1. Evolution Test Review

2. 1. Give a definition for evolution. Why do living things need to evolve?
Definition: the biological change over time by which descendants come to differ from ancestors.
As the environment changes, living things need to survive, so nature selects on those that are “fit” to survive, and those that are not. We see traits change over time based on natural selection.

3. 2. How are fossils dated?
Radiometric/ Radiocarbon Dating: measures the amount of radioactive isotopes in a fossil to determine its age
Pro: can give you the exact age of a fossil
Con: can’t be used on really old fossils because the radioactivity goes away with time
Relative Dating: compares the age of a fossil to other fossils found in the same rock layer
Pro: can be used to give you an estimated age of really old fossils
Con: rock layers can be shifted by earthquakes or mudslides and this can give an inaccurate estimate

4. 3. How can we get evidence for evolution from the fossil record?
The fossil record shows us how living things have changed their forms over time. We can see how nature has played upon adaptations.

5. 4. What are homologous structures. Give an example
4. What are homologous structures? Give an example. How do they provide evidence for evolution?
Similar structures with different functions found in different organisms.
Example: a human’s arm and a bat’s wing
Evidence: they show that there was a common ancestor for this development to be so similar.

6. 5. What are vestigial structures. Give an example
5. What are vestigial structures? Give an example. How do they provide evidence for evolution?
Structures that no longer serve a purpose but had a purpose in an ancestor
Example: Tailbone in humans; human appendix, wings on flightless birds
Evidence: show evidence of a common ancestor and how living organisms change over time.

7. 6. How does embryology (study of embryos/development) provide evidence for evolution?
Similarities among embryos show a common ancestor since early development is so similar among such different organisms.
Also show how things have changed over time (ex – human embryos have gill slits and tails as embryos that go away during development)

8. 7. What molecular evidence can be used to support the theory of evolution? Why does it support the theory?
Similar DNA sequences and proteins (compare proteins (amino acids) of different species.
The more close the DNA sequences and proteins are, it is thought that the more closely related the two species will be.

9. 8. How does biogeography provide evidence for evolution?
It shows that island species have a lot of similarities to animals on the closest mainland
It shows how species have adapted for the climate that they live in. Ex: Darwin’s finches

10. 9. Explain Charles Darwin’s discoveries (finches and tortoises).
Darwin noticed that where there were nuts for food, the finches had short, hard beaks
Where there was fruit and insects for food, the finches had long, thin beaks
Tortoises:
Darwin noticed that where there was low vegetation, the tortoises had short legs and necks
where there was high vegetation, the tortoises had long legs and necks

11. 10. What are adaptations? Give an example of an adaptation
Adaptation: a beneficial change that allows an organism/species to better survive
Example: thick fur on a rabbit that lives in the arctic, long neck on a giraffe to reach higher vegetation.

12. 11. What 3 things can we learn by studying cladograms?
Cladograms show:
Shared traits
The order the traits appeared in
Probable relationships

13. 12. How do you read a cladogram?
Reads from the bottom up
Oldest/most common trait at the bottom
Newest/least common trait at the top
Each organism on the cladogram has all the traits below it.

14. 13. Describe survival of the fittest.
The best adapted to the environment will survive and leave offspring behind to continue the species.
Example: the fastest running prey will be able to avoid predators and survive better than slower prey, therefore passing on the trait that helps them to be fast and in the future we see an increase in the allele frequency for the trait that allows this organisms to be fast.

15. 14. What is the purpose of sexual selection?
Different behaviors exhibited by males will be selected by females. If the female finds this to be attractive she mates with that male. The male that has the most “attractive” trait gets to mate with all the females and his genes are continuously passed on throughout the species. His traits become “ over-exaggerated” This is selection not by nature but by sexual attraction based on traits.
Example: beautiful song sung by male birds, beautiful feathers on a male peacock.

16. 15. Describe extinction (include background and mass)
15. Describe extinction (include background and mass). Why do species become extinct?
Background: happens over longer time periods at a slow rate, affects a few species
Mass: happens suddenly and drastically (wipes out lots of species on a global level)
Species become extinct because they lack the variations needed to survive. Ex: dodo bird

17. 16. Describe genetic drift
16. Describe genetic drift. Include the bottleneck effect and founder effect.
Genetic drift: changes in the alleles of a population due to chance.
Bottleneck effect: occurs when a “bottleneck event” (ex – natural disaster) drastically reduces the population so that it no longer resembles the original population. M&M’s in water bottle.
Founder effect: occurs when part of a populations colonizes a new area and most likely evolves into a new species. (Owl Island)

18. 17. What is gene flow? Movement of alleles between populations
Example: migration
Allows species to stay similar and not evolve separately (no speciation).
Ex: Yellow M&M’s travel to the brown side (more variation).

19. 18.. What does it mean to be biologically fit?
Fitness when it comes to biology means that one is “fit” to be successful in its environment. Those that we say are “fit” are those that have the best adaptations for that environment. Nature selects them to live on and pass on those traits over time.

20. 19. What are variations. Give an example
19. What are variations? Give an example. Where does variation come from?
Differences in a population (example, everyone in this room is of a different height, that is a variation amongst all of you).
Example: different beak types in finches, different neck length in turtles, different colors of fur in mice.
Variations come from mutations and recombination of chromosomes

21. 20. What is a gene pool?
All the genes (alleles) that exist in a population.

22. 21. What are allele frequencies. What can they tell you
21. What are allele frequencies? What can they tell you? What do we expect to happen to the frequency of beneficial alleles?
A measure of how often certain alleles are seen in a population.
They can tell you which genes better help a population survive (a more common gene would be thought to be more beneficial)
We expect beneficial alleles to increase over time in a population (this is why they are beneficial).

23. 22. What is natural selection?
Nature will decide which organisms have beneficial adaptations based on the environment that will help them survive. Those with the beneficial adaptations will leave behind more offspring than other individuals based on their ability to survive better and reproduce at a higher rate.

24. 23. What is reproductive isolation?
Reproductive isolation is when a specie can no longer successfully mate with each other. This is the last step before speciation (separation) of the species occurs.

25. 24. What are 3 isolating mechanisms? How can they lead to speciation?
The three isolating mechanisms are:
Geographic isolation
Behavioral isolation
Temporal isolation
They lead to speciation because gene flow between the species stops. They are either separated by a barrier, their behavior changes, or the timing of reproduction is off so they no longer mate.

26. 25. Describe directional selection, give an example that fits, and draw the graph.
Directional: favors phenotype at one extreme
Example: light colored moths used to be favored but overtime dark moths became favored because tree bark became darker.

27. 26. Describe stabilizing selection, give an example, draw a graph.
Stabilizing: favors the intermediate phenotype, selects against the two extreme phenotypes.
Example: medium birth weight in babies is favored over very small and very large birth weight in babies.

28. 27. Describe disruptive selection, give examples, draw the graph.
Disruptive: favors both extreme phenotypes, selects against the intermediate.
Example: black and brown fur rabbits which are the extreme can blend in, white which is the intermediate cannot blend in therefore they are eaten more. We see the intermediate shrink and the 2 extremes grow because of this.

29. Study hard!!!!
Good luck on the test!