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Lecture 10

BIOA01H3 Lecture Notes - Lecture 10: Genetic Drift, Zygote, Sympatry


Department
Biological Sciences
Course Code
BIOA01H3
Professor
Mark Fitzpatrick
Lecture
10

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Lecture 10: Evolution Speciation
- Consider the wings of bats and birds. Which of the following
statements is correct?
B. the limbs are homologous; their wings represent homoplasy
Hair on mammals, when compared to other vertebrates, is an
example
A) shared derived character
Speciation
- when gene flow is reduced between populations, may diverge
genetically as a result of mutation, natural selection, and
genetic drift
- the genetic divergence may eventually lead to speciation, the
creation of new species.
- Speciation creates two or more distinct species from a single
ancestral group
- Speciation occurs when the two populations are no longer
able to produce fertile offspring.
Types of Isolation
- Prezygotic isolation occurs when individuals of different species
are prevented from mating
- Postzygotic isolation occurs when individuals from different
populations do not mate, but hybrid offspring produced have
low fitness and tend not to survive
Prezygotic Isolation
- Isolation prior to mating, prior to the zygote
- Breed in different places
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Postzygotic Isolation
- Isolation occurs after fertilization
- Involve some genetic incompatibility
Isolation and Divergence Allopatry
- Genetic isolations happen when populations become
physically separated
- Physical isolation occurs:
- Dispersal occurs when a population moves to a new habitat,
colonizes it and forms a new population
- Vicariance occurs when a physical barrier splits a widespread
population into subgroups that are physically isolated from
each other. Continental drift
Allopatric: speciation with no gene flow between diverging
populations
- Speciation begins with physical isolation via either dispersal or
vicariance is known as allopatric speciation
- Populations that live in different area are said to be in allopatry
- Biogeography: the study of how species and populations are
distributed geographically- can tell us how colonization and
range splitting events occur.
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