Although Colleen learned about the gymnosperm life cycle, she observed that most spermatophytes are angiosperms.
View the slideshow below to learn about the life cycle of angiosperms.
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Flowers are reproductive structures and are the main characteristic of angiosperms. Although there is a tremendous variation among flowers, the reproductive parts are similar. The female reproductive part, the pistil, consists of the stigma and style. The male reproductive part, the stamen, consists of the anther and filament. Flowers that are scented and colorful produce nectar, a sweet liquid, to attract and feed animals, especially bees, which helps with the flower's reproduction. Flowers that lack color, scent, and nectar, use the wind primarily as their reproductive aid. How can you tell by smelling and looking at a flower whether its reproductive aid is primarily animals or wind?
If a flower is scented and colorful, then it depends primarily on insects to help with its reproduction. If a flower is unscented and lacks a lot of color, then it depends primarily on the wind to help with its reproduction. Microspore
The male gamete, a microspore, forms within the anther. The diploid microspore undergoes meiosis to produce four haploid cells. These haploid cells undergo mitosis to create a pollen grain (microgametophyte). Pollen grains are light weight and can travel long distances by the wind or on animals. Which cellular division, meiosis or mitosis, is considered a "reductive" process?
Meiosis is considered a reductive process because it reduces the amount of DNA to half. Macrospore
The female gamete, a macrospore, develops within the ovary. After the diploid macrospore undergoes meiosis, four haploid cells are produced. These haploid cells undergo mitosis to produce eggs and a nutritive embryo sac. The prefix "micro-" means "small" and the prefix "mega-" means "large." If the male gamete (the microgametophyte) is small in order to help it travel, what is the advantage of the female gamete's (the megagametophyte) being large?
The female gamete is large in order to store nutrients. Seed Formation
During pollination, pollen grains land on the stigma. The pollen grain grows a tube down the style, which provides a pathway for sperm to fertilize the egg, located in the ovary, producing a seed and a nutritive endosperm. Within the seed is a diploid zygote that undergoes mitosis to form an embryo. The embryo is nourished by the endosperm and protected by a seed coat. What are the three parts of a seed?
The three parts of a seed are the embryo, the endosperm, and the seed coat. Seed Germination
Under favorable conditions, the seed will germinate (develop into a plant). What is the difference between fertilization and germination?
Fertilization occurs when the sperm and egg nuclei fuse. Germination is when a seed starts developing into a plant. Life Cycle
Looking at the angiosperm life cycle in its entirety, notice that the diploid sporophyte generation is the dominant form of angiosperms, which produce gametes. The haploid megagametophyte and microgametophyte generation produce seeds. Angiosperm seeds are further protected by being enclosed in a fruit (not shown). Which generation of the angiosperm life cycle is asexual?
The asexual generation of the angiosperm life cycle is the sporophyte. |
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Question
What protection do angiosperm seeds have that gymnosperm seeds lack?
