Prothallus is

Options

A. small, multicellular, free living, photosynthetic thalloid sporophyte
B. small, multicellular, free living, photosynthetic gametophyte
C. large, multicellular, free-living, photosynthetic thalloid gametophyte
D. large, multicellular, free living, non photosynthetic sporophyte

Answer

**Step-by-Step Solution:**

1. **Understanding the Term "Prothallus":**
- Prothallus, also known as Prothallium, is derived from Latin and Greek roots. The Latin word "pro" means "forward," and the Greek word "thallos" means "twig." This indicates that the term refers to a small, forward-growing structure.

2. **Identifying the Life Stage:**
- Prothallus represents the gametophyte stage in the life cycle of ferns and other pteridophytes. This is crucial as it distinguishes it from the sporophyte stage.

3. **Characteristics of Prothallus:**
- Prothallus is a small, multicellular structure.
- It is photosynthetic, meaning it can perform photosynthesis to produce its own food.
- It is free-living, which means it does not depend on the sporophyte for sustenance.

4. **Evaluating the Options:**
- Option 1 describes it as a "small, multicellular, free living, photosynthetic thaloid sporophyte." This is incorrect because it refers to it as a sporophyte instead of a gametophyte.
- Option 2 describes it as "small, multicellular, free living, photosynthetic gametophyte." This matches our understanding of prothallus and is therefore correct.
- Options 3 and 4 describe it as "large," which contradicts the known characteristics of prothallus.

5. **Conclusion:**
- The correct answer is Option 2: "small, multicellular, free living, photosynthetic gametophyte."

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