1. Natural Selection and the Evidence for Evolution
The theory of evolution is the most fundamental
concept in biology.

2. What is the origin of evolution?
Fossil records have been important to science since the 18th century.
Fossils have formed concepts & answers questions
Several ideas have been proposed but only 1 ideas accepted today by scientists.

3. Early scientists proposed ideas about evolution.
Evolution is the biological change process by which descendants come to differ from their ancestors.
A species is a group of organisms that can reproduce and have fertile offspring.

4. Three theories of geologic change set the stage for Darwin’s theory.
1. Catastrophism:
Volcanoes, Floods and Earthquakes once believed responsible for mass extinction and land formation
2. Gradualism:
The idea that changes on earth occurred in small steps over long periods of time
3.Uniformitarinism:
Geological processes over long periods of time cause the greatest change

5. Uniformitarianism is the prevailing theory of geologic change.

6. Charles Darwin and the Theory of Evolution

7. Charles Darwin (1809-1882) English scientists-founder of
modern evolutionary theory
1831 – naturalists
Collect, study & store specimens while on ship HMS Beagle
Developed theory to explain how evolution occurs

8. HMS Beagle

9. Darwin on HMS Beagle

10. Snoopy discovers Darwin's "Voyage of the Beagle" is not about his favorite dog, but about biological evolution

11. Darwin on the HMS Beagle
He began in 1831 at age 22 when he took a job as a naturalist on the English ship HMS Beagle, which sailed around the world on a five-year scientific journey.
As the ship’s naturalist, Darwin studied and collected biological and fossil specimens at every port along the route
For the next 20 years, Darwin’s work refined his explanations for how species change over time.

12. In the Galapagos
On the Galapagos Islands, Darwin studied many species of animals and plants that are unique to the islands but similar to species elsewhere.
He realized that individuals struggle to compete in changing environmental conditions.

13. Galapagos tortoise are the largest
On Earth, different from other
Tortoises in body size and shape
Galapagos marine iguanas
Eat algae from the ocean
Large claws help to cling
To slippery rocks
Galapagos finch
Is adapted to feed
On cacti.

14. Darwin observed differences among island species.
Variation is a difference in a physical trait.
Galápagos tortoises that live in areas with tall plants have long necks and legs.
Galápagos finches that live in areas with hard-shelled nuts have strong beaks.

15. An adaptation is a feature that allow an organism to better survive in its environment.
Species are able to adapt to their environment.
Adaptations can lead to genetic change in a population.

16. Darwin observed fossil and geologic evidence supporting an ancient Earth.
Darwin found fossils of extinct animals that resemble modern animals.
Darwin found fossil shells high up in the Andes mountains.

17. Darwin continues his studies
How did this help Darwin?
He knew that many species produced large number of offspring
He also knew that such species had not overrun Earth.
Only some individuals survive the competition and produce offspring
Darwin proposed Natural Selection as a mechanism for Evolution

18. Artificial Selection
artificial selection is the process of intentional or unintentional modification of a species through human actions which encourage the breeding of certain traits over others
Darwin hypothesis that there was a force in nature that worked like artificial selection

19. Several key insights led to Darwin’s idea for natural selection.
Darwin noticed a lot of variation in domesticated plants and animals.
In artificial selection humans can select specific traits through breeding
neck feathers
crop
tail feathers

20. Natural selection is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals.
Heritability is the ability of a trait to be passed down.
There is a struggle for survival due to overpopulation and limited resources.
Darwin proposed that adaptations arose over many generations.

21. Natural selection explains how evolution can occur.
There are four main principles to the theory of natural selection.
variation
overproduction
adaptation
descent with modification
About 11,000 years ago, large cats faced extinction due to food shortage in mammals so they had to eat reptiles.
In the Jaguar population, teeth and jaw size became an important variation for survival

22. 1. Variation Some natural variations are heritable
Over time, offspring with certain variations make up most of the population and may look entirely different from their ancestors.
1. Variation
Some Jaguars may be born with a slightly larger jaws and teach which is directly due to variation in the population
VARIATION

23. 2. Overproduction
A Jaguars may produce many offspring but few will survive due to competition for resources
Many offspring will increase the chance of competition between organisms
OVERPRODUCTION

24. 3. Adaptation
When an organism needs to compete against its environment for survival
According to Darwin’s theory, adaptations in species develop over many generations.
ADAPTATION

25. 4. Decent with Modification
Large teeth and jaws become a heritable trait
Overtime Natural selection will result in species with adaptations that are well suited for survival and reproduction in an environment
More individuals will have the trait over time as long as the environmental conditions do not change
Fitness is the measure of survival ability and ability to produce more offspring.

