Microevolution

Question 1

Process of evolution by natural selection is:

Answer 1

Variation in heritable traits within a population + differential survival and/or reproduction = change in traits over time

Question 2

Population

Answer 2

Localized group of individuals capable of interbreeding and producing fertile offspring (smallest unit)

Question 3

Heritable traits

Answer 3

Traits with a genetic basis

Question 4

Genotype

Answer 4

Genetic composition of an individual

Question 5

Phenotype

Answer 5

Observable characteristics of an individual

Question 6

Alleles

Answer 6

Alternative versions of genes that produce a different phenotypic effect (selection acts on phenotype)

Question 7

Microevolution

Answer 7

Change in allele frequencies in a population from 1 generation to the next

• no variation = no evolution
• must have potential to change in order to change

Question 8

Why is genetic variation important?

Answer 8

• variation is the raw material for evolution

- environment (and thus selection pressure) is unlikely to remain constant

Question 9

Gene pool

Answer 9

All of the alleles for all the loci in a population

Question 10

Polymorphism

Answer 10

When there are less than 1 version of a trait in a population (less than 1 allele for a particular trait in a population)

Question 11

An allele becomes fixed (fixation) when:

Answer 11

Entire population is homozygous at a certain locus

Question 12

Mutation

Answer 12

Change in structure of a gene or chromosome (change in genotype due to influence or error)

Question 13

Sex

Answer 13

Combining existing alleles in new ways (meiosis –> fertilization)

Question 14

4 basic processes that cause changes in allele frequencies between generations: mutations

Answer 14

• creation of novel alleles
• occurrence of new mutation directly changes allele frequencies
• relatively low mutation rates in most organisms
• can be positive, negative, or have no effect at all

Question 15

4 basic processes that cause changes in allele frequencies between generations: genetic drift

Answer 15

• tends to reduce genetic variation through the loss of alleles
• always present to some degree (especially in small populations)
• can be positive, negative, or have no effect at all

Question 16

Genetic drift

Answer 16

Change in allele frequencies between generations due to random (chance) events

Question 17

Events that can lead to large amounts of (genetic) drift: (2 events)

Answer 17

• founder effect: large population -> few individuals are selected -> chance of eliminating certain alleles completely -> fixed allele is left
• bottleneck effect: large population -> bottleneck event (i.e. natural disaster) -> surviving population (smaller than before)

Question 18

Gene flow

Answer 18

Change in allele frequencies between generations due to input of individuals or gametes (i.e. pollen) from other populations

Question 19

4 basic processes that cause changes in allele frequencies between generations: gene flow

Answer 19

• reduce variation among population/increasing similarity
• large population ————-> large population (flow of gametes) —^^ (unbalanced allele frequency)
• can be positive, negative, or have no effect at all

Question 20

4 basic processes that cause changes in allele frequencies between generations: natural selection

Answer 20

Three ways natural selection can alter allele frequencies:

1. directional selection
2. disruptive/diversifying selection
3. stabilizing selection
   - only 1 of 4 processes that consistently has positive effects on the degree of adaptation of the target population

Question 21

Directional selection

Answer 21

Favors individuals at 1 end of phenotypic range

Question 22

Disruptive/Diversifying selection

Answer 22

Favors individuals at opposite ends of phenotypic range

Question 23

Stabilizing selection

Answer 23

Favors individuals at the middle of the phenotypic range

Question 24

Conservation focus: why are we concerned about small populations? (3 reasons)

Answer 24

1. population sizes of other organisms may be small (habitat destruction, degradation, invasive species)
2. small populations experience greater effects of (genetic) drift (bottleneck effect, continued genetic drift)
3. in small populations, (genetic) drift can actually become more important than selection (loss of genetic variation, erodes heterozygosity, accumulation of deleterious mutations/alleles)

Question 25

Sexual selection

Answer 25

Natural selection that is related to mating success

Question 26

2 types of sexual selection:

Answer 26

1. intrasexual selection: acts on traits that affect success in competition with members of the same sex for mates (male vs. male/female vs. female)
2. intersexual selection: acts on traits that affect success in being selected for mating by opposite sex (mate choice)

Question 27

Sexual dimorphism

Answer 27

Differences in size, color, shape, behavior, etc. between sexes

Question 28

Why might natural selection not produce perfectly adapted organisms?

Answer 28

1. natural selection works on available variation
   - constrained by past
   - unaware of future
2. natural selection can vary in time and space (heterogenious)
3. selection may be opposed by another evolutionary force (genetic drift, gene flow, mutation, etc.)
4. there are trade offs
5. not all genetic variation is subject to variation (natural selection)
   - neutral variation (i.e. human fingerprints)
6. evolution by natural selection takes time

Question 29

Evolutionary trap

Answer 29

A previously adaptive choice is no longer adaptive due to rapid environmental change