1. Evolution , Natural Selection, and the History of Life
The Stories of Charles Darwin and Alfred Russell Wallace

2. What is your “working definition” of Evolution?
I don’t need the book answer, I would like “your” answer.

3. A Quick History of Life The Earth formed 4.6 BILLION years ago
Early Earth was very unstable and too hot for life to exist.
3.9 Billion years ago Earth cooled enough for water vapor to condense to form rain and seas.
3.5 Billion years ago the first living organisms appear.

4. I. Origin Of Life
Life began during the first billion years of Earth’s history (which is 4.5 billion years old).
The ocean received organic matter from the land and the atmosphere, as well as from meteorites and comets.
Substances such as water, carbon dioxide, methane, and hydrogen cyanide formed key molecules such as sugars, amino acids, and nucleotides - the building blocks of proteins and nucleic acids.

5. How it may have started
Planetary processes such as ocean chemistry (mixing of organic matter), a turbulent atmosphere (lightning, clouds, solar radiation) and volcanic activity together led to the formation of life.

6. Early life
Life began as single-celled microorganisms, most likely anaerobic bacteria since no oxygen was present in the atmosphere 3.5 billion years ago. Their fossilized structure suggests that they were photosynthetic.
Between 1 & 2 bya, the single-celled eukaryotic organisms with their complex system of organelles and membranes evolved into multi-cellular organisms.

7. Increasing in complexity
The evolution of the plants and animals most familiar to us occurred only in the last 550 million years.

8. Evidence of Early life: The Fossil Record
Microbial life of the simplest type was discovered in fossils and dated to come from a time period of 3.5 billion years ago.
The oldest evidence of more complex organisms (eukaryotic bacteria) has been discovered in fossils sealed in rocks approximately 2 billion years old.
Multi-cellular organisms (the familiar fungi, plants, and animals) have been found only in younger fossils:

9. Millions of Years Since First Known Appearance
Life Form
Millions of Years Since First Known Appearance
Microbial (prokaryotic cells)
Complex (eukaryotic cells)
First multi-cellular animals
Shell-bearing animals
Vertebrates (simple fishes)
Amphibians
Reptiles
Mammals
Nonhuman primates
Earliest apes
Human ancestors
Modern humans
3500
2000
670
540
490
350
310
200 60 25 4
0.15 (150,000 years)

10. Many intermediate forms have been discovered between fish and amphibians, between amphibians and reptiles, between reptiles and mammals, and along the primate lines of descent in the fossil record, showing the evolution between species.

11. The origin of life according to the scientific method.
Spontaneous generation – The process by which life was thought to be produced by non-living matter.
Disproved by Francesco Redi
Biogenesis – The idea that living organisms come only from other living organisms.
Proved by Louis Pasteur
Miller and Urey test the theory of life starting in the oceans.

12. Evolution of Cells
Protocell – A large ordered structure that carries out some activities associated with life such as growth, division , or metabolism.
The first cells used organic molecules for food and were prokaryotic cells referred to as heterotrophic prokaryotes
Archeabacteria – prokaryotes that live in harsh conditions. Glucose is made by chemosynthesis

13. The theory of Evolution
Charles Darwin is credited with the concept of Evolution, but he was not the first person to suggest that organisms change over time.
Several scientists before Darwin alluded to the concept of Evolution. They never explained how it could happen.
Darwin gets the credit for the theory of evolution because he described or explained how evolution could occur.

14. Lets do a little research on the history behind evolutionary thought

15. Evolution Defined
Evolutions was first define as a change in a species over time.
This first general definition was too vague and general. It allowed for much debate.
A current and less arguable definition of Evolution is:
Evolution is the change in gene frequency in a population over time.

16. Jean Baptiste de Lamarck
1. In the early 1800’s, Lamarck, a French biologist, developed a theory of evolution based on his belief in two biological processes.
1 The use and disuse of organs. Lamarck believed that organisms respond to changes in the environment by developing new organs or modifying old ones (acquired characteristics). Disuse results in the disappearance of the organ.
Inheritance of acquired traits. Lamarck believed that these acquired characteristics were then passed on to offspring.

