Principles of Biology II
Principles of Biology II BIOL 2108
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This 4 page Class Notes was uploaded by Colby Frami on Monday October 12, 2015. The Class Notes belongs to BIOL 2108 at Georgia Southern University taught by Daniel Gleason in Fall. Since its upload, it has received 48 views. For similar materials see /class/222025/biol-2108-georgia-southern-university in Biology at Georgia Southern University.
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Date Created: 10/12/15
Chapter 24 The Origin of Species Speciation o the origin of new species Conceptual bridge between Microevolution Evolutionary change below species level o Changes in allele frequencies in population over generations Macroevolution Evolutionary change above species level o Example origin of new groups of organisms such as mammals and owering plants Two basic patterns of speciation Anagenesis phyletic evolution one species transforms into another Cladogenesis splitting of a gene pool giving rise to two or more new species What is a species Biological Species Concept A group of populations whose members can interbreed and produce viable fertile offspring Species Latin word meaning kind or appearance Reproductive Isolation key Reproductive Isolation Biological factors barriers that impede members of two species from producing viable fertile hybrids Barriers can be Prezygotic before the zygote Postzygotic after the zygote Reproductive isolation Prezygotic Barriers Fig 24 4 lmpede mating prevent mating from being successful or hinder fertilization if mating occurs Habitat isolation Two species encounter each other rarely or not at all because they occupy different habitats even though not isolated by physical barriers o African CiChIidS hundreds of closely related species in E African Lakes o Differ trophically Temporal isolation Species breed at different times of day different seasons or different years cannmrnkthdrgamebs BehavbraHsob on Courtship rituals and other behaviors unique to a species are effective barners MechanbaHsob on Morphological differences can prevent successful mating oGame cBob om oSpennofonespedesrnaynotbeabbtofe Mzeeggsofanomerspedes oREMDMMMQAWBMMJ o t wmu nmm g244 Prevent the hybrid zygote from developing into a viable fertile adult o Reduced hybrid Viability o Genes of the different parent species interact and impair the hybrid s development Reduced hybndfenHHy oanWhymwsamvbomus wynmybesbnb Hybrid breakdown Some rstgeneration hybrids are fertile but when they mate with another species or with either parent species offspring ofthe next generation are feeble or sterile Chapter 24 The Origin of Species Part 2 Limitations of the Biological Species Concept The biological species concept does notapply to o Asexual organisms for example prokaryotes Fossils Organisms about which little is known regarding their reproduction Speciation can take place with or without geographic separation Speciation can occur in two ways Allopatric speciation Sympatric speciation Allopatric Other Country Speciation Gene flow is interrupted or reduced when a population is divided into geographically isolated subpopulations o one or both populations undergo evolutionary change during the period of separation How big a barrier is needed Depends on ability oforganism to disperse Remember Speciation has occurred when reproductive isolation has been established Can divergence ofallopatric fruit y populations lead to reproductive isolation Fig 24 9 Sympatric Same Country Speciation Speciation takes place in geographically overlapping populations Poypoidy Fig 24 70 o The presence of extra sets of chromosomes due to accidents during cell division o Most common in plants EX o 1 Failure of cell division in a cell of growing diploid plant after chromosomes duplication gives rise to a tetraploid branch or other tissue o 2 Gametes produced by owers on this tetraploid branch are diploid o 3 Offspring with tetraploid karyotypes may be viable and fertilea new biological species Allopatric and Sympatric Speciation A Summary ln allopatric speciation a new species forms while geographically isolated from its parent population ln sympatric speciation a pre or postzygotic reproductive barrier isolates a subset of a population without geographic separation from the parent species How long does speciation take o Patterns in fossil record Punctuated equilibria and gradual evolution Fig 2417 How long does speciation take Takes millions of years 65 million on average and rarely less than 500000 yrs There is no speciation clock that produces new species at regular intervals Reminder Exam 1 Thursday February 4 2010 1230 pm sharp Bring elnstruction key pad calculator Covers Introduction through Origin of Species Chapts 1 22 23 24
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