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Essay / Research Paper Abstract
This 3 page essay explores the biological evolution of male and female gametophytes from the earliest periods to artifical manipulation today. Bibliography lists 3 sources.
Page Count:
3 pages (~225 words per page)
File: JV57_JVgametophytes.rtf
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Unformatted sample text from the term paper:
Seed plants dominate modern plant biodiversity. They are responsible for food, wood, and all types of plants used for human existence. Plant lineage has evolved through a continuous reduction of
the gametophytes (ovules and pollen grains) of seed plants within the bryophyte life cycle. In Biology (2007), Campbell & Reece state that
the ancestors of the bryophyte were the Charophyceae, or green algae, which were protected in a water environment, and early land plants, such as mosses, which had waxy cuticles to
protect the plants from drying out. Mosses, liverworts and thornworts were also the first to possess a means of protecting gametes and embryos from UV radiation and other harsh aspects
of the environment. The sperm would travel, via free swimming through water in order to reach the egg. Therefore, they are considered nonvascular plants, although they do have some tube
structures, which were necessary for evolution of the bryophyte. Evolving out of these structures were true vascular systems, as in seedless ferns in
the Carboniferous period. Vascular systems have a much more efficient method of conducting fluids and transporting food through xylem and phloem that allows them to be more efficient on land.
As part of the evolution, the male gametophyte continued to move through water, but during this period, this generation underwent progressive reductions in size of the gametophytes. One purpose was
so that the male gametophyte could swim through the vascular waters of the leaves of the plant to fertilize the female gametophyte.
This led to the sporophyte phase of the life cycle, which gave rise to the origin of the seed, which write Campbell & Reece (2007), came to predominate. It was
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