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Chapter 15. copyright cmassengale 2 Evidence for Evolution – The Fossil Record.

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Presentation on theme: "Chapter 15. copyright cmassengale 2 Evidence for Evolution – The Fossil Record."— Presentation transcript:

1 Chapter 15

2 copyright cmassengale 2 Evidence for Evolution – The Fossil Record

3 FOSSIL…. a trace of a long-dead organism usually left in sedimentary rock and can be seen in different layers (strata) examples: trace (footprints, scat), mold (imprint), cast (rocklike model), replacement, petrified, amber, original material (bones, shells, seeds, feathers)

4 Mold – an imprint in rock Cast – rocklike model of the organism

5 The fossil record traces history of life and allows us to study history of particular organisms Through radioactive dating, geologists estimate the age of the earth at about 4.6 billion years

6 Fossils are at least 10,000 years old and include skeletons, shells, seeds, insects trapped in amber, imprints of organisms, organisms frozen in ice (wooly mammoth), or trapped in tar pits (saber-toothed tiger) Transitional forms reveal links between groups (Example: Therapsids were mammal-like reptiles and Pterosaurs were bird like reptiles)

7 Robert Hooke (1668) One of the first scientists to study fossils, principally petrified wood, with the aid of a microscope. He hypothesized that living organisms had somehow turned to rock.

8 Nicolaus Steno (1669) Proposed the law of superposition which states that successive layers of rock or soil were deposited on top of one another by wind or water. Relative age of fossils

9 The layer of strata on the bottom is the oldest and the layer on the top is the youngest. Using this law scientists can estimate the relative age of a fossil by comparing a fossil to others found in the same layer.

10 The 2 most common ways are… Relative Dating: based on law of superposition (lower fossils are older) Radiometric Dating: based on half-life (uses the decay of radioactive isotopes to measure the age – half life)

11 Extinction occurs when previous adaptations are no longer suitable to a changed environment The fossil record indicates that there were several mass extinctions. Some of these life-forms were unlike any organism alive today.


13 e·ra/ ˈ i( ə )r ə / Noun: A long and distinct period of history with a particular feature or characteristic. A system of chronology dating from a particular noteworthy event.

14 The Precambrian Era is Earth's first era of time. It began with the creation of the Earth around 4.6 billion years ago and lasted until 570 million years ago. The Precambrian saw many drastic changes during this time. The five major events of the Precambrian are: 1. The formation of the Sun and light. 2. The creation of the Earth. 3. The creation of the atmosphere through volcanic out-gassing. 4. The creation of the oceans. After rainfall, the Earth's surface was cooled down and the rainwater collected into low areas which formed oceans and seas. The ocean became stable around 1 bya when no more salt from rocks could be dissolved into the water. 5. The creation of life (Prokaryotes, then eukaryotes). This actual process remains open to debate as to how it all took place.

15 The Paleozoic era began when the Precambrian era ended. There was an explosion of life marking the beginning of the Paleozoic. Paleozoic means ancient life. There are six periods within the Paleozoic Era. These periods include the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian.

16 The Cambrian Period lasted for 70 million years. The Cambrian is the first period of the Paleozoic Era. The Cambrian is quite different from the Precambrian in that the animals could see, think, and they had exoskeletons. All life existed in the oceans at this time because the ozone layer was not developed to withstand ultraviolet rays from the Sun. The most advanced animal of this period was the trilobite. The Cambrian is known as "the age of the trilobites."

17 The Ordovician Period existed for 60 million years. The Ordovician was shorter than the Cambrian period. All life still existed in the ocean because of the lack of proper ozone levels. The trilobite became larger and smarter during this time. The major life form of this time period was the shell fish. The Ordovician is called "the age of the shell fish."

18 The Silurian Period lasted for 40 million years. The Silurian marks the first time that life existed on land. These life forms were simple plants such as Psilophyton, a vine-type plant. Plants of this period did not possess leaves or flowers. The Silurian is called "the age of the first life on land." Ozone levels have reached the required thickness to protect life on land from now on.

