Evolution Test Review

1. Give a definition for evolution. Why do living things need to evolve?

• Definition: living things changing over time by which descendants come to differ from ancestors.

• As the environment changes, living things need to survive, so they too must change as time goes on.

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

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

4. What are homologous structures? Give an example. How do they

provide evidence for evolution?

• Similar structures with different functions• Example: a human’s arm and a bat’s wing• Evidence: they show that there was a

common ancestor

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: Appendix & tailbone in humans; wings on flightless birds

• Evidence: show how things change over time, gives evidence of a common ancestor (i.e. wings on both flightless birds and regular birds point to a common ancestor).

6. How does embryology (study of embryos/development) provide

evidence for evolution?

• Similarities among embryos show a common ancestor

• Also show how things have changed over time (ex – human embryos have gill slits and tails as embryos that go away during development)

7. What molecular evidence can be used to support the theory of

evolution? Why does it support the theory?

• Similar DNA sequences and proteins• The more close the DNA sequences and

proteins are, it is thought that the more closely related the two species will be

• Shows evidence of a common ancestor

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 environment that they live in, but also must have evolved from a common ancestor

9. Explain Charles Darwin’s discoveries (finches and tortoises).

• Finches: – 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

10. What are adaptations? Give an example of an adaptation

• Adaptation: a beneficial change that allows an organism/species to better survive in its environment compared to those that don’t have that version of the trait.

• Example: thick fur on a rabbit that lives in the arctic

11. What 3 things can we learn by studying cladograms?

• Cladograms show:– Probable relationships– Probable sequence of organisms (which organisms

evolved first).– Shared derived characters (which species share

certain heritable traits)

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

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

14. What is the purpose of sexual selection?

• Gives males traits to attract the best females to mate with. Males with these traits pass their alleles on more to the next generation.

• This allows the species to better survive (more offspring)

15. Describe extinction (include background and mass). Why do

species become extinct?• Background: happens over longer time

periods at a slow rate• 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 in the new environment

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

• Founder effect: occurs when part of a populations colonizes a new area and may evolve into a new species

17. What is gene flow?

• Movement of alleles between populations– Example: migration

– Lack of gene flow between populations may lead the two populations to evolve into different species.

18. What does it mean to be biologically fit?

• It means that the individuals are able to survive and reproduce

19. What are variations? Give an example.

• Differences in a certain trait in a population• Example: different beak types in finches

20. What is a gene pool?

• All the alleles of a gene available to a population

21. What are allele frequencies?

• How often certain alleles are seen in a population

• They can tell you which alleles better help a population survive (a more common allele would be thought to be more beneficial)

22. What is natural selection?

• Organisms will inherit beneficial adaptations that will help them survive and leave behind more offspring than other individuals without those adaptations.

23. What is reproductive isolation? Describe the 3 isolating mechanisms and how they lead to

speciation.• Reproductive isolation is when members of different

populations can no longer mate successfully with one another-final step before speciation (when two or more species arise from one existing species) due to no gene flow. This may occur due to:– Behavioral isolation: differences in courtship behaviors

between populations– Geographic isolation: physical barriers separate

populations– Temporal isolation: timing of mating prevents

reproduction between population

24. Describe directional, stabilizing, and disruptive selection. Give examples.

• Directional: favors phenotype at one extreme– Example: bacteria that are resistant to antibiotics will survive and

shift the population to all (mostly) have that same trait• Stabilizing: favors the intermediate phenotype– Example: gall flies lay their eggs in plants and that creates a “gall”

in the plant – the medium sized galls are left alone while the small galls are destroyed by wasps and the large galls are destroyed by woodpeckers

• Disruptive: favors both extreme phenotypes– Example: bright blue (dominant trait) male buntings (birds) will

attack and kill blue-brown (intermediate pheno.) males and leave the brown (recessive) males alone