CBSE Class 11 Biology Exemplar NCERT Solutions: Cell Cycle and Cell Division

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NCERT Solutions PDF Class 11 PDF

This resource provides detailed NCERT Solutions for CBSE Class 11 Biology Exemplar, Chapter 10: Cell Cycle and Cell Division. It covers key concepts related to meiosis and mitosis, including the stages, purposes, and outcomes of these fundamental cell processes. The solutions explain how meiosis leads to gamete formation, genetic variation, and chromosome number reduction, while mitosis ensures equal cell division for growth and asexual reproduction. Understanding these processes is crucial for comprehending inheritance and organismal development. These solutions offer step-by-step explanations and clear answers to help students grasp complex topics, revise effectively, and prepare for their examinations.

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Quick info

BoardCBSE
ClassClass 11
SubjectBiology Exemplar
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 10

Chapter summary

Chapter 10 of the CBSE Class 11 Biology Exemplar focuses on the Cell Cycle and Cell Division. The NCERT Solutions provided here clarify the processes of mitosis and meiosis. They detail the significance of each type of division, including chromosome behavior, genetic variation, and the maintenance of chromosome number across generations. This chapter is essential for understanding reproduction and growth at the cellular level.

Learning outcomes

  • Understand the purpose and outcome of meiosis in diploid organisms.
  • Identify the stage in meiosis where the genetic constitution of gametes is determined.
  • Differentiate between meiosis and mitosis.
  • Explain the events occurring during Anaphase-I of meiosis.
  • Recognize that meiosis is associated with sexual reproduction.

Topics covered

Paper topics

  • Cell Cycle
  • Cell Division
  • Mitosis
  • Meiosis
  • Chromosome Number
  • Gamete Formation
  • Genetic Variation
  • Anaphase I
  • Sexual Reproduction
  • Vegetative Reproduction
  • Reduction Division
  • Equal Division

Important topics

  • Meiosis and its significance
  • Stages of Meiosis
  • Mitosis vs. Meiosis
  • Role of Anaphase I
  • Genetic constitution of gametes
  • Chromosome number maintenance

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Questions and Solutions

Q. 1

Meiosis in diploid organisms results in:
  1. production of gametes
  2. reduction in the number of chromosomes
  3. introduction of variation
  4. All of the above
Solution: Meiosis is a specialized type of cell division that occurs in sexually reproducing organisms. It leads to the production of gametes (sperm and egg cells), which are haploid, meaning they contain half the number of chromosomes as the parent diploid cell. This reduction in chromosome number is essential for maintaining the species' characteristic chromosome count after fertilization. Furthermore, during meiosis, processes like crossing over and independent assortment of homologous chromosomes occur, which shuffle the genetic material and introduce genetic variations in the gametes. These variations are vital for the evolution and adaptation of species. Therefore, all the listed outcomes are characteristic features of meiotic cell division.

Answer: (d) All of the above

Q. 2

At which stage of meiosis does the genetic constitution of gametes is finally decided?
  1. Metaphase-I
  2. Anaphase-II
  3. Metaphase-II
  4. Anaphase-I
Solution: The genetic constitution of the gametes is finally determined during Anaphase-I of meiosis. In this stage, homologous chromosomes separate and move towards opposite poles. Each chromosome still consists of two sister chromatids. The specific combination of chromosomes that moves to each pole will form the genetic makeup of the daughter cells, which will eventually develop into gametes. While Anaphase-II involves the separation of sister chromatids, the fundamental decision about which homologous chromosomes go to which daughter cell is made in Anaphase-I. Metaphase stages involve the alignment of chromosomes on the metaphase plate, not the final segregation of genetic material.

