Evolution of Populations Flashcards
Microevolution:
a change in allele frequency in a population over generations
Introns
noncoding segments in a gene that lie between coding regions
Exons:
other regions of a gene that are eventually expressed, and typically translated into amino acid sequences
Natural selection can only act on variation with a ____ component.
genetic
____ variability is not equal to ____ variation
Nucleotide/Genotypic; Phenotypic
What are examples of nucleotide variability?
changes in amino acid sequences
Which gene regions are affected by natural selection?
Exon regions – this would change the protein
Average Heterozygosity
Measures the average percent of loci that are heterozygous in a population
At what level does gene variation occur?
the whole gene level
Phenotypic Plasticity
Variation that is not the result of genotypic differences among individuals
What external changes can lead to phenotypical changes?
Environmental
What are the sources of GENETIC variation?
changes in the nucleotide sequence of DNA, particularly in cells that produce gametes (mutations)
Mutations
changes in the genetic information (nucleotide sequence) of a cell
Population
localized group of individuals capable of interbreeding and producing fertile offspring
Gene Pool
consists of all the alleles for all loci in a population
In what circumstance would a locus be fixed?
If all individuals in a population are HOMOzygous for the SAME allele
Hardy-Weinberg Equilibrium Equation
p2+2pq+q2=1
Conditions for Hardy-Weinberg Equilibrium (5):
- No mutations
- No natural selection
- No gene flow: no new individuals
- Random mating
- Extremely large population size
What major factors alter allele frequency (3)?
- Natural selection
- Genetic drift
- Gene flow
Directional Selection
favors individuals at one end of the phenotypic range
Disruptive Selection
favors individuals at both extremes of phenotypic range
Stabilizing Selection
favors intermediate variants and acts against extreme phenotypes
Relative fitness
Contribution an individual makes to the gene pool of the next generation
Selection favors certain (geno/phenotypes) by acting on (geno/phenotypes) of certain organisms.
genotypes; phenotypes
Genetic Drift
chance events cause allele frequencies to fluctuate unpredictably from generation to generation
Genetic drift tends to (de/increase) genetic variation through (gain/loss) of alleles
decrease; loss
The Founder Effect
A few individuals become isolated from a larger population
The Bottleneck Effect
A sudden reduction in population size due to a change in the environment
Gene Flow
The movement of alleles among populations
How are alleles transferred/allowed to flow?
Movement of fertile individuals/gametes
Gene flow tends to (de/increase) differences between populations
decrease
Gene flow leads to the (de/increase) in fitness of a population
increase
What dictates notable evolution?
A change in allele frequency
Adaptive Evolution
Occurs as the match between an organism and its environment increases
Sexual Selection
natural selection for mating that can result in sexual dimorphism
Sexual Dimorphism
idea that individuals of different sexes within a population have different physical characteristics
Intrasexual Selection
competition within a species between members of the same sex to gain opportunities to mate
Evolution is limited by _____ constraints
Historical
_____ , natural selection, and the _____ interact
chance; environment
