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On the Origin of Species developed two main ideas. What are they?
- Evolution Explains life unity and diversity - Natural selection is a cause of adaptive evolution
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What were the names of the 7 scientists who set the stage for evolutionary theory to develop? (pre-Darwin)
-Linnaeus -Hutton & Lyell-Malthus-Cuvier-Lamarck-Mendel-Wallace
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What did Linnaeus establish theories on?
Classification
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What did Hutton and Lyell establish theories on?
Geological Change
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What did Malthus establish a theory on?
Population growth resources
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What did Cuvier establish a theory on?
Fossils and extinction
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What did Lamarck establish a theory on?
Species Change
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What did Mendel establish a theory on?
Inheritance patterns
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What did Wallace establish a theory on?
Evolution & Natural selection
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What summarizes Darwin's perception of the Unity of Life?
"Descent with Modification"
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Inductive reasoning
A type of logic in which generalizations are based on a large number of specific observations
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Deductive reasoning
A type of logic in which specific results are predicted from a general premise.
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What did Ernst Mayr do with Darwin's theory?
He made three basic inferences based on five observations.
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What were Ernst Mayr's observations?
-Population sizes would increase if everything survived. -Populations tend to be stable in size except in seasonal fluctuation -Resources are limited-Much variation is heritable
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Ernst Mayr's Inferences?
-When more individuals than environment can support leads to a struggle for existence-Survival depends in part on inherited traits-Over many generations this unequal survival will yield changes in the population
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Biological Evolution is:
The change in genetic properties of populations over generations.
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Evidence of biological evolution?
-Artificial selection-Direct Observations in the wild -Homology-Fossil Record-Biogeography
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Biogeography
Study of patterns of distrubution of animals
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What occurs in populations, evolution or natural selection?
Evolution
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What occurs in individuals, evolution or natural selection?
natural selection
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Gregor Mendel: Years? What experiments?What knowledge was he lacking?
-1822-1884-Did experiments on pea plants to determine patterns of inheritance-He did NOT know about DNA
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What is a chromosome?
A strand of DNA
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What types of organism's chromosomes are in homologous pairs?
Diploid organisms
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What is a Gene Locus?
A specific place on a chromosome that codes for a specific trait
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What is an allele?
-An alternate form of a gene-Dominant masks recessive in phenotype
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What is a gene?
A discreet hereditary unit found in DNA
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What is a genotype?
An individuals genetic composition
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What is a phenotype?
A visible characteristic of an individual it is also an interaction of genotype and environment.
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What does population genetics study?
-Why there is so much variation in populations-Future characteristics of population
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Gene Pool
All alleles together in a population (May be 1, 2, 3, or many many more.) NOTE: Individuals only have TWO alleles.
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Population
Group of individuals of the same species that live in the same area and interbreed, producing fertile offspring.
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Frequency =
p+q = 1- where p = Frequency of Dominate allele and q = frequency of recessive allele
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Can populations with identical allele frequencies have different genotype frequencies?
YES!
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How can you figure out allele frequencies if you only hvae phenotype frequencies?
Using the Hardy-Weinberg Equation
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What is the Hardy-Weinberg priciple?
A principle that states that the frequencies of alleles and genotypes in a population will remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work.
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What is Hardy-Weinberg equillibrium?
A gene pool where the only forces at work are mendelian segregation and recombination of alleles.
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What is the hardy-weinberg equation?
p^2 + 2pq + q^2 = 1
- p=expected frequency of genotype C^RC^R
- pq= expected frequency of genotype C^RC^W
- q=expected frequency of genotype C^WC^W
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What is the hardy-weinberg equation used for?
Examining allele and genotype frequencies in populations
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In the hardy-weinberg equation, to find the probability of have a homozygous recesive allele you would take...
q*q
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In the hardy-weinberg equation, to find the probability of having a homozygous dominant allele you would take...
p*p
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In the hardy-weinberg equation, to find the probability of having heterozygous alleles you would take
2*p*q
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Hardy-Weinberg Assumptions:
- 1.) No mutations
- 2.) Random Mating (NO preferentioal mating)
- 3.) No natural selection
- 4.) Extremely large population size
- 5.) NO gene flow
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Problems with H-W assumption of No mutations:
- *Due to accidents in DNA.
