BIO 102 Lecture (Ch. 24 The Origin of Species) Notes
BIO 102 Lecture (Ch. 24 The Origin of Species) Notes BIO 102
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This 2 page Class Notes was uploaded by Zach Notetaker on Wednesday August 31, 2016. The Class Notes belongs to BIO 102 at University of South Carolina taught by Mihaly Czako in Fall 2016. Since its upload, it has received 51 views.
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Date Created: 08/31/16
BIOL 102 Lecture Notes 8/30/16 (Chapter 24) The Origin of Species Speciation: origin of new species, focal point of evolutionary theory o Must explain how new species originate and how populations evolve Microevolution: consists of changes in allele frequencies in population over time Macroevolution: broad patterns of evolutionary change above species level, by same mechanisms that cause microevolution Species Latin meaning “kind” or “appearance” Biologists compare morphology, physiology, biochemistry, DNA sequences Biological Species Concept: species = group of populations whose members can interbreed in nature and produce viable, fertile offspring; DON’T breed successfully with members of other populations o Gene flow b/w populations of same species holds a species together genetically Limitations: Can’t be applied to fossils or asexual organisms Emphasizes absence of gene flow BUT gene flow can occur b/w distinct species when some barrier is broken naturally or artificially Reproductive Isolation: existence of biological factors (barriers) impeding two species from producing viable, fertile offspring Hybrids: offspring of crosses b/w different species o Pre or post fertilization Prezygotic barriers: block fertilization from occurring by… o Impeding different species attempting to mate o Preventing successful completion of mating o Hindering fertilization if mating successful Postzygotic barriers: prevent hybrid zygote from developing into viable, fertile adult o Reduced hybrid viability o Reduced hybrid fertility o Hybrid breakdown Morphological Species Concept: defines species by structural features o Applies sexual and asexual species but relies on subjective criteria Ecological Species Concept: views a species in terms of its ecological niche o Applies sexual and asexual species and emphasizes role of disruptive selection Phylogenetic Species Concept: defines species as smallest group of individuals on phylogenetic tree o Applies to sexual and asexual species but can be difficult to determine degree of difference required for separate species Allopatric (“Other Country”) Speciation: gene flow interrupted or reduced when population divided into geographically isolated subpopulations ex) flightless cormorant of Galapagos originated from fliying species on mainland o Definition of barrier depends on ability of population to disperse ex) canyon can create barrier for small rodents, NOT birds, coyotes, or pollen o Separate populations can eveole independently thru mutation, natural selection, genetic drift o Reproductive isolation can arise as byproduct of genetic divergence Increases as distance b/w species increases o Regions with lots of geographic barriers have typically have more species than do regions w/ fewer barriers Physical separation alone isn’t biological barrier, reproductive barrier are intrinsic to organisms themselves Sympatric (“Same Country”) Speciation: speciation takes place in geographically overlapping populations o Reproductive barrier isolates subset of population w/out geographic separation from parent species o Can occur if gene flow is reduced by following factors: Polyploidy: presence of extra sets of chromosomes due to accidents during cell division Much more common on plants than animals Can produce new biological species in sympatry w/in single generation o Autopolyploid: individual with more than 2 sets of chromosome sets (derived from single species) o Allopolyploid: species with multiple sets of chromosomes derived from different species Sexual Selection: can drive sympatric speciation Habitat differentiation: appearance of new ecological niches ex) North American maggot fly can live on native hawthorn trees & more recently introduced apple trees
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