Evolution Types

Question 1

Evolution by Natural Selection

Answer 1

occurs when certain genotypes produce more offspring than other genotypes in response to the environment
- non-random change in allele frequencies from one generation to the next

Question 2

Darwin’s 4 Postulates for NS

Answer 2

1. trait under selection must be VARIABLE in the population, so that the encoding gene has more than one variant, or allele
2. trait under selection must be HERITABLE, encoded by a gene/genes
3. THE STRUGGLE OF EXISTENCE (many more offspring are born than can survive in the environment), SELECTIVE AGENTS such as predators, competition for resources, etc.
4. Individuals with different alleles have DIFFERENTIAL SURVIVAL AND REPRODUCTION that is governed by the fitness of the organism to its environment

Question 3

Fitness

Answer 3

organisms that better math their environment will have relatively greater SURVIVAL + REPRODUCTION than those that match less well
- VIABLE AND FERTILE
- individuals that produce more surviving progeny that can reproduce = higher fitness

Question 4

Adaptation

Answer 4

a heritable trait that increases the survival and reproduction odds for those who carry that trait
- only natural selection results in adaptations

Question 5

Diversifying/Disruptive Selection

Answer 5

• extreme values for a trait are valued over the intermediate value
• 2 distinct groups in the population (the 2 extremes)

Question 6

Stabilizing Selection

Answer 6

• non-extreme trait value is favored over both extreme values

Question 7

Directional Selection

Answer 7

• one extreme phenotype is favored over the other extreme and intermediate phenotypes

Question 8

Mutation

Answer 8

random, nondirected change in the genetic material of a cell or organism

• variation created through the random process of mutation must be present for evolution to occur
• create new, heritable phenotypes, irrespective of fitness or adaptation
• occurs at a low rate so it does not effect evolution as much unless paired with other mechanisms of evolution

MUTATIONS DONT ARISE IN RESPONSE TO SELECTION

Question 9

Evolution by Genetic Drift

Answer 9

RANDOM (due to chance alone) change in the allele frequency
- allele frequency changes
- populations are constantly under the influence of genetic drift

Question 10

Bottleneck Effect

Answer 10

GENETIC DRIFT

• phenomenon that occurs when a population’s size is suddenly reduced, which can lead to a loss of genetic variation and a bias in the population’s gene pool
• EX: fire, bomb (random organisms survive)

Question 11

Founder Effect

Answer 11

GENETIC DRIFT

• the reduced genetic diversity which results when a small group of individuals becomes separated from a larger population
• bottleneck associated with invasion of a new habitat by a small number of immigrants
• EX: the Amish moving away from society

Question 12

Evolution by Gene Flow

Answer 12

movement of genetic material from one population to another
- caused when an organism migrates to a different population and brings a new + different allele frequency
- GENETIC EXCHANGE
- makes the allele frequencies in the two populations more similar
- can occur through movement of individuals or gametes

Question 13

Non-Random Mating

Answer 13

some individuals are more/less likely to mate with others of a particular genotype compared to other genotypes
- choosing mating partners
- much more common than random mating
- NRM with “like” individuals shift genotype frequencies in favor of homozygous genotypes (positive phenotypic assortment)
- non-random mating = sexual selection

Question 14

Types of Mutation

Answer 14

• Point mutations (EX: Sickle Cell Disease)
• Deletions
• Rearrangements
• Duplications
• Gene fusions