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CBSE Class 10 Science Chapter 8 Heredity Worksheet with Answers

Heredity remains one of the most scoring yet conceptually rich chapters in CBSE Class 10 Science, contributing around 6-7 marks in the board exam. This worksheet consolidates every key idea from NCERT Chapter 8 — Mendel's experiments with pea plants, monohybrid and dihybrid ratios, sex chromosomes, and the critical difference between traits you inherit and those you acquire. Whether you are revising a week before exams or solving extra questions for mastery, this resource mirrors real board paper difficulty and offers instant feedback through detailed answers.

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Key takeaways

✓40+ graded questions covering Mendel's laws, sex determination, and trait inheritance as per NCERT Class 10 Science Chapter 8
✓Complete answer key with brief explanations for every MCQ, fill-in-the-blank, and descriptive question
✓One case-study question mirroring the 2025 CBSE Class 10 board exam pattern for competency-based assessment
✓Difficulty level: Moderate; suggested time: 90 minutes for full worksheet completion under exam conditions
✓Includes HOTS questions on Punnett squares, genetic crosses, and evolutionary significance of heredity
✓Printable PDF-friendly format for offline practice and self-assessment before term or board exams

Quick Chapter Recap: Heredity

Chapter 8 of NCERT Class 10 Science introduces heredity as the transmission of traits from parents to offspring through genes. Gregor Mendel's pioneering work with garden pea plants established the foundational laws of inheritance: the Law of Dominance, Law of Segregation, and Law of Independent Assortment. The chapter distinguishes inherited traits — controlled by genes on chromosomes — from acquired traits, which result from environmental influences and cannot be passed to the next generation. Sex determination in humans follows the XX-XY system, where the father's sperm determines the child's biological sex. Understanding genotype versus phenotype, dominant versus recessive alleles, and the role of DNA in heredity forms the conceptual backbone of this chapter. The CBSE board frequently tests monohybrid cross ratios (3:1), dihybrid ratios (9:3:3:1), and real-life applications like genetic disorders and speciation. Mastery of Punnett squares and genetic diagrams is essential for scoring full marks in long-answer and case-study questions.

Inherited traits: Controlled by genes; passed through DNA (e.g., eye colour, blood group)
Acquired traits: Develop during lifetime; not heritable (e.g., muscle tone, scars)
Mendel's Laws: Dominance, Segregation, Independent Assortment
Sex determination: Human males are XY, females XX; father determines baby's sex
Monohybrid cross: 3:1 phenotypic ratio in F₂ generation
Dihybrid cross: 9:3:3:1 ratio when two traits are studied together

Worksheet Overview: Difficulty Level and Time Allocation

This worksheet has been designed at a moderate difficulty level, reflecting the standard of questions seen in recent CBSE Class 10 Science board papers and school unit tests. It comprises 40+ questions distributed across five sections — MCQs, fill-in-the-blanks, true/false statements, short-answer questions, and long-answer or higher-order thinking (HOTS) questions — plus one case-study item. Students should allocate approximately 90 minutes to complete the entire worksheet under timed, exam-like conditions. Section A (MCQs) should take about 15 minutes, Section B (fill-in-the-blanks) around 10 minutes, Section C (matching or true/false) roughly 8 minutes, Section D (short answers) about 25 minutes, Section E (long answers and HOTS) around 25 minutes, and the case study another 7 minutes. This distribution mirrors the actual board exam's time pressure and helps students develop pacing strategies. Parents can use the detailed answer key at the end to mark their child's work and identify weak areas for focused revision. Regular practice with such worksheets has been shown to improve retention of genetic terminology and problem-solving speed, both critical for scoring above 90 percent in CBSE Class 10 Science.

Total questions: 40+ across five graded sections plus one case study
Suggested time: 90 minutes (mimic board exam conditions)
Difficulty: Moderate — suitable for term exam and board preparation
Marking scheme provided for self-assessment and parent evaluation
Covers NCERT textbook exercises, intext questions, and additional HOTS problems

Section A: Multiple Choice Questions (MCQs)

Multiple-choice questions test instant recall and conceptual clarity. In the CBSE Class 10 Science board paper, MCQs carry one mark each and often feature diagrams, Punnett squares, or scenario-based stems. This section presents six carefully curated MCQs covering Mendel's experiments, genetic terminology, sex determination, and the difference between inherited and acquired traits. Each question has four options, with only one correct answer. Students should read the stem carefully, eliminate obviously incorrect options, and apply NCERT definitions. Common traps include confusing genotype with phenotype, mixing up dominant and recessive symbols, or misinterpreting the role of the mother versus father in sex determination. Practice with these MCQs sharpens decision-making under time pressure and builds confidence for objective-type questions. The answer key at the end provides not just the correct option but also a brief rationale, helping students learn from mistakes and reinforce core concepts for long-term retention.

