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Chapter 23c
| Question | Answer | |
|---|---|---|
| ___is evolution at a small scale. it is the change in allele frequencies in a population over generations (time) | microevolution | |
| three mechanisms cause allele frequency change and bring about most evolutionary change: | 1. natural selection 2. genetic drift 3. gene flow (transfer of alleles between populations) | |
| ____is based on differential success in survival and reproduction -individuals have variations in their heritable traits -those with traits better suited to the environment produce more offspring than others | natural selection | |
| _____ results in alleles being passed to the next generation in proportions that differ from those in the present generation | natural selection | |
| ____evolve not individuals | populations | |
| Natural selection can cause____, a process in which traits that enhance survival or reproduction will increase in frequency over time | adaptive evolution | |
| ____is a process in which chance events cause allele frequencies to fluctuate unpredictably from one generation to the next | genetic drift | |
| ____tends to reduce genetic variation through the random loss of alleles. The smaller the sample, the greater the chance of random deviation from a predicted result | genetic drift | |
| the ____occurs when a few individuals become isolated from a larger population. Allele frequencies in the smaller founder population are different from those in the parent population | founder effect ex. genetic drift (founder) could occur if a few individuals are indiscriminately blown to a new island by a storm | |
| the ____ occurs when there is a drastic reduction in population size due to a sudden change in the environment | bottleneck effect | the resulting gene pool may no longer be reflective of the original population’s gene pool. if the population remains small, it may be further affected by genetic drift |
| how is less genetic diversity a negative thing? | increases the risk of extinction of a population through inbreeding | |
| Ex. Loss of prairie habitat caused a severe reduction in the population of greater prairie chickens in Illinois | the surviving birds had low levels of genetic variation, and only 50% of their eggs hatched | genetic drift during the bottleneck likely reduced genetic variation and increased the frequency of harmful alleles. genetic variation declined and harmful alleles likely increased in frequency in the current population |
| effects of genetic drift: a summary | 1. genetic drift is significant in small populations 2. genetic drift can cause allele frequencies to change at random 3. genetic drift can lead to a loss of genetic variation within populations 4. genetic drift can cause harmful alleles to be fixed | |
| ____consists of the movement of alleles among populations. Alleles can be transferred through the movement of fertile individuals or gametes (for example, pollen) | gene flow | affects adaptation to local environments ex. mainland and island populations of Lake Erie water snakes have different color patterns. -since no bands are favorable on the islands, we would expect all island snakes to not have bands but that not case |
| why are banded snakes on the island? | ongoing migration of banded snakes from the mainland population transports the genes associated with those snakes to the island | |
| gene flow tends to reduce variation among populations over time. | consider the spread of alleles for resistance to insecticides | -insecticides have been used to target mosquitoes that carry West Nile virus and other diseases -alleles have evolved in some populations that confer insecticide resistance to these mosquitoes -the flow of resistance alleles into a new population |
Created by:
Taylormorey