Ch. 21 The Evolution Of Populations Flashcards
Differences among individuals in the composition of their genes or other DNA sequences
Genetic variation
Molecular level of DNA
Nucleotide variability
Genetic variation at the whole-gene level
Gene variability
A group of individuals of the same species that live in the same area and interbreed
Population
Consists of all copies of every type of allele at every locus in all members of population
Gene pool
Hardy Weinberg equation
P^2+2pq+q^2=1
5 conditions of Hardy-Weinberg equilibrium
- No mutations
- Random mating
- No natural selection
- Extremely large population size
- No gene flow
Chance events causing allele frequencies to fluctuate unpredictably from one generation to the next; especially in small populations
Genetic drift
A new population whose gene pool differs from the source population
Founder effect
A severe drop in population size
Bottleneck effect
Genetic drift is significant in…..
Small population
Genetic drift can cause allele frequencies to change at …..
Random
Genetic drift can lead to …
Loss of genetic variation within populations
Genetic drift can cause harmful alleles to become..
Fixed
The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes
Gene flow
The contribution an individual makes the gene pool of the next generation relative to the contributions of other individuals
Relative fitness
Conditions are favor individuals at one extreme of a phenotypic range
Directional selection
Conditions favor individuals at both extremes of a phenotypic range over individuals w/ intermediate phenotypes
Disruptive selection
Acts against both extreme phenotypes and favors intermediate variants
Stabilizing selection
A difference in secondary sexual characteristics between males and females of the same species
Sexual dimorphism
Occurs when natural selection maintains two or more forms in a population
Balancing selection
The fitness of a phenotype depends on how common it is in the population
Frequency dependent selection
Why natural selection cannot fashion perfect organisms?
- Selections can act only on existing variations
- Evolution is limited by historical constraints
- Adaptions are often compromises
- Chance, natural selection, and environment interact
As a change in allele frequencies in a population over generations
Microevolution
What makes evolution possible?
Genetic variation
What three things can alter allele frequencies?
Natural selection, genetic drift, gene flow
What is the only mechanism that consistently caused adaptive evolution?
Natural selection