Q1. Which of the following is an acquired trait? (a) Eye colour (b) Scar from an accident (c) Blood group (d) Skin colour
Q2. In a monohybrid cross between two heterozygous tall pea plants (Tt × Tt), what is the phenotypic ratio in the F₂ generation? (a) 1:1 (b) 2:1 (c) 3:1 (d) 9:3:3:1
Q3. The sex of a human child is determined by: (a) The mother's X chromosome (b) The father's sperm carrying X or Y (c) Environmental factors (d) Nutrition during pregnancy
Q4. A gene is: (a) A unit of heredity (b) A type of cell (c) An acquired character (d) A hormone
Q5. In humans, the sex chromosome pair in males is: (a) XX (b) XY (c) YY (d) XO
Q6. The contrasting pairs of traits studied by Mendel are called: (a) Alleles (b) Chromosomes (c) Genes (d) Gametes

Section B: Fill in the Blanks

Fill-in-the-blank questions assess precise knowledge of terminology and definitions from the NCERT Class 10 Science textbook. This section contains five statements, each missing one or two key terms. Students must supply the exact word or phrase that completes the sentence accurately. Common topics include Mendel's laws, the terms genotype and phenotype, chromosome numbers, and the mechanisms of sex determination. CBSE mark schemes award full credit only when the answer matches the NCERT glossary or chapter text verbatim, so approximate or colloquial terms may not earn marks. To excel, students should review the bold terms and intext definitions in Chapter 8, make flashcards for genetic vocabulary, and practice writing answers in complete, grammatically correct sentences. This section reinforces spelling and the ability to recall information without contextual clues, a skill tested in board exams through one-word or very short answer items worth one mark each. The answer key provides the standard NCERT term, ensuring students learn the board-approved language for heredity concepts.

Q7. The transmission of characters from parents to offspring is called __________.
Q8. Mendel's experiments were performed on the __________ plant.
Q9. Traits that are passed on through genes are termed __________ traits.
Q10. The genetic makeup of an organism is called its __________, while the observable characteristics are its __________.
Q11. In humans, a normal female has __________ sex chromosomes, and a normal male has __________ sex chromosomes.

Section C: True or False Statements

True or false questions require students to evaluate the scientific accuracy of a statement and justify their choice with a brief explanation. This format appears less frequently in the latest CBSE papers but remains a valuable self-assessment tool because it exposes misconceptions. Section C presents five declarative sentences about heredity, Mendel's laws, acquired versus inherited traits, and sex determination. For each, students write 'True' or 'False' and, ideally, add a one-line reason. For instance, the statement 'Acquired traits are inherited by offspring' is false because NCERT clearly states that only traits coded in DNA can be passed on. This exercise trains critical reading and the ability to spot subtle errors in wording — skills that help avoid negative marking in MCQs. The answer key provides both the correct Boolean value and a concise NCERT-based justification, turning each item into a mini-learning opportunity. Regular practice with true/false items builds confidence in distinguishing fact from common myths, such as the idea that a mother determines the baby's sex or that environmental changes alter genes directly.

Q12. Acquired characters are inherited by the next generation. (True / False)
Q13. In a dihybrid cross, Mendel obtained a 9:3:3:1 ratio in the F₂ generation. (True / False)
Q14. The human male determines the sex of the child. (True / False)
Q15. Genes are located on chromosomes. (True / False)
Q16. All recessive traits are harmful. (True / False)

Section D: Short Answer Questions (3 Marks Each)

Short-answer questions in CBSE Class 10 Science typically carry three marks and demand structured, point-wise responses within 50-60 words. This section offers five questions covering Mendel's experiments, the difference between inherited and acquired traits, sex determination, and basic genetic problem-solving. Students should write in complete sentences, use scientific terminology from NCERT, and include examples or diagrams where helpful. For instance, when asked to explain Mendel's Law of Segregation, a full-credit answer will define the law, mention that alleles separate during gamete formation, and cite the 3:1 monohybrid ratio as evidence. CBSE marking schemes reward clarity, correct use of terms like 'allele,' 'gamete,' 'genotype,' and logical flow. Avoid long, vague paragraphs; instead, break the answer into three distinct points if the question has multiple parts. Time management is crucial: spend about 5 minutes per short answer, leaving room for quick revision. The detailed answer key in this worksheet models the ideal structure, helping students internalize how to frame biology answers for maximum marks under board exam conditions.

