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Lec_5_S07

Lec_5_S07 - 1 Key Concepts Evolutionary Processes • Each...

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Unformatted text preview: 1 Key Concepts: Evolutionary Processes • Each mechanism has different consequences, only natural selection produces adaptation • The Hardy-Weinberg principle serves as a null hypothesis Where do species come from? The microevolutionary outlook on speciation 2 Speciation • The processes that generate new species have interested biologists for a very long time • Defining and categorizing species is dependant on the criteria that are used • Criteria that are often used are: appearance, behavior, habitat use, genetics or other traits Remind yourself about the definition of evolution What is a species? • Evolutionarily independent population(s), there is no gene flow between species • There are genetic differences between species because mutation, selection and drift act independently on a speceis regardless of what is happening in other poualtions. 3 Species Concepts • Biological species – Pre-zygotic isolating mechanisms – Post-zygotic isolating mechanisms • Morphospecies – Distinction based on morphology • Phylogenetic species – Monophyletic groups What about subspecies? 4 Kangaroo Rats • Live in arid regions, habitat distruction • Dipodomys nitratoides – nitratoides – brevinasus – exilis New species arise when two populations diverge from one another 5 Divergent evolution can be seen here in the hind right foot of the great apes. The bones and digits are all homologous. Radiation • Many species diverging from a single ancestor • There are some classic examples of this in nature • Your book talks about “star phylogenies” (later chapter) 6 Lake Malawi Lake Tanganyika 7 What happens when we see things that look alike? • Convergent evolution • Wings and flight • Fins • Natural selection may “favor” certain traits as adaptations in a specific environment How do species arise?...
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Lec_5_S07 - 1 Key Concepts Evolutionary Processes • Each...

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