Adpatation

Question 1

adaptation (2)

Answer 1

• a trait, or integrated suite of traits, that enables (or enhances the probability of) an organism to survive and reproduce
• outcome of evolution by natural selection

Question 2

how do you begin testing adaptive hypotheses? (3)

Answer 2

• state your question(s) clearly
• state your hypotheses
• design a study that allows you to discriminate among your hypotheses

Question 3

what kind of studies can be conducted? (3)

Answer 3

• manipulative experiments
• observational studies
• comparative studies (the “comparative method”)

Question 4

examples of manipulative experiments (2)

Answer 4

• lizard fever study

- tephritid fly mimicry

Question 5

tephritid fly mimicry

• question: what is the function of the wing markings and wing-waving display of the tephritid fly Zonosemata?
• based on this question, what are the three hypotheses?

Answer 5

1. tephritid flies don’t mimic jumping spiders. Patterns and behaviours are just coincidental.
2. tephritid flies mimic jumping spiders, but to deter other nonspider predators.
3. tephritid flies mimic jumping spiders to avoid predation by jumping spiders.

Question 6

what are the controls for the tephritid fly experiment? (3)

Answer 6

• tephritid fly untreated
• tephritid fly with wings cut and glued back on
• house fly untreated

Question 7

what are the experimental groups for the tephritid fly experiment? (2)

Answer 7

• tephritid fly with house fly wings

- house fly with tephritid fly wings

Question 8

under hypothesis 1: tephritid flies don’t mimic jumping spiders. Patterns and behaviours are just coincidental, what is expected to be seen?

Answer 8

• all flies are attacked by both the jumping spiders and other predators

Question 9

under hypothesis 2: tephritid flies mimic jumping spiders, but to deter other nonspider predators, what is expected to be seen? (2)

Answer 9

• other predators will retreat from the tephritid fly untreated and the tetraphid fly with its wing cut and glued back on
• jumping spiders will attack all groups and other predators will attack all other groups

Question 10

under hypothesis 3: tephritid flies mimic jumping spiders to avoid predation by jumping spiders, what is expected to be seen? (2)

Answer 10

• jumping spiders will retreat from untreated tephritid flies and tephritid flies with their wings cut and glued back on
• jumping spiders will attack all other groups and other predators will attack all groups

Question 11

what components are necessary for manipulative experiments? (4)

Answer 11

• control
• replicate
• randomize
• perform experiments “blind” to avoid biases and subjectivity

Question 12

examples of observational studies (2)

Answer 12

• Grant’s Galapagos finches study

- Garter snake thermoregulation

Question 13

Garter snake thermoregulation experiment

• question: do Garter snakes make adaptive choices when choosing a night-retreat
• what are the 2 hypotheses based on this question?

Answer 13

1. Garter snakes choose medium-sized rocks that allow optimal thermoregulation
2. (null) Garter snakes take whatever rock is available

Question 14

Garter snake thermoregulation experiment
- If under the Hypothesis 1: Garter snakes choose medium-sized rocks that allow optimal thermoregulation and ~30% of all rock types available, what are the expected results? (3)

Answer 14

• <33% choose thin rocks
• > > > > 33% choose medium rocks
• <33% choose large rocks

Question 15

Garter snake thermoregulation experiment
- If under the Hypothesis 2: (null) Garter snakes take whatever rock is available and ~30% of all rock types available, what are the expected results? (3)

Answer 15

• ~33% choose small rocks
• ~33% choose medium rocks
• ~33% choose large rocks

Question 16

what are the potential drawbacks of observational studies? (2)

Answer 16

• many confounding variables

- cannot conclude causation, only correlation

Question 17

confounding variable

Answer 17

• variable that influence both independent and dependent variable, causing an association

Question 18

what are the potential drawbacks of the finches observational study? (2)

Answer 18

• correlation between larger size of the birds and better territories (inflate heritability)
• offspring sired by males other than social partner (deflate heritability)

