Practicing Heredity and Evolution Class 10 Science MCQs is one of the quickest ways to revise Chapter 9 and assess your understanding before exams. This chapter covers important concepts such as heredity, genes, DNA, variation, Mendel's experiments, and evolution, which are frequently tested in CBSE Board assessments.
This page provides chapter-wise MCQ practice for quick revision and concept reinforcement. For more objective questions, explore our complete MCQs collection, browse all subjects in Class 10 MCQs, or access every chapter from our Class 10 Science MCQs section.
All questions are based on the latest CBSE syllabus and are designed to support effective exam preparation through focused practice and self-assessment.
Quick Chapter Overview
| Chapter Details | Information |
|---|---|
| Chapter Name | Heredity and Evolution |
| Subject | Science |
| Class | 10 |
| Board | CBSE |
| Chapter Number | 9 |
| Main Topics | Heredity, Variation, Mendel's Experiments, Evolution, Speciation, DNA |
| Question Type | MCQs with Answers and Explanations |
| Exam Relevance | High |
What will you learn in this chapter?
This chapter explains how traits are passed from parents to offspring and how living organisms change over generations. Students learn about inherited characteristics, variations, genes, chromosomes, evolution, and the evidence that supports evolutionary changes in living organisms.
Heredity and Evolution Class 10 Science MCQs With Answers
Before attempting the questions, make sure you have revised important concepts such as dominant and recessive traits, Mendel's experiments, evolution, and sources of variation. These areas frequently appear in board examinations and school assessments.
Q. A gene in a tomato plant controls the production of a red pigment through an enzyme. Another plant has a mutated gene that produces a non-functional enzyme. How do these genes affect fruit color?
(a) DNA directly acts as a red pigment.
(b) DNA codes for an enzyme that produces the pigment, while a mutated gene cannot produce a functional enzyme.
(c) The mutated gene destroys existing pigments.
(d) The gene directly absorbs red light.
Answer: (b)
Explanation: Genes contain instructions for making proteins, many of which function as enzymes. These enzymes control chemical reactions within cells. In tomato plants, the enzyme helps produce the red pigment responsible for fruit color. A functional gene produces a working enzyme, resulting in normal pigment formation. If the gene is mutated, the enzyme may become inactive or ineffective, reducing or preventing pigment production and changing the fruit's appearance.
Q. Why do sexually reproducing beetles show more variation than asexually reproducing yeast?
(a) Asexual reproduction creates many DNA errors.
(b) Sexual reproduction combines genetic material from two parents.
(c) Yeast choose not to change their genes.
(d) Mitosis removes mutations.
Answer: (b)
Explanation: Sexual reproduction increases genetic variation because offspring inherit genetic material from two different parents. During meiosis and fertilization, genes are shuffled and combined in unique ways, creating new trait combinations. Asexual reproduction produces genetically similar offspring through mitosis, with variation arising only from occasional mutations. This is why sexually reproducing populations generally display much greater diversity than asexually reproducing populations.
Q. A pure tall pea plant (TT) is crossed with a pure short pea plant (tt). The F₁ plants are self-pollinated. Out of 800 F₂ plants, how many are expected to be heterozygous tall?
(a) 200
(b) 400
(c) 600
(d) 800
Answer: (b)
Explanation: Crossing TT with tt produces F₁ offspring with genotype Tt. When these heterozygous plants self-pollinate (Tt × Tt), the F₂ generation follows a genotypic ratio of 1 TT : 2 Tt : 1 tt. Since half of the offspring are expected to be heterozygous tall (Tt), 50% of 800 plants equals 400 plants. This result directly follows Mendel's monohybrid inheritance pattern.
Q. Why did Gregor Mendel choose garden pea plants for his experiments?
(a) Long life cycle
(b) One seed per generation
(c) Easy self-pollination, controlled cross-pollination, and contrasting traits
(d) No chromosomes
Answer: (c)
Explanation: Garden pea plants were ideal for genetic experiments because they possess clear contrasting traits such as tall and dwarf plants. They naturally self-pollinate, allowing pure breeding lines to be maintained, but can also be cross-pollinated manually when needed. Additionally, they grow quickly and produce many seeds. These characteristics helped Mendel observe inheritance patterns accurately and establish the fundamental laws of genetics.
