Evolution by Natura l Selection

1. Evolution by Natural Selection

2. Life’s Natural History isa Record of Succession& Extinction

3. Evolution of life has altered the Earth

4. Inhistoricalcontext • Darwin did not originate the idea of evolution!!!

5. Charles Darwin (1809 – 1882) • English naturalist who proposed the theory of evolution by natural selection

6. HMS Beagle Voyage 1831-1836 • Darwin sailed around the world on the HMS Beagle and carefully studied thousands of different plants and animals

8. The Galapagos Islands Most of animal species on the Galápagos livenowhere else inworld,buttheyresemble species living on South American mainland. 800kmwestofmainland

9. Uniquespecies

10. Galapagos Giant Tortiose

11. Blue-footed Booby

14. The Birds… • Galápagosbirds • 22of the 29 species of birds on the Galapagos are endemic-found only on these islands • One particular group… • at first, he paid little note toa series of small but distinctive birds • some were woodpecker- like, some warbler-like,& some finch-like

15. Darwin’s finches • Darwin was amazed to find out they wereallfinches • 14species • but onlyonespeciesonmainlandof SouthAmerica - 800kmaway • all presumablyoriginatedfrommainland

16. Correlation of species to food source Adaptive radiation - divergent evolution in which ancestral species evolve into an array of species to fit a number of diverse habitats.

17. Darwin’s finches • Differences in beaks • associated with eating different foods • adaptations to foods available on islands • Darwin’s conclusions • when original South American finches reached islands, adapted to available food in different environments • over many generations, the finches changed anatomically & behaviorally • accumulationoffavorabletraits led to the emergenceof different species

18. Darwin’s finches • Finches with beak differences allowed them to… • successfully feed • successfully compete • successfully reproduce • pass successful traits onto their offspring

19. Evolution by Natural Selection • Evolutionis the gradual change in a species, or populations over time, not individuals. • Darwin was the first scientist to realize that evolution can work by natural selection. • Natural Selection – Is a mechanism for change in populations. It occurs when organisms with favorable variations survive, reproduce, and pass their variations to the next generation • E.g. Thick fur is a favorable trait in cold environments

23. Essence of Darwin’s ideas • His theory was simple… • Variationexists in natural populations • Manymoreoffspringareborneachseason than can possibly survive to maturity • Asa result, there isa struggleforexistence • Characteristicsbeneficialin the struggle for existence will tend to become more common in the population, changing the characteristicsofaspecies • Over time, and givena steady input of new variation into a population, these processes lead to theemergenceof new species

24. Natural Selection • Darwin referred to all of these factors together asnaturalselection: • Variation • productionofmore offspring than can survive • Competition • forfood, for mates& nesting spots, to escapepredators • differential survival based on traits

25. Variation in Populations • Evolution by natural selection happens in populations, not individuals. A single organism cannot evolve. Populations evolve. • Populations evolve because there is variation • Variation causes some organisms to be better fit than others. Better fit organisms are more likely to survive and pass their genes to the next generation

26. Witness to Evolution • PepperedMoth • dark vs. light variants Peppered moth

27. Peppered moth Year %dark% light

28. Peppered moth • Why did the population change? • early 1800s = pre-industrial England • low pollution • lichen growing on trees= light colored bark • late1800s=industrialEngland • factories= soot coated trees • killed lichen= dark colored bark • mid 1900s = pollution controls • clean air laws • return of lichen= light colored bark • industrialmelanism

29. Evolution by Artificial Selection • Artificial Selection: Humans choose individuals with certain traits for breeding • After many generations of selection, dramatic evolutionary changes can result • Dogs • Fruits/Vegetables • Livestock

34. Evidence for Evolution • Adaptations • Structural • Mimicry • Camouflage • Physiological • Fossil Record • Comparative Anatomy • Homologous • Analogous • Vestigial • Embryological Development • DNA Similarities

35. Evidence #1 - Adaptations • All organisms have adaptations which help them survivein their particular environment • Adaptation: a structure or behavior that helps an organism better survive in its environment

37. Adaptations #1 - Structural Evolution of Mole Rats

38. Adaptations #2 - Mimicry • Mimicry: a structural adaptation that enables one species to resembleanother species • E.g. A harmless species might mimic a poisonous one

42. Adaptations #3 - Camouflage • Camouflage: a structural adaptation that allows a species to blendin with its surroundings

47. Adaptations #4 - Physiological • Many bacteria have evolved resistance to antibiotics in the last 50 years • Pests have evolved resistance to pesticides

48. Natural selection in action • Insecticide&drugresistance • insecticidedidn’t kill all individuals • resistant survivors reproduce • resistanceis inherited • insecticide becomes less& less effective

49. Evidence #2 - Fossil Evidence • Fossil: Any trace of a dead organism • Fossils show the evolution of species over the past millions of years • Fossil evidence proves that modern species have evolved from ancient species

50. Archaeopteryx