1. Evolution, Biodiversity, and Community Processes
Chapter 5 Notes

3. Fossils
Oldest fossils are the approximately billion-year-old microfossils from the Apex Chert, Australia
colonies of cyanobacteria (formerly called blue-green algae) which
built real reefs

4. Fossils
1600's - Danish scientist Nicholas Steno studied the relative positions of sedimentary rocks
Layering is the most obvious feature of sedimentary rocks
formed particle by particle and bed by bed, and the layers are piled one on top of the other
any sequence of layered rocks, a given bed must be older than any bed on top of it
Law of Superposition is fundamental to the interpretation of Earth history, because at any one location it indicates the relative ages of rock layers and the fossils in them.

5. EVOLUTION gradual change

6. Four causes of evolutionary change:
Mutation: fundamental origin of all genetic (DNA) change.

7. Four causes of evolutionary change:
Mutation: fundamental origin of all genetic (DNA) change.
Point mutation
…some at base-pair level

8. Four causes of evolutionary change:
Mutation: fundamental origin of all genetic (DNA) change.
Crossing-over
…others at grosser chromosome level

9. Four causes of evolutionary change:
Mutation: fundamental genetic shifts.
Genetic Drift: isolated populations accumulate different mutations over time.
In a continuous population, genetic novelty can spread locally.

10. Four causes of evolutionary change:
Mutation: fundamental genetic shifts.
Genetic Drift: isolated populations accumulate different mutations over time.
Local spreading of alleles

11. Four causes of evolutionary change:
Mutation: fundamental genetic shifts.
Genetic Drift: isolated populations accumulate different mutations over time.
Local spreading of alleles

12. Four causes of evolutionary change:
Mutation: fundamental genetic shifts.
Genetic Drift: isolated populations accumulate different mutations over time.
Spreading process known as ‘gene flow’.

13. Four causes of evolutionary change
Mutation: fundamental genetic shifts.
Genetic Drift: isolation  accumulate mutations
Founder Effect: sampling bias during immigration. When a new population is formed, its genetic composition depends largely on the gene frequencies within the group of first settlers.

14. Founder Effect.--
Human example: your tribe had to live near the Bering land bridge…

15. Founder Effect.--
…to invade & settle the ‘New World’!

16. Founder Effect
Human examples: consider penal colonies

17. Galapagos Finches
Audeskirk & Audeskirk, 1993

18. Four causes of evolutionary change:
Mutation: fundamental genetic shifts.
Genetic Drift: isolation  accumulation of mutations
Founder Effect: immigrant sampling bias.
Natural Selection: differential reproduction of individuals in the same population based on genetic differences among them.

19. Four causes of evolutionary change:
Mutation: fundamental genetic shifts.
Genetic Drift: isolation  accumulation of mutations
Founder Effect: immigrant sampling bias.
Natural Selection: reproductive race
These 4 interact synergistically

20. Evidence of Evolution Biogeography:
Geographical distribution of species

21. Evidence of Evolution 2. Fossil Record:
Fossils and the order in which they appear in layers of sedimentary rock (strongest evidence)

22. Evidence of Evolution Comparative Embryology:
Study of structures that appear during embryonic development

23. Old Theories of Evolution
Jean Baptiste Lamarck (early 1800’s) proposed:
“The inheritance of acquired characteristics”
He proposed that by using or not using its body parts, an individual tends to develop certain characteristics, which it passes on to its offspring.

24. “The Inheritance of Acquired Characteristics”
Example:
A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring.

26. Charles Darwin
Influenced by Charles Lyell who published “Principles of Geology”.
Darwin realized
that natural forces gradually change Earth’s surface
the forces of the past are still operating in modern times.

27. Movement of Earth’s Crust
Sea level
Sea level
Sedimentary rocks form in horizontal layers.
When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers.
As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed.
New sediment is then deposited above the exposed older rock surface.

28. Charles Darwin
Darwin set sail on the H.M.S. Beagle ( ) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and animals.
On the Galapagos Islands, Darwin observed species that lived no where else in the world.
These observations led Darwin to write a book

30. Giant Tortoises of the Galápagos Islands
Pinta
Tower
Pinta Island Intermediate shell
Marchena
James
Fernandina
Santa Cruz
Isabela
Santa Fe
Hood Island
Saddle-backed shell
Floreana
Hood
Isabela Island
Dome-shaped shell

31. “On the Origin of Species by Means of Natural Selection”
Charles Darwin
Wrote in 1859:
“On the Origin of Species by Means of Natural Selection”
Two main conclusions:
Species were not created in their present form, but evolved from ancestral species.
Proposed a mechanism for evolution: NATURAL SELECTION

