Gymnosperms - ) and lower tracheophytes such as ferns. For...

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Gymnosperms Gymnosperms are commonly known as conifers, and includes spruces, firs, hemlocks, and othercommon evergreens. Like all tracheophytes, gymnosperms contain vascular tissues. They have developed seeds and nonflagellated sperm; male gametes (carried inside pollen grains) are moved by the wind instead of through water. The dominant phase in the gymnosperm life cycle is the diploid (sporophyte) stage; the gametophytes are very small and cannot exist independent of the parent plant. Male and female cones, the reproductive structures of the sporophyte, produce two different kinds of haploid spores: microspores (male) and megaspores (female). This phenomenon is called heterospory. These spores give rise to gametophytes of the same sex, which in turn produce the gametes. Figure %: Gymnosperm Life Cycle The separation of sexes in the gametophyte stage is a step forward from the dual- sex gametophytes of bryophytes
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Unformatted text preview: ) and lower tracheophytes such as ferns. For more information on the life cycles of plants, see Alternation of Generations . Gymnosperm are also characterized by a specialized fertilization process, involving differentiated male and female gametophytes. Fertilization occurs when pollen grains (male gametophytes) are carried by the wind to the open end of an ovule, which contains the eggs, or female gametophyte. For a (much) more detailed exploration of this process, see gymnosperm fertilization Monocots Monocots, a class of angiosperms that includes grasses, grains, and spring- flowering bulbs, are named for the presence of a single cotyledon (leaf) during embryonic development. In general, the veins of monocot leaves are parallel, the flower parts occur in multiples of three, and a fibrous root system is present. Bundles of vascular tissue are scattered throughout the stem instead of appearing in a single ring....
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This note was uploaded on 01/27/2012 for the course BIOLOGY BSC1005 taught by Professor Rodriguez during the Winter '09 term at Broward College.

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Gymnosperms - ) and lower tracheophytes such as ferns. For...

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