Exam Review 4 Flashcards
What are mutations?
Mutations are changes in the nucleotide sequence of DNA &; the ultimate source of new alleles.
Sexual reproduction shuffles alleles to produce new combinations in what 3 ways?
- Homologous chromosomes sort independently as they separate during anaphase 1 of meiosis.
- During Prophase 1 of meiosis, pairs of homologous chromosomes cross over and exchange genes
- Further variation arises when sperm randomly unite with eggs in fertilization
What are the 3 main causes of evolutionary change?
- Natural selection
- Genetic drift
- Gene flow
What is genetic drift?
A change in the gene pod of a population due to chance.
What is gene flow?
Results from the founder effect, when a few individuals colonize a new habitat.
Can a small group adequately represent the genetic diversity in the ancestral population?
No it cannot!
What does natural selection do?
Natural selection leads adaptive evolution and also is a blend of chance and sorting.
Finish the sentence: an individuals relative fitness is the contribution it makes to the…
Gene pool of the next generation relative to the contribution of other individuals.
Can everyone reproduce?
Not everyone gets to reproduce only the fittest individuals are those that produce the largest numbers of offspring.
What does stabilizing selection favor?
Stabilizing selection favors immediate phenotypes acting against extreme phenotypes
What does directional selection do?
It acts against individuals at one of the phenotypic extremes.
What does disruptive selection favor?
Disruptive selection favors individuals at both extremes of the phenotypic range.
Sexual selection is a form of?
Natural selection.
What is sexual dimorphism?
In animal species, males and females show distinctly different appearances.
What does sexual selection mean?
Individuals with certain characteristics are more likely than other individuals to obtain mates.
What does Intrasexual selection (within the same sex) involve?
It involves competition for males, usually by males. “Fighting males”
What is intersexual selection (between sexes) or mate choice, individuals of one sex (usually females)?
-that they are choosy picking their mates and often select flashy colorful mates. “Females pick”
What prevents natural selection from eliminating unfavorable genotypes?
- in diploid organisms, recessive alleles are usually not subject to natural selection heterozygotes.
Also balancing selection.
What is balancing selection?
Maintains stable frequencies cies of two or more phenotypes in a population.
What is heterozygote advantage?
Heterozygotes have greater reproductive success than homozygotes.
What is frequency dependent selection?
A type of balancing selection that maintains two different phenotypes in a population.
The evolution of organisms constrained:
- Selection can only act on existing variation. New, advantageous alleles do not arise on demand.
- Evolution is limited by historical constraints. Evolution co opts existing structures and adapts them to new situations.
- Adaptions are often compromises. The same structure often performs many functions.
- Chance, natural selection, and the environment interact. Environments often change unpredictability.
What are fossils?
Fossils are imprints or remains of organisms that lived in the past.
What do fossils suggest?
That species changed over time.