Q. Why is meiosis important in sexually reproducing organisms?
(a) It doubles chromosome number.
(b) It halves chromosome number in gametes.
(c) It converts all alleles into dominant forms.
(d) It changes sex chromosomes into autosomes.
Answer: (b)
Explanation: Meiosis is a reduction division that produces haploid gametes containing half the chromosome number of body cells. During fertilization, two haploid gametes fuse and restore the diploid chromosome number in the offspring. This process prevents chromosome numbers from doubling in each generation. Meiosis also contributes to genetic variation through recombination and independent assortment, making it essential for sexual reproduction.
Q. A human cheek cell contains 46 chromosomes. How are these chromosomes classified?
(a) 46 pairs of autosomes
(b) 22 pairs of autosomes and 1 pair of sex chromosomes
(c) 23 pairs of sex chromosomes
(d) 44 pairs of autosomes and 2 pairs of sex chromosomes
Answer: (b)
Explanation: Human somatic cells contain 46 chromosomes arranged into 23 pairs. Out of these, 22 pairs are autosomes that control general body characteristics. The remaining pair consists of sex chromosomes, which determine biological sex. Females have XX chromosomes, while males have XY chromosomes. Therefore, a human cheek cell contains 22 pairs of autosomes and 1 pair of sex chromosomes.
Q. Two heterozygous tall pea plants (Tt × Tt) produce some short offspring. Why?
(a) T changed into t.
(b) T and t blended together.
(c) Recessive alleles paired to form tt offspring.
(d) The recessive allele was recreated.
Answer: (c)
Explanation: Mendel's Law of Segregation states that the two alleles of a trait separate during gamete formation. Each parent produces T and t gametes. During fertilization, two recessive t alleles may combine to form a tt genotype. Since the recessive trait is expressed only in homozygous recessive individuals, these offspring appear short even though both parents are tall.
Q. Jagged leaf margins (J) are dominant over smooth margins (j). A smooth-margined plant is self-pollinated. What will be the offspring phenotype?
(a) 100% jagged
(b) 50% jagged and 50% smooth
(c) 100% smooth
(d) 75% jagged and 25% smooth
Answer: (c)
Explanation: A smooth-margined plant must have the genotype jj because smooth margins are recessive. When a jj plant self-pollinates, all gametes carry only the j allele. As a result, every offspring receives a j allele from each parent and has genotype jj. Since all offspring possess the recessive genotype, they all express the smooth leaf margin phenotype.
Q. Two genetically identical plants are grown under different environmental conditions. One becomes tall while the other remains short due to poor nutrition. Their seeds are later grown under identical conditions. What is expected?
(a) Tall parent's offspring remain tall and short parent's offspring remain short.
(b) Both groups remain short.
(c) Both groups grow normally because environmental effects are not inherited.
(d) Short parent's offspring become taller due to mutations.
Answer: (c)
Explanation: The difference in height was caused by environmental conditions rather than genetic differences. Such acquired traits affect only body tissues and do not change the DNA present in reproductive cells. Since inheritance depends on genetic information passed through gametes, the offspring will not inherit the environmentally caused stunted growth. Under favorable conditions, both sets of offspring can express their normal genetic potential.
Q. A black-furred rabbit (BB) is crossed with a black-furred rabbit (Bb). What is the probability of obtaining a white-furred offspring?
(a) 0%
(b) 25%
(c) 50%
(d) 75%
Answer: (a)
Explanation: The homozygous dominant parent (BB) contributes only the dominant B allele. The heterozygous parent (Bb) contributes either B or b. Therefore, the offspring can only have genotypes BB or Bb. Both genotypes contain at least one dominant allele and express black fur. Since the recessive genotype bb cannot be formed in this cross, the probability of obtaining a white-furred offspring is 0%.
Q. A dihybrid cross is performed between RRYY and rryy plants. What proportion of F₂ plants will show recombinant traits?
