Sexual reproduction in Volvox is

The correct option is Oogamous.

To understand why sexual reproduction in Volvox is oogamous, let us break down the types of sexual reproduction found in algae and examine the specific process in Volvox:

1. Understanding Sexual Reproduction Types:
In algae, sexual reproduction can be classified into three main types based on the morphology and behavior of the gametes:
- Isogamous: Fusion of gametes that are similar in size and structure (e.g., both motile or both non-motile).
- Anisogamous: Fusion of gametes that differ in size (usually the male gamete is smaller and the female gamete is larger), but both may still be motile.
- Oogamous: Fusion between a small, highly motile male gamete (spermatozoid or antherozoid) and a large, non-motile female gamete (egg or oosphere).

2. Sexual Reproduction in Volvox:
- Volvox is a hollow, spherical colony of green algae.
- During its sexual phase, specialized cells differentiate into male and female reproductive structures.
- The male structures produce small, spindle-shaped, biflagellate, motile male gametes (antherozoids).
- The female structures produce a single large, round, non-motile female gamete containing food reserves (egg or oosphere).
- The motile male gamete swims to and fertilizes the non-motile female gamete within the colony to form a diploid zygote.

Because this process involves a small, motile male gamete fusing with a large, non-motile female gamete, it is a classic example of oogamous reproduction.