BIO153H5 Chapter Notes - Chapter 30: Endosperm, Cycad, Gnetum
Document Summary
Chapter 30: plant diversity ii: the evolution of seed plants. Seeds and pollen grains are key adaptations for life on land. In addition to seeds, the following are common to all seed plants: Ovules and production of eggs integuments: an ovule consists of a megasporangium, megaspore, and one or more protective, a fertilized ovule becomes a seed, gymnosperm megaspores have one integument, angiosperm megaspores usually have two integuments. Pollen and production of sperm: microspores develop into pollen grains, which contain the male gametophytes, pollination is the transfer of pollen from the male to the female part containing the ovules. Pollen eliminates the need for a film of water and can be dispersed great distances by air or animals. If a pollen grain germinates, it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule.
