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Significance of Mitosis & Meiosis | Class 11 Notes, MCQs

Significance of Mitosis & Meiosis | Class 11 Notes, MCQs 

Educational diagram comparing mitosis and meiosis stages showing chromosome division and formation of daughter cells.
Comparison of Mitosis and Meiosis showing stages of cell division and chromosome behavior in Class 11 Biology.

- Dr.Sanjaykumar Pawar 

🌿 Significance of Mitosis (Equational Division)

  • Mitosis is a type of cell division where one cell forms two identical daughter cells.
  • It is also called equational division because chromosome number remains the same.
  • Mostly occurs in diploid (2n) cells.
  • In some lower plants and social insects, even haploid cells can undergo mitosis.

📌 Main Importance of Mitosis

  • Mitosis produces genetically identical daughter cells (same DNA as parent cell).
  • It is responsible for growth of multicellular organisms.
  • As cells grow, the nucleus-cytoplasm ratio gets disturbed.
  • So, mitosis helps to restore proper nucleus–cytoplasm balance.

🌱 Role in Growth and Repair

  • Mitosis helps in increase in number of cells → growth of body.
  • It is essential for repair and replacement of worn-out cells.
  • Examples:
    • Cells of skin (epidermis) are continuously replaced.
    • Cells lining the gut (intestine) are regularly renewed.
    • Blood cells are continuously produced in bone marrow.

🌳 Mitosis in Plants

  • In plants, mitosis occurs in meristematic tissues.
  • Two main meristems:
    • Apical meristem → increases length (primary growth)
    • Lateral cambium → increases thickness (secondary growth)
  • This leads to continuous growth throughout plant life.

🧬 Introduction to Meiosis

  • Meiosis is a special type of cell division.
  • It produces gametes (sex cells) like sperm and egg.
  • It reduces chromosome number from diploid (2n) → haploid (n).

📌 Importance of Meiosis

  • It is essential for sexual reproduction.
  • It ensures formation of haploid gametes.
  • After fertilization, diploid number is restored.
  • Maintains constant chromosome number across generations.

🔑 Key Features of Meiosis

  • Two divisions occur:
    • Meiosis I
    • Meiosis II
  • Only one DNA replication occurs before division.
  • Homologous chromosomes pair up (synapsis).
  • Crossing over (recombination) occurs between non-sister chromatids.
  • Results in formation of 4 haploid daughter cells.

🔄 Stages of Meiosis

Meiosis I

  • Prophase I
  • Metaphase I
  • Anaphase I
  • Telophase I

Meiosis II

  • Prophase II
  • Metaphase II
  • Anaphase II
  • Telophase II

Below is a complete CBSE Class 11 NEET/Board exam practice set based on Mitosis & Meiosis covering all question types.

🧬 1. Very Short Answer Questions (1 Mark)

Q1. What is mitosis?

Ans: Mitosis is equational cell division producing two identical daughter cells.

Q2. What is meiosis?

Ans: Meiosis is reductional division forming four haploid cells from one diploid cell.

Q3. Where does mitosis occur in plants?

Ans: In meristematic tissues (apical and lateral cambium).

Q4. How many daughter cells are formed in meiosis?

Ans: Four haploid daughter cells.

Q5. What is crossing over?

Ans: Exchange of genetic material between non-sister chromatids during prophase I of meiosis.

✍️ 2. Short Answer Questions (2–3 Marks)

Q1. Write two differences between mitosis and meiosis.

Ans:

  • Mitosis: one division; Meiosis: two divisions
  • Mitosis: produces 2 diploid cells; Meiosis: produces 4 haploid cells

Q2. Why is mitosis important for multicellular organisms?

Ans:

  • Helps in growth of body
  • Repairs damaged tissues
  • Maintains nucleus-cytoplasm ratio

Q3. What is the significance of meiosis?

Ans:

  • Produces haploid gametes
  • Maintains chromosome number after fertilization
  • Introduces genetic variation

📘 3. Long Answer Questions (5 Marks)

Q1. Explain significance of mitosis.

Ans:

  • Produces genetically identical cells
  • Helps in growth of multicellular organisms
  • Maintains nucleus-cytoplasm ratio
  • Responsible for repair and regeneration
  • Continuous replacement of cells (skin, gut, blood)
  • Plant growth via meristematic tissues

Q2. Describe meiosis and its stages briefly.

