chapter 16: evolution of populations
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DESCRIPTIONChapter 16: Evolution of Populations. 16.1 Genes and Variation 16.2 Evolution as Genetic Change 16.3 The Process of Speciation. Population Genetics. Evolutionary thought today is tightly linked to genetics. Remember, populations, not individuals evolve . - PowerPoint PPT Presentation
Chapter 16: Evolution of Populations16.1 Genes and Variation16.2 Evolution as Genetic Change16.3 The Process of Speciation
Chapter 16 Concept Map
Different Types of Natural Selection
single gene trait
Chapter 16 Concept Map
Evolutionary thought today is tightly linked to genetics.Remember, populations, not individuals evolve.All the alleles in a pop. added together are called the gene pool.
Blue People of Kentucky
Population GeneticsThe frequency that any one allele is seen in the population is called the allele frequency (relative frequency).Is the frequency of the dominant Huntingtons allele high?Is the frequency of the dominant allele causing 6 fingers high?
If the frequency of the alleles doesnt change over time, the population is at genetic equilibrium.Hardy-Weinberg Principlesee page 401
Population GeneticsWhen alleles are brought in and out of a population due to migration of individuals, it is called gene flow.
Population GeneticsWhen isolated chance events can alter gene frequencies in a population (therefore disrupting gene equilibrium) you have what is called genetic drift.Common in small isolated populations such as the Amish of Lancaster, PADarwins finches (perhaps)founder effect: change as a result of migration
Population GeneticsSources of Genetic Variation:MutationsGene ShufflingSingle gene traitPolygenic trait
Population GeneticsTypes of selection: When natural selection of a trait favors the average individuals in the pop. it is called stabilizing selection.
Types of selection:
When natural selection favors both extreme phenotypes of a trait in a pop., it is called disruptive selection.
Population GeneticsTypes of selection:
When natural selection favors one extreme phenotype of a trait, it is called directional selection.
Population GeneticsType of Selection??Grey mice are preyed upon but black and white mice are left alone?
The longer a giraffes neck gets the more food is available, while short necked giraffes die of starvation before they can reproduce?
A slow gazelle is easily caught by a cheetah, but one too fast breaks its legs easily and is eaten by hyenas??
Population GeneticsArtificial Selection: Selection for traits that are determined and monitored by man.Ex. Breeding animals such as dogs or cats.Sexual Selection: Selection by one gender for another gender.Ex. Peacock feathers, body hair disappearance in humans, walrus tusks.
SpeciationSpeciation is when a new species is formed. This means that the individuals in the new species can no longer produce successful offspring with the population from which they came.
SpeciationGeographic Isolation can cause speciation over long periods of time.The seperated organisms are adapting to different environments and responding differently.Eventually if a mating is attempted, they can no longer produce successful offspring with one another.
SpeciationReproductive Isolation is when a population can no longer successfully interbreed with its parent population (the pop. it came from).Reproduction if attempted will fail.Ex. One group breeds in the fall, one in the spring and over time the populations become new species incapable of interbreeding.Mating CallsCourtship rituals differ
SpeciationTemporal Isolation:Two or more species reproduce at different timesExample: orchid in the rainforest
SpeciationChanges in chromosome number can cause speciation.Some cases of polyploidy (more common in plants) produce individuals that can only mate with other polyploids in a pop.
17.4 SpeciationCan occur rapidlyPunctuated EquilibriumGouldCan occur very slowlyGradualismDarwinsee page 439
17.4 Patterns of EvolutionAdaptive Radiation: When an ancestral species evolves into several different species, each filling a specific niche.Darwins finchesHawaiian Honeycreepers (p. 406 &436).
17.4 Patterns of EvolutionDivergent Evolution: Species that once were similar or closely related become very different.New Species are very different from each other.Ex. Adaptive Radiation
17.4 Patterns of EvolutionConvergent Evolution: Unrelated species that live in similar environments evolve the same adaptations in order to survive.Ex. Tasmanian Wolf and North American Wolf.P. 437
Patterns of EvolutionCoevolution: the process by which two species evolve in response to changes in each other over time.Example: flowering plants and their pollinatorPage 437http://biology.clc.uc.edu/courses/bio303/coevolution.htm
17.4 NoteCommon genetic occurrences we have studied such as polyploidy, crossing over, and point mutations can provide the genetic basis for evolution. Although these genetic changes are not evolution themselves, they can begin the long process of evolution by affecting one individual in a population in a positive way. But only if the trait is passed on, and on, and on