ECOL 170C1 Lecture Notes - Lecture 9: Pollen, Conifer Cone, Pollen Tube
9 Feb 2017
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Document Summary
Angiosperms are only about 140 million y. o. But include about 86% of all plant species (~300k-350k species) Graphs show that non-angiosperm plants (ferns, cycads, lycopods) became diverse about 300 million y. a. Angiosperms took over world 100 million y. a. Makes both male cone (pollen cone) and female cone (ovulate cone) Pollen spreads between plants via wind or insects. Pollen grain produces sperm that fertilizes egg. Zygote develops into embryo surrounded by seed coat (seed drops out of cone onto ground) In flower, pollen produced in anther (tip of stamen) and egg in ovary (base of pistil) Pollen spreads between plants mostly by animals. Pollen grain adheres to stigma of pistil and pollen grows into ovary. Pollen tube grows into ovary and releases two sperm cells. One sperm cell unites with the egg cell to form the diploid zygote. Other sperm cell unites with two haploid cells from the ovary to form the triploid endosperm.