27. Other structural adaptations
Mimicry is a structural adaptation that enables one species to resemble another species

28. opossum plays possum well
Caterpillar mimics
Bird droppings
Butterfly markings mimics predators eyes

29. 1. Batesian Mimicry When a harmless animal resembles a harmful animal.
Example: the king snake resembles the coral snake

30. 2. Mullerian Mimicry
When two or more dangerous or distasteful species look similar
Yellow Jacket
Wasp

31. Caterpillar mimics a viper
In both looks & movement
The tasty Viceroy Butterfly (left),
Mimics the bitter tasting Monarch on
The Right

32. Camouflage Camouflage allows animals to blend with their surroundings
Tartan Hawk fish – blends with
Bright gorgonian fans
A narrow-headed frog native to
Madagascar, blends with the mud &
Tree trunks in its environment

33. Its’ difficult to see in its environment
Disruptive coloration of zebras

34. Can you spot the Snow Leopard?

35. Evidence for Evolution

36. Evidence for evolution in Darwin’s time came from several sources.
1. Fossils provide evidence of evolution.
Fossils in older layers are more primitive than those in the upper layers.

37. Extinct fossils resemble modern animals This shows common ancestry
Fossils are important in Evolution
Because they provide a record
of early life and history

38. 2. The study of geography provides evidence of evolution.
island species most closely resemble nearest mainland species
populations can show variation from one island to another

39. 3. Embryology provides evidence of evolution.
identical larvae, different adult body forms
similar embryos, diverse organisms
Larva
Adult barnacle
Adult crab

40. 4. The study of anatomy provides evidence of evolution.
A. Homologous structures are similar in structure but different in function and are evidence of a common ancestor.

41. B. Analogous structures have a similar body parts in function, but no evidence of a common ancestor
Bat wing
Fly wing

42. Human appendix, wisdom teeth, tailbone
C. Vestigial structures are body structures in a present day organism that no longer serves its original purpose, but was useful to the ancestor.
Ostrich wings
Human appendix, wisdom teeth, tailbone

43. Natural Selection in Populations
Populations, not individuals, evolve.

44. Natural selection acts on distributions of traits.
A normal distribution graphs as a bell-shaped curve.
highest frequency near mean value
frequencies decrease toward each extreme value
Traits not undergoing natural selection have a normal distribution.

45. Natural selection can change the distribution of a trait in one of three ways.
1. Directional Selection
2. Stabilizing Selection
3. Disruptive Selection

46. Directional selection favors phenotypes at one extreme.
Selection for longer beaks
Normal
variation

47. Stabilizing selection favors the intermediate phenotype (average individual).
Selection for
average size
spiders
Normal variation

48. Disruptive selection favors both extreme phenotypes.

49. The Effects Of Natural Selection
Natural selection can significantly alter the genetic equilibrium of a population’s gene pool over time
Significant changes in the gene pool could lead to the evolution of a new species over time

50. The isolation of populations can lead to speciation.
Populations become isolated when there is no gene flow.
Isolated populations adapt to their own environments.
Genetic differences can add up over generations.

51. Reproductive isolation can occur between isolated populations.
members of different populations cannot mate successfully
final step to becoming separate species
Speciation is the rise of two or more species from one existing species.

52. Speciation
The evolution of new species, a process called speciation occurs when members of similar populations no longer interbreed to produce fertile offspring within their natural environment.

53. Geographic barriers can cause isolation.
called geographic isolation
physical barriers divide population
Temporal barriers can cause isolation.
called temporal isolation
timing of reproductive periods prevents mating

55. Geographic Isolation
Geographic isolation occurs whenever a physical barrier divides a population
Isolated habitat fragments are similar to islands in the way in which the species living there are effected.

58. Evolution through natural selection is not random.
Natural selection can have direction.
The effects of natural selection add up over time.

59. Has analogous structures, and are NOT closely related
Convergent evolution when two distinct species with differing ancestries evolve to display similar features
Has analogous structures, and are NOT closely related

60. Divergent evolution when closely related species evolve in different directions they become increasingly different .
ancestor
red fox
kit fox
Ex: Red Fox and Kit Fox though closely related they have developed different characteristics based on the environment they live in

61. Diversity in a New Environment
Divergent evolution occurs when populations change as they adapt to different environmental conditions, eventually resulting in new species.

62. Species can shape each other over time.
Two or more species can evolve together through coevolution.
evolutionary paths become connected
species evolve in response to changes in each other
Coevolution can occur in beneficial relationships.

63. Coevolution can occur in competitive relationships, sometimes called evolutionary.

64. Species can become extinct.
Extinction is the elimination of a species from Earth.

65. Background extinctions occur continuously at a very low rate.
occur at roughly the same rate as speciation
usually affects a few species in a small area
caused by local changes in environment
A steady rate of natural extinction
Species that are unfit to survive die out

66. Mass extinctions are rare but much more intense.
destroy many species at global level
thought to be caused by catastrophic events
at least five mass extinctions in last 600 million years
Can be a single event or a concentrated period of time