BIOL 2200 Lecture Notes - Lecture 18: Seed Dispersal, Gametophyte, Double Fertilization

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Key innovation: flowers: specialized shoots with up to 4 types of modified leaves. Sepals cover flower buds and protect them. Stamens comprised of anther and filament (male part) Carpal made of stigma ( that accepts pollen), style (supports stigma) and ovule (where fruit grows: provides more species specific breeding systems, flowers lead to effective pollen transfer. Key innovation: fruits: development of ovary wall; thickens around seed and becomes fruit, protects seed, aids in dispersal, fruits also include nuts and not all fruits are edible. Derived traits in life cycle: microspores: male gametophytes with 2 haploid cells. Microspores, through cell division, becomes male gametes. One haploid cell forms 2 sperm, while the other haploid cell forms tube cells: megaspore: female gametophyte with a few cells. Derived traits in life cycle: double fertilization (advance) Pollen enters ovule, 2 sperm cells release and one fertilizes the egg.

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