17. Example of Lamarck’s theory
Lamarck believed that at one time giraffes had short necks and ate grass. Then either grass became scarce or other animals out-competed the giraffes for the grass so they started eating leaves off trees. As lower leaves became scarce, they stretched to reach higher leaves. Their necks gradually got longer and they passed the longer necks to their offspring.

18. Alfred Russell Wallace
Another Naturalist that was interested in Biology and Geology.
Younger than Darwin, but came up with the idea of organisms changing over time.
Wallace new that Darwin had already been working on an explanation of evolution and sent him a draft of his theory.

19. Wallace and Darwin
Darwin read the theory and was worried that Wallace would publish before him, but encouraged the young naturalist.
Darwin was very methodical, in fact, his friends thought too methodical.
Everyone “knew” Darwin had a theory regarding evolution but was not publishing it
After much pressure from friends he presented his information, along with Wallace at a meeting.
Shortly after the meeting he published On the Origin of Species

20. Darwin
Was a pigeon breeder and noticed that people could select and breed for specific traits.
Artificial selection – A technique in which breeders select for a particular trait.
Darwin applied the idea of artificial selection to the natural environment and termed it Natural Selection.

21. Natural Selection
A mechanism for change in populations that occurs when organisms with favorable variations for a particular environment survive, reproduce, and pass on these variations on to the next generation.

22. Darwin
1. As a naturalist, Darwin traveled to South America on the ship the H.M.S. Beagle. While there he found evidence that the Earth was very old by observing an earthquake and discovering marine fossils on mountaintops. He also found evidence of evolution.

23. Darwin
While on the Galapagos Islands, Darwin noticed that plants and animals were like those on the mainland, but not exactly alike. He realized that the species came from the mainland and changed into a new species. He came up with his theory of Evolution by Natural Selection.

24. Darwin observed that:
Individuals in a population have traits that vary
Many of these traits are heritable (passed from parents to offspring)
More offspring are produced than survive
Competition is inevitable
Species generally suit their environment

25. Darwin inferred that:
Individuals that are best suited to their environment are more likely to survive and reproduce
Over time, more individuals in a population will have the advantageous traits
In other words, the natural environment “selects” for beneficial traits

26. Darwin’s theory had 5 main points:
1. Variation exists among individuals of a species.
For example, some gorillas have longer arms than others, some ladybugs have more spots than others, etc.

27. Darwin Evolution by Natural Selection
2. All organisms compete for the same limited resources.
Such competition would lead to the death of some individuals, while others would survive.
3.Organisms produce more offspring than can survive.
The available resources cannot support all these individuals.

28. 4. The environment selects organisms with beneficial traits.
Darwin Evolution by Natural Selection
4. The environment selects organisms with beneficial traits.
5. Organisms with traits best suited to the environment will reproduce and pass on these traits at a greater rate than organisms less suited to the environment. This “survival of the fittest” is called Natural Selection.

29. Conditions Necessary for Natural Selection
Over production of offspring
Variation of traits
Individuals with favorable variations survive and pass on variations to the next generation.
Gradually offspring make-up a larger proportion of the population
See handout

30. Origin of Variation
From where do the “fittest” get their beneficial traits? Variations must be genetic (in the sex cells) to be passed on to offspring. There are two fundamental sources of variation in a species:
Mutation - a change in the chemical structure of the gene, so it will be passed on to the offspring.
Genetic recombination - mixing of the genes between chromosomes during meiosis.

31. Selection Pressure
Selection Pressure is the force exerted by nature which directs an organisms evolution and causes one trait to b better than another.

