BIOL 152 Lecture Notes - Lecture 12: Sporophyte, Monophyly, Gynoecium
Document Summary
Spore-bearing vascular plants: lycophytes, lobed cylinder of xylem, simple leaves (one vein, diversity, giant lycophytes in the carboniferous era, ferns and horsetails, monophyletic group, multi-veined leaves, fiddleheads, polypods=most diverse group. Why are polypod ferns so diverse: ferns evolved 360 mya, polypods diversified ~120 mya (after angiosperms, result of new habitats, 40% of ferns are epiphytic. What are the advantages of dispersing gametes and offspring: generates genetic diversity, outcrossing (rather than inbreeding, settle in a less crowded spot, avoid competition, pathogens and parasites. Gymnosperm life cycle: pollen= multicellular male gametophyte, no need to release swimming sperm, male cones, ovule= multicellular female gametophyte, female cones, water not needed for fertilization. Major advances of seed plants: 1) male gametes never exposed to environment, 2) ovule, when fertilized, develops into a seed, 3) reversed sporophyte and gametophyte dominance. Advantages of seeds: multicellular, can store resources for embryo, carry embryo and resources needed for germination low metabolic activity (some can go dormant for long periods)
