1. Evolution
AP Biology
Unit 4

2. History of Evolutionary Theory
Linnaeus
Developed a system of classification based on body structures (morphology)
Lamarck
Said species could “will” themselves to change
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3. History of Evolutionary Theory
Darwin
Natural Selection causes species to change
Mendel
Genetics – now used as another way to look at evolution
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4. Natural Selection 5 parts:
Population growth has the ability to be exponential.
Populations tend to be stable in size (despite #1).
Resources are limited.
Individuals vary in phenotype.
5. Much phenotypic variation is heritable.
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5. Natural Selection (in summary)
There are more individuals produced than the environment can support  leads to competition for resources.
Individuals with advantageous traits in this competition will survive to reproduce and pass on those advantageous traits to the next generation.

6. Artificial Selection
Breeding animals or plants to have the desired traits
Ex. Dog & Cat breeds
American curl cat
Shar-Pei
Great Dane
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7. Newer developments in Artificial Selection
Cocker spaniel + poodle = Cockapoo
Labrador + Poodle = Labradoodle
Why mix with poodles?
Their fur tends to shed less– they were originally bred in an effort to create a guide dog for people who were allergic to dogs.

8. Vestigial Structures Structures that are no longer used in an organism
Ex. Appendix, tail bone
Many structures present in embryos are also used to show common ancestry -- developmental biology
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9. A fictional vestigial structure 

10. Analogous Structures Similar functions, different structures
Indicates different ancestors
Ex. Bird wing, butterfly wing
Result from convergent evolution: similar selection pressures cause similar structures to evolve.

11. Homologous structures
Similar structure, different functions
Indicate a common ancestor
Ex. Human hand, seal flipper, bat wing

12. Biogeography Study of distribution of organisms (past and present)
Demonstrate that organisms can evolve similarly to one another in similar environments from different ancestors
Ex. Marsupials in Australia – they are only found in Australia but some share similar characteristics with other organisms

13. Genetic Drift Changes in the gene pool caused by random events
Examples: Bottleneck Effect, Founder Effect, Geographic Isolation

14. Bottleneck Effect
drastic reduction in population (due to natural disasters, predators, etc.)

15. Example of Bottleneck Effect: Pingapalese People
example...Pingelapese people of Eastern Caroline islands in Micronesia....5% of currrent population of 3000 have certain type of colorblindness (complete colorblindness) (autosomal recessive)....elsewhere in world it is 1 in 50, ,000.  Prevalence can be attributed to a typhoon in 1775 where only 20 people survived and population was inbred from those remaining 20 people. A small region on chromosome 8 is the location of the achromatopsia gene. This gene—CNGB3—is responsible for the defective response of the cones, which are the color-detecting photoreceptors of the eye.
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16. Example of Bottleneck Effect: Cheetahs
another example...cheetahs....until 10,000 yrs ago they were more prevalent.  Now, the remaining few thousand are very similar genetically and can be attributed to two bottlenecks...one at the end of most recent ice age and one when they were hunted in 1800's.  Genetic diversity is gone...will suffer from recessive problems.
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17. Founder Effect
A few individuals become isolated from the original population
The resulting population is not representative of the original population

18. Example of Founder Effect
blood typing of native north american population...look at south america % have type O...could be attributed to founder effect

19. Another Example of Founder Effect: Ellis-van Creveld Syndrome
Amish people...small population that has a high incidence of certain traits...ex...Ellis-van Creveld Syndrome (short-limbed dwarfism, extra fingers, heart disease, teeth at birth and fused bones)...occurs in 7% of births.
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20. Geographic Isolation
When physical separation/isolation results in the formation of new species
Is a cause of founder effect
Adaptive radiation = many species evolving from one original ancestor
Example: when a group of American finches colonized the Hawaiian islands, the group became geographically isolated from other populations of the species. these finches eventually gave rise to the 23 species of Hawaiian honeycreepers.->adaptive radiation

21. Example of Geographic Isolation
Example 2: Geologic evidence from a study of wave patterns in sedimentary rocks indicates that most of Death Valley was covered by a huge lake during the last ice age. When the ice age ended, the region became dry. Only small, spring fed ponds remained. Members of a fish species that previously formed a single population in the lake may have become isolated in different ponds. The environments of the isolated ponds differed enough that natural selection and perhaps genetic drift acted on the separate populations
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22. Gene Flow · Migration (immigration, emigration)
Breeding across prior barriers (cultural barriers, for instance, as in human populations)
Changes allelic frequencies
Ex. Human migration

23. Phenotypic Polymorphism
Defined as variety of physical traits
Due to
genetic variation
genetic polymorphism
nonheritable variation

24. Fitness
·  fitness = contribution of individual to gene pool, relative to others’ contributions
·  relative fitness = contribution of a genotype (all individuals alike)
·  fitness of 1 means you (or your genotype) contribute at a maximum (100%)
fitness of 0 means you (or your genotype) do not reproduce at all

25. Types of Selection
Selection = Environment chooses those with the best adaptations to survive

26. Stabilizing Selection = middle phenotype is selected for

27. Disruptive Selection The two extremes are selected for Ex. Snails
marine snails...white and tan....tan ones can live among white barnacles on tan rocks, tan ones can live on tan rocks

28. Directional Selection = one phenotype is selected for
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Industrial melanism

29. Heterozygote Advantage
When being heterozygous gives you an advantage
Explains why a harmful recessive allele does not get eliminated from a population
Ex. Sickle cell anemia – heterozygotes are resistant to malaria
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30. Sexual Selection Genders appear different due to Sexual Dimorphism
Competition is inter- and intragender specific
Ultimately has to do with competition for higher fitness

31. Constraints on Natural Selection
Populations are not perfectly suited to their environments because
Environments constantly change and offer new challenges– individuals present might not have been the ones who would be best suited (Ex. A new population of people marooned from a breaking ship begin a new population. They do not necessarily represent the best of the gene pool)

32. Constraints on Natural Selection
Populations are not perfectly suited to their environments because
Evolution is slow and dramatic new structures rarely form/appear; instead, old structures are used for new structures (Ex. Birds have 2 wings rather than 4, which could help with flight, because they evolved from a 4-appendage reptile; 2 wings and 2 legs)

33. Constraints on Natural Selection
Populations are not perfectly suited to their environments because
Adaptations are often compromised (Ex. seal legs would help in land motion, but swimming with legs is less efficient than with flippers)

34. Constraints on Natural Selection
Populations are not perfectly suited to their environments because
Natural selection can only pick the best variation—it can’t create variations