32. IV. Processes of Evolution
5 main processes that upset the genetic equilibrium of a population:
A. Natural Selection – Disrupts a normal population by allowing fit individuals to survive and reproduce at higher rates than less fit individuals. There are three types of natural selection:

33. Natural Selection
1. Directional Selection – Natural selection that proceeds in a given direction.
Ex.) Necks of giraffes – evolution has proceeded in the direction of longer necks.

34. Natural Selection
2. Stabilizing Selection – Selection that eliminates the extremes of a trait causing a reduction in variation of a species.
Ex.) Leg length of rabbits – long legs are eliminated because the rabbits can’t crawl into a hole to escape predators, short legs are eliminated because they cannot run fast enough to escape predators.

35. Natural Selection
3. Disruptive Selection – Selects against the average and favors the extremes of a trait.
Acorns – squirrels do not eat the smallest, not enough food. Squirrels do not eat the largest, to hard to carry. Squirrels eat the average, after many years the average become eliminated.

37. Migration
B. Migration – The movement of organisms into or out of a population.
A herd of caribou lives in Canada. A second, genetically different herd migrates to mix with the first herd. The gene pools of the two herds mix, genetically changing the original population.

38. 2 Types Of Migration
1. Immigration – The movement of new individuals into a population.
2. Emigration – The movement of individuals out of a population.

39. Genetic Drift
C. Genetic Drift – The change in gene frequency of a population due to chance.
Ex.) In a population of 16 long-horned beetles, 15 are black and 1 is red. If random mating occurs, there is a chance the red won’t mate, thus eliminating that trait from the population.

40. Isolation
D. Isolation – Isolation occurs when a geographic boundary separates a population into groups that can no longer interact. Boundaries can include rivers, mountains and canyons. Isolation often results in the evolution of a new species.
Ex.) The camel originated in the U.S. It spread to Asia and South America over land bridges during the Ice Ages. Over time the separated populations evolved and became different species – the camel in Asia and the llama in South America.

41. Mutation
E. Mutation – Harmful mutations are eliminated from a population because the organism usually doesn’t live to reproduce. Beneficial mutations are passed on to offspring, thus changing the population.

42. Sexual selection
A form of natural selection in which individuals with certain traits are more likely than others to obtain mates.
Mate choice based on a trait

43. V. Patterns of Evolution
A. Divergent Evolution – The process by which related organisms become less alike.

44. Divergent Evolution
1. Speciation – Divergent evolution results in a new species.
Ex.) A group of brown bears becomes isolated from another group. The isolated group moves into northern Canada and eventually develops heads and necks suited for swimming and white fur, thus diverged from their ancestors.

45. Adaptive Radiation
2. Adaptive Radiation – Process by which individuals of a new species adapt to a variety of habitats.
Ex.) Darwin’s finches adapt to eating different types of food by changing beak types.

46. 4 Types of Speciation
1. Allopatric speciation - physical barrier divides population
2. Peripatric speciation - small founding population enters isolated niche
3. Parapatric speciation - new niche found adjacent to original one
4. Sympatric speciation - speciation occurs without physical separation

47. Allopatric Speciation
A population splits into two geographically isolated populations.
The isolated populations then undergo genotypic and/or phenotypic divergence.
become subjected to dissimilar selective pressures
independently undergo genetic drift.
When the populations come back into contact, they have evolved such that they are reproductively isolated.
Examples:
Differnces between organisms on Komodo island.
Darwin's Galápagos Finches.

48. Peripatric Speciation
New species are formed in isolated, small peripheral populations that are prevented from exchanging genes with the main population.
Related to the concept of a founder effect, since small populations often undergo bottlenecks.
Genetic drift is often proposed to play a significant role in peripatric speciation.
Examples:
The Australian bird Petroica multicolor
The London Underground mosquito

49. Parapatric Speciation
A form of speciation that occurs due to variations in the mating habits of a population within a continuous geographical area.
In this model, the parent species lives in a continuous habitat
In contrast with allopatric speciation and peripatric speciation where subpopulations become geographically isolated.
Niches in this habitat can differ along an environmental gradient, hampering gene flow, and thus creating a cline.
Example: the grass Anthoxanthum tolerant to high mineral content in soil near abandoned mines.

