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BIOL 1102 Exam One
Jan 28 Lec
| Question | Answer |
|---|---|
| What do the types of natural selection refer to? | how phenotypes change over time |
| What are the four types of natural selection? | directional selection, stabilizing selection, diversifying (disruptive) selection, frequency-dependent selection |
| How does directional selection work? | the distribution of phenotypes shifts to one side |
| How does diversifying/disruptive selection work? | the distribution of phenotypes shifts to the extremes |
| How does stabilizing selection work? | the distribution of phenotypes converges toward a central value |
| What type of selection did the galapagos finches show? | directional selection |
| How did galapagos finches show this type of selection? | before a drought -> big and small seeds, after the drought, only big seeds survivd, birds with larger beaks were able to eat, size of finch beaks increased over time |
| What is an example of stabilizing selection? | human birth weight - if baby is too small, chances of survival is too low, and if too big there is complications during delivery |
| What is an example of disruptive selectoin? | flies feeding on apple and hawthorn fruits, flies whose life cycles coordinate with the fruiting of specific trees have greater fitness that those whose life cycles place them between the fruiting of either tree species |
| What is positive frequency-dependent selection? | more common phenotypes have a higher fitness |
| What is negative frequency-dependent selection? | more rare phenotypes have a higher fitness |
| Which type of frequency-dependent selection can maintain genetic diversity for phenotypes? | negative selection |
| What is an example of positive frequency-dependent selection? | a common morph of butterfly will already have been learned by birds not to be eaten, but rarer morphs are more likely to be the prey to a bird and survives less |
| What is an example of negative frequency-dependent selection? | grove snails - song thrushes tend to eat snails with common shell types, giving snails with rare shell types a selective advantage |
| What is genetic drift? | allele frequencies within a population change by chance alone as a result of random sampling from generation to generation |
| What is genetic drift's relation to adaption? | genetic drift occurs due to random factors, it is an evolutionary force that does not lead to adaptation |
| When is genetic drift more popular? | sampling error occurs with a smaller sample/population |
| When can genetic drift occur? | due to chances of survival randomly after a disaster, also result from random reproduction of certain individuals in a population (when some reproduce while others don't, causing the random change of allele frequency across generations) |
| What are some consequences of genetic drift? | harmful alleles may increase in frequency by drift, and advantageous alleles may be lost by drift |
| What is the bottleneck effect? | occurs when a large, random portion of a population is killed, leaving few survivors |
| What is the founder effect? | occurs when a small group splits off to establish a new population, often with different allele frequencies than the original |
| What is an example of founder effect? | the amish population -> marrying within increases the number of people who are homozygous for rare recessive alleles |
| What is gene flow/migration in population genetics? | transfer of genetic material, in the form of alleles, from one population to another |
| How are two ways gene flow changes alleles? | add new alleles to a population or change the frequencies of existing alleles? |
| What does gene flow prevent a population from doing? | genetically diverging |
| What are three factors that affect gene flow? | habitat fragmentation, species mobility, and location |
| How does species mobility affect gene flow? | birds can fly long distance, plants must remain in place but pollen and seeds can move, fish in lakes or ponds can't easily move |
| How does location affect gene flow? | populations on islands don't easily exchange genetic material |
Created by:
goldengalleon