MECHANISMS FOR EVOLUTION DO POPULATIONS OR INDIVIDUALS EVOLVE? DO POPULATIONS OR INDIVIDUALS EVOLVE?...
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Transcript of MECHANISMS FOR EVOLUTION DO POPULATIONS OR INDIVIDUALS EVOLVE? DO POPULATIONS OR INDIVIDUALS EVOLVE?...
MECHANISMS FOR EVOLUTION• DO POPULATIONS OR INDIVIDUALS EVOLVE?DO POPULATIONS OR INDIVIDUALS EVOLVE?• WHAT IS A GENE POOLWHAT IS A GENE POOL• HOW CAN THE GENE POOL CHANGE?HOW CAN THE GENE POOL CHANGE?
– MUTATIONMUTATION– GENETIC DRIFTGENETIC DRIFT– GENE FLOWGENE FLOW– NON-RANDOM MATINGNON-RANDOM MATING– NATURAL SELECTIONNATURAL SELECTION
• WOULD THESE THINGS EFFECT A LARGE WOULD THESE THINGS EFFECT A LARGE POPULATION OR A SMALL POPULATION MORE?POPULATION OR A SMALL POPULATION MORE?
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.
CAUSES OF MICROEVOLUTIONMUTATIONS – provide new alleles in a
population and provide the variation for evolution to occur, should the mutation lead to some adaptive advantage.Mutation alone does not cause evolution, but
provide a selective advantage that due to natural selection can lead to a shift in allele frequency.
CAUSES OF MICROEVOLUTION
• GENETIC DRIFT – in small populations the frequencies of alleles can be drastically affected by chance events– BOTTLENECK EFFECT – if populations are
driven to the point of extinction the remaining individuals do not carry a true representation of the original gene pool.
– FOUNDER EFFECT – when a small number of individuals colonize a new area they only carry with them a small representation of the total number of the alleles from the gene pool.
GENE FLOW – genetic exchange between populations due to migration
NONRANDON MATINGBreed with other members of the
“neighborhood” promotes inbreedingAssortative mating – mate with others
like themselves . This is the premise behind artificial selection.
CAUSES OF MICROEVOLUTIONNATURAL SELECTION – any environmental
factor that leads to a particular allele having some adaptive advantage.
There are three ways that natural selection can affect the frequency of traits:Stabilizing selectionDirectional selectionDisruptive selection
Page 693
Sexual SelectionSexual reproduction has evolved
independently numerous times throughout history.External InternalMotility and Numbers (sperm)Pheromones/sexual behaviors/attractants
Sexual Dimorphism – differences between males and females in looks and behaviors.
Benefits of SexIt costs a lot so why do it????
Sex creates diversity