chapter 16: evolution of populations 16.1 genes and variation 16.2 evolution as genetic change ...
TRANSCRIPT
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Chapter 16: Evolution of Populations
16.1 Genes and Variation16.2 Evolution as Genetic Change16.3 The Process of Speciation
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Chapter 16 Concept MapGene Pool
Different Types of Natural Selection
Stabilizing Selection
Directional Selection
Disruptive Selection
example
example
example
Relative Frequency
Genetic Equilibrium
Genetic Drift
Hardy-Weinberg Principle
founder effect
single gene trait
polygenic trait
Pg. 398-399
Pg. 395-401
Pg. 393-394
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Chapter 16 Concept MapSpeciation
Geographic Isolation
example
Reproduction Isolation
example example example
17.4…. Macroevolution
extinctionadaptive radiation
example
example
convergent evolution
coevolutionpunctuated equilibriumgradualism
example
BehavorialIsolation
Temporal Isolation
Divergent
Pg. 404-409
Pg. 435-440
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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.
Population Genetics
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Blue People of Kentucky
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Population Genetics The frequency that any one allele is seen
in the population is called the allele frequency (relative frequency). Is the frequency of the dominant
Huntington’s allele high? Is the frequency of the dominant allele causing 6 fingers high?
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If the frequency of the alleles doesn’t change over time, the population is at genetic equilibrium.
Hardy-Weinberg Principle see page 401
Population Genetics
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Population GeneticsWhen alleles are brought in and out
of a population due to migration of individuals, it is called gene flow.
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Population Genetics When 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, PA
Darwin’s finches (perhaps) founder effect: change as a
result of migration
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Population Genetics
Sources of Genetic Variation: Mutations Gene Shuffling Single gene trait Polygenic trait
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Population GeneticsTypes of selection:
When natural selection of a trait favors the average individuals in the pop. it is called stabilizing selection.
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Population Genetics
Types of selection: When natural selection favors both extreme phenotypes of a trait in a pop., it is called disruptive selection.
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Population Genetics
Types of selection: When natural selection favors one extreme phenotype of a trait, it is called directional selection.
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Population Genetics Type of Selection??
Grey mice are preyed upon but black and white mice are left alone?
The longer a giraffe’s 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??
Disruptive
Directional
Stabilizng
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Population Genetics
Artificial 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.
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Speciation
Speciation 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.
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Speciation
Geographic 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.
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Speciation Reproductive 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 Calls Courtship rituals differ
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Speciation
Temporal Isolation: Two or more species reproduce at
different times Example: orchid in the rainforest
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Speciation
Changes 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.
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17.4 Speciation
Can occur rapidly Punctuated Equilibrium Gould
Can occur very slowly Gradualism Darwin see page 439
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17.4 Patterns of EvolutionAdaptive Radiation: When an
ancestral species evolves into several different species, each filling a specific niche. Darwin’s finches Hawaiian Honeycreepers (p. 406 &436).
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17.4 Patterns of Evolution
Divergent Evolution: Species that once were similar or closely related become very different. New Species are very different from
each other. Ex. Adaptive Radiation
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17.4 Patterns of Evolution Convergent
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
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Patterns of Evolution
Coevolution: the process by which two species evolve in response to changes in each other over time. Example: flowering plants
and their pollinator Page 437
http://biology.clc.uc.edu/courses/bio303/coevolution.htm
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17.4 Note
Common 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…