1. Evolution Evidence and Theory
Chapter 15
Lab Biology

2. Vocabulary Absolute age cast Stratum mold Fossil extinct
Acquired trait law of superposition
Relative age adapt
Natural selection analogous
Vestigial convergent evolution
Artificial selection divergent evolution
Coevolution homologous
Adaptive radiation fitness

3. A genetic change within a population over time!
Evolution
A genetic change within a population over time!

4. Fossils Fossil is a trace of a long-dead organism. Found:
1. Sedimentary rock - formed by dust, sand, or mud deposited by wind or water over dead organism
Usually formed by hard body parts of an organism—shell, bones, teeth, or woody stems
Hard minerals replace the tissue of the organism leaving rocklike structures

5. Sedimentary Rock

6. Continue Fossils 2. mold – imprint in rock in the shape of an organsim
- limestone
3. cast – forms when molds are filled with hard minerals

7. Limestone
Limestone is the most abundant of the non-classic sedimentary rocks. Limestone is produced from the mineral calcite (calcium carbonate) and sediment. The main source of limestone is the limy ooze formed in the ocean. The calcium carbonate can be precipitated from ocean water or it can be formed from sea creatures that secrete lime such as algae and coral.
Chalk is another type of limestone that is made up of very small single-celled organisms. Chalk is usually white or gray in color.

8. Cast !

9. Robert Hooke
He concluded that fossils are remains of plants and animals
He mostly studied “petrified wood” with the aid of the microscope
He hypothesized that living organisms had somehow been turned to rock

10. Petrified Wood Wood that has turned to stone!

11. How is Petrified Wood Formed?
The mud that covered the logs contained volcanic ash, a key ingredient in the petrification process. When the volcanic ash began to decompose it released chemicals into the water and mud. As the water seeped into the wood the chemicals from the volcanic ash reacted to the wood and formed into quartz crystals. As the crystals grew over time, the wood became encased in the crystals which, over millions of years, turned the wood into stone.

12. Distribution of Fossils
Nicolaus Steno ( )
“Law of Superpositon” – states that the top layers of stratum contain the youngest fossils while the lower ones are older
This technique helps scientists to determine the “relative age” of a fossil
“absolute age”- age in years determined by radiological evidence

13. Succession of Forms
Mass Extinctions – brief periods during which large numbers of species disappears.
Some of these life forms were unlike any organisms alive today
Probably resulted from drastic changes in the environment, volcanic activity or collisions with asteroids (may have blocked sunlight for long periods of time and decreased temp.)

14. Biogeography
Biogeography – is the study of the geographical distribution of fossils and of living organisms.
A comparison of recently formed fossil types with types of living organisms in the same geographic area shows that new organisms arise in areas where similar forms already lived.
Ex: armadillos in North & South America where glyptodonts lived in the past.

15. Armadillos

16. Glyptodonts

17. Scaphognathus crassirostris Lab Fossil

18. Theories of Evolution I. Lamarck’s Explanation:
French scientist ( )
Proposed that similar species descended from a common ancestor (fossil records)
He hypothesized that acquired traits were passed on to offspring.

19. Acquired Trait It’s not determined by genes!
Instead, it arises during an organism’s lifetime as a result of the organism’s experience or behavior.
Ex: 1. webbed foot on water birds resulted from repeated stretching of the membrane between the toes
2. tails – if you don’t use it you loose it!

20. Beginning of Modern Evolutionary Theory
II. Charles Darwin ( ) & Alfred Wallace ( )
“natural selection”-hypothesis that organisms best suited to their environment reproduced more successfully than other organisms
Darwin & Wallace announced their hypotheses at the same time
Darwin’s name became more associated with evolution The Origin of Species published

21. Darwin’s Voyage on the Beagle
Sailed in 1831 for five years
Collected specimens and kept careful records of his observations
Sailed to South America (Galapagos Islands) and the South Pacific

22. Darwin’s Findings 1. returned to England in October 1836
2. collected 13 similar but separate species of finches.
3. Each finch species had a distinctive bill for specialized food source.
Implied that the finches shared a recent common ancestor

23. Darwin’s Finches

24. Darwin’s Findings

25. A GRUB!!!!!!! !

26. Darwin’s Theories TWO THEORIES;
1. DESCENT WITH MODIFICATION – The newer forms appearing in the fossil record are actually the modified descendants of older species
Organisms similar to each other come from a recent common ancestor, organisms that are more dissimilar such as finches and armadillos share a more remote ancestor

27. Continue…
2. MODIFICATION BY NATURAL SELECTION – states HOW evolution occurs.
Organisms having traits that make them better suited for survival tend to leave more offspring than organisms with fewer beneficial traits. Darwin called the different degrees of successful reproduction among organisms in a population NATURAL SELECTION

28. Evidence of Evolution
1. HOMOLOGOUS STRUCTURES: similar features that originated in a shared ancestor
Similar in structure BUT differ in function!!
Ex: penguin, bat, alligator, & human (all derive from the same embryological structures)
These examples i.e. share a fairly recent common ancestor

29. Homologous Structures

30. Continue…
2. ANALOGOUS STRUCTURES: Similar functions BUT differ in structure and embryological development
Ex: wings of a hummingbird and humming moth – both can hover to feed

31. Analogous Structures

32. Continue…
3. Vestigial Structure: Features that were useful to an ancestor, but they are not useful to the modern organism that has them.
Ex: tailbone in humans, appendix, some snakes have tiny pelvic bones and limb bones, some whales have pelvic bones along with four chambered stomach like a cow!

