Chapter 27.3 Microevolution Flashcards
Define microevolution
Evolution occurring at the population level
Genetice changes occur within a ________
population
________ do not evolve
individuals
Define Evolution (within microevolution)
A change in gene frequencies within a population over time
What happens when two populations diverge?
They can become separate species
Define population (within population genetics)
all members of a species occupying a particular area at the same time
Gene Population
the sum total of all alleles of all genes in a population
Hardy-Weinberg Equilibrium
allele frequencies are stable
What are the conditions that must be met in order to be at Hard-Weinberg equilibrium? (5)
- No mutation
- No genetic drift
- No gene flow
- Mating is random
- No natural selection
What is Hardy-Weinberg Equilibrium a null hypothesis?
- Assumes evolutionary forces are absent
2. Deviations from equilibrium implies evolution
What are the known evolutionary mechanisms? (5)
- Mutation
- Genetic drift
- Gene flow
- Nonrandom mating
- Natural selection
_____ is any change in DNA.
Mutation
The origin of genetic variation (new alleles)
Random in respect to needs of organism
Most mutations are harmful or neutral
Could be advantageous if conditions change
Mutation rates are low— 1:1,000,000 loci
Mutation is the ____ of genetic variation
origin
Genetic Drift
Random changes in allele frequencies
- Occurs without a selective force
- Trait doesn’t affect survival or reproduction
- Gene frequencies randomly fluctuate
Population bottleneck
population reduced dramatically, surviving population has fewer alleles
Founder Effect
small group colonizes new location, arriving population has fewer alleles
Gene Flow
New alleles brought into population
What causes a gene flow?
Results from the migration of individuals into population
What is the effect of a gene flow?
new alleles arrive or gene frequency changed
Nonrandom Mating
Individuals choose mates with particular phenotypes
-If a trait is preferred, that trait will leave more copies
Sexual selection
Individuals with preferred traits have a higher reproductive success
- Acts on characters that determine reproductive success.
- If an individual survives but does not reproduce, it makes no contribution to the next generation.
Dramatic differences between sexes are known as s_____ d_______.
sexual dimorphism
Natural Selection
Only acts on phenotype – “Survival of the FIttest”
The best phenotype survives
What is Fitness (within natural selection)?
the reproductive contribution of a phenotype to subsequent generations (# of offspring).
Changes in the relative
