BIOL120 Lecture Notes - Lecture 6: Microspore, Natural Selection, Coevolution
7 Jul 2016
School
Department
Course
Professor
Document Summary
Asexual reproduction: mitosis (same chromosomes) so that offspring are genetic cloned useful for stable environments where propogation can be rapid. Sexual reproduction offspring that are genetically different = genetic variation. Enhances adaptability to changing environments and facilitates colonization of new environments. Seed plants: sporophyte dominant, gametophyte dependent, reduced. Sporophyte cells undergo meisos (half chromosomes) producing haploit spores. Spore undergoes mitosis (same chromosomes n in total) to produce multicellular haploid gametophytes. Gametophyte some cells specialize to sperm and egg. Fertilization occurs when a sperm and egg fuse to produce a diploit zygote. Zygote undergoes mitosis (same chromosomes 2n in total) to develop into a mature diploid sporophyte. Bryophtes single type of spore gives rise to separate male and female gametophyte. Ferns single type of spore gives rise to a bisexual gametophytes. Seed plants 2 types of spores (mega female; micro male) for gametophytes. Cone axis gives rise to sporophylls (spore-forming leaves), which produce pollen: pollen shed each season.