- * Happen ALL the time, but slowly
- * Sorce of all genetic variation
- * Required for evolution
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Problems with H-W assumption of Random Mating
- * Males often compete for territories or mates
- * Competition occurs through ornamentation, vocalization, fighting, etc.
- *Female choice plays a roll
- * Female choice ex: = lekking behavior
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Lekking Behavior
When males congregate and do their display and then the females choose the mate. Generally one or few males do ALL of the mating.
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Problems with H-W assumption of no migration in or out
Migration changes allele frequencies! Migration is generally always occuring.
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Problems with H-W assumptoin of an infinitely large population?
ALL populations are finite. Moreover, populations risk genetic drift and sample error. Both of those are more likely to happen in smaller populations.
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What are two examples of genetic drift?
- * Population bottle neck
- * Founder Effect
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Population bottleneck
- An example of genetic drift. This takes place when a population crashes, and a once rare allele becomes a prominant / common allele. These can be as small as one generation.
- EX: Elephants and cheetahs both had this occur to them and now they have low genetic variation and great problems with converation because of this.
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Founder Effect
- An example of genetic drift.
- When a few individuals leave a group and start a new population. Once rare alleles can become very common alleles in the new population.
- EX: Omish community that inbread and often have 6 fingers.
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Problems with H-W assumption of no natural selection?
Adaptation always occurs. Traits favoring survival and reproduction will outlive those that don't.
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Natural selection basics
- *More individuals are produced than survive due to competition for limited resources
- * Individuals vary within populatinos
- *Some variants have more offspring
- *Individuals with favorable traits reproduce / survival of the fittest
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What is biological fitness?
The ability to pass along many copies of your genes onto the next generation.
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Does natural selection act on phenotypes or genotypes?
Phenotypes!
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Directional Selection
Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals.
EX: White polar bears VS black polar bears
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Stabilizing Selection
Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes. Likely in a stable envioronment. Variance in phenotypes reduced.
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Diversifying selection
Natural selection which favors extreme phenotypes. Variance increases. Possible in variable or patchy environments.
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Adaptation
A trait that enhances fitness. Depends on many environmental factors and depends on other genes.
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Sexual Selection
Natural selection in which both inter and intrasexual selection. Differential reproduction due to variation in ability to obtain mates. May lead to trade off.
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What are the results of sexual selection?
- Increase fitness via sexual selection
- decrease selection via other natural selection
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Is all evolution adaptive?
NO. Drift and mutation are random. They MAY encounter NS but not necessarily.
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Is natural selection goal oriented or mindless?
Mindless.
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What are all of the reasons that natural selection does not creat perfect organisms?
- *Adaptation is a comprimise, different selective forces at one time. Selective forces change over time
- * Not all evolution is adaptive. (drift and mutation)
- * Historical Constraints (Starting materials for a pop)
- * Not enough variation (This doesn't allow for change!)
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What type of alleles help to maintain evolution the most? Homozygous recessive? Homozgous dominant? Heterozygotes?
Heterozygotes!
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What is the heterozygote advantage?
- They are the most fit because they have the most variance.
- Ex: sickle cell animia : aa = anemic but Aa = malaria resistant . . . Aa is not infected but IS a carrier, keeping the sickle cell population allive and viable to be passed down
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How does a rare allele help you in frequency dependent slection?
- * Rare individuals may survive parasites
- * Predators search out similar traits each time (if you're different - wa la)
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How does timing of selection maintain evolution?
Selective forces change over time.
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Neutral Variation
Sometimes a variation doesn't do anything, but over time it very well may as the environment changes or a new predator shows up, etc.
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Continuous Variation
Usually within a single species within a population where you see a casual change as you move across the population.
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Discontinuous variation
One population varying greatly among another population of the same species. (What we normally talk about in bio)
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Sympatric Speciation
Speciation occuring in populations that live in the same geographic area.
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Allopatric Speciation
Gene flow is interrupted when a population is divided into geopgraphically isolated subpopulations.
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What helps to maintain continuous variation?
- *Sympatry
- *Successful interbreeding
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