1. EVOLUTION
CHAPTER 15

2. Natural Selection & the Evidence for Evolution
Ch. 15, Sec. 1

3. Evolution Gradual change in a species over time due to adaptations,
There are exceptions
Science is Tentative
Development of new organisms from preexisting types of organisms
Living things come from other living things
New species come from other species

4. Characteristic changes in a population involve changes to genes
These changes then get passed along through the genes
Who do you get your genes from?
Supported by a lot of evidence and data
Fossil, Anatomical, & DNA

5. Charles Darwin (1809-1882) Started off studying medicine
1831 signed on for a 5 year journey of South America on the HMS Beagle
Enjoyed nature & making observations
Noticed similar looking organisms on different continents

7. Darwin’s Clues Collected fossils
Observed the adaptations of plants & animals allowing them to survive in particular environments
Adaptation = a trait (which is coded for by DNA in a gene) that allows an organism to be successful in its environment
Like tools that help them get the job done

8. How are these organisms adapted to their environment?

9. Galapagos Islands One of Darwin’s stops on the Beagle
Group of volcanic islands off the west coast of South America

10. Home to several species of finches
Each species is adapted to the type of food eaten

11. Darwin’s Hypotheses
Darwin hypothesized that all the species descended from ancestral finches
The ancestral finches flew to the Galapagos Islands over from mainland South America
Population changed over time to adapt to the environment

12. Darwin’s Observations
1. Overproduction
Most species produce large numbers of offspring (ex: rabbits)
But why isn’t the earth overrun by rabbits?
The environment will set a limit on how big the population gets by causing deaths or limiting births
2. Competition within a species.

13. Observations cont. 3. Variation
Within populations organisms have different traits because of variations in genes
Variations can be inherited (who do you get your genes from?)
Populations have multiple alleles for any given trait (dark fur/light fur, tall ears/short ears, etc.)

14. In summary… What “chooses” the superior traits?
Organism’s that have superior traits/tools are better adapted
Therefore they’re more likely to survive
Therefore they’re more likely to reproduce and pass on the genes for the superior traits/tools
What “chooses” the superior traits?

15. Artificial Selection
Darwin worked with breeding different variations on pigeons
Artificial Selection = humans select good traits in organisms to breed
Ex: prettier roses, bigger chickens, sweeter oranges
YOU see it all the time
Darwin hypothesized:
Something like Artificial Selection must be acting on the organisms living in the wild

16. Natural Selection
Natural Selection = mechanism for change in populations; organisms with favorable variations survive, reproduce, & pass on the variation to the next generation (offspring)
Organisms with the best adaptations (helpful traits, good “tools”) are most likely to survive & reproduce
Through inheritance the adaptations will become more frequent in the population

17. Who gets to evolve?
It is the population that evolves, not the individual
If you like swimming, can you choose to evolve gills?
An individual can be born with a mutation
If the mutation is an advantage (good “tool”) for living in a particular environment then that individual will be more likely to survive & pass on that mutation to its offspring

19. Structural Adaptations
Why are these structures adaptations?

20. Mimicry = structural adaptation allowing one species to resemble another species

21. Camouflage = adaptations allows species to blend in with surroundings

22. Rapidly Developing Physiological Adaptations
Evolution is not always a slow process
Evident in antibiotic resistance (bacteria evolve too)

23. Resistance of insects to pesticides

24. Increased toxicity of snake poison

25. Fossil Evidence
Fossils show that over time species have gradually changed their form
A transitional species will have characteristics of both the ancient and modern organism
there has to be something in between
Ex: Do children automatically become adults?
Ex: Modern whales evolved from an ancient, land mammal

28. Anatomy Evidence
Studying anatomy can uncover structural evidence of a common ancestor
Homologous Structure = similar in build, different function; anatomical structures in different species inherited from a common ancestor

29. Homologous Structures
An early ancestor of all 4 species had a forelimb with similar structure (common ancestor)

30. Analogous Structures
Have closely related functions, but are built differently; does not indicate a common ancestor

31. Vestigial Structures = serve no function but resemble structures with functional roles in other animals

32. Embryology Embryology = the study of how organisms develop
Early stages of vertebrate embryos look very similar
As development continues embryos of different species start looking less alike

34. DNA Evidence All living organisms have DNA in common
DNA codes for proteins
The more closely related two species are….
The more similar their DNA….
The more similar the proteins made in their bodies are

35. Mechanisms of Evolution
Ch. 15, Sec. 2

36. Population Genetics
Gene Pool = all the alleles for a particular trait in a population are “pooled” together
ex: all the alleles for short fur and long fur, all the alleles for brown fur and black fur
Allelic Frequency = percentage of a specific allele in the gene pool
% of brown fur alleles & % of black fur alleles
Genetic Equilibrium = maintaining the same frequency of alleles over time

37. Changes in Genetic Equilibrium
Mutations can cause variations to be added to the gene pool of a population
Genetic Drift = chance events changing a population’s genetic equilibrium

38. Natural Selection Acts on Variations - red (before) blue (after)
Stabilizing selection = natural selection that favors average individuals in a population

39. Natural Selection Acts on Variations - red (before) blue (after)
Directional selection = natural selection favors one of the extreme variations of a trait

40. Natural Selection Acts on Variations - red (before) blue (after)
Disruptive selection = individuals with either extreme of a trait’s variation are selected for

41. Evolution of a Species
Changes to a gene pool can lead to the evolution of a new species
Speciation = members of similar populations can no longer interbreed

42. Biogeography – Field Video
Geological Isolation = physical barriers divide a population 
Over time, the  divided populations may become two species that can no longer interbreed, even if reunited

43. Reproductive Isolation = occurs when formerly interbreeding organisms can no longer mate and produce fertile offspring; 2 types
1. Genetic Isolation = genes of two populations are so different they cannot produce fertile offspring
2. Behavioral isolation (ex: one population mates in the spring, another population mates in the fall)

44. Change in Chromosome Numbers = mistakes in cell division lead polyploid individuals (abnormal sets of chromosomes)
Polyploids can be sterile, unable to reproduce
Polyploids can also reproduce and generate a new species through interbreeding

45. Speciation Rates
Gradualism = species originate through gradual change of adaptations
Punctuated Equilibrium = speciation occurs in quick, rapid bursts

47. Patterns of Evolution
Divergent Evolution = species that were once similar evolve to look differently
Adaptive Radiation = ancestral species evolving to fit into a lots of different habitats

48. Field Museum Video
Convergent Evolution = very distantly related organisms evolving similar traits

50. Hummingbird moths are night-flying insects whose behavior and appearance are similar to those of hummingbirds. Explain how these two organisms demonstrate convergent evolution and analogous structures. (1 paragraph, 5-8 sentences)