32. Darwin’s Observations
Most species produce more offspring than can be supported by the environment
Environmental resources are limited
Most populations are stable in size
Individuals vary greatly in their characteristics (phenotypes)
Variation is heritable (genotypes)

33. Natural Selection
Individuals with favorable traits are more likely to leave more offspring better suited for their environment
Also known as “Differential Reproduction”
Example:
English peppered
moth (Biston betularia)

34. Modes of Action Natural selection has three modes of action:
1. Stabilizing selection
2. Directional selection
3. Diversifying selection
Number of
Individuals
Size of individuals
Small Large

35. 1. Stabilizing Selection
Acts upon extremes and favors the intermediate.
Number of
Individuals
Size of individuals
Small Large

36. Stabilizing Selection
Individuals exhibiting the average phenotype in a population are selected for
Example: Different grass plants in a population range in length from 8 cm to 28 cm. The 8-10 cm grass blades receive little sunlight, and the cm grass blades are eaten quickly by grazing animals.

37. 2. Directional Selection
Favors variants of one extreme.
Number of
Individuals
Size of individuals
Small Large

38. Directional Selection
Individuals at one extreme are favored
Example: Members of a population of Amazon tree frogs hop from tree to tree searching for food in the rain forest. They vary in leg length. Events result in massive destruction of the forest’s trees. After several generations, only long-legged tree frogs remain alive. (other examples include the famous peppered moths and bacterial resistance to antibiotics)

39. 3. Diversifying Selection
Favors variants of opposite extremes.
Number of
Individuals
Size of individuals
Small Large

40. Disruptive Selection
Individuals at both extremes of a range of phenotypes are favored over those in the middle – population is split into two groups – may result in speciation!
Example: The spines of a sea urchin population’s members vary in length The short-spined sea urchins are camouflaged easily on the seafloor. However, long-spined sea urchins are well defended against predators

41. Modes of Natural Selection

42. Speciation
The evolution of new species.

43. Speciation
When environmental conditions change, a species must: Evolve (adapt), Move (migrate), or Die (extinction)
# New species - # extinctions = Biodiversity
The Extinction of one species creates an opportunity for another species to arise

44. Evidence for Natural Selection

45. Artificial Selection
The selective breeding of domesticated plants and animals by man.
Question: What’s the ancestor of the domesticated dog?

46. The science of genetic change in population – Hardy-Weinberg
Population Genetics
The science of genetic change in population – Hardy-Weinberg
Population
A localized group of individuals belonging to the same species

47. The total collection of genes in a population at any one time
Species
A group of populations whose individuals have the potential to interbreed and produce viable offspring
Gene Pool
The total collection of genes in a population at any one time

48. Speciation, Extinction, and Biodiversity
Geographic isolation
Reproductive isolation
Fig. 5-8 p. 105

49. Adaptive Radiation
Emergence of numerous species from a common ancestor introduced to new and diverse environments.
Example:
Hawaiian Honeycreepers

50. Convergent Evolution
Species from different evolutionary branches may come to resemble one another if they live in very similar environments.
Example:
1. Ostrich (Africa) and Emu (Australia).
2. Sidewinder (Mojave Desert) and
Horned Viper (Middle East Desert)

52. Coevolution
Evolutionary change, in which one species act as a selective force on a second species, inducing adaptations that in turn act as selective force on the first species.
Example:
1. Acacia ants and Acacia trees
Yucca Plants and Yucca moths
Lichen

54. Extinction
Background extinction - species disappear at a low rate as local conditions change
Mass extinction - catastrophic, wide-spread events --> abrupt increase in extinction rate
Five mass extinctions in past 500 million years
Adaptive radiation - new species evolve during recovery period following mass extinction

55. Date of the Extinction Event Marine vertebrates and invertebrates
Mass Extinctions
Date of the Extinction Event
Percent Species Lost
Species Affected
65 mya
(million
years ago) 85
Dinosaurs, plants (except ferns and seed bearing plants), marine vertebrates and invertebrates. Most mammals, birds, turtles, crocodiles, lizards, snakes, and amphibians were unaffected.
213 mya 44
Marine vertebrates and invertebrates
248 mya
75-95
380 mya 70
Marine invertebrates
450 mya 50

56. Niche
a species’ functional role in its ecosystem; includes anything affecting species survival and reproduction
Range of tolerance for various physical and chemical conditions
Types of resources used
Interactions with living and nonliving components of ecosystems
Role played in flow of energy and matter cycling

57. the species’ occupation and its
Niche is
the species’ occupation and its
Habitat
location of species
(its address)

58. Niche
Fundamental niche: set of conditions under which a species might exist in the absence of interactions with other species
Realized niche: more restricted set of conditions under which the species actually exists due to interactions with other species