Intro to Evolution – Ch 15
Objective: 3.05 Examine the development of the
theory of evolution by natural selection including:
development of the theory; the origin and history of life;
The Fossil Record
Chapter 15.1
Objective: Examine the development of the theory of evolution by
natural selection including: fossil and biochemical evidence;
mechanisms of evolution; applications (pesticide and antibiotic
resistance)
Why use fossils?
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Scientists have used the fossil record to
construct a history of life on Earth.
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Earth’s life forms appeared 3.5 billion years ago
Fossil record is not complete, but pretty good for
general information
Fossils
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Trace of long-dead organism
Formed in sediment – dust, sand, mud – by
wind or water
Hard body parts frozen in time
Minerals replace soft tissue > rocks
Types of fossils
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Mold – imprint of organism
Cast – imprint replaced with minerals – looks
like a model
Evidence of behavior – footprints/tracks
Insects petrified and frozen in amber
Dating Fossils
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Relative Dating
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Rock layers are put down in order
Oldest on bottom, youngest layers on top
Radiometric Dating
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Use Carbon-14 for ages 50,000 years or less
Half-life is 5730 years
Nicolaus Steno
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Law of superposition – successive layers of
rock or soil were deposited on top of one
another by wind or water
Stratum (lowest layer) – or layer in cross
section is the oldest, top layer is youngest
Earth’s age ~ 4.6 billion years
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Relative age – age by comparison
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e.g. I am older than you by comparison yet you
don’t know my exact age
E.g. the cement in the foundation of the building
is older than the roof by comparison yet I don’t
know the exact age in years of the building
Absolute age – age in years by radiometric
dating (carbon -14)
Succession of forms
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Extinct – disappeared from existence
Mass extinctions – large numbers of species
disappeared
– drastic environmental change like volcanic
activity, collisions with asteroids
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First organisms begin with prokaryotes in
Precambrian era (540 mya)
Biogeography – study of the geographical
distribution of fossils
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Indicates that organisms arise in areas where
similar body forms lived suggesting that they are
the new-improved model! A modified version
Theories of Evolution
Chapter 15.2
Objective: 3.05 Examine the development of the
theory of evolution by natural selection including:
development of the theory; the origin and history of life;
Processes of science vs.
processes of faith
Science:
Observe  Ask questions  Propose hypotheses 
Conduct Investigation  Alter hypotheses
 Faith:
Religious faith is a belief; Faith is not altered to fit
evidence
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I ask students to learn theory of evolution – they don’t
have to “believe” in it just understand it.
I will not teach creationism nor intelligent design – they
are not science
Evolutionary Timeline
Jean Baptiste de LaMarck
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inheritance of acquired traits – characteristic passed
to offspring; not determined by genes
 repeated use or disuse of body part during their
lifetime was then passed down to offspring or
inherited
 E.g. webbed feet of duck
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Related fossils to living organisms based on similar
appearance
1st to say organisms change over time
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Use & Disuse Organisms Could Change
The Size Or Shape Of
Organs By Using Them
Or Not Using Them
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Blacksmiths & Their
Sons (muscular arms)
Giraffe’s Necks Longer
from stretching)
Inheritance Of Acquired Traits
Traits Acquired During Ones Lifetime Would Be
Passed To Offspring
Clipped ears of dogs could be passed to offspring!
Charles Darwin & Alfred Wallace
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Independently propose that species were modified
by natural selection – when organisms with traits
well suited to the environment reproduce more
successfully than other organisms
Published Origin of the Species
Sailed on HMS Beagle to Galapagos Islands, west
of S. America
What is the Theory of Evolution
by Natural Selection?
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Populations would grow exponentially if there were
unlimited resources
Environmental factors limit reproductive capacity
Organisms compete for resources
There is variation within populations and those with useful
adaptations survive
The survivors reproduce and pass on their genes
The new generation will have a greater frequency of the
adaptive traits
Over a long period of time, the differences are so great that
the result could be a new species
HMS Beagle voyage
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Naturalist
Read Principles of Geology by Charles Lyell
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Uniformitarianism – geological cycles observed
today are the same processes from long ago
e.g. volcanoes erupt the same today as millions of
years ago
Darwin sailed on the Beagle for 5 years making observations as the ship’s naturalist.
He studied: tortoises, finches & more
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Island species varied from mainland species
AND from island-to-island species
Each island had long or short neck tortoises
Finches:
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Finches on the islands resembled 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
Evolved from a common remote ancestor
phylogenetic tree - shows evolutionary relationships
Phylogenetic Tree or Ancestral Tree showing proposed evolution
Darwin’s 2 theories:
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Descent with modification
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Newer organisms in fossil record are modified
descendants of older species
All species descended from original type of life
Modification by natural selection
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Organisms with favorable traits have more offspring
than others without them– adaptive advantage
Can adapt to environment therefore more fit
Survival of the Fittest
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Fitness
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Ability of an Individual To Survive &
Reproduce
Adaptation
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Inherited Characteristic That Increases
an Organisms Chance for Survival
Survival of the Fittest
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Adaptations Can Be:
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Physical
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Speed, Camouflage, Claws, Quills, etc.
Behavioral
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Solitary, Herds, Packs, Activity, etc.
Survival of the Fittest
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Fitness Is Central To The Process Of
Evolution
Individuals With Low Fitness
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Die
Produce Few Offspring
Survival of the Fittest AKA Natural Selection
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
Descent With Modification
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Takes Place Over Long Periods of
Time
Natural Selection Can Be Observed As
Changes In
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Body Structures
Ecological Niches
Habitats
Descent With Modification
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Species Today Look Different From
Their Ancestors
Each Living Species Has
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Descended
With Changes
From Other Species
Over Time
Descent With Modification
EVIDENCE for EVOLUTION
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Evidence from fossils.
 The Geographical Distribution of Living
Species
 Homologous Structures of Living
Organisms
 Similarities In Early Development
Homologous Body Structures
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Structures That Have Different Mature Forms
But Develop From The Same Embryonic Tissues
Homologous Body Structures
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Scientists Noticed Animals With Backbones
(Vertebrates) Had Similar Bone Structure
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May Differ In Form or Function
Limb Bones Develop In Similar Patterns
 Arms, Wings, Legs, Flippers
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Homologous Body Structures
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Not All Serve Important Functions
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Vestigial Organs
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Appendix In Man
Legs On Skinks
Similarities In Early Development
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Embryonic Structures Of Different Species
Show Significant Similarities
Embryo – early stages of vertebrate
development
Similarities In Embryonic Development
Evidence from genetics.
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All organisms share the same basic
mechanism of heredity (DNA/RNA)
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E.g.: mtDNA evidence for human evolution
A branching tree radiating from a
common ancestor – phylogenetic tree
We can conduct research on other species to
understand our own genes.
Similarities in
DNA Sequence
Evolution in action.
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Many bacterial pathogens (origin of feeling –
what started the disease) have evolved resistance
to antibiotics
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In the case of HIV, which causes AIDS, significant
viral evolution occurs within the course of infection
of a single patient
Evolution of drug-resistance in HIV
•Many agricultural pests have
evolved resistance to chemicals
that farmers have used for only a
few decades.
•Moreover, scientists can perform
experiments to study evolution
in real time using bacteria and
fruit flies that reproduce quickly.
Evolution
of pesticide
resistance
in response
to selection