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Forces of Evolution
| Question | Answer |
|---|---|
| Evolutionary factors | Migrations, mutation, genetic drift, and natural selection |
| What is evolution? | The change of allele frequency from one generation to the next |
| What changes the allele frequency? | Any evolutionary factor |
| What happens if no evolutionary factors act on a population? | The allele frequencies will not change from one generation to the next |
| How is the change in allele frequencies best known for? | The Hardy-Weinberg Law |
| What is the purpose of the Hardy-Weinberg Law? | To define the forces of evolution |
| What is mutation? | The change in DNA |
| When base changes, what else changes? | Amino acids and possibly the enzyme function |
| Most mutations are... | Deleterious |
| If there is no mutation... | There is no evolution |
| Deleterious | Harmful |
| What deleterious do? | Reduces enzyme function. Likely harmful |
| Example of a deleterious mutation | Cytochrome C (104 aa's) |
| Example of a beneficial Mutation | Houseflies resistant to DDT or bacteria resistant to various antibotics |
| DDT | Used in World War 2 |
| Mutations are... | Random |
| Mutations are not directed by | Environment |
| What environmental factors can increase mutation rate? | X-rays, ultraviolet light, chemicals |
| Define migration | The movement of individuals among populations |
| Migration by itself | Not a strong evolutionary force |
| What is Migration best used for? | Help endangered species increase or maintain genetic variability |
| Rhinos | Pouchers removed the Rhinos horns in believing they wouldn't attack |
| Where is their no genetic variability? | Zoos |
| Genetic Drift | Accidental change in allele frequency |
| Genetic drift has a higher effect in small or large populations? | Small populations |
| Two types of genetic drift's that change allele frequencies | Bottleneck Effect and Founder Effect |
| Example of genetic drift in a small population | Gray squirrel fairy tale |
| Squirrels: gray vs. black vs. white- what can they do? | They can interbreed because they are the same species |
| If all the white squirrels are wiped out, what happens? | Possible the gray squirrels carry the white gene to reproduce new white squirrels |
| Bottleneck Effect | Change in allele frequency when a population decreases in size |
| Result of Bottleneck | Rare alleles lost |
| Example of Bottleneck | Northern Elephant Seals |
| Northern Elephant Seals hunted till... | Extinction |
| Why were they hunted for? | Blubber used for oil lamps |
| Variability lost when... | Population decreased |
| What do the seals not have? | Genetic Variability |
| Another example of lose of genetic variability | Cheetahs |
| Low genetic variability results | Vulnerable to diseases and trouble reproducing |
| Founder Effect | New population started by a small group |
| When it is founder effect | Allele frequencies are different from the orginial |
| Natural Selection | Non-Random; differences due to either differential survival or reproduction |
| Natural selection is the ONLY evolutionary force that leads to ... | Adaptation |
| Natural Selection acts in 3 ways | Stabilizing, Directional, and Disruptive selection |
| Stabilizing Selection | Reduces the amount of variation in a trait (centers in the middle) |
| Directional Selection | Changes the average value of a trait (shifts to the right) |
| Examples of Directional Selection | Medium ground finch during drought in Galapagos and peppered moth in England |
| Disruptive Selection | Increase the amount of variation in a trait (splits the center in half/shifts to both sides) |
| Example of Natural Selection | Guppies varying in color among different parts of the streams |
| Why are upstream fishes brighter than downstream fishes? | Females prefer to mate with brightly colored males |
| What is different between upstream and downstream guppies? | Predators |
| Upstream predators that eat small guppies | Killifishes |
| Downstream predators that eats adult guppies | Cichilds |
| How do you test whether predators have an affect on guppy colors? | Get a right amount of guppy stock / build up a large population varying in color / split into artificial ponds / let guppies reproduce and measure colors |
| Artificial ponds (3) | No predators, Killifish ONLY, and Cichilds ONLY |
| Results in artificial ponds | --- |
| No predators | Males got brighter |
| Killifish ONLY | Males got brighter |
| Cichilds ONLY | Males got duler |
| When researchers moved the dull male guppies to the Killifish-ONLY areas what happened? | The males got brighter |
| What factors act as agents for natural selection? | Predator behavior and female prefernce |
| Artificial Selection | Domesticated plants and animals |
| Natural Selection in nature | Grant's study in ground finches and evolution of guppy colors |
Created by:
animalsavior
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