Ch 3 classifies the plant kingdom from simplest (algae) to most complex (angiosperms), covering each group's characteristics, reproduction, and the concept of alternation of generations.
Algae: aquatic, autotrophic thallophytes. Chlorophyceae (green, freshwater), Phaeophyceae (brown, marine), Rhodophyceae (red, deep marine). Bryophytes: "amphibians of the plant kingdom" — depend on water for fertilisation. Liverworts (flat thalli) and mosses (leafy). Dominant phase: gametophyte.
Pteridophytes: first vascular plants (xylem + phloem). Ferns, horsetails. Dominant: sporophyte. Gymnosperms: naked seeds (not in fruit). Pinus, Cycas, Ginkgo. Angiosperms: seeds enclosed in fruit, have flowers. Monocots (one cotyledon, parallel veins) vs dicots (two cotyledons, reticulate veins). Angiosperms are dominant on Earth.
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Alternation of generations is a life cycle pattern where a multicellular diploid sporophyte (2n) alternates with a multicellular haploid gametophyte (n). Sporophyte produces spores (by meiosis) → spores grow into gametophyte → gametophyte produces gametes (by mitosis) → fertilisation → zygote → new sporophyte. In bryophytes, gametophyte dominates; in ferns and seed plants, sporophyte dominates.
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