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
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
What did Linnaeus establish theories on?
What did Hutton and Lyell establish theories on?
What did Malthus establish a theory on?
Population growth resources
What did Cuvier establish a theory on?
Fossils and extinction
What did Lamarck establish a theory on?
What did Mendel establish a theory on?
What did Wallace establish a theory on?
Evolution & Natural selection
What summarizes Darwin's perception of the Unity of Life?
"Descent with Modification"
A type of logic in which generalizations are based on a large number of specific observations
A type of logic in which specific results are predicted from a general premise.
What did Ernst Mayr do with Darwin's theory?
He made three basic inferences based on five observations.
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
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
Biological Evolution is:
The change in genetic properties of populations over generations.
Evidence of biological evolution?
-Artificial selection-Direct Observations in the wild -Homology-Fossil Record-Biogeography
Study of patterns of distrubution of animals
What occurs in populations, evolution or natural selection?
What occurs in individuals, evolution or natural selection?
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
What is a chromosome?
A strand of DNA
What types of organism's chromosomes are in homologous pairs?
What is a Gene Locus?
A specific place on a chromosome that codes for a specific trait
What is an allele?
-An alternate form of a gene-Dominant masks recessive in phenotype
What is a gene?
A discreet hereditary unit found in DNA
What is a genotype?
An individuals genetic composition
What is a phenotype?
A visible characteristic of an individual it is also an interaction of genotype and environment.
What does population genetics study?
-Why there is so much variation in populations-Future characteristics of population
All alleles together in a population (May be 1, 2, 3, or many many more.) NOTE: Individuals only have TWO alleles.
Group of individuals of the same species that live in the same area and interbreed, producing fertile offspring.
p+q = 1- where p = Frequency of Dominate allele and q = frequency of recessive allele
Can populations with identical allele frequencies have different genotype frequencies?
How can you figure out allele frequencies if you only hvae phenotype frequencies?
Using the Hardy-Weinberg Equation
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.
What is Hardy-Weinberg equillibrium?
A gene pool where the only forces at work are mendelian segregation and recombination of alleles.
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
What is the hardy-weinberg equation used for?
Examining allele and genotype frequencies in populations
In the hardy-weinberg equation, to find the probability of have a homozygous recesive allele you would take...
In the hardy-weinberg equation, to find the probability of having a homozygous dominant allele you would take...
In the hardy-weinberg equation, to find the probability of having heterozygous alleles you would take
- 1.) No mutations
- 2.) Random Mating (NO preferentioal mating)
- 3.) No natural selection
- 4.) Extremely large population size
- 5.) NO gene flow
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
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
When males congregate and do their display and then the females choose the mate. Generally one or few males do ALL of the mating.
Problems with H-W assumption of no migration in or out
Migration changes allele frequencies! Migration is generally always occuring.
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.
What are two examples of genetic drift?
- * Population bottle neck
- * Founder Effect
- 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.
- 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.
Problems with H-W assumption of no natural selection?
Adaptation always occurs. Traits favoring survival and reproduction will outlive those that don't.
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
What is biological fitness?
The ability to pass along many copies of your genes onto the next generation.
Does natural selection act on phenotypes or genotypes?
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
Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes. Likely in a stable envioronment. Variance in phenotypes reduced.
Natural selection which favors extreme phenotypes. Variance increases. Possible in variable or patchy environments.
A trait that enhances fitness. Depends on many environmental factors and depends on other genes.
Natural selection in which both inter and intrasexual selection. Differential reproduction due to variation in ability to obtain mates. May lead to trade off.
What are the results of sexual selection?
- Increase fitness via sexual selection
- decrease selection via other natural selection
Is all evolution adaptive?
NO. Drift and mutation are random. They MAY encounter NS but not necessarily.
Is natural selection goal oriented or mindless?
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!)
What type of alleles help to maintain evolution the most? Homozygous recessive? Homozgous dominant? Heterozygotes?
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
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)
How does timing of selection maintain evolution?
Selective forces change over time.
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.
Usually within a single species within a population where you see a casual change as you move across the population.
One population varying greatly among another population of the same species. (What we normally talk about in bio)
Speciation occuring in populations that live in the same geographic area.
Gene flow is interrupted when a population is divided into geopgraphically isolated subpopulations.
What helps to maintain continuous variation?
- *Successful interbreeding