BIOL 225 Study Guide - Midterm Guide: Seed Dormancy, Mycorrhiza, Stratum Basale
17 Sep 2018
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Lifeless terrestrial surface for first 3 billion years. 500mya, small plants, fungi, and animals emerged on land. Since colonizing land, plants have diversified into 290,000 species. Charophytes (green algae) closest relatives of land plants. Circular rings of proteins that synthesize cellulose. Sporopollenin: protects zygote from drying in charophytes and protects gametophytes in land plants. Plant life cycle: gametophyte produces haploid gametes via mitosis, gametes unite to form diploid zygote, zygote develops into multicellular diploid sporophyte, sporophyte produces haploid spores via meiosis, spores develop into multicellular haploid gametophytes. Alternation of generations and multicellular, dependent embryos. Protected from drying, nourished from maternal tissue. Localized regions of cell division at tips of shoots and roots, differentiate into epidermis and leaves. Secondary compounds (defend from herbivores or parasites) Lycophytes lived in swamps for millions of years. Seed consists of embryo and nutrients in protective coat. Secondary compounds of seed plants used in medicine. Three basic ones: roots, stems, and leaves.
