BIS 2C Lecture Notes - Lecture 20: Welwitschia, Sequoia Sempervirens, Sequoiadendron Giganteum
1 Mar 2018
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Document Summary
20 ovule, pollen, seed, gymnosperm pollen doesnt release sperm into environment, uses other things like animals, air, to get close to female gametophyte. Suspect it arose through the sterilization of sporangia. This whole structure is called ovule one haploid megaspore develops into the female gametophyte by mitosis. Megagametophyte depends on the sporophyte for food and water. Megasporangium with megaspore in it sperm are released from the tube, fertilization results in a diploid zygote. Embryo (new sporophyte) pine nuts are the female gametophyte with embryo inside! many have adaptations for dispersal seeds are the major reason for the success of seed plants. Each seed is three generations! embryo: diploid megagametophyte: haploid megasporangium: diploid integument: diploid seeds can undergo dormancy and provide the next generation with a growth advantage in early stages they are nourished by parent sporophyte gymnosperm diversity. Multi agellate sperm even though delivered by pollen tube relic of swimming sperm ancestry.
