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Evolution: Evidence and Theory

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1 Evolution: Evidence and Theory
Chapter 15 Evolution: Evidence and Theory

2 Evidence for Evolution – The Fossil Record
copyright cmassengale

3 Fossil Evidence 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 The difference between a mold and a cast
Mold – an imprint in rock Cast – rocklike model of the organism

5 Fossil Record 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 Fossil Record 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 Scientists 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 Scientist 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 Superposition 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 Dating Fossils 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 Succession of Forms 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 What is an ERa e·ra/ˈi(ə)rə/ 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 Precambrian era 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 Paleozoic Era 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 Cambrian 570 mya to 500 mya 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 Ordovician 500 mya to 440 mya 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 Silurian 440 mya to 400 mya 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 Devonian 400 mya to 350 mya 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 Carboniferous 350 mya to 280 mya
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 Permian 280 mya to 225 mya 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 Mesozoic Era 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 Triassic 225 mya to 195 mya 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 Jurassic 195 mya to 135 mya 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 Cretaceous 135 mya to 65 mya 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 Dinosaurs were extinguished by five reasons:
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 Cenozoic era 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 Tertiary 65 mya to 2 mya 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 The Seven Epochs are: 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 Quaternary Period Pleistocene (2 mya to 10,000 years ago - The Rise of Man) Holocene (10,000 years ago to present - Modern Man)

31 The Seven Epochs represent changes in climate such as ice ages and the rise of different species of mammals.

32 Quaternary 2 mya to present
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 Biogeographical Evidence:
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 Lamarck’s Theory of Evolution
copyright cmassengale Lamarck’s Theory of Evolution 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 organism’s lifetime Said acquired changes were passed to offspring

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

36 Lamarck’s Theory of Evolution
copyright cmassengale Lamarck’s Theory of Evolution 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

37 Geographic Distribution of Living Species
Different Animals On Different Continents But Similar Adaptations To Shared Environments

38 Lamarck’s Theory of Evolution
copyright cmassengale Lamarck’s Theory of Evolution Use & Disuse - Organisms Could Change The Size Or Shape Of Organs By Using Them Or Not Using Them Blacksmiths & Their Sons (muscular arms) Giraffe’s Necks Longer from stretching)

39 copyright cmassengale

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

41 Lamarck’s Theory of Evolution
copyright cmassengale Lamarck’s Theory of Evolution 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

42 Genes Are NOT Changed By Activities In Life
copyright cmassengale Lamarck’s Mistakes 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

43 Charles Darwin the Naturalist

44 Voyage of the Beagle 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 Evolutionary Timeline

46 Contributor’s to Darwin’s thinking included:
Charles Lyell –uniformatarianism Georges Cuvier – species extinction (Catastrophism) Thomas Malthus – struggle for existence (resources)

47 Contributor’s to Darwin’s thinking included:
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 Charles Lyell Proposed theory of Uniformitarianism
Geological processes at uniform rates building & wearing down Earth’s crust Proposed that the Earth was millions of years instead of a few thousand years old

49 HMS Beagle’s Voyage

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

51 The Galapagos Islands 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


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

54 Publication of “On The Origin of Species”
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 Publication of “On The Origin of Species”
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 Cannot Be Seen Directly
Darwin’s theories Cannot Be Seen Directly It Can Only Be Observed As Changes In A Population Over Many Successive Generations Radiation Fossil Record

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

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

59 Descent With Modification

60 Descent With Modification
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 Major Problem in Darwin’s Theory
No mechanism to explain natural selection How could favorable variations be transmitted to later generations? With the rediscovery of Mendel’s work in the first half of the 20th century, the missing link in evolutionary theory was found .

62 Ideas That Shaped Darwin’s Thinking
Thomas Malthus Ideas That Shaped Darwin’s Thinking

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

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

65 Population Growth 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 Population Growth Darwin Realized Malthus’s Principles Were Visible In Nature Plants & Animals Produce Far More Offspring Than Can Be Supported Most Die If They Didn’t – Earth Would Be Overrun

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

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


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

73 Darwin’s Observations
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 Darwin’s Conclusion 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 Darwin’s Theory of Evolution
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 evolve

76 Let’s review

77 Evolution By Natural Selection Concepts
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 Survival of the Fittest
Fitness Ability of an Individual To Survive & Reproduce Adaptation Inherited Characteristic That Increases an Organisms Chance for Survival

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

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

81 Survival of the Fittest
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 Theory of Evolution Today
Supporting Evidence Theory of Evolution Today

83 Homologous Structures - structures having different mature forms but develop from a common ancestor Example: forelimbs of human, cat, whale and bat

84 Analogous Structures – structures having similar functions but develop from different ancestors Example: wings of insect, pterodactyl, bird and bat

85 Vestigial Structures/Vestigial Organs - structures that serve no useful function in an organism Example: appendix in man, dew claw on dogs

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

87 similarities in the biochemistry of species indicates common ancestry
Biochemical Evidence 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 Patterns of Evolution Coevolution Convergent evolution
Divergent evolution

90 Coevolution 2 or more organisms evolving together

91 Convergent Evolution unrelated species become more similar as they adapt to same kind of environment

92 Divergent Evolution related species becoming more dissimilar

93 Adaptive radiation 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 Artificial Selection All domestic dogs were originally bred from wolves.

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