Question

A protozoan reproduces by binary fission. What will be the number of protozoans in its population after six generations?
A) $128$
B) $24$
C) $64$
D) $32$

Answer 1

Binary fission is the division of a single entity into two or more parts and the regeneration of these parts to separate entities which is similar to the original. The object undergoing fission is usually a cell. The fission can either be binary fission where a single organism produces two parts or multiple fission where a single organism produces multiple parts.

Complete answer:
Organisms that belong to the domains of Archaea and Bacteria reproduce by binary fission. This form of asexual reproduction and cell division is used by some organelles within eukaryotic organisms like mitochondria. Binary fission results in the production of a living prokaryotic cell by dividing the cell into two parts, each of which has the potential to grow to the size of the original.

By binary fission, an individual protozoan can divide into two. Hence, the number of protozoans in its population after six generations is calculated in the following way,
$1st{\text{ division}} - {\text{ }}1 \to 2$
$2nd{\text{ division}} - {\text{ }}2 \to 4$
$3rd{\text{ division}} - {\text{ }}4 \to 8$
$4th{\text{ division}} - {\text{ }}8 \to 16$
$5th{\text{ division}}{\text{ }}16 \to 32$
$6th{\text{ division}} - {\text{ }}32 \to 64$
Hence, the number of protozoans in its population after six generations is found to be sixty-four.
Therefore, we can come to the conclusion options A, B and C are incorrect.

So, the correct answer is option C which is $64$.

Note: Protozoan is an informal term for a group of single-celled eukaryotes, which can either be free-living or parasitic, that feeds on organic matter like other microorganisms or organic tissues and debris. Few examples of protozoa are Amoeba, Paramecium, Euglena and Trypanosoma. Many protozoans can also exchange genetic material by a sexual process usually, by conjugation, but this is decoupled from the process of reproduction and does not immediately result in the increase in population.