Q17. Differentiate between inherited traits and acquired traits with one example each. (3 marks)
Q18. State Mendel's Law of Dominance. (3 marks)
Q19. Explain with a suitable example how sex is determined in human beings. (3 marks)
Q20. What is meant by a monohybrid cross? Illustrate with a Punnett square. (3 marks)
Q21. Why are traits acquired during the lifetime of an individual not inherited? (3 marks)

Section E: Long Answer and HOTS Questions (5 Marks Each)

Long-answer and higher-order thinking questions carry five marks each and test deep conceptual understanding, the ability to integrate multiple ideas, and skill in genetic problem-solving. This section includes three questions: one on a dihybrid cross with a full Punnett square, one on the evolutionary significance of variation arising from heredity, and one application-based HOTS question linking Mendel's laws to modern genetic counselling or plant breeding. Students should allocate around 8-10 minutes per question, write 100-120 words, and include labelled diagrams or charts where appropriate. For dihybrid crosses, clearly show gamete formation, construct a 4×4 Punnett square, and state the 9:3:3:1 ratio with phenotypes. For theoretical questions, cite NCERT concepts such as 'variation provides raw material for natural selection' or 'independent assortment increases genetic diversity.' CBSE examiners award step-wise marks, so even if the final answer is incomplete, partial credit is given for correct method or reasoning. Practicing these long answers builds stamina for the board exam's Section B and hones the skill of turning biological knowledge into coherent, examiner-friendly prose.

Q22. Describe Mendel's dihybrid cross experiment. Draw a Punnett square for the F₂ generation and state the phenotypic ratio obtained. (5 marks)
Q23. Explain the evolutionary significance of heredity and variation. How does variation contribute to the survival of a species? (5 marks)
Q24. A plant breeder wants to develop a new variety of pea plant that is both tall and has yellow seeds. Using your knowledge of Mendel's laws, suggest a breeding strategy and explain the expected results. (5 marks)

Case-Study Question

Case-study or competency-based questions appeared in CBSE Class 10 board papers from 2021 onward, carrying four to five marks. They present a real-world scenario — a genetic counselling session, a farmer's crop-breeding challenge, or data from a pedigree chart — followed by three or four sub-questions testing comprehension, application, and analysis. This worksheet includes one case study about a family's inheritance pattern for a trait such as attached versus free earlobes. Students read a short paragraph, examine a simple pedigree, and answer sub-questions on identifying dominant/recessive traits, predicting offspring genotypes, and explaining the genetic basis. The format mirrors the board exam's intent to assess scientific literacy and the ability to apply Mendel's laws beyond textbook exercises. To score full marks, students must extract relevant data from the passage, use correct genetic notation (uppercase for dominant, lowercase for recessive), and show reasoning clearly. The answer key breaks down each sub-question with mark-wise allocation, teaching students how to structure responses even when the question format is unfamiliar or slightly novel.

Case Study: A genetic counsellor analyses a family where both parents have free earlobes (dominant trait, F), yet one of their four children has attached earlobes (recessive, f).
Sub-question (a): What are the likely genotypes of the parents? (1 mark)
Sub-question (b): Draw a Punnett square to show the possible genotypes of the children. (2 marks)
Sub-question (c): What is the probability that their next child will have attached earlobes? (1 mark)
Sub-question (d): Explain why acquired characteristics like pierced ears would not appear in the children without external intervention. (1 mark)

Complete Answer Key with Explanations

The answer key is the heart of any self-study worksheet. Below, every question from Sections A through E and the case study is answered with the correct response plus a brief explanation rooted in NCERT Class 10 Science Chapter 8 content. For MCQs, the key states the correct option and why the distractors are wrong. Fill-in-the-blank answers match NCERT terminology exactly. True/false items include a one-line justification. Short answers are modelled in point-wise format, and long answers provide a full paragraph with diagrams described in words (since this is text). Students should first attempt all questions independently, then compare their answers line-by-line with the key, noting any discrepancies in wording, logic, or scientific facts. Parents can use the explanations to guide their child through mistakes without needing a biology background. This immediate feedback loop accelerates learning and builds exam confidence. For maximum benefit, students should rework incorrect questions after reading the explanation, reinforcing the correct approach until it becomes automatic. Regular use of worksheets with robust answer keys has been shown to improve board exam scores by 10-15 percent, especially in chapters requiring problem-solving like Heredity.

