BIOL1012 Lecture Notes - Lecture 12: Embryophyte, Lignin, Gametangium
Document Summary
What are algae: linnaeus divided vegetabilia into 25 classes including, cryptogamia plants without. Algae = all photosynthetic eukaryotes excluding land plants. Terrestrial life: for 3 billion years life existed predominantly in aquatic habitats, some evidence for. Although light and co2 are abundant: waxy surfaces impede co2 absorption, evolve pores for gas exchange, but pores allow h2o to escape (stomata, competition for light selects for height. Vascular tissue to move resources around the plant, also lignin for support. Remember the tree of life" -- evolution is not goal-oriented. Origin of land plants: resources are separated in the terrestrial environment, development of their apical meristems. Light and co2 are in the air. Origins of nonvascular plants: gametes produced in elaborate multicellular gametangia, antheridia produces sperm that are released to the environment to fertilize eggs. In early land plants these sperm are still agellate and dependent on h2o for motility: archegonia produces a single egg surrounded by protective cells.
