Section 1B Concise

Key Concepts:
- Seeds and pollen grains as adaptations for land life.
- Gymnosperms have "naked seeds" on cones.
- Angiosperms use flowers and fruits in reproduction.
Evolution of Seed Plants:
- Seeds emerged ~360 million years ago, revolutionizing plant evolution.
- Key for dispersal (by wind, etc.) and dominance in ecosystems.
Seed Structure:
- Composed of an embryo, nutrients, and a protective coat.
- Dandelion seeds have a pappus for wind dispersal.

Reduced Gametophytes:
- Gametophytes are microscopic and develop within parent sporophyte tissues, providing protection and nutrition.
Heterospory:
- Seed plants produce two types of spores: megaspores (female) and microspores (male).
- Megasporangia yield one megaspore, while microsporangia yield many microspores that develop into pollen.
Ovules:
- Comprises a megasporangium and protective integuments.
- Female gametophyte develops in the ovule producing eggs.
Pollen:
- Encloses male gametophytes and is resistant to environmental challenges, eliminating the need for water in reproduction.
- Pollen grain germination leads to sperm delivery via a pollen tube.

Definition:
- Gymnosperms: "naked seeds" typically housed in cones (strobili).
- Main groups: Cycadophyta, Ginkgophyta, Gnetophyta, and Coniferophyta (cone-bearing).

Characteristics:
- Classified under phylum Anthophyta, distinguished by flowers and fruits.
- Angiosperms are the most diverse plant group (~90% of species).
Flowers:
- Structure for sexual reproduction, with features that attract pollinators.
- Composed of sepals, petals, stamens, and carpels.
Pollination:
- Pollen transfer mechanisms favor cross-pollination, enhancing genetic variability.
Fruits:
- Formed from ovary wall thickening post-fertilization, providing protection and aiding in seed dispersal.
- Various adaptations exist to assist seed movement by wind, water, or animals.