Biology 150: 2/8-2/10 Notes
Biology 150: 2/8-2/10 Notes Biology 150
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This 4 page Class Notes was uploaded by Shea Flannery on Friday February 12, 2016. The Class Notes belongs to Biology 150 at University of Tennessee - Knoxville taught by Dr. Brian O'Meara in Spring 2016. Since its upload, it has received 89 views. For similar materials see Organismal and Ecological Biology in Biology at University of Tennessee - Knoxville.
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Date Created: 02/12/16
2/8 – Other Mechanisms of Evolution Self-fertilization (selfing) is the most extreme type of inbreeding. Inbreeding increases the number of homozygotes. Inbreeding does not cause evolution because allele frequencies do not change. Inbreeding can speed up the rate of evolution by increasing the rate at which alleles with lower fitness are eliminated. Inbreeding depression results from: o Many recessive alleles represent loss-of-function mutations. heterozygous individuals contain most of the loss-of- function alleles, so they are eliminated quickly. o Many genes are under intense selection for heterozygote advantage (favors genetic diversity). homozygous individuals have less fitness for these specific genes. Genetic drift: o is random. o occurs in small populations more than in large populations. o can lead to random loss of alleles. random loss of alleles can cause less genetic variation o increases the genetic differences between populations. Evolution happens because of genetic drift. When some individuals move to a different area and create a new population (founder event), the new population will most likely have a different allele frequency than the original population. Population bottleneck – a population suddenly decreases in size. o Can be caused by natural disasters and disease. Gene flow can cause the two populations to have more similar allele frequencies. Breeding captive populations with wild populations may actually decrease the number of that species. If alleles in a population are lost due to genetic drift, genetic flow can increase genetic diversity by introducing new alleles. Mutations: o Point mutations o Chromosome-level mutations can cause gene duplication o Lateral gene transfer (horizontal gene transfer) Mutations increase genetic diversity. Mutations are random. Because organisms are already well adapted to their environment, mutations normally create things that do not work as well. Mutation alone does not occur frequently enough to affect the change in allele frequencies. Mutation has a huge effect on evolution when it’s paired with genetic drift, gene flow, and natural selection. 2/10 – Speciation 3 ways to identify species: o Biological species concept – if different populations cannot interbreed (prezygotic isolation) or do not produce fertile offspring (postzygotic isolation), the populations are different species. Cannot be used for asexual organisms or fossils. Difficult to use for populations that do not geographically live near each other. o Morphospecies concept – determining species by identifying differences in traits. Can be used for any population. Can accidentally name two species that are actually the same species. Cannot identify cryptic species. o Phylogenetic species concept – comparing populations’ evolutionary history. Based off of Darwin’s theory that all species have a common ancestor. Species are the smallest monophyletic groups on the tree of life. Synapomorphies help identify monophyletic groups. Can be used for any population. Phylogenies are only available for a few of the populations on the tree of life. Geographic isolation can cause allopatric speciation. Geographic isolation can happen in two ways: o Part of a population emigrates, settles somewhere else, and breeds (dispersal). o A barrier splits a population (vicariance). Speciation can still occur even if populations live geographically near each other (sympatric speciation) due to: o External events – selection for different phenotypes based on different niches. o Internal events – chromosomal mutations. Types of polyploidy (important mutation in speciation) – doubling of chromosome number in meiosis or mitosis. o Autopolyploid – doubling of chromosome during meiosis. The tetraploid offspring can only mate with other tetraploid offspring. o Allopolyploid – doubling of chromosomes during mitosis. 3 features of adaptive radiation: o Population is a monophyletic group. o Population speciated quickly. o Population uses a wide variety of resources and lives in varying habitats. 2 things can cause adaptive radiation: o New resources o New ways to exploit resources The Cambrian explosion is composed of: o Doushantuo fossils o Ediacaran fossils o Cambrian fossils Possible causes of the Cambrian explosion: o Higher oxygen levels allowed for larger organisms o Predation forced prey to evolve in order to survive o Once organisms could move off of the ocean floor, they could use more resources and created new niches o Hox genes (help organize cells in an embryo) became present and more diverse Words to Know Inbreeding Mutation Morphospecies Concept Deleterious Beneficial Polymorphic Species Inbreeding Species Depression Cryptic Species Sexual Selection Phylogenic Species Concept Genetic Drift Monophyletic Group Sampling Error Synapomorphy Genetic Marker Biological Species Subspecies Founder Effect Concept Allopatry Genetic Bottleneck Prezygotic Isolation Allopatric Speciation Gene Flow Postzygotic Isolation Sister Species Allopolyploidy Sympatry Adaptive Radiation Sympatric Speciation Cambrian Explosion Niche Fauna Vicariance Polyploidy Biogeography Autopolyploidy
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