Speciation
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Transcript of Speciation
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Speciation
Family TreesShow relationships between species.
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Human Evolution
• Humans did not evolve from chimpanzee. Humans and chimps share a common ancestor.
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Defining a Species
• A species is often defined as a group of individuals that actually or potentially interbreed in nature. In this sense, a species is the biggest gene pool possible under natural conditions.
• For example, these happy face spiders look different, but since they can interbreed, they are considered the same species: Theridion grallator.
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Defining Speciation
• Speciation is a lineage-splitting event that produces two or more separate species.
• Branching point on the tree, is a speciation event. • At that point genetic changes resulted in two separate fruit fly lineages,
where previously there had just been one lineage. But why and how did it happen?
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Types of Evolution
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Convergent Evolution
• the independent evolution of similar structures in species, often due to similar lifestyles and selection pressures.
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Divergent Evolution
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Analogous Structures
• Separate evolutionary origins • Similar because they evolved to serve the
same function. (they both fly)• Analogies are the result of convergent
evolution.
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Birds and BatsDo not share common ancestor
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Homologies
• Characters in different organisms that are similar because they were inherited from a common ancestor
• Birds, bats, mice, and crocodiles all have four limbs. Sharks and bony fish do not.
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Geographic Isolation
Flies are living on A group of Banana’s
A storm carries them To a different island
The flies are separated And can no longer breedWith the mainland flies
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Reproductive isolation• The evolution of different mating location, mating time, or mating
rituals:Genetically-based changes to these aspects of mating could complete the process of reproductive isolation and speciation.
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Punctuated Equilibrium
• Generally Evolution is slow, changing over millions of years.
• Sometimes a rapid change in the environment results in burst of new species.
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Adaptive Radiation
• Organism’s that share a common ancestor and adaptive to different environments.