Population, Genetics, And Evolution Flashcards
Three structural features of an evolutionary system
- Variations- in the population
- Reproduction- mechanism for those variations to reproduce
- Differential Reproduction- environmental constraints that allow favorable variations to be reproduced more than others
In biology, differential reproduction is accomplished by?
Natural selection
Refers to the tendency of certain phenotypes to be favored in terms of reproduction. It is the mechanism through which evolution takes place.
Natural Selection
ONLY refers to the chance of reproduction associated with a certain phenotype compared to baseline. It MUST be defined in terms of specific environmental constraints.
Fitness
Natural selection could act on the level of the group, not the individual
Group Selection
Expands the rigorous evolutionary definition of fitness to account not just for individuals but their relatives, who can be expected to share many of the same alleles
Inclusive fitness
How can altruistic behavior be advantageous in the point of view of a gene?
If the altruistic behavior or even self-sacrifice can ensure the survival of more copies of the gene.
The combined set of all genes/alleles in a population. It is often used to describe the genetic status of a population.
Gene pool
Hardy-Weinberg equilibrium is used to model _________ gene pools
STABLE
For Hardy-Weinberg equilibrium to apply to a population, it must meet the 6 characteristics
- Organisms must be diploid and reproduce sexually
- Mating is random
- The population size is very large
- Alleles are randomly distributed by sex
- No mutations occur.
- There is no migration into or out of the population
Hardy-Weinberg equilibrium equations
- p + q =1
2. p^2 + 2pq + q^2 = 1
What does it mean when features are “polygenic“?
Multiple genes contribute to them
Occurs if both extremes are selected against. For ex, very short and very tall have lower reproductive fitness, the height of the population will be maintained within a tight range
Stabilizing Selection
Occurs if only one extreme phenotype is selected against and the other extreme is favored.
Directional Selection
Occurs when median phenotype is selected against.
Disruptive selection
Refers to the role of chance, in the absence of strong selective pressures, in determining the reproductive fitness of various alleles. A certain allele may randomly happen to be reproduced more or less often.
Genetic Drift
Occurs when some external event dramatically reduces the size of a population in a way that is essentially random with regard to most if not all alleles. Ex. Tay-Sachs disease in Ashkenazi Jews
Evolutionary bottleneck
How new species evolves through evolution
Speciation
Term for when considerable phenotypic variation exist within a single species. Give an example.
Polymorphism- can help set the stage for speciation
Ex. ABO Blood type
Anything that stops reproduction before the formation of a zygote, such as occupying different ecological niches, having different patterns of breeding, not engaging in reproductive behavior with members of the other species, etc.
Prezygotic barriers
Various forms of reproductive isolation that can occur after a zygote is formed.
Postzygotic barriers
Term for when hybrids are fertile but fertility breaks down in the second generation
Hybrid breakdown
On the level of the gene pool, genes can sometimes travel between species, in what is known as?
Leakage
Since random errors accumulate on the genome at a relatively fixed rate, the extent to which two genomes differ serves as a proxy for how long ago they had a shared common ancestor. What is the term that describes this?
Molecular clock