Answer: (d) Anaphase-I

Q. 3

Meiosis occurs in organisms during:
  1. sexual reproduction
  2. vegetative reproduction
  3. Both (a) and (b)
  4. None of these
Solution: Meiosis is a specialized cell division process that is intrinsically linked to sexual reproduction. Its primary role is to produce haploid gametes (like sperm and eggs) from diploid germ cells. The fusion of these haploid gametes during fertilization restores the diploid chromosome number in the offspring. Vegetative reproduction, on the other hand, is a form of asexual reproduction where new individuals arise from vegetative parts of the parent plant (like stems, roots, or leaves) and does not involve gamete formation or fusion. Therefore, meiosis occurs only during sexual reproduction.

Answer: (a) sexual reproduction

Q. 4

During Anaphase-I of meiosis:
  1. homologous chromosomes separate
  2. non-homologous autosomes separate
  3. sister chromatids separate
  4. non-sister chromatids separate
Solution: Anaphase-I is a critical stage in meiosis I. During this phase, the homologous chromosomes, which are paired up during the preceding stages, are pulled apart by the spindle fibers and move towards opposite poles of the cell. Each chromosome at this point still consists of two sister chromatids attached at the centromere. The separation of non-homologous autosomes or sister chromatids occurs in mitosis or Anaphase-II of meiosis, respectively.

Answer: (a) homologous chromosomes separate

Q. 5

Mitosis is characterised by:
  1. reduction division
  2. equal division
  3. Both (a) and (b)
  4. pairing of homologous chromosomes
Solution: Mitosis is a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth. This is why it is referred to as an 'equal division'. In contrast, meiosis is known as 'reduction division' because it reduces the chromosome number by half. The pairing of homologous chromosomes (synapsis) is characteristic of Prophase-I of meiosis, not mitosis.

Answer: (b) equal division

Common mistakes

  • Confusing the stages of meiosis and mitosis.
  • Incorrectly identifying the stage where genetic constitution is finalized.
  • Misunderstanding the role of meiosis in sexual reproduction versus mitosis in asexual reproduction.
  • Confusing homologous chromosome separation with sister chromatid separation.

Revision tips

  • Focus on the key differences between meiosis and mitosis.
  • Memorize the specific events of each meiotic stage, especially Anaphase-I.
  • Relate the process of meiosis to its outcome: gamete formation and genetic variation.
  • Use diagrams to visualize chromosome movement during different cell division stages.

Practice MCQs

Q1. Meiosis in diploid organisms is primarily responsible for:

Q2. The genetic makeup of gametes is finally determined during which phase of meiosis?

Q3. Meiosis is a characteristic process occurring in organisms during:

Q4. What is the key event during Anaphase-I of meiosis?

Q5. Mitosis is best described as:

Frequently asked questions

What is the main purpose of meiosis in diploid organisms?

Meiosis in diploid organisms is crucial for sexual reproduction. It produces haploid gametes (sperm and egg cells) by reducing the chromosome number by half, and it also introduces genetic variation through processes like crossing over and independent assortment.

Which stage of meiosis is critical for deciding the genetic makeup of gametes?

Anaphase I of meiosis is the stage where the genetic constitution of gametes is finally decided. This is because homologous chromosomes separate, and their distribution into daughter cells determines the unique combination of genes each gamete will carry.

How does mitosis differ from meiosis?

Mitosis is an 'equal division' that produces two genetically identical diploid daughter cells, used for growth and repair. Meiosis is a 'reduction division' that produces four genetically different haploid cells (gametes) through two rounds of division, essential for sexual reproduction.

Does meiosis occur during vegetative reproduction?

No, meiosis does not occur during vegetative reproduction. Vegetative reproduction is a form of asexual reproduction that involves somatic cells and does not involve the formation or fusion of gametes. Meiosis is specifically linked to sexual reproduction.

What happens during Anaphase-I of meiosis?

During Anaphase-I of meiosis, homologous chromosomes separate from each other and move towards opposite poles of the cell. Importantly, the sister chromatids remain attached at their centromeres.

Why is meiosis important for maintaining chromosome number across generations?

Meiosis reduces the chromosome number by half in gametes. When these haploid gametes fuse during fertilization, the diploid chromosome number is restored in the zygote, ensuring that the chromosome number remains constant from one generation to the next.

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