1. Evolution
Chapter 15

2. 15-1 Darwin’s Theory of Natural Selection
Objectives
Discuss the evidence that species could change over time
List the four major principals of natural selection
Show how natural selection could change a population

3. Who was Darwin? 1809-1982 Naturalist and geologist
Studied at University of Edinburgh and Cambridge
5 year voyage on the HMS Beagle ( )
1859 published
On Origin of Species

4. Darwin on the HMS Beagle
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
Darwin on the HMS Beagle
Darwin’s role on the ship was as naturalist and companion to the captain.
His job was to collect biological and geological specimens during the ship’s travel.

5. Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
The Galápagos Islands
Darwin began to collect mockingbirds, finches, and other animals on the four islands.
He noticed that the different islands seemed to have their own, slightly different varieties of animals.

7. Populations from the mainland changed after reaching the Galápagos.
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
Almost every specimen that Darwin had collected on the islands was new to European scientists.
Populations from the mainland changed after reaching the Galápagos.

8. Darwin Continued His Studies
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15.1 Darwin’s Theory of Natural Selection
Darwin Continued His Studies
Darwin hypothesized that new species could appear gradually through small changes in ancestral species.
Darwin inferred that if humans could change species by artificial selection, then perhaps the same process could work in nature.

9. Basic Principals of Natural Selection
Chapter 15
Evolution
Basic Principals of Natural Selection
Individuals in a population show variations.
Variations can be inherited.
Organisms have more offspring than can survive on available resources.
Variations that increase reproductive success will have a greater chance of being passed on.

10. Darwin’s theory of natural selection is not synonymous with evolution.
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
The Origin of Species
Darwin published On the Origin of Species by Means of Natural Selection in 1859.
Darwin’s theory of natural selection is not synonymous with evolution.
It is a means of explaining how evolution works.

11. Darwin’s Dangerous Idea – Part 1

12. 15-2 Evidence for Evolution
Objectives
Describe how fossils provide evidence for evolution
Discuss morphological evidence for evolution
Explain how biochemistry provides evidence for evolution

13. 15.2 Evidence of Evolution Support for Evolution The fossil record
Chapter 15
Evolution
15.2 Evidence of Evolution
Support for Evolution
The fossil record
Fossils provide a record of species that lived long ago.
Fossils show that ancient species share similarities with species that now live on Earth.
Glyptodont
Armadillo

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Evolution
15.2 Evidence of Evolution
Derived traits are newly evolved features, such as feathers, that do not appear in the fossils of common ancestors.
Ancestral traits are more primitive features, such as teeth and tails, that do appear in ancestral forms.
Anatomically similar structures inherited from a common ancestor are called homologous structures.

15. Anatomically similar structures inherited from a common ancestor are called homologous structures.

16. predicts that features of ancestors that no
Chapter 15
Evolution
15.2 Evidence of Evolution
Vestigial Structures
Structures that are the reduced forms of functional structures in other organisms.
Evolutionary theory
predicts that features of ancestors that no
longer have a function for that species will
become smaller over time until they are lost.

17. Chapter 15
Evolution
15.2 Evidence of Evolution
Analogous structures can be used for the same purpose and can be superficially similar in construction, but are not
inherited from a
common ancestor.
Show that functionally similar features can evolve independently in similar environments

18. Comparative Embryology
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15.2 Evidence of Evolution
Comparative Embryology
Vertebrate embryos exhibit homologous structures during certain phases of development but become totally different structures in the adult forms.

20. Comparative Biochemistry
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15.2 Evidence of Evolution
Comparative Biochemistry
Common ancestry can be seen in the complex metabolic molecules that many different organisms share.

21. Chapter 15
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15.2 Evidence of Evolution
Comparisons of the similarities in these molecules across species reflect evolutionary patterns seen in comparative anatomy and in the fossil record.
Organisms with closely related morphological features have more closely related molecular features.

22. Geographic Distribution
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15.2 Evidence of Evolution
Geographic Distribution
The distribution of plants and animals that Darwin saw first suggested evolution to Darwin.
Rabbit
Mara

23. Evolution is intimately linked with climate and geological forces.
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15.2 Evidence of Evolution
Patterns of migration were critical to Darwin when he was developing his theory.
Evolution is intimately linked with climate and geological forces.

24. Chapter 15
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15.2 Evidence of Evolution
Types of Adaptation
An adaptation is a trait shaped by natural selection that increases an organism’s reproductive success.
Fitness is a measure of the relative contribution an individual trait makes to the next generation.

