BSC 2011C Lecture Notes - Lecture 7: Gametangium, Global Warming, Archegonium
Document Summary
Land before plants: cyanobacterial film, photosynthesis. Origin of land plants: ordovician, 470 million years ago. Charophyceans: semi-terrestrial algae, distant relative of land plants. Shared ancestral traits between algae and land plants: eukaryote, multicellular, photosynthetic, cell walls with cellulose. Cuticle: epidermal polymer that acts as waterproofing. Soropollenin: polymer prevents spores and pollen from drying out. Derived plant traits: apical meristems, alternation of generations, sporangia with walled spores, multicellular gametangia, multicellular dependent embryos. Alternation of generations: multicellular 2n individuals alternates with multicellular n individuals. Apical meristem: growth tissue at apex of roots and shoots. Non-vascular plant diversity: liverworts, hornworts, mosses. Silurian: 425 million years ago, vascular. Vascular tissue: tubes transport nutrients, xylem and phloem. Vascular plant adaptations: sporophyte is dominant phase, roots, leaves, sporophylls. 3 types of leaves: microphyll, megaphyll, sporophyll. Microphyll: spine shaped leaf, unbracnhed, vascular. Megaphyll: broad leaf, vascular network, evolved by branched webbing. Sporophyll: modified leaf that bear sporangia. Vascular seedless plants: sporophyte is always dominant stage.
