Origin of seed habit can be traced in pteridophytes

Explanation:

The correct statement among the given options is option 'D', which states that the origin of seed habit can be traced in pteridophytes. Let's understand why this statement is correct.

1. Introduction to Pteridophytes:
Pteridophytes are a group of vascular plants that reproduce and disperse through spores. They include ferns, horsetails, and clubmosses. These plants do not produce seeds; instead, they reproduce by releasing spores.

2. Origin of Seed Habit:
The seed habit is a significant evolutionary adaptation that allowed plants to colonize diverse terrestrial habitats. The origin of seed habit can be traced back to the pteridophytes. The first seed plants evolved from a group of pteridophytes known as the progymnosperms.

3. Characteristics of Pteridophytes:
Pteridophytes have certain characteristics that paved the way for the evolution of seed habit:

- Vascular Tissue: Pteridophytes possess specialized vascular tissues (xylem and phloem) that transport water, nutrients, and sugars within the plant.

- Sporophyte Dominance: Pteridophytes have a dominant sporophyte generation, which is the main photosynthetic and reproductive phase of the plant.

- Independent Gametophyte: Pteridophytes have an independent gametophyte phase. The gametophyte is a small, multicellular structure that produces gametes (sperm and egg) through mitosis.

4. Evolution of Seed Habit:
The evolution of seed habit in pteridophytes involved the following changes:

- Reduction in Gametophyte Dependency: The gametophyte generation became progressively reduced in size and dependent on the sporophyte generation.

- Heterospory: Pteridophytes evolved heterospory, where two types of spores (microspores and megaspores) are produced. This allowed for the development of male and female gametophytes.

- Embryo Protection: The female gametophyte, also known as the megagametophyte, became enclosed within sporophytic tissues, providing protection and nourishment to the developing embryo.

- Seed Formation: The fertilized egg within the megagametophyte develops into an embryo, and seed coats develop around it. The seed contains the embryo, stored food, and protective coverings.

5. Significance of Seed Habit:
The evolution of the seed habit in pteridophytes provided several advantages:

- Protection and Dispersal: Seeds offer protection to the developing embryo and provide a means for dispersal, allowing plants to colonize new habitats.

- Dormancy: Seeds can enter a dormant state, enabling them to withstand unfavorable conditions and germinate when suitable environmental conditions are met.

- Nutrient Reserve: Seeds contain stored food reserves, ensuring a good start for the germinating embryo.

In conclusion, the statement that the origin of seed habit can be traced in pteridophytes is correct. Pteridophytes played a crucial role in the evolutionary transition from spore-based reproduction to seed