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Understanding Paramecium

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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Postby Khaiy » Tue Mar 14, 2006 9:38 pm

bionewbie wrote:In plants, there is also a differentiate between male and female gametes right? so how does alternation of generation fit in?


As far as variations in the gender of each gamete is concerned, it's a lot like in animals. Plants produce eggs which are then fertilized by sperm (which can be anything from the sperm that swim through moist media like in ferns, or pollen like in angiosperms).

Exactly how the alternation of generations is handled depends on the type of plant. For example, in ferns the gametophyte generation is dominant in the life cycle, but they still produce spores that give rise to the haploid generation, which is the part of the plant that you see.. But in angiosperms, divisions of the megaspore are the only component of the gametophyte generation, and the plants you see are sporophytes.

Plants have 'gender', similar to animals (although plants tend to have both reproductive structures). Alternation of generations only describes whether or not the plant is haploid or diploid, having nothing to do with gender.
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Postby bionewbie » Thu Mar 16, 2006 12:56 am

There are both haploid and diploid components involved during the plant cycle, right?
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Postby Khaiy » Thu Mar 16, 2006 4:41 am

Yup. The haploid part goes through mitosis to produce haploid reproductive cells, which are the gametes. These are just like the gametes in humans, n chromosomes that fuse with another gamete to create the diploid individual.

The diploid individual will produce spores by meiosis (making haploid cells). These spores give rise to the haploid individuals, which starts the alternation of generations cycle all over again.
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