19 The Devonian Period lasted for 50 million years. The Devonian is called "the age of the fishes." Two types of fish developed during this time period: jawless and jawed fish. The jawless fish were armor plated with bones and used suction to feed through their mouths. Some jawed fish developed lungs, and the first animal life walked upon the land at this time. Sharks also made their début at this time.

20 The Carboniferous Period, also called the Mississippian and Pennsylvanian Periods, lasted for 70 million years. The Carboniferous is often called "the age of swamps and coal." During this time period much of the land was covered by swamps and seas. The climate was extremely warm during this period. Giant insects and plants dominated this period. Much of the coal supplies world-wide originated from this period.

21 The Permian Period existed for 55 million years. The Permian period saw the rise of dinosaurs and mammals. It is often called "the age of mass extinction" or "the age of amphibians." Giant amphibians ruled the land during this period. This period marks the end of the Paleozoic Era when an asteroid around 10 miles in diameter struck the North American Continent at Hudson Bay, Canada. The asteroid strike was so devastating that 98% of life on Earth was wiped out! This destruction was caused when dust from the impact circled the globe via the jet stream and blocked out the Sun for many years, freezing most life on Earth.

22 The Mesozoic Era existed from 225 mya to 65 mya. The Mesozoic Era is divided into three periods of time. These periods are: the Triassic, Jurassic and Cretaceous.

23 The Triassic Period lasted 30 million years. The Triassic is called "the age of dinosaurs." Shortly after the asteroid strike, the dinosaurs and mammals were left on Earth. Dinosaurs, being reptiles, had advantages over mammals in that they were "ready to go" when born, they could reproduce higher numbers of young and they were larger. This helped dinosaurs take control of the Earth during this period.

24 The Jurassic Period lasted 60 million years. The Jurassic saw many changes in dinosaurs during this period. The dinosaurs were mainly herbivores in that they ate plants. The dinosaurs of this period grew to 140 feet long in some cases! The Jurassic is often marked as "the first time period when life existed in the sky." The first bird-like dinosaur was called the Archaeopteryx.

25 The Cretaceous Period lasted for 70 million years. The Cretaceous is known as "the age of the carnivores." This time period saw the rise of meat eaters such as T- Rex, which required 2 tons of meat a day to survive. The Cretaceous time period saw the first flowers on plants. The Cretaceous is also marked by a mass extinction event that ended the Mesozoic Era. An asteroid around a few miles in diameter struck the Earth at the Yutan peninsula in Mexico. This created a global dust cloud around the world and wiped out 65% of all life on Earth. This ended the age of the dinosaurs.

26 1. They grew too big to support their feeding habits. 2. They suffered from diseases such as cancer. 3. Their climate changed as the continents moved to northern or far southern latitudes. 4. Mammals, such as rats, destroyed their eggs faster than they could produce them. 5. The asteroid strike was the final blow. There is a theory out there that suggests that dinosaurs became birds, and there is some evidence to support that. Next time you see a bird, maybe T-Rex is looking back at you!

27 The Cenozoic Era began when the Mesozoic ended 65 mya. The Cenozoic gave witness to the rise of mammals. The Cenozoic Era is called "the era of mammals." The Cenozoic Era is divided into two periods and six epochs. The two periods are the Tertiary and the Quaternary. The seven epochs include: the Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene and Holocene. The Cenozoic Era is marked by the rise and diversification of mammals as they gained dominance over the Earth. The era is also marked by repeated ice ages which altered and modified not just the land, but also life itself.

28 The Tertiary lasted 63 million years. This period is called "the age of the rise of mammals." Mankind also appeared for the first time in the fossil record around 5 million years ago late in the Tertiary Period. The Tertiary Period includes the Paleocene, Eocene, Oligocene, Miocene and Pliocene epochs.

