Chapter 24 Notes
Chapter 24 Notes BIOL 102 001
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This 3 page Class Notes was uploaded by Kaeli on Thursday September 1, 2016. The Class Notes belongs to BIOL 102 001 at University of South Carolina taught by Mihaly Czako in Fall 2016. Since its upload, it has received 43 views.
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Date Created: 09/01/16
Chapter 24 Notes Speciation o The process of forming new species o Consists of Morphology Physiology Behavior Biochemistry DNA o Allopatric Separate gene pools Locations prevent interbreeding Caused by genetic drift o Sympatric Same habitat, different evolutionary course Divergence is not location based Caused by reduced gene flow by… Polyploidy o More chromosomes than normal o Cytokinesis does not complete and chromosomes do not separate o Must be a viable organism to count Odd # of chromosomes are not viable Sterile organisms may experience a reproductive error and create a new viable species Usually meiotic o Allopolyploid New species originating from 2 different parent species o Mostly asexual organisms o At least 5 examples have originated since 1850 Example T. Dubius o A lot of crops, corn wheat, oats, cotton, potatoes are polyploids Sexual selection o Mates of different phenotypes are preferred Creates new species Example P. pundamilla & P. nyererei in Lake Victoria Habitat differentiation o Appearance of new ecological niches Example maggot fly can live on hawthorn trees and apple trees, may lead to apple only flies o Current questions How long does it have to take? Can range from 4,000 to 40 million years o Average of 6.5 million How many genes have to differ? Only one if it’s important enough o Pollination differences can lead to this difference Microevolution o Changes in allele frequencies Macroevolution o Evolutionary changes above the speciesspecific level o Caused by many speciation and extinction events o Ongoing cycle Speciation Extinction Species Group of populations o Biological species Potential to interbreed Produce fertile offspring Do not successfully breed with other populations Gene flow between populations holds them together genetically Species can have diversity o Morphological species Structural features Objective Asexual inclusive o Ecological species Terms of ecological niche Emphasizes disruptive selection o Phylogenetic concept Smallest group on phylogenetic tree Difficult to determine degree of difference required for separate species o Limits of species concept Cannot apply to fossils or prokaryotes Emphasizes absence of gene flow Can occur when barrier is broken down o Example: “Grolar bear” Reproductive isolation o Barriers that impede two species from producing viable offspring Can be before or after reproduction Barriers are subjective Canyon is a barrier for mice, but not birds o Hybrids are the exception o Prezygotic isolation Premating attempt Zygote won’t form Temporal (timebased) isolation o Example: nocturnal and not cannot be active and thus cannot mate Habitat isolation o Distance divides species o Leads to allopatric speciation o More habitat isolation leads to more species Behavioral isolation Postmating attempt Mechanical isolation Genetic isolation o Postzygotic isolation Zygote formed but… Reduced or no fertility Reduced or no viability Hybrid breakdown
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