Name the type of asexual reproduction in which two individuals are formed from a single parent and the parental identity is lost. Draw the initial and the final stages of this type of reproduction. State the event with which this reproduction starts.

Q: Name the type of asexual reproduction in which two individuals are formed from a single parent and the parental identity is lost. Draw the initial and the final stages of this type of reproduction. State the event with which this reproduction starts.

### 1. Type of Asexual Reproduction The type of asexual reproduction is **Binary Fission** (e.g., in *Amoeba*). In this process, a single-celled parent organism divides into two equal halves, and the parental identity is lost because the parent cell itself becomes the two new daughter cells. ### 2. Initial and Final Stages of Binary Fission Below is the representation of the initial and final stages of binary fission in *Amoeba*: ```diagram {"xrange": [-1.0, 1.0], "yrange": [-10.08, 1.08], "lines": [{"from": [0.0, 0.0], "to": [0.0, -3.0], "label": "Cell Division"}, {"from": [0.0, -3.0], "to": [0.0, -6.0], "label": ""}, {"from": [0.0, -3.0], "to": [0.0, -9.0], "label": ""}], "points": [{"x": 0.0, "y": 0.0, "label": "INITIAL STAGE\n(Parent Amoeba)\n- Single cell\n- Central nucleus\n- Cytoplasm"}, {"x": 0.0, "y": -3.0, "label": "FINAL STAGE\n(Two Daughter Cells)"}, {"x": 0.0, "y": -6.0, "label": "Daughter Cell 1\n(with nucleus)"}, {"x": 0.0, "y": -9.0, "label": "Daughter Cell 2\n(with nucleus)"}]} ``` * **Initial Stage:** A single parent *Amoeba* cell with an intact nucleus and cytoplasm. * **Final Stage:** Two separate, independent, and identical daughter cells, each containing its own nucleus and cellular apparatus. ### 3. Starting Event of Reproduction This reproduction starts with the **creation of a DNA copy** (DNA replication) through chemical reactions in the parent cell, which is accompanied by the creation of an additional cellular apparatus before the nucleus and cytoplasm divide.

How do Organisms Reproduce?

Fission

Official Answer

1. Type of Asexual Reproduction

The type of asexual reproduction is Binary Fission (e.g., in Amoeba). In this process, a single-celled parent organism divides into two equal halves, and the parental identity is lost because the parent cell itself becomes the two new daughter cells.

2. Initial and Final Stages of Binary Fission

Below is the representation of the initial and final stages of binary fission in Amoeba:

Initial Stage: A single parent Amoeba* cell with an intact nucleus and cytoplasm.

Final Stage: Two separate, independent, and identical daughter cells, each containing its own nucleus and cellular apparatus.

3. Starting Event of Reproduction

This reproduction starts with the creation of a DNA copy (DNA replication) through chemical reactions in the parent cell, which is accompanied by the creation of an additional cellular apparatus before the nucleus and cytoplasm divide.

Binary fissionAmoebaParent cellDaughter cellsDNA copyDNA copyingNucleus

Marking Scheme

1Naming the type of asexual reproduction (Binary Fission) (0.5 marks)
2Drawing/describing the Initial Stage (Parent cell with nucleus) (0.5 marks)
3Drawing/describing the Final Stage (Two separate daughter cells with nuclei) (0.5 marks)
4Stating the starting event (Creation of a DNA copy / DNA replication) (0.5 marks)

Hint

Think of a unicellular organism like Amoeba. When it reproduces, the single parent cell splits completely into two. The very first step of any reproduction is making a copy of the genetic material (DNA).

Quick Oral Answer

Binary fission is a type of asexual reproduction where a single parent cell divides into two equal, identical daughter cells. It starts with the replication of DNA, followed by nuclear division (karyokinesis) and then cytoplasmic division (cytokinesis). The parental identity is lost because the parent's body itself becomes the offspring.

Analysis & Explanation

According to the NCERT textbook, unicellular organisms like Amoeba reproduce via cell division or fission.

Binary Fission: In Amoeba, the splitting of the cell into two equal halves can take place in any plane. Since the parent cell completely divides to form two new daughter cells, the parent cell's individual identity is lost.
Starting Event: The text explicitly states that "a basic event in reproduction is the creation of a DNA copy." Cells use chemical reactions to build copies of their DNA. This is followed by the separation of the DNA copies, each with its own cellular apparatus, leading to cell division.

Common Mistakes

1Confusing binary fission with fragmentation. Fragmentation occurs in multicellular organisms with simple body designs (like Spirogyra), whereas binary fission occurs in unicellular organisms.
2Forgetting to draw or mention the nucleus in both of the final daughter cells.
3Stating that the process starts with cytoplasmic division instead of DNA copying.

Interesting Facts

While Amoeba can split in any plane during binary fission, other unicellular organisms like Leishmania (which causes kala-azar) have a whip-like structure at one end and must undergo binary fission in a definite orientation relative to this structure.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2015?

This question carries 2 marks in the CBSE Class 10 Science 2015 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.

What type of question is this in the CBSE Class 10 Science 2015 paper?

This is a Short Answer question from Section B in the CBSE Class 10 Science 2015 paper.