25. Allows organisms to become almost invisible to predators
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15.2 Evidence of Evolution
Camouflage
Allows organisms to become almost invisible to predators
Leafy sea dragon

26. One species evolves to resemble another species.
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15.2 Evidence of Evolution
Mimicry
One species evolves to resemble another species.
Western coral snake
California kingsnake

27. Consequences of Adaptations
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15.2 Evidence of Evolution
Consequences of Adaptations
Some features of an organism might be consequences of other evolved characteristics.
They do not increase reproductive success.
Features likely arose as an unavoidable consequence of prior evolutionary change.

28. 15-3 Shaping Evolutionary Theory
Objectives
Discuss patterns observed in evolution
Describe factors that influence speciation
Compare gradualism with punctuated equilibrium

29. Darwin’s theory of natural selection explains how organisms adapt to their environment and how variations can lead to new species
Natural selection in not the only mechanism

30. Population Genetics
Evolution will not occur in a population unless the allele frequency changed
Factors that affect genetic equilibrium (rather evolution occurs)
Natural selectin
Gene flow
Mutations
Non random mating
Genetic drift

31. Chapter 15
Evolution
Mechanisms for evolution
1. Genetic Drift
A change in the allelic frequencies in a population that is due to chance or random mating
In smaller populations, the effects of genetic drift become more pronounced, and the chance of losing an allele becomes greater.

32. Chapter 15
Evolution
Examples of Genetic Drift
a. Founder Effect
Occurs when a small sample of a population settles in a location separated from the rest of the population (ex. Amish and Mennonites)
Alleles that were uncommon in the original population might be common in the new population.

33. Chapter 15
Evolution
b. Bottleneck
Occurs when a population declines to a very low number and then rebounds

34. Chapter 15
Evolution
2. Gene Flow
Increases genetic variation within a population and reduces differences between populations
Random movement, migration
3. Nonrandom Mating
Promotes inbreeding and could lead to a change in allelic proportions favoring individuals that are homozygous for particular traits

35. 4. Mutation - can change allele frequency - can be harmful, lethal, or provide an advantage - provides the raw material for natural selection

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Evolution
5. Natural Selection
Acts to select the individuals that are best adapted for survival and reproduction

37. Chapter 15
Evolution
Stabilizing selection operates to eliminate extreme expressions of a trait when the average expression leads to higher fitness.

38. Directional selection makes an organism more fit.
Chapter 15
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15.3 Shaping Evolutionary Theory
Directional selection makes an organism more fit.

39. Chapter 15
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15.3 Shaping Evolutionary Theory
Disruptive selection is a process that splits a population into two groups.

40. Sexual Selection
The evolutionary fitness of an organism not only depends upon its ability to survive but also its ability to reproduce.
To reproduce, an individual must obtain a mate and produce viable offspring.
Natural selection favors traits that maximize the ability of an individual to compete for and attract mates, and/or the ability to produce offspring — this is called sexual selection
Sexual Selection: A type of selection in which the forces determined by mate choice act to cause one genotype to mate more frequently than another genotype..

41. Speciation
is the evolutionary process by which new biological species arise
A population must diverge and then be reproductively isolated
Long process

42. Chapter 15
Evolution
Types of Speciation
Allopatric Speciation
A physical barrier (mountain ranges, channels, rivers, lava flows) divides one population into two or more populations.
Abert squirrel
Kaibab squirrel

43. A species evolves into a new species without a physical barrier.
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Sympatric Speciation
A species evolves into a new species without a physical barrier.
The ancestor species and the new species live side by side during the speciation process.

44. Patterns in evolution

45. Adaptive Radiation (divergent evolution)
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Evolution
Adaptive Radiation (divergent evolution)
Can occur in a relatively short time when one species
gives rise to
many different
species in
response to the
creation of new
habitat or some
other ecological
opportunity
cichids
Follows large-scale extinction events

46. Chapter 15
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15.3 Shaping Evolutionary Theory
Convergent Evolution
Unrelated species evolve similar traits even though they live in different parts of the world.

47. Coevolutionary arms race
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15.3 Shaping Evolutionary Theory
Coevolution
The relationship between two species might be so close that the evolution of one species affects the evolution of the other species.
Mutualism
Coevolutionary arms race

48. Speciation video (do not show)

49. Evolutionary Biology

50. Scientists determine evolutionary relationships by look at:
Structure
Breeding behavior
Distribution
Chromosomes
biochemistry

51. Species that share a common ancestor share common evolutionary history
Phylogeny-evolutionary history of a species

52. Classification systems based on evolutionary relationships
Cladistics- system based on phylogeny
Cladogram-branching diagram that shows evolutionary relationships

54. Phylogenic diagram- fan-like model superimposed on the geologic timescale