Sunday, April 24, 2011

Angiosperms?

When I say angiosperms, the average person would not assume I am discussing flowering plants. An angiosperm is one of three clades of vascular plants. The seed plants are broken down into two groups, gymnosperms and angiosperms. Gymnosperms are characterized by the lack of encasement around their seeds. The angiosperms differ from the gymnosperms because their seeds develop in chambers. The ovary that contains the seed is found within the flower and the flower, ultimately becomes a fruit.

So why are angiosperms and their life cycle important? Angiosperms make up 90% of living plant species. The two major characteristics of an angiosperm are the flower and the fruit, which play a critical role in the life cycle of the plant. The flower is necessary for sexual reproduction. The angiosperms rely on pollinators, such as insects, to transfer the pollen from flower to flower. The organs within the flower are the sepals, petals, stamens, and carpels. The bright color of the flower petals are an adaption necessary for attracting pollinators. The fruit is used to protect the seeds and help in dispersing the mature seeds. Some angiosperm fruits are not conventionally recognized as a fruit. In maples and dandelions, the fruits have adapted with propellers or parachutes to enhance the movement of the seeds by wind dispersion.

The angiosperm life cycle appears complex and has many characteristic attributes. The haploid part of the cycle begins with the production of the male and female gametophytes. The male gametophyte has two haploid cells that form the tube cell and two sperm. The female gametophyte consists of an embryo sac that holds the egg. After pollution, the sperm are discharged into the ovule. The fertilization signals that transition from a haploid to a diploid stage of the cycle. Angiosperms have double fertilization, which means that one sperm from the male gametophyte fertilizes the egg and the other sperm fertilization a central cell in the ovary and forms an endosperm, which is the food supply for the seed, while it is dormant within the fruit. The seed develops into the sporophyte, which is diploid. Then the life cycle begins again. The adaptive nature of the angiosperms provides the beauty of spring and the nutrition fruits.

1 comment:

  1. Nice post, it brought back memories from Botany! You did a great job explaining the angiosperm life cycle amd, I think the bottom image was a great addition. It really makes the explanation more clear with a representation of the cycle.

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