Chapter 11- Evolution Of Populations Flashcards
A measure of how common a certain allele is in a population (different for each allele)
Allele frequency
Where does genetic variation come from?
Mutations and recombination
The frequency is the highest near the mean value and decreases toward each extreme end of the range.
Normal distribution
The observable change in the allele frequencies of a population over time
Microevolution
Natural selection can lead to microevolution through what 3 paths?
Directional, stabilizing, or disruptive selection
Type of selection that favors phenotype at one extreme of a trait’s range
Directional selection
The intermediate phenotype is favored and becomes more common in the population.
Stabilizing selection
Occurs when BOTH extreme phenotype a are favor d while individuals with intermediate phenotype are selected against by nature.
Disruptive selection
The movement of alleles from 1 population to another
Gene flow
Change in allele frequencies due to chance alone, occurring most commonly in small populations
Genetic drift
Genetic drift that occurs after an event greatly reduces the size of a population
Bottleneck effect
Genetic drift that occurs after a small number of individuals colonize a new area.
Founder effect
When certain traits increase mating success.
Sexual selection
Competition among males
Intrasexual selection
When males display certain traits that attract females.
Intersexual selection
Condition in which a population’s allele frequencies for a given trait don’t change from generation to generation.
Hardy-Weinberg Equilibrium
What are the 5 conditions need for Hardy-Weinberg Equilibrium?
Very large population, no emigration or immigration, no mutations, random mating, and no natural selection
What is the equation for Hardy-Weinberg Equilibrium?
P^2+2pq+q^2 (p= dominant allele frequency/q= recessive allele frequency)
What are the 5 conditions needed for evolution?
Genetic drift, gene flow, mutations, sexual selection, no natural selection
Occurs when members of different populations can no longer mate successfully with each other.
Reproductive isolation
Rise of 2 species from one existing species
Speciation
What are the 3 ways populations can become isolated?
Behavioral, geographic, and temporal isolation
Isolation caused by differences in courtship or mating behaviors
Behavioral isolation
Involves physical barriers that divide a population into 2 or more groups
Geographic isolation
Exists when timing prevents reproduction between populations
Temporal isolation
The combined alleles of all of the individuals in a population
Gene pool
A difference of chemical s cents between 2 populations is an example of what kind of isolation?
Behavioral
An earthquake causes an ocean channel to open up on an island where a low are previously existed. The island’s lizard population is now separated on the 2 parts of the island providing an example of what isolation?
Geographic
What kind of isolation occurs when 2 populations of birds have different courtship dances?
Behavioral
What is considered to be random?
Genetic mutation
Like all flowering plants, the snapdragon must be pollinated to reproduce, but its flowers are closed. A bumblebee has just enough weight to open a snapdragon flower by landing on it. This adaptation is an example of what?
Coevolution
Evolution toward similar characteristics in unrelated species.
Convergent evolution
Analogous structures are an example of what?
Convergent evolution
When closely related species evolve in different directions and become increasingly different.
Divergent evolution
The process in which two or more species evolve in response to changes in each other.
Convolution
Species responds to pressure from the other through better adaptations over many generations. (Convolution can also occur in competitive relationships)
Evolutionary arms races
The elimination of a species from Earth
Extinction
This occurs when a species as a whole is unable to adapt to a change in its environment.
Extinction
Extinctions occur continuously but at a very low rate, usually affect one or a few species in a relatively small area, and can be caused by local changes in the environment.
Background extinction
Thought to occur suddenly in geologic time due to a catastrophic event, operates at a global level, destroys many species, and more rare than the other extinction.
Mass extinctions
States that episodes of speciation occur suddenly in geologic time and are followed by long periods of little evolutionary change (bursts of evolutionary activity is followed by a long period of stability). Proposed by Miles Eldredge and Stephen Joy Gould.
Punctuated equilibrium
The rapid evolution of many diverse species from ancestral specie that are usually adapted to a wide range of environments.
Adaptive radiation
What is said to occur when a population is divided and becomes so different from each other that they can no longer mate together.
Speciation
What 3 barriers are believed to lead to reproductive isolation?
Geographic, behavioral, temporal
What theory states that bursts of evolutionary activity have occurred at geologic time and are then followed by periods of stability with little to no change?
The theory of punctuated equilibrium
