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13 Macroevolution 1

13 Macroevolution 1 - 1 Macroevolution Created by Jason...

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1 Macroevolution Created by Jason Mayberry for Bio200, Evolutionary Biology University at Buffalo, Fall 2007
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2 Macroevolution Macroevolution Speciation: Creation of New Species, and… Extinction of Old Generally though to result from Microevolutionary processes over geologic time periods. Summary How do we know when speciation has occurred? General Means of Speciation Linear Radiating Specific Mechanisms for Speciation Allopatric Sympatric Type-specific Speciation vs. Making new Types Pace of Evolution Animal Fungi Protista Plant Amoeba, etc Brown Algae Red Algae Green Algae Archaea Bacteria Origin of Life “Birth” of Nucleus LUCA Lost Cell Lineages Multicellularity
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3 Identifying Species Boundaries The term “species” only has meaning in reference to another different species (you cannot talk about a species meaningfully without at least implying that it is compared to another) Comparing two extinct (fossil) species Comparing an existing species to an fossil species Comparing two existing species We typically identify species in three ways 1.Morphology (Physical Shape) Representatives from two populations which differ significantly in appearance are assumed to be species. Used for distinguishing fossilized species to other fossils or existing species (the only tool we have in these cases) Used for distinguishing two existing populations incapable of sexual reproduction 2.Reproduction: Representatives from two populations that are incapable of producing fertile offspring are always considered distinct species. Used for distinguishing two existing populations capable of sexual reproduction 3.Genetics Representative from two populations which differ significantly in their gene content and order are considered distinct species Used for distinguishing two existing populations incapable of sexual reproduction (especially prokaryotes) Regardless of the criterion used for distinguishing species, there are always fuzzy boundaries. Why is this not F. horse M. Donkey Mule Comparison of Gene locations of two bacterial species: B.thuringiensis v. B.halodurans http://cinteny.cchmc.org Two Mesozoic Era Fish Fossils
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4 Reproductive Blocks (review) Reproductive Blocks which Prevent Mating (Pre Zygotic) Geologic : Mountain building, Isolation of individuals on an island, Continental Drift, Rift Valleys, Rivers, etc. Ecological : niche/habitat differences prevent individuals from meeting Behavioral : time of mating, mate preferences Temporal : Species reproduce in different seasons or at different times of the day Mechanical : Structural differences prevent mating (Great Dane and a Chihuahua?) Reproductive Blocks which occur after Mating Pre-Zygotic (zygote=fertilized oocyte) Gamete Recognition : Sperm and Oocyte have species specific receptors which allow them to identify each other Post Zygotic Aborted Development : Fertilization occurs but the chromosomes are so
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