1. We can see evolution in action. 1)Short Generation times. a. Reproduce quickly 2)High mutation rates. 3)Selective pressure is very great. 1)Short Generation times. a. Reproduce quickly 2)High mutation rates. 3)Selective pressure is very great. This usually happens because of one or both of the following:

2. 1) Bacteria reproduce extremely quickly, often mutate, and many can double their population in under an hour. Bacteria can quickly evolve to be resistant to antibiotics if the drugs are not administered properly or for the entire duration of the infection. If any bacteria are not fully wiped out by the antibiotics, the more resistant ones that remain will continue to reproduce. PBS Microbe Clock

3. An example of rapid evolution due to very high selection pressure is taking place among African elephants. As prized sources of ivory, they are being hunted closer and closer to extinction mainly for their tusks. 1. Since the elephants with the largest tusks are being hunted most, there is a heightened selection pressure (in this case, humans) that is wiping out large-tusked elephants. 1. Since the elephants with the largest tusks are being hunted most, there is a heightened selection pressure (in this case, humans) that is wiping out large-tusked elephants. 2. The remaining population has higher frequency of smaller- tusked elephants(alleles), and some with no tusks at all! 2. The remaining population has higher frequency of smaller- tusked elephants(alleles), and some with no tusks at all! 3. So overall, it appears that elephant tusks are shrinking. 3. So overall, it appears that elephant tusks are shrinking.

4. 1. Natural Selection is at work when individuals reproduce. 2. Finding a mate is part of the struggle to reproduce. Tale of the Peacock Video

5. Natural Selection in Action 3 Facts, 1 Lie A. Salamander of the Sierra Nevada use camouflage to adapt to their environment. B. Coastal mountain salamanders use mimicry to survive their environment. C. Geographic separation can cause speciation. D. Hybrid salamanders are the best adapted type of salamanders. NOVA: Natural Selection in Action Video

6. II. Speciation A. Speciation – The formation of a new species by the change of allele frequency (genetic variation) due to natural selection. B. Species: a group of organisms that can interbreed and produce fertile offspring.

7. 3 Steps of Speciation 1. Separation: part of a population becomes isolated from the rest. What events could cause separation?

8. 3 Steps of Speciation 2. Adaptation: Natural selection improves the fit between species & environment created from changes in the gene pool. 3. Divergence: Enough differences accumulate no longer allowing the populations to interbreed, which leads to a NEW SPECIES.

9. Example #1: Fruit Flies 3. Divergence - Natural selection changes physical features, food preferences, and mating rituals A population of fruit flies lay their eggs in some rotting bananas along a beach. 1. Separation - A hurricane washes the bananas and eggs out to sea and onto a nearby island. The flies hatch and are genetically isolated from the mainland fruit flies. 2. Adaptation - Environmental conditions are different on the island, so the island flies evolve different adaptations. If the two populations were to by chance meet again they would unlikely mate with each other due to the differences in their gene pools creating differences in the characteristics listed above, especially mating rituals.

10. Example #1: Fruit Flies 3. Divergence - Natural selection changes physical features, food preferences, and mating rituals A population of fruit flies lay their eggs in some rotting bananas along a beach. 1. Separation - A hurricane washes the bananas and eggs out to sea and onto a nearby island. The flies hatch and are genetically isolated from the mainland fruit flies. 2. Adaptation - Environmental conditions are different on the island, so the island flies evolve different adaptations. If the two populations were to by chance meet again they would unlikely mate with each other due to the differences in their gene pools creating differences in the characteristics listed above, especially mating rituals.

11. a) Founders Arrive b) Separation of Populations c) Changes in the Gene Pool d) Reproductive Isolation e) Ecological Competition f) Continued Evolution South America Galapagos Islands A A A A B A B B A B C A B C E D Example 3: Darwin’s Finches in the Galapagos Islands

12. Factors Contributing to Speciation Isolating Mechanisms Genetic Drift / Founders Effect

13. Isolating Mechanisms Genetic differences that prevent breeding between two species (helping to cause speciation) This can happen before or after mating. **(Remember) Species: a group of organisms that can interbreed and produce fertile offspring Pre-mating Examples - mating rituals, behaviors, songs or calls, time of mating Post-mating Examples – hybrids are usually sterile

14. Genetic Drift A loss of genetic variation (alleles) brought about by chance, not adaptation. Usually occurs in small populations. Causes less of a chance for speciation since the species does not have the genetic diversity to adapt to changes.

15. Genetic Drift Mountain Gorilla less than 720 left, due to habitat loss Cheetahs (decline in population 1,000s yrs ago during Ice Age); most highly endangered species due to habitat loss

16. Founders Effect Loss of genetic variation due to an isolated small founding population (could contain some rare variations (alleles) making the gene pool different from the original) Examples – Amish (founded by a few couples of German immigrants in 1770; unusually high frequency of dwarfism & polydactyly (extra fingers) Why? Because of continuous marring within the group, recessive gene diseases are more likely to show up in offspring

17. At what pace does evolution occur? GRADUALISM states that evolution occurs slowly over time and includes many transitions (Darwin’s model) PUNCTUATED EQUILIBRIUM states that evolution occurs in short bursts followed by long periods of stasis (no evolving). Developed in 1970’s by Stephen Gould