50. Sympatric Speciation Species diverge while inhabiting the same place.
Examples of sympatric speciation are found in insects that become dependent on different host plants in the same area.
Fig wasps, cichlid fish
The existence of sympatric speciation as a mechanism of speciation is still hotly contested

51. Types of Speciation (graphical)

52. Two other types of speciation
Polyploidization - change in the number of chromosomes via mutation or reproduction.
Example: various plants and some amphibians
Hybridization - two different species reproduce and the resulting offspring is fertile, but does not reproduce with members of the two original species.
Example: various plants

53. Convergent Evolution
B. Convergent Evolution – The process by which distantly related organisms develop similar characteristics because they share the same environment.
Ex.) Whales were once land mammals that adapted to an aquatic environment by changing from legs to flippers for swimming. They began to resemble fish, which are not closely related.

54. Convergent Evolution
Can lead to Mimicry – the evolution of one organism so it resembles another.
Ex. The Viceroy butterfly, a nontoxic insect, mimics the Monarch butterfly, a toxic insect.

55. Review: Disruptions to genetic Equilibrium
Genetic equilibrium - no change in frequency of an allele
1. Natural Selection
2. Migration (Immigration, Emigration)
3. Isolation
4. Genetic Drift
5. Sexual selection
6. Genetic recombination
7. Mutation

56. Punctuated Equilibrium
Proposed by Stephen Jay Gould
Contradicts Darwin’s concept of gradualism.
Gould proposed that that most sexually reproducing species will experience little evolutionary change for most of their geological history.
Gould termed this a state of stasis.
When evolution occurs, it is localized in rare, rapid events of branching speciation.
He termed the rapid branching cladogenesis.
Cladogenesis is the process by which species split into two distinct species, rather than one species gradually transforming into another.

57. The Tree of Life
“Unity in diversity” arises from “descent with modification”
For example, the forelimb of the bat, human, horse and the whale flipper all share a common skeletal architecture
Fossils provide additional evidence of anatomical unity from descent with modification
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

58. Darwin proposed that natural selection could cause an ancestral species to give rise to two or more descendent species
For example, the finch species of the Galápagos Islands
Evolutionary relationships are often illustrated with tree-like diagrams that show ancestors and their descendents
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

59. Cactus-flower-eaters
Fig. 1-22
Green warbler finch Certhidea olivacea
Warbler finches
Insect-eaters
COMMON
ANCESTOR
Gray warbler finch Certhidea fusca
Seed-eater
Sharp-beaked
ground finch Geospiza difficilis
Bud-eater
Vegetarian finch Platyspiza crassirostris
Mangrove finch Cactospiza heliobates
Woodpecker finch Cactospiza pallida
Tree finches
Insect-eaters
Medium tree finch Camarhynchus pauper
Large tree finch Camarhynchus psittacula
Small tree finch Camarhynchus parvulus
Large cactus
ground finch
Geospiza conirostris
Figure 1.22 Descent with modification: adaptive radiation of finches on the Galápagos Islands
Cactus-flower-eaters
Cactus ground finch
Geospiza scandens
Ground finches
Seed-eaters
Small ground finch
Geospiza fuliginosa
Medium ground finch
Geospiza fortis
Large ground finch
Geospiza magnirostris

60. Warbler finches Insect-eaters Seed-eater Bud-eater
Fig. 1-22a
Green warbler finch Certhidea olivacea
Warbler finches
Insect-eaters
Gray warbler finch Certhidea fusca
Seed-eater
Sharp-beaked
ground finch Geospiza difficilis
Figure 1.22 Descent with modification: adaptive radiation of finches on the Galápagos Islands
Bud-eater
Vegetarian finch Platyspiza crassirostris

