. A cross between black (BB) rabbit and white (bb) rabbit produced only black offspring. Which trait is dominant? Explain.

Answer:

• All offspring = Bb (black).
• Since heterozygotes (Bb) are black, black (B) is dominant and white (b) is recessive.

Q9. What is sex determination? How is sex determined in humans?

Answer:

• Sex determination: Mechanism by which sex of offspring is decided.
• In humans:
  
  • Female gametes: all eggs have X chromosome.
  • Male gametes: half sperm carry X, half carry Y.
  • Fertilization:
    

1. Egg (X) + Sperm (X) = XX → girl.
2. Egg (X) + Sperm (Y) = XY → boy.
   

So the father determines the child's sex, not the mother.

Q10. Differentiate between acquired traits and inherited traits.

‍Answer:

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Q11. What are fossils? How do they help in studying evolution?

‍Answer:

1. Fossils: Preserved remains or impressions of ancient organisms in rocks.

2. Importance:

• Provide direct evidence of past life.
• Show how organisms have changed (evolution).
• Eg: Fossil of Archaeopteryx shows features of both reptiles and birds → transitional form.

Q12. Differentiate between homologous and analogous organs. Give examples.

‍Answer:

• Homologous organs: Same basic structure, different functions → common ancestry.
  Eg: Forelimbs of human, bat, whale.
• Analogous organs: Different structure, same function → convergent evolution.
  Eg: Wings of bat (bones) and wings of insects (membrane).

Q13. What is natural selection? Give one example.

‍Answer:

• Natural selection: Process where individuals with advantageous traits survive and reproduce, while others die.
• Example: Peppered moth during the Industrial Revolution.
  
  • Dark moths survived on soot-covered trees (camouflage).
  • White moths got eaten by birds.
    
• Over time, dark variety became more common.

Q14. How does gene flow and genetic drift cause evolution?

‍Answer:

• Gene flow: Movement of genes between populations (migration, interbreeding). Introduces new traits.
• Genetic drift: Random changes in gene frequency, especially in small populations. Some traits may disappear by chance.
• Example: Island populations show unique features due to isolation (Darwin’s finches).

Q15. Explain the role of DNA in inheritance.

‍Answer:

• DNA carries genetic information in sequence of nitrogen bases.
• Genes - small segments of DNA controlling traits (like eye color).
• During reproduction, DNA is copied and passed to offspring.
• Small changes (mutations) in DNA cause variations.

Q16. State the contribution of Charles Darwin to evolution.

‍Answer:

• Charles Darwin is widely considered to be a trailblazer in the field of Human evolution; he is credited to have proposed  the “Theory of Natural Selection.”
• Observed finches in Galápagos Islands → different beak shapes suited for different food sources.
• Concluded that:
  
  1. Overproduction of offspring occurs.
  2. Those with advantageous traits survive.
  3. Favorable traits passed to the next generation.
• This explains the gradual evolution of species.

Q17. How does evolution prove common ancestry? Give two pieces of evidence.

‍Answer:

1. Homologous structures (same design, different functions). Eg: human hand & whale flipper.
2. Fossil record showing gradual change in organisms over time.
3. Similar embryonic development in vertebrates → common origin.

Q18. Differentiate between microevolution and macroevolution.

‍Answer:

• Microevolution: Small changes within a species over a short period. Eg: color change in moths.
• Macroevolution: Large changes leading to new species over a long time. Eg: reptiles → birds.

Q19. Explain the evolution of eyes in animals.

Answer:

• Primitive organisms had only light-sensitive spots (Euglena).
• Flatworms developed light-sensitive cups.
• Insects have compound eyes for detecting movement.
• Humans and octopuses have complex camera-like eyes with lens, retina, iris.
• Shows evolution is gradual and builds upon existing designs.

Q20. What is the modern theory of evolution?

Answer: Called Modern Synthetic Theory of Evolution, it combines:

• Darwin’s natural selection, and
• Modern genetics (DNA, mutations, genetic drift, recombination). It explains evolution as a result of:

1. Genetic variations (mutation, recombination).
2. Natural selection.

Isolation of populations.

Video Lecture: Must-watch for Quick Revision

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Extra Questions for Practice!!

Q1. Differentiate between dominant and recessive traits with examples.

Q2. Why did Mendel not see blending of traits in his experiments?

Q3. A tall plant (Tt) is crossed with dwarf (tt). Write expected ratio of tall to dwarf.

Q4. Explain how fossils are formed.

Q5. Write a note on embryological evidence for evolution.

Q6. What are vestigial organs? Give two examples in humans.

Q7. Explain sex-linked inheritance with one example.

Q8. What is speciation? State its factors.

Q9. Differentiate between Lamarck’s and Darwin’s theory of evolution.

Q10. What is molecular evidence of evolution? Give one example.

Study Diagrams and Tables

• Practice drawing monohybrid and dihybrid crosses, ensuring you can label and explain each step clearly.
• Familiarise yourself with how traits are passed from parents to offspring using Punnett squares and family pedigree charts.
• Learn diagrams illustrating homologous and analogous structures, such as forelimbs of vertebrates or wings of birds and bats.
• Represent the fossil record, showcasing transitional forms like Archaeopteryx.
• Create tables summarising Mendel’s observations, evolutionary examples, and the differences between homologous and analogous organs.

Practice Questions Regularly

Consistent practice is the key to understanding complex concepts and knowing problem-solving techniques better than ever.

• To build a strong foundation, begin by solving the in-text and end-of-chapter questions from your NCERT textbook.
• Work on problems involving genetic disorders, sex determination, and real-life examples of natural selection (e.g., industrial melanism).
• Attempt CBSE sample papers and previous years’ questions to understand the exam pattern and improve time management.
• Pay attention to diagram-based and long-answer questions, common in board exams.

FAQs

Q1. How many marks are usually allotted to this chapter in Class 10 board exams?

Ans. This chapter usually carries 6 to 8 marks, often including one question based on inheritance or a reasoning-type question on evolution.

Q2. Which topics are most important for exams?

Ans. Mendel’s experiments, laws of inheritance, sex determination, homologous and analogous organs, and Darwin’s theory of natural selection are the most important topics.

Q3. How can I remember Mendel’s laws easily?

Ans.  Connect each law with an example. For example, the Law of Segregation can be remembered through the 3:1 ratio seen in pea plant experiments.

Q4. Do I need to draw diagrams in this chapter?

Ans.  Yes, Punnett squares, crosses, and evolutionary relationships are best explained through diagrams. Clear labeling can help you gain full marks.

Q5. How can I revise this chapter quickly before exams?

Ans. Use your short notes to review definitions, laws, and examples. Practice one or two inheritance problems and review evidence of evolution like fossils and organs.