**Oogamous Sexual Reproduction in Volvox**

**Introduction:**
Volvox is a colonial green algae that exhibits a complex life cycle and sexual reproduction. It is a multicellular organism composed of numerous individual cells that are interconnected to form a spherical colony.

**Types of Sexual Reproduction:**
There are three types of sexual reproduction commonly found in algae, including Volvox:

**1. Isogamous Reproduction:**
In isogamous reproduction, the gametes are morphologically similar and indistinguishable. They are usually motile and flagellated. However, Volvox does not undergo isogamous reproduction.

**2. Anisogamous Reproduction:**
In anisogamous reproduction, the gametes are morphologically different. There are two types of gametes: smaller non-motile gametes (eggs) and larger motile gametes (sperm). They are involved in the fertilization process. However, Volvox does not undergo anisogamous reproduction.

**3. Oogamous Reproduction:**
In oogamous reproduction, the gametes are morphologically distinct. There are two types of gametes: smaller non-motile eggs and larger motile sperm. The sperm is usually flagellated and actively moves towards the egg for fertilization. Volvox undergoes oogamous reproduction.

**Oogamous Reproduction in Volvox:**
Volvox exhibits oogamous reproduction, where the female colonies produce eggs and the male colonies produce sperm. The male colonies release their sperm into the surrounding water, and the sperm actively swim towards the female colonies. The sperm then fuse with the eggs to form zygotes. The zygotes develop into new colonies that are released from the parent colonies.

This type of sexual reproduction ensures genetic diversity among the offspring and increases the chances of successful reproduction. It also allows for the exchange of genetic material between different colonies, contributing to the overall genetic variation within the species.

In conclusion, the correct answer is option 'c' - oogamous. Volvox exhibits oogamous sexual reproduction, where female colonies produce eggs and male colonies produce sperm. The sperm actively swim towards the eggs for fertilization, resulting in the formation of zygotes and the development of new colonies.