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SPECIATION Macroevolution Review: Microevolution Changes in allele freq. of a population over time. Review: Microevolution Macroevolution Speciation: Formation of a new species Biological Species Concept A population or group of populations whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring, but who cannot successfully interbreed with members of other species Definition of a Species Population of interbreeding organisms Speciation begins with isolation ISOLATION MECHANISMS AP Biology Ch. 24 Pre-zygotic Isolation Mechanisms Habitat Isolation Populations are geographically separated. Behavioral Isolation Populations respond to different mating cues Hyla chrysoscelis Hyla versicolor Temporal Isolation Populations breed during different times Mechanical Isolation Populations anatomically prevent reproduction Gamete Isolation Populations sperm are unable to fertilize different eggs Post-zygotic Isolation Mechanisms Hybrid Sterility Hybrid offspring is not fertile Hybrid Breakdown Hybrid may be fertile but subsequent generations are not Limitations to BSC Does not account for Asexually reproducing species: bacteria Hybrid species: Mule Fossil species: Trilobite Speciation in Action http://www.youtube.com/watch?v=YCoEiLOV8jc https://www.youtube.com/watch?v=8yvEDqrc3XE MODES OF SPECIATION Ch 24.2 Review Universe formed ~13.8 bya Earth formed ~4.6 bya Life present ~3.5 bya Microevolution & Macroevolution genetic changes within a population natural selection acts upon phenotypes Diversity of Life on Earth Today Review Isolation Mechanisms (How) Habitat Isolation Behavioral Isolation Temporal Isolation Mechanical Isolation Gametic Isolation Hybrid Sterility Hybrid Breakdown Modes of Speciation (Where) Allopatric Speciation: Speciation Peripatric Speciation Speciation occurs with small population isolation Parapatric Speciation Speciation occurs with geographic isolation occurs between adjacent populations Sympatric speciation Speciation occurs within a population Allopatric Speciation Ex: Biogeography Rhacophorinae frogs (310 sp. in India) Mantellinae frogs (100 sp. in Madagascar) Geology and DNA evidence suggest 88 mya Peripatric Speciation Ex: Founder Effect Ursus maritimus & Ursus arctos Geology and DNA suggest 150 tya Parapatric Speciation • Ex: Ring Species • • Ensatina Salamanders Currently happening http://www.youtube.com/watch?v=YCoEiLOV8jc Sympatric Speciation Ex: Polyploidy in Plants 1900, Europeans brought Tragopogon sp. Tragopogon miscellus is now found! DNA shows tetraploidy (4N) Sympatric Speciation Ex: Sympatry in animals Amphilophus citrinellus & Amphilophus zaliosus Nicaragua Crater Lake formed 10 tya SPECIATION, PATTERNS & TIME AP Biology Ch 24.3 Review: Speciation Process of making a species Biological Species Concept: Populations are no longer capable of interbreeding Speciation & Time Is speciation a slow process? Fast process? Both? Speciation & Time Charles Darwin Phyletic Gradualism: Slower process gradually developing species Support: Various fossil lineages Variation in large populations Allopatric speciation Ex: Homo sapiens Speciation & Time Stephen J. Gould Punctuated Rapid Equilibrium: process & is followed by long periods of stasis Support: Various fossil lineages Parapatric speciation Sympatric speciation Adaptive Radiation Ex: Tyrannosaurus Rex Speciation & Time Adaptive Radiation: Presence of new ecological conditions leads to the diversification of many species Patterns in Speciation Divergent Evolution: Anagenesis One species evolves into another species Cladogenesis One species evolves into separate species Patterns in Speciation Convergent Evolution: Distantly Bats, related species converge on similar structures Birds, Butterflies wings are analogous structures Patterns in Speciation Parallel Evolution: Similar environments produce many similar species Patterns in Speciation Coevolution? Probably incorrectly applied to interspecific competition Speciation Misconceptions Evolution is not goal oriented! There is no primary body plan for any species Natural Selection must work with current body plan Ex: 6 wings on birds would be awesome Adaptations Ex: are often compromises Seal flippers instead of legs
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