Aquatic ancestry of bryophytes is evidenced by :-

Options

A. Their green colour
B. thread like protonema
C. Many aquatic bryophytes
D. Flagellted male gametes

Answer

**Step-by-Step Solution:**

1. **Understanding Bryophytes**: Bryophytes are non-vascular plants, commonly known as mosses, liverworts, and hornworts. They are considered to be the first land plants, but they have retained some characteristics that suggest an aquatic ancestry.

2. **Aquatic Ancestry Evidence**: The aquatic ancestry of bryophytes is evidenced by several key features:
- **Flagellated Male Gametes**: Bryophytes produce male gametes (sperm) that are flagellated, meaning they have tails that allow them to swim. This characteristic indicates a reliance on water for reproduction, as these sperm must swim through water to reach the female gametes.
- **Need for Water in Reproduction**: Bryophytes require a moist environment for fertilization to occur. The sperm must swim through water to fertilize the egg, which is enclosed in the female reproductive structure called the archegonium.
- **Protonema Stage**: The thread-like protonema is the first stage of development in bryophytes after the spore germinates. This structure is often found in aquatic environments, further supporting their aquatic ancestry.

3. **Conclusion**: The combination of these features—flagellated male gametes, the necessity of water for fertilization, and the presence of a protonema—strongly supports the idea that bryophytes have an aquatic ancestry.

4. **Final Answer**: The aquatic ancestry of bryophytes is evidenced by their flagellated male gametes, which require water for movement and fertilization.

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