Exam 3: Causes of Evolution

Question 1

3 types of mutations

Answer 1

Deleterious: decrease fitness
Neutral: no effect on fitness
Beneficial: increase fitness
most are neutral or deleterious

Question 2

Mutation

Answer 2

change in DNA (random)

Question 3

Fitness

Answer 3

Higher fitness= more offspring
the traits fit best within the population and produce offspring that will have higher chances of survival

Question 4

Gene Flow

Answer 4

movement of alleles from one pop to another (“migration”)
Ex. Humans reproducing with those from other places which favor certain features that make us all look different

Question 5

Genetic Drift

Answer 5

not natural selection, random change in allele frequency
most pronounced in small populations
ex. Tsunami wipes out species and one left over is the one to spread its genetics

Question 6

Founder effect

Answer 6

change in allele frequencies when a new population is established
-> few individuals isolated from larger population
-> over representation or under representation of certain alleles
Ex. Amish and polydactyly (extra fingers or toes)
- this is gene is over represented in their smaller communities, but as a whole human population it is not common

Question 7

Disruptive Selection

Answer 7

favors individuals with extreme traits
Effect: variation increases (ex. Small & big fish have advantage while medium size fish don’t)

Question 8

Directional Selection

Answer 8

favors individuals at one end of distribution & increases or decreases average trait value
Ex. Dark colored moths favored during industrial revolution because they could camouflage well compared to light moths

Question 9

Stabilizing selection

Answer 9

avors individuals w/ trait values near mean & Average trait value stable, but variation reduced (balance)
ex. 4 eggs is perfect amount because too few may not survive and too many can be hard to feed

Question 10

4 causes of evolution

Answer 10

• mutation -natural selection -genetic drift -gene flow