Ans:

  • Meiosis is reduction division forming haploid cells
  • Two divisions: Meiosis I and II
  • Meiosis I reduces chromosome number
  • Meiosis II separates chromatids
  • Final result: 4 haploid cells
  • Stages: Prophase, Metaphase, Anaphase, Telophase (I & II)

🎯 4. MCQs (Multiple Choice Questions)

Q1. Mitosis results in:

A) Haploid cells
B) Four cells
C) Two identical diploid cells
D) Gametes
Ans: C

Q2. Meiosis occurs in:

A) Body cells
B) Germ cells
C) Skin cells
D) Muscle cells
Ans: B

Q3. Crossing over occurs in:

A) Metaphase I
B) Prophase I
C) Anaphase II
D) Telophase I
Ans: B

Q4. Number of divisions in meiosis:

A) One
B) Two
C) Three
D) Four
Ans: B

Q5. Mitosis helps in:

A) Gamete formation
B) Growth and repair
C) Fertilization
D) Reduction division
Ans: B

⚖️ 5. Assertion and Reason

Q1.

Assertion (A): Mitosis produces identical daughter cells.
Reason (R): Genetic material is equally distributed.

Ans: Both A and R are true and R is correct explanation.

Q2.

Assertion (A): Meiosis reduces chromosome number to half.
Reason (R): It involves two nuclear divisions.

Ans: Both A and R are true but R is not correct explanation.

Q3.

Assertion (A): Mitosis occurs in gamete formation.
Reason (R): Gametes are formed by reduction division.

Ans: A is false, R is true.

🧩 6. Fill in the Blanks

  1. Mitosis is also called ______ division.
    Ans: equational

  2. Meiosis produces ______ haploid cells.
    Ans: four

  3. Crossing over occurs in ______ I.
    Ans: Prophase

  4. Mitosis occurs in ______ cells.
    Ans: somatic

  5. Meiosis is important for ______ reproduction.
    Ans: sexual

📊 7. Match the Columns

Column A Column B
Mitosis Growth
Meiosis Gamete formation
Crossing over Prophase I
Apical meristem Plant growth
Reduction division Meiosis

Answers:

  • Mitosis → Growth
  • Meiosis → Gamete formation
  • Crossing over → Prophase I
  • Apical meristem → Plant growth
  • Reduction division → Meiosis

📚 8. Case Study Question

Case:

A student observed that skin cells are continuously replaced, but sperm cells are formed in testes through a different process that reduces chromosome number.

Questions:

Q1. Which type of division occurs in skin cells?
Ans: Mitosis

Q2. Which division forms sperm cells?
Ans: Meiosis

Q3. Why is meiosis important in sperm formation?
Ans: It reduces chromosome number to haploid state

Q4. What would happen if meiosis did not occur?
Ans: Chromosome number would double after fertilization . 


🔗INTERNAL LINKS 

/class11-biology-cell-cycle-and-cell-division

/mitosis-vs-meiosis-differences-chart

/neat-biology-important-mcqs-cell-division

/gametogenesis-in-plants-and-animals

/ncert-class11-biology-notes

Mitosis & Meiosis Mind Map

Cell Division Mind Map (NEET)

  • Cell Division
    • Mitosis (Equational Division)
      • Definition: One cell → Two identical daughter cells
      • Occurs in:
        • Diploid cells (mostly)
        • Some haploid cells (lower plants, insects)
      • Significance:
        • Growth of organism
        • Cell repair and replacement
        • Maintains nucleus-cytoplasm ratio
      • Examples:
        • Skin epidermis cells
        • Gut lining cells
        • Blood cells formation
        • Plant meristems (apical & lateral)
    • Meiosis (Reduction Division)
      • Definition: Diploid cell → Four haploid cells
      • Purpose:
        • Formation of gametes
        • Sexual reproduction
        • Maintains chromosome number across generations
      • Key Features:
        • Two divisions: Meiosis I & II
        • One DNA replication only
        • Crossing over occurs
        • Produces 4 haploid cells
      • Stages:
        • Meiosis I:
          • Prophase I
          • Metaphase I
          • Anaphase I
          • Telophase I
        • Meiosis II:
          • Prophase II
          • Metaphase II
          • Anaphase II
          • Telophase II
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