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19 Cards in this Set

  • Front
  • Back
What are some practical uses of phylogenetic trees?
1)forensics (ex: whale harvesting)
2) HIV origins
3. HIV forensics
4. Human ancestors
Convergence as evidence for adaptation: what are examples of convergent evolution?
wings of birds and bats, the eyes of octopi and fish, and the placement of eyes of crok and hippo
How is the squirrel-predation test an example of convergent evolution?
The similar suites of behavioral characteristics observed in these phyletically diverse groups might suggest convergent evolution in response to selection pressures imposed by colonizing open habitats requiring construction of burrows to avoid predation.
what is an adaptation?
A trait that increases the ability of an individual to survive or reproduce compared to individuals without the trait.
what's HIS definition of adaptation?
A trait MODIFIED BY SELECTION that increases the ability of an individual to survive or reproduce compared to individuals without the trait
What are the 2 potential ways of determining whether a trait is adaptive?
1) experiment on existing variation
2) study the evolutionary context of changes in the trait
Hypothetical example: white and green rabbits.
Is this strong evidence of selection on fur color?
Maybe. It depends on the evolutionary history of change(s) in fur color and their association with the environment.
Why is it that some of the strongest comparative evidence for adaptation comes from convergent traits?
Traits that arise repeatedly and independently (ie convergently) in association w/ a particular selective force are likely to be causal responses (true adaptations to that force
What are these selective forces?
might be environmental (predation levels, climate, etc.), social (solitary vs. group living), etc.
Back to the green and white fur example, what needed to be included to make stronger evidence of adaptation?
independent associations b/w fur color and environment
What are sister taxa?
pairs of closest relatives w/in an evolutionary tree (each pair of sister taxa is evolutionarily and statistically independent of every other pair b/c sister taxa must have arisen in at least one lineage since their common ancestor)
What's a much more powerful method of comparative analysis?
PIC (Phylogenetically Independent Contrasts)
Explain the PIC using the male testes example.
hypothesis = bigger testes = more sperm
BUT species are not independent. In any phylogenetic tree many taxa have similar traits b/c of shared history by descent.
What is the definition of a contrast?
the change in a character b/w 2 taxa. PICs are contrasts that count every lineage in a phylogenetic tree ONLY ONCE.
What's an imporatant use of phylogenetic trees?
performing comparative analyses
And what are comparative analyses particularly appropriate for?`
studying adaptations that are difficult to address experimentally.
What are comparative analyses?
correlations that factor out biases caused by shared history
Comparative analyses are based on the idea that___________.
convergence is good evidence of adaptation
What are 2 types of comparative analysis?
1) Sister taxa comparison
2) Phylogenetically independent contrasts (PICs)