Q36
2 marksShort AnswerSection B

Draw in sequence (showing the four stages), the process of binary fission in Amoeba.

Also asked in:2017
How do Organisms Reproduce?
Fission
Official Answer

The process of binary fission in Amoeba occurs in a sequence of four distinct stages. Since Amoeba is a unicellular organism with no fixed body orientation, this splitting can take place in any plane.


Sequential Stages of Binary Fission in Amoeba:


  1. Stage 1: Parent Cell (Preparation)
  • The parent Amoeba reaches maturity. It withdraws its pseudopodia, becomes rounded, and prepares for division with a distinct nucleus.

  1. Stage 2: Karyokinesis (Nuclear Division)
  • The nucleus of the cell begins to elongate. The genetic material (DNA) is replicated and distributed as the nucleus stretches.

  1. Stage 3: Cytokinesis (Cytoplasmic Division)
  • A constriction begins to develop in the cell membrane and cytoplasm. The elongated nucleus divides into two separate nuclei, each moving towards opposite poles.

  1. Stage 4: Daughter Cells Formation
  • The constriction deepens and completely pinches off the cytoplasm. This results in the formation of two independent, identical daughter Amoebae, each containing its own nucleus and cellular apparatus.


KaryokinesisCytokinesisSeparationStage 1: Parent Amoeba - Irregular shape - Single distinct nucleusStage 2: Nuclear Division - Nucleus elongates - DNA replication completeStage 3: Cytoplasmic Constriction - Cell membrane pinches inward - Nucleus divides into twoStage 4: Two Daughter Cells - Cytoplasm completely divides - Two independent Amoebae
Binary fissionAmoebaNucleus elongationCytoplasm constrictionDaughter cells

Marking Scheme

  • 1Stage 1: Draw parent Amoeba with a distinct nucleus (0.5 marks)
  • 2Stage 2: Draw elongation of the nucleus (0.5 marks)
  • 3Stage 3: Draw constriction of cytoplasm and nuclear division (0.5 marks)
  • 4Stage 4: Draw two separate daughter cells (0.5 marks)

Hint

Start with a single cell, show the nucleus stretching like a dumbbell, then show the cell body pinching in the middle, and finally draw two separate cells.

Quick Oral Answer

Binary fission in Amoeba is a type of asexual reproduction where a single parent cell divides into two equal daughter cells. First, the nucleus elongates and divides, followed by the constriction and division of the cytoplasm.

Analysis & Explanation

Binary fission in Amoeba is a simple asexual reproduction method. Unlike Leishmania, which has a whip-like structure and divides in a definite orientation, Amoeba has an irregular body design and can split in any plane. The division of the nucleus (karyokinesis) always precedes the division of the cytoplasm (cytokinesis).

Common Mistakes

  1. 1Drawing the division in a fixed vertical or horizontal plane (Amoeba can divide in any plane).
  2. 2Dividing the cytoplasm before the nucleus has fully elongated and split.

Interesting Facts

Because the parent Amoeba simply splits to become two new daughter cells, the original parent cell never actually 'dies' of old age, making unicellular organisms like Amoeba biologically immortal!

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2017?

This question carries 2 marks in the CBSE Class 10 Science 2017 examination.

Which chapter does this question come from in Science?

This question is from the chapter "How do Organisms Reproduce?" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Fission" from CBSE Class 10 Science.

Has this question appeared in other CBSE Science papers?

Yes, a similar question appeared in the 2017 CBSE Class 10 Science paper.

What type of question is this in the CBSE Class 10 Science 2017 paper?

This is a Short Answer question from Section B in the CBSE Class 10 Science 2017 paper.