Seed Habit in Plants
The seed habit is a crucial evolutionary development in the plant kingdom. It provides several advantages for survival and reproduction.
Origin of Seed Habit
- Gymnosperms: The first group of plants to develop seeds are gymnosperms. This group includes conifers and cycads, which appeared during the Mesozoic era.
- Characteristics: Gymnosperms produce seeds that are not enclosed in an ovary. Instead, they develop on the surface of scales or leaves, typically in cones.
Importance of Seeds
- Protection: Seeds provide a protective covering for the embryo, ensuring its safety from environmental hazards and predation.
- Nutrient Supply: Seeds contain stored food, which supports the embryo during its early growth stages.
- Dispersal Mechanisms: Seeds can be dispersed by wind, water, or animals, allowing plants to colonize new areas effectively.
Comparison with Other Groups
- Pteridophytes: These plants reproduce via spores, lacking seeds altogether. Their reproductive mechanisms are less efficient than those of seed plants.
- Cycadofilicales: This is an extinct group, part of the gymnosperms, and while they had seed-like structures, true seeds were fully developed only in later gymnosperms.
- Angiosperms: Although angiosperms (flowering plants) are the most advanced in seed development, they evolved after gymnosperms.
Conclusion
In conclusion, the seed habit was first established in gymnosperms, making option 'D' the correct answer. This evolutionary development marked a significant leap in plant adaptation and success on land, leading to the diverse flora we see today.