29 Tertiary Period Paleocene (65 mya to 55 mya - Rise of Mammals) Eocene (55 mya to 38 mya - Saber Tooth Cats, Primitive Horses) Oligocene (38 mya to 25 mya - First Primates) Miocene (25 mya to 5 mya - Apes) Pliocene (5 mya to 2 mya - First Man)

30 Pleistocene (2 mya to 10,000 years ago - The Rise of Man) Holocene (10,000 years ago to present - Modern Man)


32 The Quaternary has lasted 2 million years so far. We are in the Quaternary period. This period is known as "the age of man," since mankind has dominated the Earth since the beginning of this period. The Quaternary contains the Pleistocene and Holocene epochs.

33 Biogeography is the study of the geographic distribution of life forms on earth Physical factors, such as the location of continents, determine where a population can spread Example: Placental mammals arose after Australia separated from the other continents, so only marsupials diversified in Australia

34 Jean-Baptiste Lamarck, 1809 One Of First Scientists To Understand That Change Occurs Over Time Stated that Changes Are Adaptations To Environment acquired in an organisms lifetime Said acquired changes were passed to offspring copyright cmassengale 34

35 Idea called Law of Use and Disuse If a body part were used, it got stronger If body part NOT used, it deteriorated copyright cmassengale 35

36 Inheritance of Acquired Characteristics Proposed That By Selective Use Or Disuse Of Organs, Organisms Acquired Or Lost Certain Traits During Their Lifetime These Traits Could Then Be Passed On To Their Offspring Over Time This Led To New Species copyright cmassengale 36

37 37 Different Animals On Different Continents But Similar Adaptations To Shared Environments

38 Use & Disuse - Organisms Could Change The Size Or Shape Of Organs By Using Them Or Not Using Them Blacksmiths & Their Sons (muscular arms) Giraffes Necks Longer from stretching) copyright cmassengale 38

39 copyright cmassengale 39

40 Inheritance Of Acquired Traits Traits Acquired During Ones Lifetime Would Be Passed To Offspring copyright cmassengale 40 Clipped ears of dogs could be passed to offspring!

41 Tendency Toward Perfection Organisms Are Continually Changing and Acquiring Features That Help Them Live More Successfully In Their Environment Example: Bird Ancestors Desired To Fly So They Tried Until Wings Developed copyright cmassengale 41

42 Lamarck Did NOT Know how traits were inherited (Traits are passed through genes) Genes Are NOT Changed By Activities In Life Change Through Mutation Occurs Before An Organism Is Born copyright cmassengale 42

43 43

44 44 Charles Darwin Born Feb. 12, 1809 Joined Crew of HMS Beagle, 1831 Naturalist 5 Year Voyage around world Avid Collector of Flora & Fauna Astounded By Variety of Life

45 45

46 46 : Charles Lyell –uniformatarianism Georges Cuvier – species extinction (Catastrophism) Thomas Malthus – struggle for existence (resources)

47 47 : James Hutton - Gradualism John Baptiste Lamarck – Inheritance of acquired Characteristics and Law of Use and Disuse Alfred Russel Wallace – organisms evolved from common ancestors

48 48 Proposed theory of Uniformitarianism Geological processes at uniform rates building & wearing down Earths crust Proposed that the Earth was millions of years instead of a few thousand years old

49 49

50 50 Small Group of Islands 1000 km West of South America Very Different Climates Animals On Islands Unique Tortoises Iguanas Finches

51 51 Finches on the islands resembled a mainland finch More types of finches appeared on the islands where the available food was different (seeds, nuts, berries, insects…) Finches had different types of beaks adapted to their type of food gathering

52 52

53 53 Upon His Return To England, Darwin Developed His Observations Into The Theory of Evolution But He Did Not Publish For 25 Years – Why?

