Question

The fusion of male and female gametes which are similar in size, shape, structure and behaviour is termed as
A. Oogamous
B. Anisogamous
C. Conjugation
D. Isogamous

Answer 1

Hint:
 Male and female gametes will fuse to give the progeny in the female body. The male egg has to travel to female gametes to fertilize. Their size, shape, characters will reflect in the daughter cells. The genes are transferred to the progeny.

Complete answer:
Fusion of male and female gametes give birth to an embryo that forms the offspring. The characters of the parents are passed down to the daughter cells.
Let us know the terms in the options:
> Option A: Oogamous: In the oogamy, the female egg is larger than the male sperm. Female eggs are non-motile here. Male sperm is motile which competes for fertilization.
> Option B: Anisogamous: In anisogamy, there is a fusion of two dissimilar and separate gametes. In gametophytes, the gametes are non-motile. The larger one is the female gamete and the smaller one is the male.
> Option C: Conjugation: It is the transfer of sexual eggs in the bacteria via a bridge-like structure. It is the horizontal transfer of genes. Transduction and transformation are the other two methods in bacterias for gene exchange.
> Option D: Isogamous: As the word ‘iso’ says similar, the gametes in this are similar to each other in the aspect of their size, shape, structure, behaviour etc., having similar morphology. It happens in some algae and fungi.

So the answer is option D: Isogamous.

Note:
 In isogamy, both the gametes can either be flagellated (motile) or can be non-motile. It was the first step observed in sexual reproduction. Organisms evolved to have oogamy, which is seen in humans now. In isogamy, there are + and – strains which are called mating types, only different mating types can fertilize to form an embryo.