Evolution As Genetic Change Flashcards
What is stabilizing selection
When the average individuals in the population have higher fitness and are favored
What does natural selection on single gene traits lead to
Changes in allelic frequency and this evolution
What is directional selection
When individuals at one end of the curve have higher fitness and are favored more than individuals in the middle or at the end
What is disruptive selection
When individuals at both of the extremes at the upper and lower ends of a trait are both more fit and are both more fit over the average
What is genetic drift
Occurs in small populations that are isolated
What is genetic drift caused by
The bottleneck effect - a change in the allelic frequency is caused by a dramatic reduction in the size of the population
Founder effect - a change in the allelic frequency is caused by the migration of a small subgroup of a population
What is the hardy Weinberg principle
Allelic frequencies in a population will remain constant unless one or more factors cause those frequencies to change
What are the five conditions that are required to maintain genetic equilibrium
Random mating Large populations No movement into or out of the population No mutations No natural selection
Random mating
All members of the population must have an equal opportunity to produce offspring
Large populations
A large population size is also important in maintaining genetic equilibrium so genetic drift can occur
No movement in or out of the population
Movement of individuals between different populations might bring new alleles into a population
Gene pools must be kept separate
No mutations
Most mutations are random and most harmful but sometimes the mutation can be beneficial and allow the organism to become better adapted to its environment
No natural selection
All genotypes in the population must have equal probabilities of survival and reproduction
No phenotype can have a selective advantage over another and the allelic frequency cannot change
What is one factor that drives that’s five conditions to happen
Competition and is caused by overpopulation or environmental changes
