1. Evolution by
Natural Selection

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

3. Evolution of life has altered the Earth

4. In historical context
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
Darwin sailed around the world on the HMS Beagle and carefully studied thousands of different plants and animals
main mission of the Beagle was to chart South American coastline

8. The Galapagos Islands
Most of animal species on the Galápagos live nowhere else in world, but they resemble species living on South American mainland.
800 km west of mainland

9. Unique species

10. Galapagos Giant Tortiose
Galapagos tortoises

11. Blue-footed Booby
Blue-footed booby

13. Galapagos marine iguanas

14. The Birds… Galápagos birds One particular group…
22 of the 29 species of birds on the Galapagos are endemic - found only on these islands
One particular group…
at first, he paid little note to a 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 were all finches
14 species
but only one species on mainland of South America km away
all presumably originated from mainland

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.
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 Darwin’s conclusions
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
accumulation of favorable traits led to the emergence of 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
Evolution is 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
Due to survival of the fittest.

23. Essence of Darwin’s ideas
His theory was simple…
Variation exists in natural populations
Many more offspring are born each season than can possibly survive to maturity
As a result, there is a struggle for existence
Characteristics beneficial in the struggle for existence will tend to become more common in the population, changing the characteristics of a species
Over time, and given a steady input of new variation into a population, these processes lead to the emergence of new species

24. Natural Selection
Darwin referred to all of these factors together as natural selection:
Variation
production of more offspring than can survive
Competition
for food, for mates & nesting spots, to escape predators
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 Peppered Moth dark vs. light variants

27. Peppered moth
Year
% dark % light
1848 5 95
1895 98 2
1995 19 81

28. Why did the population change?
Peppered moth
Why did the population change?
early 1800s = pre-industrial England
low pollution
lichen growing on trees = light colored bark
late 1800s = industrial England
factories = soot coated trees
killed lichen = dark colored bark
mid 1900s = pollution controls
clean air laws
return of lichen = light colored bark
industrial melanism
genetically determined melanism as a population phenomenon especially in moths in which the proportion of dark individuals tends to increase due to differential predation especially by birds which more easily find and eat lighter-colored individuals in habitats darkened by industrial pollution

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 survive in 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
Pressure from predators led them to live underground.
Structural adaptations include large teeth and claws to help them survive in their underground environment and defend themselves from predators since they are blind. Vision had no survival advantage for them.

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

42. Adaptations #3 - Camouflage
Camouflage: a structural adaptation that allows a species to blend in with its surroundings
Camouflage organisms survive to reproduce

47. Adaptations #4 - Physiological
Many bacteria have evolved resistance to antibiotics in the last 50 years
Pests have evolved resistance to pesticides
Structural adaptations develop over millions of years. Physiological evolves faster because they are changes in organism’s metabolic processes.

48. Natural selection in action
Insecticide & drug resistance
insecticide didn’t kill all individuals
resistant survivors reproduce
resistance is 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

51. Puijila the walking seal

52. Evolutionary transition from fish to amphibians
Tiktaalik

54. Evidence #3 - Comparative Anatomy
Homologous structures: Body structures on different organisms that are similar in structure (same bones) and DID evolve from a common ancestor

55. Homologous Structures

56. Comparative Anatomy
Analogous structures: Body structures on different organisms that are similar in function but DID NOT evolve from the same ancestor (bird wing and butterfly wing)

57. Moth (insect)
Pterodactyl (reptile)
Bat (mammal)
Bird
Analogous Wing Structures

58. Comparative Anatomy
Vestigial structure: body structure in an organism that no longer serves its original purpose but was useful to an ancestor (useless wings on the African ostrich)

64. Evidence #4 - Embryological Development
Early in development, human embryos and embryos of all other vertebrates are very similar, which suggests that all vertebrates are related
Embryo – earliest stage of growth and development of both plants and animals.

66. Evidence #5 - DNA Similarities
Nearly all organisms have DNA, ATP, and many of the same enzymes
The DNA (genes) of closely related organisms looks very similar