Chapter 16 - Evolution of Populations Flashcards
What is a gene pool?
Consists of all genes, including all the different alleles, that are present in a population
What is the relative frequency of an allele?
the number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur
How is relative frequency expressed as?
percentage
In genetic terms, what is evolution?
any change in the relative frequency of alleles in a population
What are the 2 main sources of genetic variation?
Mutations and genetic shuffling from sexual reproduction
The number of phenotypes produced for a given trait depends on what?
How many genes control the trait
What is a single-gene trait?
a trait controlled by a single gene
How many phenotypes does a single-gene trait have?
2
What is a polygenic trait?
trait controlled by 2 or more genes
What is directional selection?
Individuals at one end of the curve have higher fitness than individuals in the middle or at the other end
What is stabilizing selection?
Individuals near the center of the curve have higher fitness than the individuals at either end of the curve
What is disruptive selection?
Individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle
What is genetic drift?
random change in allele frequency (chance)
What size population does genetic drift mostly affect?
smaller ones
How does genetic drift occur in small populations?
individuals that carry a particular allele may leave more descendants than other individuals just by chance
What is founder effect?
a situation in which allele frequencies change as a result of the migration of a small subgroup of a population
What is genetic equilibrium?
Situation in which allele frequencies remain constant
What are the 5 conditions of the Hardy-Weinberg principle to remain genetic equilibrium?
1) must be random mating
2) large population
3) no movement into or out of the population
4) no mutations
5) no natural selection
What is speciation?
formation of new species
How does speciation occur?
The species have to become separated and isolated from each other
What is reproductive isolation?
members of 2 populations cannot interbreed and produce fertile offspring
What is behavioral isolation?
when 2 populations are capable of interbreeding but have differences in courtship rituals or reproductive behaviors
What is geographic isolation?
2 populations are separated by geographic barriers such as rivers, mountains, or bodies of water
What is temporal isolation?
2 or more species reproduce at different times
