Phenotype / genotype
Natural selection works on an organisms _ rather than its _.
Gene pool
A _ consists of all the genes, including the alleles for each gene, that are present in a population.
Alleles
A gene pool typically contains different _ for each heritable trait.
Allelic frequency
The number of times that an allele occurs in a gene pool compared with the number of times other alleles for the same gene occur is called the _ of the population.
What are mutations? When do they affect evolution?
Mutation - change in the genetic material of a cell; the offspring could get the mutation
How does sexual reproduction affect a populations genetic variation?
It can reproduce many phenotypes
Identify two ways in which genes can be recombined during meiosis
Crossing over and independent assortment (random assortment)
What is the lateral gene transfer? How does it affect variation?
The passing of genes from one organism to another organism that is not its offspring
Phenotypes
The number of _ produced for a given trait depends on how many genes control the trait.
Polygenic
Height in humans is an example of a single-gene trait.
Alleles
Each gene of a polygenic trait often has two or more _.
Genotypes
A single polygenic trait often has many possible _.
Polygenic
A symmetrical bell-shaped graph is typical of _.
Why is genetic variation important to the process of evolution?
It is important because it introduces new genes for new species, because if everyone was the same, then if one disease comes it would wipe everyone out.
If a trait made an organism less likely to survive and reproduce, what would happen to the allele for that trait?
The allele would become less frequent.
If a trait had no effect on an organisms fitness, what would likely happen to the allele for the trait?
It would just be in the background of everything, favorable traits would be selected for.
What effect does stabilizing selection have on variation in a population?
Stabilizing selection makes average sized individuals, survive more because they have higher fitness. Most individuals fall into the average size group.
Directional selection
Individuals at one end of the curve have higher fitness than individuals in the middle or at the other end.
Stabilizing selection
Individuals near the center of the curve have higher fitness than individuals at either end.
Disruptive selection
Individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle.
Alleles
In small populations, random changes in _ is called genetic drift.
Founder effect
A situation in which allele frequencies change as a result of the migration of a small subgroup of a population is known as _.
Bottleneck effect
The _ is a change in allele frequency following a dramatic reduction in the size of a population.
What does the Hardy Weinberg principle state?
That allele frequencies in a population should remain constant unless one or more factors cause those frequencies to change.
What is genetic equilibrium?
Situation in which allele frequencies in a population remain the same
List the five conditions that can disturb genetic equilibrium and cause evolution to occur.
Non random mating, small population size, immigration or emigration, mutations, and natural selection.
Explain how sexual selection results in non random mating.
When sexual selection is at work, genes for the traits selected for or against are not in equilibrium. When individuals select mates based on heritable traits.
What is speciation?
A formation of new species
What does it mean for two species to be reproductively isolated from each other?
A separation of a species or population so that they no longer interbreed and evolve into two separate species.
What must happen in order for a new species to evolve?
They must mate with other species; the gene pools of two populations must become separated, or reproductively isolated.
List three ways that reproductive isolation occurs.
Behavioral isolation, geographic isolation, and temporal isolation
Finch
Peter and Rosemary grant spent years on the Gal�pagos Islands studying changes in _ populations.
Polygenic
Many finch characteristics appear in bell-shaped distributions typical of _ traits.
South America
The ancestors of the Gal�pagos Islands finches originally came from the continent of _.
Geographically
The populations of finches on separate islands are _ isolated from one another by large stretches of open water.
Behaviorally
Big beaked finches that prefer to mate with other big beaked finches are _ isolated from small beaked finches living on the same island.
What is a molecular clock?
Method used by researchers that uses mutation rates in DNA to estimate the length of time that two species have been evolving independently.
Why are only neutral mutations useful for molecular clocks?
Neutral mutations accumulate in the DNA of different species at about hrs same rate because they are unaffected by natural selection
Genetic drift
In a small population, a random change in allele frequency is called _.
Behavioral
When birds cannot interbreed because they have different mating songs, they are separated by _ isolation.
Founder effect
A situation in which allele frequencies change as a result of the migration of a small subgroup of a population is known as the _.
Temporal
Two related species that live in the same area but mate during different seasons are separated by _ isolation.
Single gene trait
A _ is a trait controlled by only one gene.
Bottleneck effect
The _ is a change in allele frequency following a dramatic reduction in the size of a population.
Allele frequency
_ is the number of times an allele occurs in a gene pool! compared to the total number of alleles in that pool for the same gene.