Question

A student drew the following diagram upon observing a permanent slide of binary fission in Amoeba. Identify the fault in the diagram.

 

Answer 1

Hint: We have studied earlier that Amoeba is a unicellular protozoan that reproduces asexually through binary fission. Binary fission is a method of asexual reproduction, in which a single parent cell divides equally giving rise to two identical daughter cells capable of growing up to the size of parent cell. During binary fission the genetic material (nucleus) of the parent cell divides equally which is followed by cytokinesis.

Complete answer:
First we will discuss the steps involved in binary fission.
1. The genetic material, DNA, is compactly packed.
2. Replication of DNA, ribosomes, and plastids occurs.
3. The size of the cell increases as it prepares for dividing and the two strands of DNA move to the opposite sides.
4. New cell wall starts developing or constriction of cytoplasm occurs beginning the separation of the parent cell.
5. The cell wall is formed dividing the two daughter cells equally.
6. The two daughter cells separate as different individuals.

Now, we can say that during binary fission in Amoeba the nucleus divides into two and moves towards opposite sides. This is followed by the constriction of cytoplasm resulting in the formation of two daughter cells (cytokinesis).
The given diagram depicts constriction of cytoplasm before replication of the nucleus, which is wrong as the cell divides only after nuclear division has taken place.

Note:
Many organisms including bacteria, Amoeba, Paramecium etc. reproduce asexually through binary fission. In this first the nucleus division takes place followed by the division of cytoplasm.