1. Evolution Notes
Unit 6

2. Earth formed about 4.6 billion years ago.
Chapter 14
The History of Life
14.1 Fossil Evidence of Change
Land Environments
Earth formed about 4.6 billion years ago.

3. A fossil is any preserved evidence of an organism.
Chapter 14
The History of Life
14.1 Fossil Evidence of Change
Clues in Rocks
A fossil is any preserved evidence of an organism.
Why are there gaps in the fossil record?
Most organisms decompose before they have a chance to become fossilized.

4. 14.1 Fossil Evidence of Change
Chapter 14
The History of Life
14.1 Fossil Evidence of Change

5. Nearly all fossils are formed in sedimentary rock.
Chapter 14
The History of Life
14.1 Fossil Evidence of Change
Fossil Formation
Nearly all fossils are formed in sedimentary rock.

6. Chapter 14
The History of Life
14.1 Fossil Evidence of Change
Dating fossils
Relative dating is a method used to determine the age of rocks by comparing them with those in other layers.

7. Uses the decay of radioactive isotopes to measure the age of a rock
Chapter 14
The History of Life
14.1 Fossil Evidence of Change
Radiometric Dating
Uses the decay of radioactive isotopes to measure the age of a rock
Radioactive isotopes that can be
used for radiometric dating are found only in
igneous or metamorphic rocks.

8. The Geologic Time Scale
Chapter 14
The History of Life
14.1 Fossil Evidence of Change
The Geologic Time Scale
The geological time scale is a model that expresses the major geological and biological events in Earth’s history.

9. Chapter 14
The History of Life
14.1 Fossil Evidence of Change
The Paleozoic Era
The ancestors of most major animal groups diversified in what scientists call the Cambrian explosion.

10. Between 60 and 75 percent of the species alive went extinct.
Chapter 14
The History of Life
14.1 Fossil Evidence of Change
A mass extinction ended the Paleozoic era at the end of the Permian period.
Between 60 and 75 percent of the species alive went extinct.

11. Chapter 14
The History of Life
14.1 Fossil Evidence of Change
Plate tectonics describes the movement of several large plates that make up the surface of Earth.

12. Terminology to know!
Hypothesis An “If…then” statement or proposal of an outcome of an experiment.
(Ex. If I study, then I will pass the test.)
Theory A hypothesis that has withstood extensive testing by a variety of methods, and in which a higher degree of certainty may be placed (Ex. Theory of Evolution)
Law Considered universal and invariable facts of the physical world
(Ex. Law of Gravity)

13. Spontaneous generation is the idea that life arises from nonlife.
Chapter 14
The History of Life
14.2 The Origin of Life
Origins: Early Ideas
Spontaneous generation is the idea that life arises from nonlife.
Francesco Redi, an Italian scientist, tested the idea that flies arose spontaneously from rotting meat.

14. Chapter 14
The History of Life
14.2 The Origin of Life
The theory of biogenesis states that only living organisms can produce other living organisms.
Louis Pasteur designed an experiment to show that biogenesis was true even for microorganisms.

15. Scientists hypothesize that the first cells were prokaryotes.
Chapter 14
The History of Life
14.2 The Origin of Life
Cellular Evolution
Scientists hypothesize that the first cells were prokaryotes.
These would compare to our modern day bacteria

16. The Endosymbiotic Theory
Chapter 14
The History of Life
14.2 The Origin of Life
The Endosymbiotic Theory
Eukaryotic cells arose from communities formed by prokaryotic cells.
This theory explains the origin of chloroplasts and mitochondria.

17. Chapter 14
The History of Life
14.2 The Origin of Life

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

19. What can explain the large extent of biological diversity on earth?
Evolution – change over time
How life has changed over time

20. Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
The Galápagos Islands
Darwin began to collect mockingbirds, finches, & other animals on the 4 islands.
He noticed that the different islands seemed to have their own, slightly different varieties of animals.