(a) 1/16
(b) 6/16
(c) 9/16
(d) 10/16
Answer: (b)
Explanation: In a standard dihybrid cross, the F₂ generation follows a 9:3:3:1 phenotypic ratio. The parental combinations are round yellow and wrinkled green. The recombinant combinations are round green and wrinkled yellow. These recombinant phenotypes occur in proportions of 3/16 and 3/16 respectively. Adding them together gives 6/16. This demonstrates Mendel's Law of Independent Assortment, which allows new trait combinations to appear.
Q. A child has blood group O. The father has blood group B and the mother has blood group A. What must be their genotypes?
(a) IBIB and IAIA
(b) IBIO and IAIO
(c) IBIB and IAIO
(d) IOIO and IAIB
Answer: (b)
Explanation: Blood group O is a recessive trait and requires the genotype IOIO. Therefore, each parent must contribute one IO allele to the child. A father with blood group B must have genotype IBIO, while a mother with blood group A must have genotype IAIO. If either parent lacked the recessive IO allele, a child with blood group O would not be possible.
Q. When is the biological sex of a human child determined?
(a) During embryonic development
(b) At fertilization depending on X or Y sperm
(c) After implantation
(d) During egg formation
Answer: (b)
Explanation: Human females have XX chromosomes and produce eggs carrying only the X chromosome. Human males have XY chromosomes and produce two types of sperm, one carrying X and the other carrying Y. The sex of the child is determined at fertilization. An X-bearing sperm results in a female child (XX), while a Y-bearing sperm results in a male child (XY).
Q. Which organisms can show environmental sex determination?
(a) Humans and dogs
(b) Birds and fruit flies
(c) Snails and green turtles
(d) Pea plants and snails
Answer: (c)
Explanation: In some organisms, sex is influenced by environmental conditions rather than chromosomes. Green turtles are a well-known example, where incubation temperature affects the sex of developing embryos. Certain snails can also exhibit non-genetic sex determination. In contrast, humans, birds, and fruit flies primarily depend on chromosomes for determining biological sex. This shows that sex determination mechanisms vary among different species.
Q. A heterozygous tall pea plant (Tt) is crossed with a short plant (tt). Out of 500 offspring, how many are expected to be tall?
(a) 125
(b) 250
(c) 375
(d) 500
Answer: (b)
Explanation: In the cross Tt × tt, the heterozygous parent produces T and t gametes, while the recessive parent produces only t gametes. The offspring are expected to occur in a 1:1 ratio of Tt and tt. Since Tt plants are tall and tt plants are short, half of the offspring will be tall. Therefore, 50% of 500 plants equals 250 tall plants.
Q. A mutation changes the shape of a hormone-producing enzyme. What is the likely result?
(a) The plant copies a healthy gene.
(b) The enzyme may become non-functional and the trait may not be expressed.
(c) The chromosome number doubles.
(d) Proteins do not affect traits.
Answer: (b)
Explanation: Genes direct the synthesis of proteins, including enzymes that control essential biochemical reactions. A mutation can alter the amino acid sequence of an enzyme, changing its shape and function. If the enzyme no longer works properly, hormone production may decrease or stop completely. As a result, the associated trait may fail to develop or appear differently, demonstrating how genes influence observable characteristics.
Q. Two pink-flowered plants produce 25% red, 50% pink, and 25% white offspring. This inheritance pattern represents:
(a) Polygenic inheritance
(b) Incomplete dominance
(c) Environmental mutation
(d) Dominant white allele
Answer: (b)
Explanation: In incomplete dominance, neither allele completely masks the other. As a result, heterozygous individuals display an intermediate phenotype. In this example, pink flowers represent the heterozygous condition, while red and white flowers represent the two homozygous forms. Crossing two pink-flowered plants produces a 1:2:1 ratio of red, pink, and white flowers, which is a classic example of incomplete dominance.
Q. In a dihybrid cross (RrYy × RrYy), 1600 seeds are produced. How many are expected to be wrinkled yellow?
(a) 100
(b) 300
(c) 900
(d) 1200
Answer: (b)
Explanation: A dihybrid cross produces offspring in a phenotypic ratio of 9:3:3:1. Wrinkled yellow seeds represent the combination of recessive seed shape and dominant seed color, which occurs in 3/16 of the offspring. To calculate the expected number, multiply 1600 by 3/16. This gives 300 seeds. Such numerical problems are commonly based on Mendelian inheritance and probability principles.