Question 19

examples of comparative studies (3)

Answer 19

• nematode virulence study
• testes size in fruit bats; sleep study
• flu evolution at the molecular level

Question 20

what is the goal of comparative studies

Answer 20

• test for correlation between state of trait and variable proposed to be responsible for the pattern (ie. environmental condition, state of another trait, etc) by comparing across species (ie. using nature’s experiments)

Question 21

potential problem of comparative studies (2)

Answer 21

• related species may share same combination of traits due to common ancestry
• phylogenetic non-independence

Question 22

what the solution for the problem of comparative studies?

Answer 22

• correct for phylogeny to obtain species pairs that can be treated as phylogenetically independent

Question 23

phylogenetic trees (3)

Answer 23

• hypotheses of how species/individuals are related to one another
• consist of terminal nodes connected by branches to internal nodes, which represent inferred ancestors
• can be built using morphological characters, amino acids or nucleotide suquences

Question 24

phylogenetic non-independence problem

Answer 24

• species at all terminal nodes cannot be taken as independent data points

Question 25

how to correct for phylogenetic non-independence (4)

Answer 25

- find internal nodes - graph the internal nodes by taking the descendant species and plotting them on a graph connected by a line - move smaller x- value point on each line to the origin - only keep the point where the larger x-value point was

Question 26

testes size in fruit bats experiment - question: why do some bat species have bigger testes, for their body size? - what is the hypothesis for this question

Answer 26

- larger testes may be an adaptation for sperm competition

Question 27

how are fruit bats affects by sperm competition? (2)

Answer 27

- group size varies from few to tens of thousands across species - greater opportunity for sperm competition in larger groups

Question 28

testes size in fruit bats experiment prediction based on the hypothesis: larger testes may be an adaptation for sperm competition

Answer 28

- species roosting in larger groups should have males with larger testes relative to their body size

Question 29

how can correction for phylogenetic non-independence affect results of an experiment?

Answer 29

- may remove or reveal a correlation

Question 30

how can molecular phylogenetic trees be used? (2)

Answer 30

- obtain evidence of selection | - non-synonymous or synonymous mutations can be used to infer neutral drift, positive selection, or purifying selection

Question 31

neutral drift (basic)

Answer 31

- NS/S = 3/3

Question 32

positive selection (basic)

Answer 32

- NS/S = 6/0

Question 33

purifying selection (basic)

Answer 33

- NS/S = 0/6

Question 34

non-synonymous mutation (NS)

Answer 34

- a nucleotide mutation that alters the amino acid sequence of a protein

Question 35

synonymous mutation

Answer 35

- do not alter amino acid sequences, sometimes silent mutations

Question 36

what ratio is used to correct phylogenetic tree ratios for what is expected by chance? (2)

Answer 36

- NSexp : Sexp = ~3:1 | - due to the degenerate nature of the genetic code, ~25% of possible sequence changes are expected to be synonymous

Question 37

what formulas are used to correct for phylogenetic tree ration for what is expected by chance? (2)

Answer 37

- K(A) = NSobs/NSexp | - K(S) = Sobs/Sexp

Question 38

neutral drift (2)

Answer 38

- K(A)/K(S) = 1 | - K(A) = K(S)

Question 39

positive selection (2)

Answer 39

- K(A)/K(S) > 1 | - K(A) >> K(S)

Question 40

purifying selection (2)

Answer 40

- K(A)/K(S) < 1 | - K(A) << K(S)

Question 41

other evidence of purifying selection

Answer 41

- emerging strong deleterious variants are quickly purged from the population so that all alleles are non-deleterious after selection

Question 42

other evidence of positive selection (2)

Answer 42

- classic hard sweep | - new advantageous variant emerges and quickly purges all other alleles after selection occurs

Question 43

other evidence of balancing selection

Answer 43

- heterozygote advantage