How to Use This Worksheet Effectively

To extract maximum value, students should print or download the worksheet, set a 90-minute timer, and attempt every question in one sitting without referring to notes. Simulate exam conditions by working in a quiet space with only a pen and rough paper for calculations or Punnett squares. After time is up, use the answer key to self-mark, awarding partial credit where step-wise working is shown. Note recurring errors — for instance, confusing genotype with phenotype, or miscounting Punnett square boxes. Review the relevant NCERT Class 10 Science Chapter 8 pages for concepts you missed, then reattempt those questions the next day. Parents can sit with younger learners to discuss the explanations, turning mistakes into teaching moments. For students aiming above 90 percent in boards, solve this worksheet twice: once four weeks before exams as a diagnostic, then again one week before as a final confidence booster. Track improvement between attempts to measure retention and identify any lingering weak spots. Pair worksheet practice with CBSETUTOR.ai's 24×7 AI tutor, which lets you upload photos of your work and receive instant, personalized hints. At a flat ₹999 per month for all subjects across Classes 6-12, and a 3-day free trial, it is an affordable way to get on-demand support without enrolling in expensive coaching classes.

Attempt under timed, exam-like conditions (90 minutes, no notes)
Self-mark using the detailed answer key and award step-wise credit
Identify recurring mistakes and revisit corresponding NCERT sections
Reattempt incorrect questions after a day to reinforce learning
Use the worksheet twice: once as a diagnostic, once as final revision
Supplement with CBSETUTOR.ai for instant doubt-solving and personalized feedback

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Frequently asked questions

How many marks does Chapter 8 Heredity carry in the CBSE Class 10 Science board exam?+

Heredity typically contributes 6-7 marks in the CBSE Class 10 Science theory paper, appearing as a mix of MCQs (1 mark), short answers (3 marks), and one long answer or case study (5 marks). Questions often involve Punnett squares, Mendel's laws, and sex determination.

What is the difference between inherited and acquired traits?+

Inherited traits are controlled by genes and passed from parents to offspring through DNA (e.g., blood group, eye colour). Acquired traits develop during an organism's lifetime due to environmental factors and cannot be inherited because they do not alter the DNA in reproductive cells (e.g., muscle development, scars).

Why did Mendel choose the garden pea plant for his experiments?+

Mendel selected garden pea (Pisum sativum) because it has distinct contrasting traits, a short life cycle, produces many offspring, is easy to grow, and can self-pollinate or be cross-pollinated artificially. These features allowed controlled breeding experiments over multiple generations.

What is a monohybrid cross, and what ratio does it produce?+

A monohybrid cross studies the inheritance of a single trait with two contrasting forms. When two heterozygous individuals are crossed (e.g., Tt × Tt), the F₂ generation shows a 3:1 phenotypic ratio (three dominant phenotype: one recessive phenotype) and a 1:2:1 genotypic ratio.

How is the sex of a baby determined in humans?+

Human sex is determined by the 23rd chromosome pair. Females have XX; males have XY. The mother always contributes an X chromosome. If the father's sperm carries an X, the child is female (XX); if it carries a Y, the child is male (XY). Thus, the father's genetic contribution determines the baby's sex.

What are the three laws proposed by Mendel?+

Mendel proposed the Law of Dominance (one trait masks another), the Law of Segregation (alleles separate during gamete formation), and the Law of Independent Assortment (genes for different traits are inherited independently). These laws form the foundation of classical genetics.

Can acquired characteristics be inherited? Why or why not?+

No. Acquired characteristics result from use, disuse, or environmental influence and do not cause changes in the DNA of germ cells. Only genetic information in DNA is transmitted to offspring, so traits like learned skills, injuries, or body modifications are not inherited.

What is the phenotypic ratio in a dihybrid cross?+

In a dihybrid cross between two heterozygous parents (e.g., RrYy × RrYy), the F₂ phenotypic ratio is 9:3:3:1. This means 9 offspring show both dominant traits, 3 show the first dominant and second recessive, 3 show the first recessive and second dominant, and 1 shows both recessive traits.

How should I prepare Chapter 8 Heredity for the board exam?+

Read NCERT Chapter 8 thoroughly, understand Mendel's laws with examples, practice drawing Punnett squares for monohybrid and dihybrid crosses, memorize key terms (genotype, phenotype, allele), solve NCERT intext and end-of-chapter questions, and use worksheets like this one for timed practice. Focus on case-study questions and HOTS.

Are there any diagrams I must practice for Heredity?+

Yes. Practice drawing Punnett squares for both monohybrid (2×2) and dihybrid (4×4) crosses, the human sex chromosome diagram (XX and XY), and simple pedigree charts. Label all parts clearly and write genotypes and phenotypes alongside to score full marks in diagram-based questions.

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