Selaginella and Salvinia are considered to represent a significant step toward evolution of seed habit because

Options

A. Female gametophyte is free and gets dispersed like seeds
B. Female gametophyte lacks archegonia
C. Megaspores possess endosperm and embryo surrounded by seed coat
D. Embryo develops in female gametophyte which is retained on parent sporophyte

Answer

**Step-by-Step Solution:**

1. **Understanding Selaginella and Salvinia**: Both Selaginella and Salvinia are classified as heterosporous plants. This means they produce two different types of spores: microspores (male) and megaspores (female).

2. **Free Female Gamete**: In these plants, the female gamete is not dependent on water for fertilization and can disperse like seeds. This is a significant evolutionary advancement as it allows for greater reproductive success in varying environments.

3. **Lack of Archegonia**: The female gametophyte in Selaginella and Salvinia does not have archegonia, which are structures that typically house the egg in many other plant groups. This adaptation signifies a shift towards more advanced reproductive strategies.

4. **Presence of Endosperm**: The megaspores in these plants possess endosperm, which provides nutrition to the developing embryo. This is a crucial feature that is also found in seeds, indicating a step towards seed evolution.

5. **Embryo Development**: The embryo develops within the female gametophyte, which is retained on the parent sporophyte. This retention is significant as it allows the young embryo to receive nourishment and protection directly from the parent plant.

6. **Conclusion**: Therefore, Selaginella and Salvinia are considered to represent a significant step toward the evolution of seed habit because they exhibit features such as the development of the embryo within the female gametophyte retained on the parent sporophyte, the presence of endosperm, and the ability of the female gamete to disperse.

**Final Answer**: Selaginella and Salvinia represent a significant step toward the evolution of seed habit because the embryo develops in the female gametophyte, which is retained on the parent sporophyte.

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