Summary:
This video begins with a introduction about alternation of generations. The sporophyte (diploid) generation of plants produces spores, which germinate and grow into the gametophyte (haploid) generation, which produces male and female gametes, which combine into a zygote, which grows into a sporophyte. Vascular plants provide us with food, oxygen, and some trivial stuff. Nonvascular plant reproduction is briefly explained (a different episode). Nonvascular plants are gametophyte dominant, so the sporophyte stage grows in or on the gametophyte. Vascular plants are the opposite, and the gametophyte grows on or in the sporophyte.
Pteridophyte (includes ferns) reproduction is explained. Ferns reproduce a lot like bryophytes (nonvascular plants). The fern is the sporophyte stage and the gametophyte is tiny and has both male and female parts. Some ferns probably evolved to have seeds and then became extinct or evolved into gymnosperms.
Pollen contains the male gametophyte in gymnosperms. Ovules are the female gametophytes and are fertilized by the pollen. The zygote becomes a seed, ripens, and grows into a sporophyte. The sporophytes produce pollen and ovules. Water isn't needed for gymnosperms to reproduce. Gymnosperms include conifers, ginkgoes, and cycads. Gymnosperms have cones for reproductive structures. The ovules are exposed on the cone scale surface. Female cones are large and spiky, but male cones are small and spongy and produce pollen. Pollen is spread by the wind. Seeds contain zygotes and food. Seeds have a tough casing to protect the zygote. Mature seeds fall from the cone. Some gymnosperms require certain conditions before seeds mature. The Lodgepole Pine seeds have to endure a forest fire before germinating. That way, they have no competition while growing.
Angiosperms are flowering plants. Animals are used to pollinate flowers, and the pollinators and angiosperms probably co-evolved. The flowers provide nectar to the insects and the insects fertilize the flowers. It's a mutualistic relationship. The angiosperm's sporophyte is the plant, and the gametophyte is the pollen and ovum. Some flowers are both male and female, sometimes there are male and female flowers on one plant, and sometimes there are male and female plants. Flowers with both male and female parts are called perfect flowers. Sepals are green leaves that protected developing buds. Petals are colorful leaves that attract pollinators. The male organs, the stamens, consist of an anther which produces pollen and is at the end of a long filament. The female organs, the carpels, consist of an ovary which contains ovules, a neck called a style, and an opening at the top of the neck called a stigma. Pollination is the process of pollen landing on the stigma of a flower and fertilizing the egg. Insects, birds, and some bats are pollinators. The fertilized ovule becomes a seed, and the surrounding ovary becomes a fruit. Biologically, a fruit is anything that develops from an ovary. Many things that you didn't think are fruits actually are. Some fruits are spread by wind and others are eaten and pooped out somewhere far away. The end.
Relevance:
In class, we have been learning about all different kinds of plants, and mostly vascular plants. We have learned about their reproductive cycles. We learned about alternation of generations and how it is used by pteridophytes, gymnosperms, and angiosperms. We learned about pollen, seeds, flowers, and fruits, and the anatomy of each. We also learned about the differences between these different kinds of plants. We learned about how plants spread their spores, pollen and seeds, and how pollinators are important to angiosperms.
http://www.youtube.com/watch?v=ExaQ8shhkw8
Creator: crashcourse
Uploaded Oct. 5, 2012
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