33. Vestigial Structures

34. Continue… 4. Similarities in Embryology
Ex: all vertebrate embryos are similar, but those similarities fade as development proceeds – evidence that indicates that vertebrates share a common ancestor

35. Vertebrate Embryos

36. Continue…
5. Similarities in Macromolecules: The more similar homologous proteins are in different species, the more closely related the species are thought to be.
Ex: the amino acid sequence in human hemoglobin and gorilla hemoglobin differ by ONE amino acid
While the Hb of humans and frogs differ by 67 amino acids!!

37. Patterns of Evolution
1. Coevolution: Evolution in which one organism causes another to change since they live in close association.
Predators and their prey sometimes co-evolve
Ex: “tropical region” bats feed on nectar
Bats have slender muzzle and long tongue that help them to feed,flowers are light in color which helps bats to see them at night and have a fruity odor that is attractive to the bats.

38. Tropical Bats!

39. Baby Bats!!

40. CLOSE UP!!!!
COOL!

41. Flowers with Nectar!

42. Continue…
2. Convergent Evolution: Ecological pressures cause a similarity in structure or function, but NOT from a common ancestor.
Analogous structures, such as similiar fins in very different animals, are associated with convergent evolution
Ex: sharks and porpoises

43. Porpoises

44. Sharks

45. Continue…
3. Divergent Evolution: two or more related populations or species become more and more dissimilar. Divergence is nearly always a response to differing habitats and can result in new species
A) adaptive radiation: many related species evolve from a single ancestral species ex: Galapagos finches
B) artificial selection: all domestic dogs are the same species “Canis familiaris”

46. Canis familiaris !

47. Continue… 4. Punctuated Equilibrium:
Evolution is stable for a time and suddenly jumps to new forms.

48. Punctuated Equilibrium

49. Darwin understood evol
Darwin understood evol., but didn’t understand the genetic basis of a population change…
Today we know:
Spontaneous mutations may produce new traits
Segregation & indep. Assort. Produce variations in gametes & thus in offspring
Genes are passed through gametes from parents to offspring

50. MODERN SYNTHESIS Theory developed in the 1940’s
Includes genetics and evolution!!
POPULATIONS ARE THE UNITS OF EVOLUTION BASED ON NATURAL SELECTION

51. CONTINUE..
Modern synthesis deals with THE RELATIONSHIP BETWEEN POPULATIONS AND SPECIES
SPECIES=group of organisms that can reproduce fertile offspring!

52. Where the species live matters!
Species distributed over a geographic range –> have different gene pool
THAN
Species localized  due to water, islands, mountains etc.!!!

53. Studying evolution at the population level scientist focus on the GENE POOL
GENE POOL IS THE SUM OF THE GENES IN A POLULATION!
(It’s where all members of the next generation get their genes!)

54. MICROEVOLUTION
When allele frequencies in a population change over generations, this is evolution at its smallest scale.
(genes are represented by alleles) Ex: gene for the color of your eyes has many alleles – B,b)….

55. There are several potential cause of microevolution:
1. Genetic Drift:
- a) bottleneck effect
- founder effect
2. Gene Flow
3. Mutation

56. Genetic Drift
A change in the gene pool of a small population due to chance!

57. Genetic Drift
Ex: Northern Elephant Seal (extinct)

58. The Bottleneck Effect
Genetic drift resulting from an event that drastically reduces population size! Ex: hunting to the point of extinction!

60. The Bottleneck Effect *

61. Bottleneck Effect !

62. The Founder Effect
Genetic drift that results from the colonization of a new location by a small number of individuals – small size, less representative of the gene pool.

63. Founder Effect
Ex: Amish residents of Lancaster County, PA – Ellis-van Creveld Syndrome

64. Genetic Drift & Founder Effect
Symptoms: short arms & legs, extra fingers, & in some cases heart defects.

66. Gene flow
When fertile individuals move into or out of a population or when gametes are transferred between populations.

67. Gene Flow *

68. Gene flow *

69. A random change in an organism’s DNA that may create a new allele.
Mutations
A random change in an organism’s DNA that may create a new allele.

70. mutation
HUH??