Gene Pools and Speciation (10.3)
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See Topic 5.2 for connections to Natural selection and notes
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Gene Pools
A gene pool is a group of specific alleles within a population.
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Speciation
Speciation is the separation of one population into two distinct species.
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Causes of Speciation
Speciation can be caused by a variety of factors that would force reproductive isolation from a population.
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Types of Speciation
Speciation can occur in three different manners:
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In this example with Newts and Snakes.
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Graduated vs Punctuated Equilibrium
No one is really sure how speciation occurs, or how quickly or how slowly it occurs. Speciation is said to occur gradually or abruptly
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Speciation in Plants
Speciation in plants is "funny" mostly because of all multicellular organisms plants seem to be able to gain chromosomes and larger genetic changes and still reproduce. The same problems in mammals kills us! Hence plants are funny. :)
Two major ways speciation occurs in plants:
Two major ways speciation occurs in plants:
- Can occur by hybridization (combining of different species to form new varieities)
- Hard to quantify because most varieties can still reproduce
- Ploidy Changes (Ploidy refers to the number pairs of chromosomes in the cell. (Humans are diploid- 2 pairs))
- Plants are one of the few classifications of organisms that can survive more than 2 copies of each chromosome
- Species can be created by a plant gaining an entire new set of chromosome copies
- Causes them to be reproductively isolated from other plants because they can no longer produce fertile offspring (see meiosis for more information)