Evolutionary Processes

Question 1

locus

Answer 1

A location where a gene can occur

Question 2

allele

Answer 2

A particular version of a gene

- Complex organisms usually have two alleles at each locus

Question 3

heterozygous

Answer 3

An organism with different alleles at a particular locus

Question 4

homozygous

Answer 4

An organism with two copies of the same allele at a particular locus

Question 5

genotype

Answer 5

collection of an individual’s genes

Question 6

phenotype

Answer 6

collection of an individual’s physiological and physical traits

Question 7

Dominant vs Recessive

Answer 7

If individuals with genotype XY have the same phenotype (on average) as those with XX, we say that X is a dominant allele and Y is a recessive allele

Question 8

incompletely dominant

Answer 8

If XY individuals have an intermediate phenotype (between XX and YY), we say X and Y are incompletely dominant.

Question 9

Hardy-Weinberg equilibrium assumptions

Answer 9

• Random mating within a closed population
• No differences in fitness between genotypes
• No mutation
• No drift

Question 10

null model

Answer 10

tells us what to expect if complicating effects are absent

Question 11

Directional selection

Answer 11

moves a population in a particular direction

ex: giraffe necks

Question 12

Multi-directional selection

Answer 12

Directional selection can change through time with the environment
ex: finch beaks get thicker when food scarce and smaller when food abundant

Question 13

Stabilizing selection

Answer 13

tends to keep the population where it is

• begins as directional, then meets target and stabilizes
  ex: human birthweights

Question 14

Disruptive selection

Answer 14

favors phenotypes different from the average value

ex: animals that get eaten a lot may want to look different from peers
- may lead to speciation

Question 15

speciation

Answer 15

the formation of new species

Question 16

Balancing selection

Answer 16

tends to maintain allele diversity

Question 17

Heterozygote advantage

Answer 17

when heterozygotes have higher fitness

Question 18

Frequency dependence

Answer 18

when rare types have higher fitness

Question 19

Genetic drift

Answer 19

change in allele frequencies due to random sampling

• Some individuals have more offspring than others due to chance events
• Offspring receive certain parental alleles, and not others

Question 20

Founder effects

Answer 20

occur when a new population is started by a small number of individuals

Question 21

Bottlenecks

Answer 21

occur when a population becomes small, then large again

Question 22

lost

Answer 22

An allele may drift to a frequency of 0

- disadvantageous alleles are often lost

Question 23

fixed

Answer 23

An allele may drift to a frequency of 1

- Advantageous alleles are usually fixed

Question 24

Gene flow

Answer 24

movement of alleles from one population to another

Question 25

Mutations

Answer 25

heritable errors in copying DNA

Question 26

Sex

Answer 26

• does not directly change allele frequencies

- not a source of new alleles but it is a source of new combinations

Question 27

Inbreeding

Answer 27

mating between close relatives

• commom in smaller pop
• more homozygous loci
• usually leads to decrease fitness

Question 28

Sexual selection

Answer 28

Occurs when there is heritable variation in traits related to success in obtaining mates

Question 29

Sexual dimorphism

Answer 29

trait differences between males and females

Question 30

Investment in reproduction

Who invests more? Results?

Answer 30

females invest much more in each offspring than males do
- If females invest a lot in each offspring, they can maximize fitness by being choosy
about mates
- If males invest little in each offspring, they can maximize fitness by mating as much as possible

Question 31

Variation in reproductive success

Who has higher VRS and the effects of such?

Answer 31

Males often have greater variation in reproductive success than females do
(means that winning contests is more impor- tant to male fitness)
- Side-effect of the fact that females usually invest a lot in each offspring:
– Reduces potential total number of offspring – Makes females desirable to males