Chapter 14 Flashcards
Population
group of individuals of the same species living the same area and interbreeding
Gene pool
total collection of genes in a population at any one time
Change in relative frequencies of alleles in a population over generations =
evolution
____ _____ is the basis of evolution
genetic variation
Mendel discovered the
heredity processes required for natural selection
What increase genetic variation in a population
mutations and sexual reproduction
Many characters result from..
the combined effect of several genes
Not all variation in populations is..
heritable
Mutation
random change in the nucleotide sequence of DNA
Duplication of genes or small pieces of DNA by meiosis may lead to
new genes
Mutations rarely _____ the adaptation of an individual to its environment
improve
Only mutations in ___ can be inherited by offspring
gametes
Mutations in multicellular organisms..
do not significantly affect genetic variation
Mutations is prokaryoytes quickly generate
genetic variation
Sexual reproduction
most genetic variation results from unique combination of alleles each individual inherits
Gametes of same individual vary significantly in
genetic make up
Mircoevolution
genetic change in a population over time
Individuels dont evolve..
populations evolve over generations
Mutations are the origin of all new…
genes and alleles
3 main causes of evolutionary change are
- natural selection
- genetic drift
- gene flow
Natural selection
if individuals differ ion their survival reproductive success, natural selection will alter allele frequencies
Genetic drift
a change in the gene pool of a population due to chance
In small population chance event may lead to..
l.oss of genetic diversity
Bottleneck effect leads to a
a loss of genetic diversity when a population is greatly reduced
Founder effect
when a few individuals colonize a new habitat, results in genetic drift
Gene flow
population may gain of lose alleles when fertile individuals move in/out of population
Gene flow can alter
frequencies in a population
Natural selection is a blend of
chance and sorting
Because of sorting only natural selection consistently lead to..
adaptive evolution
Relative fitness
contribution it makes to the gene pool of the next generation relative to the contribution of other individuals
The fittest individuals are those that
- produce the largest number of viable, fertile offspring
- pass on the most genes to the next generation
Natural selection can alter the _____ of phenotypes in a population
distribution
Relative fitness of organisms varies and may alter the
distribution and frequency of phenotypes in the next generation
Natural selection can affect the striation of phenotypes in a population in 3 ways
- stabilizing selection
- directional selection
- disruptive selection
Stabilizing selection
favours intermediate phenotypes accoutring against extreme phenotypes
Directional selection
acts against individuals at one of the phenotypic extremes
Disruptive selection
favours individuals at both extremes of the phenotypic range
Sexual selection
form of natural selection in which individuals with certain traits are more likely than others to obtain mate
Some traits may not seem adaptive but if they increase ability to find mate…
the trait will be reinforced over generations
Sexual dimorphism
males and females show distinctly different appearance
Intrasexual selection
sexual selection between same sex (often contest of physical combat)
Inter sexual selection
sexual selection between sexes, one sex is choosy in selecting mates
“Good genes” hypothesis
females are choosy in mate selection belays they prefer male traits that are correlated with “good genes”
Why organisms aren’t perfectly “engineered” for their environment
- selection can only act on existing variations
- evolution is limited by historical constraints
- adaptations are often comprises
- chance, natural selection, and environment interact