61. Tree finches Insect-eaters
Fig. 1-22b
Mangrove finch Cactospiza heliobates
Woodpecker finch Cactospiza pallida
Tree finches
Insect-eaters
Medium tree finch Camarhynchus pauper
Large tree finch Camarhynchus psittacula
Figure 1.22 Descent with modification: adaptive radiation of finches on the Galápagos Islands
Small tree finch Camarhynchus parvulus

62. Cactus-flower-eaters
Fig. 1-22c
Large cactus
ground finch
Geospiza conirostris
Cactus-flower-eaters
Cactus ground finch
Geospiza scandens
Ground finches
Seed-eaters
Small ground finch
Geospiza fuliginosa
Medium ground finch
Geospiza fortis
Figure 1.22 Descent with modification: adaptive radiation of finches on the Galápagos Islands
Large ground finch
Geospiza magnirostris

63. Fig. 1-UN1

65. Evidence For Evolution
Fossil record
1. Microbial life of the simplest type was discovered in fossils and dated to come from a time period of 3.5 billion years ago.
2. The oldest evidence of more complex organisms (eukaryotic bacteria) has been discovered in fossils sealed in rocks approximately 2 billion years old.
3. Multi-cellular organisms (the familiar fungi, plants, and animals) have been found only in younger fossils:

66. The Fossil record
4. Many intermediate forms have been discovered between fish and amphibians, between amphibians and reptiles, between reptiles and mammals, and along the primate lines of descent in the fossil record, showing the evolution between species.

67. The Fossil Record
5. There is also consistent evidence of systematic change through time -- of descent with modification (evolutionary changes between classes of animals). That is, fish came first, then amphibians, followed by reptiles and finally mammals.
No two classes made their first appearance in the fossil record at the same time.

68. B. Anatomical Evidence
1. Body parts with the same basic structure are called Homologous Structures.
These are structures in which the size and shape are different, but the number and arrangement of bones are the same.
Homologous structures found in different organisms suggest that these organisms share a common ancestor.

69. An example of homologous structures is:
whale flipper - lion leg -
4. Examples of homologous structures can also be grouped by function.

71. Anatomical Structures (Continued)
Vestigial Structures, structures that have been greatly reduced in size and no longer serve an important function, also provide evidence for evolution.
An example of this is the small hipbones in whales and snakes suggesting the whale and snake came from an ancestor with hips, and the splint-like bone in horses that indicated an ancestor with a side toe.

73. Human Vestigial Structures:

74. Ear muscles help monkey’s move ears to sense danger, but do nothing in humans.

75. Appendix - used by ancestors to digest cellulose
of plants.

76. Coccyx (tail bone) - No longer needed for original
function of balance and mobility.

77. plica semilunaris - remnant of the nictitating membrane
(the "third eyelid") which is present in other animals.

78. 5. Wisdom teeth - third molars that human ancestors used to help in grinding down plant tissue.

79. 6. Goose bumps - its purpose in human evolutionary ancestors was to raise the body's hair, making the ancestor appear larger and scaring off predators. Raising the hair is also used to trap an extra layer of air, keeping an animal warm.

80. Anatomical Structures (continued)
Analogous Structures, body parts that are similar in function but not in basic structure, are not evidence of evolution.
a. An example of this type of structure are the wings of birds, insects, bats dinosaurs.

81. A. Moth B. Pterosaur C. Bird D. Bat
Wing Wing Wing Wing
All of these organisms use their wings to fly, but they are composed of different structures.

82. C. Embryological Evidence
1. Studying organisms at very early stages of development, while they are still embryos, suggests different vertebrate species share common genetic instructions for embryo development.

84. The final bit of evidence for Evolution is:
Similarity in DNA

85. Video: Albatross Courtship Ritual
Video: Blue-footed Boobies Courtship Ritual
Video: Galápagos Islands Overview
Video: Galápagos Marine Iguana
Video: Galápagos Sea Lion
Video: Galápagos Tortoise
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings