BIO SCI 94 Lecture Notes - Lecture 9: Green Algae, Adaptive Radiation, Synapomorphy
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Green plants constitute a clade and monophyletic group. Chloroplasts contain chlorophyll a, b, and beta carotene. Land plants are embryophytes which mean that fertilization and early development takes place on parent. Benefits of land plants transitioning on land: more co2 and sunlight. Disadvantages: how to obtain water; how will sperm reach egg. With transition to land, traits found in algae: Spore: a single cell produced by meiosis, can develop into a multicellular adult. Sporopollenin : tough coat; durable polymer and water tight material; encases pollen. Cuticle - waxy layer on outermost cell layer, prevents desiccation. Stomata: pores with guard cells that permit gas exchange for photosynthesis; found on surface. When stomata closes, water cannot escape out of pores. Alternations of generations: multicellular haploid phase (gametophyte) to multicellular diploid (sporophyte) Evolved with common ancestor of land plants. Mitosis: 2n 2n or 1n 1n. Rhizoids (structure), but no roots, stems, leaves. Resistant to desiccation but needs water for sexual reproduction.