54 54 Darwin Knew That His Theory Would Be Extremely Controversial And Would Be Attacked His Theory Challenged Established Religious & Scientific Beliefs, Particularly About The Creation Of Man

55 55 He Refused To Publish Until He Received An Essay From Alfred Wallace Fellow Naturalist Independently Developed The Same Theory After 25 Years, Someone Else Had Come To The Same Conclusions From Their Observations Of Nature

56 56 Cannot Be Seen Directly It Can Only Be Observed As Changes In A Population Over Many Successive Generations Radiation Fossil Record

57 57 Takes Place Over Long Periods of Time Natural Selection Can Be Observed As Changes In Body Structures Ecological Niches Habitats

58 58 Species Today Look Different From Their Ancestors Each Living Species Has Descended With Changes From Other Species Over Time

59 59

60 60 Implies All Living Organisms Are Related Single Tree of Life DNA, Body Structures, Energy Sources Common Descent All Species, Living & Extinct, Were Derived From Common Ancestors

61 61. MAJOR PROBLEM IN DARWINS THEORY No mechanism to explain natural selection How could favorable variations be transmitted to later generations? With the rediscovery of Mendels work in the first half of the 20th century, the missing link in evolutionary theory was found

62 62 Thomas Malthus

63 63 Thomas Malthus, 1798 Economist Observed Babies Being Born Faster Than People Were Dying Population size limited by resources such as the Food Supply

64 64 Malthus Influence: High Birth Rates & Limited Resources Would Force Life & Death Competition Each Species Struggles For: Food Living Space Mates

65 65 Malthus Reasoned That If The Human Population Continued To Grow Unchecked, Sooner or Later There Would Be Insufficient Living Space & Food For Everyone Death Rate Will Increase To Balance Population size & Food Supply

66 66 Darwin Realized Malthuss Principles Were Visible In Nature Plants & Animals Produce Far More Offspring Than Can Be Supported Most Die If They Didnt – Earth Would Be Overrun

67 67. NATURAL SELECTION Driving force for evolution During the struggle for resources, strongest survive & reproduce Idea that at least some of the differences between individuals, which impact their survival and fertility, are inheritable

68 68 Abandoned The Idea That Species Were Perfect & Unchanging Observed Significant Variation in All Species Observed Observed Farmers Use Variation To Improve Crops & Livestock Called Selective Breeding

69 69 Natural Variation Differences Among Individuals Of A Species Artificial Selection Selective Breeding To Enhance Desired Traits Among Stock or Crops

70 70 Key Concept: In Artificial Selection, Nature Provided The Variation Among Different Organisms, And Humans Selected Those Variations That They Found Useful

71 71

72 72 Evolution is the slow, gradual change in a population of organisms over time

73 73 Left unchecked, the number of organisms of each species will increase exponentially, generation to generation In nature, populations tend to remain stable in size Environmental resources are limited

74 74 Production of more individuals than can be supported by the environment leads to a struggle for existence among individuals Only a fraction of offspring survive each generation Survival of the Fittest

75 75 The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations (natural selection)The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations (natural selection) New species evolveNew species evolve Darwins Theory of Evolution


77 77 The Struggle for Existence (compete for food, mates, space, water, etc.) Survival of the Fittest (strongest able to survive and reproduce) Descent with Modification (new species arise from common ancestor replacing less fit species)

78 78 Fitness Ability of an Individual To Survive & Reproduce Adaptation Inherited Characteristic That Increases an Organisms Chance for Survival

79 79 Adaptations Can Be: Physical Speed, Camouflage, Claws, Quills, etc. Behavioral Solitary, Herds, Packs, Activity, etc.

80 80 Fitness Is Central To The Process Of Evolution Individuals With Low Fitness Die Produce Few Offspring Survival of the Fittest AKA Natural Selection

81 81 Key Concept Over Time, Natural Selection Results In Changes In The Inherited Characteristics Of A Population. These Changes Increase A Species Fitness In Its Environment

82 82 Supporting Evidence




86 86 Evidence for Evolution - Comparative Embryology Similarities In Embryonic Development

87 similarities in the biochemistry of species indicates common ancestry almost all living organisms have the same molecules: DNA, RNA, ATP, enzymes, etc. amino acid sequences are similar genetic code = A T C G (in ALL living things)


89 Coevolution Convergent evolution Divergent evolution



92 Divergent Evolution related species becoming more dissimilar

93 The Galapagos finches are an example of adaptive radiation. They diverged in response to the availability of different types of food in their different habitats

94 All domestic dogs were originally bred from wolves.

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