21. The Galapagos Islands West of South America
Group of islands each with different climates
Tortoises varied from island to island in neck length and shell shape
Finches varied in beak shape
Characteristics of plants and animals varied from island to island

22. 15.1 Darwin’s Theory of Natural Selection
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection

23. Darwin Continued His Studies
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
Darwin Continued His Studies
Darwin inferred that if humans could change species by artificial selection, then perhaps the same process could work in nature.

24. Individuals in a population show variations.
Chapter 15
Evolution
15.1 Darwin’s Theory of Natural Selection
Natural Selection
Individuals in a population show variations.
Variations can be inherited.
Organisms have more offspring than can survive with available resources.
Variations that increase reproductive success will have a greater chance of being passed on.
“Survival of the Fittest”

25. It is a means of explaining how evolution works.
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.
It is a means of explaining how evolution works.

26. Lamarck’s Theory Pre-Darwin scientist Inheritance of acquired traits
Organs used a lot could grow and change shape
Organs not used would shrivel and disappear
Theory was incorrect but significant because he was the first scientist to recognize that organisms had changed over time

27. 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
Provide a record of species that lived long ago.
Show that ancient species share similarities with species that now live.
Glyptodont
Armadillo

28. Chapter 15
Evolution
15.2 Evidence of Evolution
Support for Evolution
Geographic Distribution
The distribution of plants and animals that Darwin saw first suggested evolution to Darwin.
Rabbit
Mara

29. Chapter 15
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.

30. Homologous Structures
Anatomically similar structures inherited from a common ancestor

31. Same function but different structure
Chapter 15
Evolution
Analogous Structures
Same function but different structure
NOT inherited from
common ancestor.

32. Vestigial Structures 15.2 Evidence of Evolution
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.

33. Chapter 15
Evolution
15.2 Evidence of Evolution
Comparisons of the similarities in organisms are seen in comparative anatomy and in the fossil record.
Organisms with closely related morphological features have more closely related molecular features.

34. More Terms
Fitness – ability of an individual to survive and reproduce in a specific environment
Adaptation – inherited characteristic that increases an organism’s chance of survival
Can be physical traits as well as behavioral traits

35. Allows organisms to become almost invisible to predators
Chapter 15
Evolution
15.2 Evidence of Evolution
Camouflage
Allows organisms to become almost invisible to predators
Leafy sea dragon

36. One species evolves to resemble another species.
Chapter 15
Evolution
15.2 Evidence of Evolution
Mimicry
One species evolves to resemble another species.
Western coral snake
California kingsnake

37. Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Natural Selection
Acts to select the individuals that are best adapted for survival and reproduction

38. Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Stabilizing selection operates to eliminate extreme expressions of a trait when the average expression leads to higher fitness.
Ex. Siberian Husky
Stabilizing selection favors the norm, the common, average traits in a population. Look at the Siberian Husky, a dog bred for working in the snow. The Siberian Husky is a medium dog, males weighing 16-27kg (35-60lbs). These dogs have strong pectoral and leg muscles, allowing it to move through dense snow. The Siberian Husky is well designed for working in the snow. If the Siberian Husky had heavier muscles, it would sink deeper into the snow, so they would move slower or would sink and get stuck in the snow. Yet if the Siberian Husky had lighter muscles, it would not be strong enough to pull sleds and equipment, so the dog would have little value as a working dog. So stabilizing selection has chosen a norm for the the size of the Siberian Husky.

39. Directional selection makes an organism more fit.
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Directional selection makes an organism more fit.
Favors the extremes
Ex. Greyhound Dog
Directional selection favors those individuals who have extreme variations in traits within a population. A useful example can be found in the breeding of the greyhound dog. Early breeders were interested in dog with the greatest speed. They carefully selected from a group of hounds those who ran the fastest. From their offspring, the greyhound breeders again selected those dogs who ran the fastest. By continuing this selection for those dogs who ran faster than most of the hound dog population, they gradually produced a dog who could run up to 64km/h (40mph).