Q. Assertion (A): In green turtles, sex is determined by incubation temperature.
Reason (R): High temperatures produce females in turtles, while in some lizards high temperatures produce males.
(a) Both A and R are true, and R explains A.
(b) Both A and R are true, but R does not explain A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Answer: (a)
Explanation: Many reptiles exhibit temperature-dependent sex determination. In green turtles, higher incubation temperatures generally produce female offspring, while lower temperatures tend to produce males. Some lizard species show the opposite pattern. The reason directly explains how environmental temperature influences sex determination, making it the correct explanation of the assertion. This is an example of environmental factors affecting biological development.
Q. Assertion (A): The F₂ phenotypic ratio in a monohybrid cross is 3:1, while the genotypic ratio is 1:2:1.
Reason (R): Dominant alleles are expressed in both homozygous and heterozygous conditions.
(a) Both A and R are true, and R explains A.
(b) Both A and R are true, but R does not explain A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Answer: (a)
Explanation: In a monohybrid cross, the genotypes occur in the ratio 1 TT : 2 Tt : 1 tt. However, both TT and Tt express the dominant trait, while only tt expresses the recessive trait. This results in a phenotypic ratio of 3:1. Therefore, the reason correctly explains why the phenotypic ratio differs from the genotypic ratio, even though both are derived from the same genetic cross.
Q. Assertion (A): The sex of a human child is determined by the chromosome inherited from the father.
Reason (R): Human females are heterogametic (XY) and produce eggs carrying either X or Y chromosomes.
(a) Both A and R are true, and R explains A.
(b) Both A and R are true, but R does not explain A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Answer: (c)
Explanation: The assertion is correct because the father's sperm determines the sex of the child. Males produce two types of sperm, carrying either an X or a Y chromosome. However, the reason is incorrect because human females are homogametic (XX) and produce eggs carrying only X chromosomes. Therefore, the father's sperm decides whether the child will be XX (female) or XY (male).
Q. Assertion (A): Acquired traits are not inherited by offspring.
Reason (R): Environmental changes affect body cells but do not alter DNA in germ cells.
(a) Both A and R are true, and R explains A.
(b) Both A and R are true, but R does not explain A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Answer: (a)
Explanation: Acquired traits develop during an organism's lifetime due to environmental influences, injuries, or lifestyle factors. These changes affect only somatic cells and do not modify the genetic material present in reproductive cells. Since inheritance depends on DNA passed through gametes, acquired characteristics cannot be transmitted to offspring. The reason accurately explains why acquired traits are generally not inherited across generations.
Q. Assertion (A): Mendel selected pea plants because they cannot be cross-pollinated.
Reason (R): Self-pollination helps maintain pure breeding lines.
(a) Both A and R are true, and R explains A.
(b) Both A and R are true, but R does not explain A.
(c) A is false, but R is true.
(d) A is true, but R is false.
Answer: (c)
Explanation: The assertion is false because pea plants can be cross-pollinated manually by removing anthers and transferring pollen from another plant. This feature was one reason Mendel selected them for his experiments. The reason is true because repeated self-pollination helps produce pure breeding lines with stable traits. Therefore, only the reason is correct, making option (c) the right answer.
Q. Assertion (A): In a cross between RRYY and rryy plants, the F₁ generation shows all four trait combinations equally.
Reason (R): Alleles for different traits assort independently during gamete formation.
(a) Both A and R are true, and R explains A.
(b) Both A and R are true, but R does not explain A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Answer: (d)
Explanation: Crossing RRYY with rryy produces F₁ offspring with genotype RrYy, all showing the dominant phenotype of round yellow seeds. The four trait combinations appear in the F₂ generation, not the F₁ generation. However, the reason is correct because Mendel's Law of Independent Assortment states that alleles of different traits segregate independently during gamete formation. Therefore, the assertion is false but the reason is true.
Case Study: Earlobe Inheritance in Rohan's Family
Rohan's father has free earlobes, while his mother has attached earlobes. Rohan has free earlobes, but his younger sister has attached earlobes. Free earlobes (F) are dominant and attached earlobes (f) are recessive.
Q. What is the genotype of Rohan's mother?
(a) FF
(b) Ff
(c) ff
(d) FFF
Answer: (c)
Explanation: Attached earlobes are a recessive trait. A recessive trait is expressed only when an individual possesses two recessive alleles. Therefore, a person showing attached earlobes must have the genotype ff. Since Rohan's mother displays attached earlobes, her genotype must be homozygous recessive. Neither FF nor Ff would express the attached earlobe phenotype because the dominant allele would mask the recessive trait.
Q. 26. What are the genotypes of Rohan and his father?
(a) Rohan: FF; Father: FF
(b) Rohan: Ff; Father: Ff
(c) Rohan: FF; Father: Ff
(d) Rohan: ff; Father: FF
Answer: (b)
Explanation: Rohan's mother has genotype ff and can contribute only the recessive f allele. Since Rohan has free earlobes, he must have inherited a dominant F allele from his father, making his genotype Ff. Rohan's sister has attached earlobes (ff), meaning the father must also carry an f allele. Therefore, the father's genotype must be heterozygous Ff, and Rohan's genotype is also Ff.
Q. What is the probability that Rohan's parents will have another child with attached earlobes?
(a) 25%
(b) 50%
(c) 75%
(d) 100%
Answer: (b)
Explanation: The cross is between a heterozygous father (Ff) and a homozygous recessive mother (ff). The father produces F and f gametes in equal proportions, while the mother produces only f gametes. The resulting offspring are expected to be 50% Ff (free earlobes) and 50% ff (attached earlobes). Therefore, each child has a 50% probability of inheriting attached earlobes.
Case Study: Tomato Stem Inheritance
A researcher crosses green-stemmed tomato plants (GG) with purple-stemmed tomato plants (gg). All F₁ plants have green stems. The F₁ generation is then self-pollinated.
Q. What are the expected phenotypes in the F₂ generation?
(a) 100% green stems
(b) 50% green and 50% purple stems
(c) 75% green and 25% purple stems
(d) 100% purple stems
Answer: (c)
Explanation: The parental cross GG × gg produces F₁ plants with genotype Gg. Since green is dominant, all F₁ plants appear green. When these plants are self-pollinated (Gg × Gg), the F₂ generation follows a phenotypic ratio of 3:1. This means 75% of the offspring display green stems, while 25% show purple stems. This is a classic monohybrid inheritance pattern.
Q. Out of 1000 F₂ plants, how many are expected to be homozygous green?
(a) 250
(b) 500
(c) 750
(d) 1000
Answer: (a)
Explanation: The genotypic ratio in the F₂ generation of a monohybrid cross is 1 GG : 2 Gg : 1 gg. Homozygous green plants (GG) represent 25% of the total offspring. Therefore, among 1000 plants, 25% are expected to have the GG genotype. Calculating 25% of 1000 gives 250 plants. These plants carry two dominant alleles and consistently express green stems.
Q. A heterozygous green-stemmed plant (Gg) is crossed with a homozygous green-stemmed plant (GG). What will be the offspring?
(a) 50% Gg and 50% gg
(b) 100% green stems (50% GG and 50% Gg)
(c) 100% GG
(d) 75% GG and 25% gg
Answer: (b)
Explanation: In the cross Gg × GG, the heterozygous parent produces G and g gametes, while the homozygous dominant parent produces only G gametes. The resulting offspring are 50% GG and 50% Gg. Since both genotypes contain at least one dominant G allele, every offspring displays the green stem phenotype. Therefore, 100% of the offspring will have green stems, although their genotypes differ.
Important Topics Covered in Heredity and Evolution
While practicing MCQs, focus on the following concepts because most objective questions are created from these areas.
1. Heredity
The process through which characteristics are passed from parents to offspring. It explains why children often resemble their parents in many traits.
2. Mendel's Experiments
Gregor Mendel conducted experiments on pea plants and discovered the basic principles of inheritance. His work forms the foundation of modern genetics.
3. Dominant and Recessive Traits
Some traits appear even when only one gene is present, while others appear only when both genes carry the same characteristic.
4. Variation
Differences among individuals of the same species are called variations. These variations play an important role in survival and evolution.
5. Evolution
Evolution describes gradual changes in living organisms over long periods of time, leading to the development of new forms of life.
6. Speciation
Speciation is the process through which new species are formed due to accumulated differences and reproductive isolation.
7. DNA and Genes
DNA carries genetic information, while genes are segments of DNA responsible for specific inherited traits.
8. Evidence of Evolution
Scientists use fossils, homologous structures, and comparative studies to understand evolutionary relationships among organisms.
Why This Chapter Is Important for Class 10 Students
Many students find this chapter interesting because it connects everyday observations with scientific explanations.
Benefits of Learning Heredity and Evolution
Builds a strong foundation in Genetics.
Helps understand inherited and acquired traits.
Improves conceptual understanding of biological diversity.
Frequently contributes questions in school and board examinations.
Supports preparation for future competitive examinations.
Develops scientific reasoning about living organisms and their development over time.
A clear understanding of this chapter often makes Biology easier in higher classes because many advanced topics are based on the same principles.
Quick Revision Notes
Use these points for fast revision before tests and examinations.
| Topic | Quick Revision Point |
|---|---|
| Heredity | Transfer of traits from parents to offspring |
| Gene | Functional unit of heredity |
| DNA | Genetic material carrying hereditary information |
| Variation | Differences among individuals of a species |
| Mendel | Known as the Father of Genetics |
| Dominant Trait | Expressed even in the presence of another trait |
| Recessive Trait | Expressed only when dominant trait is absent |
| Evolution | Gradual development of organisms over generations |
| Speciation | Formation of new species |
| Fossils | Important evidence of evolutionary history |
Smart Tips to Solve Heredity and Evolution MCQs
Objective questions become easier when concepts are understood clearly.
Focus on Words
Words such as gene, DNA, trait, variation, evolution, and speciation often help identify the correct answer quickly.
Learn Mendel's Findings Properly
Questions related to dominant and recessive traits are very common. Understanding Mendel's observations is more useful than memorizing them.
Compare Similar Terms
Students often confuse heredity with evolution and inherited traits with acquired traits. Practice differentiating these concepts.
Revise Diagrams
Simple diagrams related to inheritance and evolutionary relationships can help answer conceptual MCQs more accurately.
Practice Regularly
Consistent MCQ practice improves speed, accuracy, and confidence during examinations.
Common Mistakes Students Make
Avoiding these mistakes can improve your score significantly.
Confusing Heredity and Evolution
Heredity explains the transmission of traits, while evolution explains long-term changes in populations.
Mixing Up Dominant and Recessive Traits
Many students remember definitions but fail to apply them in questions.
Ignoring Variation
Variation is one of the most important concepts in understanding evolution and natural selection.
Memorizing Without Understanding
Objective questions increasingly test concepts rather than direct definitions.
Overlooking Scientific Terms
Terms such as chromosome, gene pool, speciation, and genetic variation should be revised carefully.
Important Exam Focus Areas
Based on common board-level question trends, pay special attention to the following areas.
| High Priority Topics | Importance |
|---|---|
| Mendel's Experiments | Very High |
| Dominant and Recessive Traits | Very High |
| Heredity and Inheritance | Very High |
| DNA and Genes | High |
| Variation | High |
| Evolution | High |
| Speciation | Medium to High |
| Fossils as Evidence | Medium |
| Acquired vs Inherited Traits | High |
Students who master these concepts generally perform better in chapter-based objective assessments.
Conclusion
Heredity and Evolution Class 10 Science MCQs help students strengthen important concepts related to inheritance, genetics, variation, and evolution. Along with practicing objective questions, understanding the reasoning behind each concept is equally important. Focus on Mendel's experiments, DNA, inherited traits, variation, and evolutionary evidence to build confidence before examinations.
Use this page for quick revision, concept reinforcement, and chapter-wise practice. Consistent preparation and concept clarity will make answering Biology MCQs much easier and more accurate during exams.
