Lecture 6 posted - BIO 311D LECTURE 6 Macroevolution...

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Unformatted text preview: BIO 311D LECTURE 6 Macroevolution (evolution of species) Speciation What defines a species? What are the criteria we should use? Morphological species concept Based on differences in morphology Problems with the morphological species concept: 1. Gradual changes – where do you draw the line? 2. Convergent evolution Biological Species Concept Based on the ability to interbreed. Problems with the biological species concept: 1. Asexual reproduction 2. Circular overlap – neighbors can breed, but not all populations 3. Hybrids – offspring of two different species More hybrids… Reproductive isolation – mechanisms that prevent successful reproduction Example of behavioral isolation – fiddler crabs Example of mechanical isolation Summary of species definitions Models of evolution The ways in which evolution can occur Types (or patterns) of speciation – Anagenesis – Cladogenesis The outcome of the modes of speciation (a) Anagenesis (b) Cladogenesis Modes of speciation - The ways in which speciation can occur Allopatric speciation Sympatric speciation Allopatric speciation – includes a geographic barrier A. harrisi A. leucurus Allopatric speciation example: chipmunks at the Grand Canyon Sympatric speciation – no geographic barrier is involved Sympatric speciation example – evolution occurred here by sexual selection Example of sympatric speciation Ring speciation (circular overlap) Biodiversity – importance and changes Adaptive radiations (increase biodiversity globally Cambrian radiation Example of adaptive radiation – Cichlids of lakes in Africa Example of adaptive radiation: Darwin’s finches Dispersal – spread of a species across barriers - increases diversity Dispersal patterns in ceratopsian dinosaurs: Vacariance – increases diversity due to allopatric speciation Extinction – decreases (and increases?) diversity 6 major extinction events: Ordovician Devonian Permian Triassic Cretaceous ? Permian ...
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This note was uploaded on 01/31/2011 for the course BIOLOGY LE 49610 taught by Professor Hofmannjohann during the Summer '10 term at University of Texas at Austin.

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Lecture 6 posted - BIO 311D LECTURE 6 Macroevolution...

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