40. Ex. Black, White, & Gray Rabbits
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Disruptive selection is a process that splits a population into two groups.
Ex. Black, White, & Gray Rabbits
If this population of rabbits were put into an area that had very dark black rocks as well as very white colored stone, the rabbits with black fur would be able to hide from predators amongst the black rocks and the white furred rabbits would be able to hide in the white rocks, but the gray furred rabbits would stand out in both of the habitats and thus would not survive.

41. 15.3 Shaping Evolutionary Theory
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Mechanisms of Evolution
Population genetics
Hardy-Weinberg principle states that when allelic frequencies remain constant, a population is in genetic equilibrium.

42. Write these down & know these!
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Write these down & know these!

43. Genetic Drift Marble Example
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Genetic Drift
A change in the allelic frequencies in a population that is due to chance and random mating
In smaller populations, the effects of genetic drift become more pronounced, and the chance of losing an allele becomes greater.
Marble Example
As an analogy, imagine a population of organisms represented as 20 marbles in a jar, half of them red and half blue. These two colors correspond to two different gene alleles in the population. The organisms that are reproduced in a generation are represented in another jar. Each new generation the organisms will reproduce at random. To represent this reproduction, randomly pick a marble from the original jar and deposit a new marble with the same color as its "parent" in the second jar. Repeat the process until there are 20 new marbles in the second jar. The second jar will then contain a second generation of "offspring", 20 marbles of various colors. Unless the second jar contains exactly 10 red and 10 blue marbles there will have been a purely random shift in the allele frequencies.
Repeat this process a number of times, randomly reproducing each generation of marbles to form the next. The numbers of red and blue marbles picked each generation will fluctuate: sometimes more red, sometimes more blue. That is genetic drift – random variations in which organisms manage to reproduce, leading to changes over time in the allele frequencies of a population.

44. Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Nonrandom Mating
Promotes inbreeding & could lead to a change in allelic proportions favoring individuals that are homozygous for particular traits

45. Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Founder Effect
The loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population
Island 1
Island 2
Mainland
Island 3

46. Evolution
15.3 Shaping Evolutionary Theory
Bottleneck
a significant percentage of a population or species is killed or otherwise prevented from reproducing and can rebound later
Often caused by a natural disaster

47. What is a gene pool?
Gene pool – combined genetic info of all members of a population
Contains two of more alleles (genes) for the same trait
Allele frequency – number of times an allele occurs in a gene pool compared to the number of times another allele occurs (expressed in percents)

48. Relative Frequencies of Alleles
Section 16-1
allele for brown fur
allele for black fur
Sample Population
48% heterozygous black
Frequency of Alleles
16% homozygous black
36% homozygous brown

49. Gene Flow Genes entering or leaving a population AKA. Migration
Emigration Genes LEAVING a population
Immigration INCOMING genes in a population

50. What are sources for genetic variation?
Mutations – random change in the DNA, may cause evolution in future populations
Genetic shuffling – occurs in meiosis when gametes are formed

51. Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Sexual selection operates in populations where males and females differ significantly in appearance.

52. Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Prezygotic isolation prevents reproduction by making fertilization unlikely.
In behavioral isolation, patterns of courtship may be different.
In temporal isolation, different groups may not be reproductively mature at the same season, or month, or year.
In ecological isolation, not in the same habitat where they are likely to meet.
Eastern meadowlark and Western meadowlark

53. Postzygotic isolation occurs when fertilization has occurred but
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Postzygotic isolation occurs when fertilization
has occurred but
a hybrid offspring
cannot develop
or reproduce.
Prevents offspring survival or reproduction
Liger

54. Allopatric Speciation
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Allopatric Speciation
A physical barrier divides one population into two or more populations.
Abert squirrel
Kaibab squirrel

55. A species evolves into a new species without a physical barrier.
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
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.

56. 15.3 Shaping Evolutionary Theory
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Adaptive Radiation
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

57. Coevolutionary arms race
Chapter 15
Evolution
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

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

59. Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Rate of Speciation
Evolution proceeds in small, gradual steps according to a theory called gradualism.
Punctuated equilibrium explains rapid spurts of genetic change causing species to diverge quickly.

60. 15.3 Shaping Evolutionary Theory
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory