What is phenotype frequency,sympatric speciation, and postzygotic isolation?

Phenotype frequency:


Do you know what a phenotype is? It's the result of the genotype and environmental influence. In other words, it's the organism's physical characteristics (and some other things). A phenotype could be green eyes, red hair, pale skin, and freckles, or simply green eyes. The phenotype frequency is just how often that phenotype occurs in the population. So if green eyes occur in 5% of the population (note I'm just making up the number), the frequency of the phenotype green eyes is 5% or 0.05.





Sympatric speciation:


Sympatric speciation refers to speciation that occurs within a population in a single location (as opposed to speciation that occurs as the result of geographical isolation). The most frequently observed example of sympatric speciation is polyploidy in plants. In most animals, a complete extra set of chromosomes is generally really bad, but for plants it can be just fine, or even a good thing. When, through random chance, a plant receives a complete extra set of chromosomes (so it now alternates between tetraploid and diploid rather than dipliod and haploid), it can no longer produce fertile offspring with the members of the parent species (the offspring would be triploid, which makes meitosis impossible - if you'd like me to explain this in more detail, just ask). Thus the new tetraploid (4n) plants are a separate species from the original diploid (2n) plants. Becaues the new species arose without a geographical barrier (a mountain range, river, etc. separating the two populations), this is an example of sympatric speciation.





Postzygotic isolation:


For starters, do you know what a zygote is? It's the result of fertilizaition. Post- means after, so postzygotic means after fertilization. I assume you know what isolation means :), so postzygotic isolation is reproductive isolation that occurs after fertlization. Basically, the sperm of one species can successfully combine with the egg of another species, but the resulting zygote will either be inviable (i.e. it will die in the early stages of embryonic development) or grow into an infertile organism.What is phenotype frequency,sympatric speciation, and postzygotic isolation?
phenotype frequency is how many individuals in a population have a specific phenotype (physical characteristics pertaining to a given cell locus or linked cell loci)


for example if the phenotype is being tall, how many tall people do you have in the group you are studying.





sympatric speciation


http://en.wikipedia.org/wiki/Speciation

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