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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This note was uploaded on 04/24/2008 for the course LS 1 taught by Professor Thomas during the Spring '05 term at UCLA.

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

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