Adaptive Evolution

Question 1

over what scale can selection act and be detected

Answer 1

Selection can act within a generation and is detected/quantified according to the observed relation between phenotypes (traits) and fitness.

Question 2

what are the three forms of natural selection

Answer 2

Directional selection leads the mean of the trait towards a specific direction.
Disruptive selection leads a trait away from the mean in both directions
Stabilizing selection leads a trait towards the mean on both sides.

Question 3

what is directional selection like

Answer 3

Selection favouring a phenotype associated with a particular allele, can result in the allele increasing in frequency in the next generation.

Can lead to an allele being fixed.

Question 4

what is S

Answer 4

S is called the selection differential and is simply measured as the difference between the average value in the population before selection and after selection.

Question 5

When can natural selection result in adaptation

Answer 5

If phenotypic differences reflect genetic variation, then natural selection can result in changes in genotype and allele frequencies in the next generation.

Question 6

How does the HWE and selection interact

Answer 6

HWE proposes the expect result before selection but selection will often cause the results to differ, resulting in different Allele frequencies and genotype frequencies.

Question 7

What is sexual selection

Answer 7

One component of natural selection is sexual selection

• when differences among individuals in relative fitness arise due to differences in mating success
  Sexual selection = whenever a phenotypic attribute of individuals affects offspring production

Question 8

what does sexual selection explain

Answer 8

This explains the evolution of sex differences in traits that are not beneficial for survival (another component of natural selection)

Question 9

what is intrasexula selection

Answer 9

Intrasexual selection

• rescue / mate defense
• ex deer antler fencing

Question 10

what is intersexual selection

Answer 10

Intersexual selection

• mate choice
• ex birds of paradise

Question 11

what are the four steps animals go through before mating

Answer 11

1. Search
2. Guard/compete
3. Court
4. Copulate

Question 12

What is Sperm competition

Answer 12

Sperm competition: In promiscuous species sperm from multiple males compete in female reproductive tract

Question 13

what os Cryptic choice

Answer 13

Cryptic choice: Females of some species can bias paternity and use sperm preferentially after copulation. Have spermatheca which store sperm for use. Allows choice.

Some can eject sperm and stop transfer

Question 14

Which is the choosier sex, why

Answer 14

In most animal systems, females are the choosier sex since they have to facilitate the development of the embryo. Bigger resource cost.

Question 15

what is Anisogamy

Answer 15

Anisogamy - asymmetric investment into gametes

Predisposition to sex difference in investment in other characters.

Question 16

what is fitness typically for males vs females in regards to mating

Answer 16

Males: fitness is typically a simple function of number of mates

Females: Diminishing return of mating frequency

Question 17

what are some cases when males are the choosier sex

Answer 17

Sometimes the typical roles are reversed and male are the choosier sex

In Katydids a female is offered a nuptial gift which is provided by the male in exchange for mating

Male black tree crickets produce a fluid to feed females.

Question 18

give an example of sexual selection in hermaphrodites

Answer 18

Sexual selection operates in hermaphrodites too

Marine flatworms are sexually reproducing and posses both male and female functions but often engage in penis fencing where the loser gets to be the female and carry the offspring

Question 19

what is assortative mating

Answer 19

when genotypes or phenotypes bias mating towards (positive) or against (negative) mates of similiar types

Positive = like attracts

Negative = opposite attracts

Question 20

what is the breeder’s equation

Answer 20

R=h^2S

Question 21

what is R

Answer 21

the predicted evolutionary response

Question 22

how can you predict the mean of a trait for the next generation

Answer 22

The mean before selection + R = predicted mean for next generation

Question 23

how does imperfect heritability affect selection

Answer 23

Imperfect heritability essentially ‘discounts’ selection

R can be 0 if genetic variability is absent or selection is absent.