Evolution Study Guide - Key
1. What are adaptations? Inherited traits that increase an organism’s chance of survival in
a particular environment.
2. Define and give an example of each of the following: homologous structures,
analogous structures, vestigial structures. How can they be used to determine
relatedness?
Homologous – structures inherited from a common ancestor but adapted to different
functions (ex. Human hand, whale fin, and bird wing bones)
Analogous – structures used for the same function, but NOT inherited from a common
ancestor (ex. Bird wings and insect wings)
Vestigial – inherited but no longer have a function (ex. Human appendix, python hip
bones)
The more homologous and vestigial structures two species have in common, the more
closely related they are.
3. Describe and distinguish between directional selection, disruptive selection, and
stabilizing selection.
Directional – a type of natural selection in which the distribution of a trait shifts toward
one of the extremes
Disruptive – when the distribution of traits shifts to BOTH extremes
Stabilizing – when the distribution narrows in around the average
4. Describe and distinguish between geographic isolation, temporal isolation, behavioral
isolation, and reproductive isolation.
Geographic – populations are physically separated from each other by bodies of water,
canyons, mountains, etc.
Temporal – populations have different mating seasons
Behavioral – populations have different courtship rituals
Reproductive – Because of any of the previous 3, populations cannot interbreed and
produce viable offspring
5. What is a success and a failure in Darwin terms? Success = surviving, reproducing and
passing on traits to offspring. Failure = not reproducing and passing on traits.
6. What is common descent? Different species have common ancestors
7. What is natural selection? Know that it acts upon phenotypes. The process by which
organisms with favorable variations survive and reproduce at higher rates than those
without such variations.
1. There is variation within a population due to inherited traits.
2. Some variations are more favorable than others.
3. More young are produced than can survive.
4. Those with the favorable variations are more like to survive and reproduce and pass
on their favorable traits.
5. Over time, changes accumulate and gene frequencies in populations change.
8. What is biogeography? Study of the distribution of species and their ancestors.
9. What is a gene pool? The total collection of genes in a population.
10. Define evolution. A change in genetic frequencies in a population over time.
11. What is a mutation? A change in the DNA sequence.
12. What determines if an allele will increase or decrease in frequency in a population? If
it is favorable or offers an advantage to those individuals who have it, its frequency will
increase. If it is harmful to those individuals that have it, its frequency will decrease.
13. What is speciation and what is necessary for it to happen? The formation of new
species from a common ancestor. Reproductive isolation must occur.
14. What is a species? A population that can interbreed and produce viable (healthy and
fertile) offspring.
15. What is adaptive radiation? When many species arise from one common ancestor
because they all adapt to fill different niches.
16. How can amino acid sequences and DNA sequences be used to determine
relatedness? The fewer differences there are between two species, the more closely
related they are.
17. What is convergent evolution? When two species that are not closely related develop
similar characteristics because they occupy similar niches.
18. What is divergent evolution? When two species arise from one because they become
reproductively isolated.
19. What is coevolution? When different species that live in the same area evolve in
response to each other’s presence (ex. Predators become better hunters, prey blends in
to surroundings better)
20. What are acquired characteristics? Can they impact evolution? Characteristics that an
organism acquires during the course of its lifetime that CANNOT be passed on to
offspring (ex. scars, losing a limb). They CANNOT impact evolution since they cannot be
passed on to offspring.