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Evolution
Diversity of Life
Early Ideas On Earth’s
Organisms
Aristotle believed species were fixed
creations arranged by their
complexity
 Idea lasted 2000 years
 Linnaeus – 1st to group similar
organisms and assign them Latin
names (Genus species)
 Known as Binomial nomenclature

Contributor’s
to Darwin’s
Darwin’s
Ideas Did Not Develop
in a Vacuum
thinking included:
:
• Charles Lyell –uniformatarianism
• Georges Cuvier – species
extinction (Catastrophism)
• Thomas Malthus – struggle for
existence
• Jean Baptiste de Lamarck –
evolution by inheriting acquired
characteristics; Law of Use and
Disuse
Contributor’s
to Darwin’s
Darwin’s
Ideas Did Not Develop
in a Vacuum
thinking included:
:
• James Hutton - Gradualism
• Alfred Russel Wallace – organisms
evolved from common ancestors
Evolutionary Timeline
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
» Giraffe’s Necks
Lamarck’s Theory of
Evolution

Inheritance Of Acquired Traits
– Traits Acquired During Ones Lifetime
Would Be Passed To Offspring
Lamarck’s Theory of
Evolution

Lamarck’s Errors
– Did Not Know About Inheritance of
Traits
» Genes Are Not Changed By Activities In Life
» Change Through Mutation, Occurs Before An
Organism Is Born
Wallace’s Contribution
• Alfred Russel Wallace
Independently came to
the Same Conclusions as
Darwin
• Papers from Wallace and
Darwin were jointly
presented (with little
impact) to the Linnaean
Society in 1858.
Definitions
Evolution
– The process By Which Modern
Organisms Have Descended From
Ancient Organisms
– Change Over Time
 Theory
– A Well Supported, Testable
Explanation of Phenomena That
Have Occurred In The Natural
World

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
The Voyage of the Beagle
Darwin Left England in 1831
Darwin returned 5 years later in 1836
The Galapagos Islands

Small Group of Islands 1000 km
West of South America
 Very
Different Climates
 Animals On Islands Unique
»Tortoises
»Iguanas
»Finches
Voyage of the Beagle
During His Travels, Darwin
Made Numerous Observations
And Collected Evidence That
Led Him To Propose A
Revolutionary Hypothesis
About The Way Life Changes
Over Time
Darwin’s Observations



Patterns of
Diversity were
shown
Unique Adaptations
in organisms
Species Not Evenly
Distributed
» Australia,
Kangaroos, but
No Rabbits
» S. America,
Llamas
Darwin’s Observations
 Both
Living
Organisms &
Fossils collected
 Fossils included:
»Trilobites
»Giant Ground
Sloth of South
America
This species NO longer existed.
What had happened to them?
Darwin’s Observations and Inferences
Observation 1: Left unchecked, the
number of organisms of each species will
increase exponentially, generation to
generation.
Observation 2: In nature, populations tend
to remain stable in size.
Observation 3: Environmental resources are limited.
Inference 1: Production of more individuals than can be
supported by the environment leads to a struggle for existence
among individuals, with only a fraction of offspring surviving
each generation.
Darwin’s Observations and Inferences
Observation 4: Individuals of a population vary extensively in
their characteristics with no two individuals being exactly alike.
Observation 5: Much of this variation between individuals is
heritable.
Darwin’s Observations and Inferences
Inference 2: Survival in the
struggle for existence is not
random, but depends in part
on the heritable
characteristics of
individuals. Individuals
who inherit characteristics
most fit for their
environment are likely to
leave more offspring than
less fit individuals.
Darwin’s Observations and Inferences
Inference 3: 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).
These three inferences are a statement of Darwin’s Theory of
Evolution.
Evolution Holds a Unique Place in Biology
Other disciplines ask how?
Evolutionary biology asks why?
Evolution’s Core Principles
Common descent with
modification.
Evolution’s Core Principles
The Weak Link of Genetics and the Modern Synthesis
A major problem in Darwin’s theory
was the lack of a mechanism to explain
natural selection.
How could favorable variations be
transmitted to later generations?
Darwinian theory supported by
genetics is known as the modern
synthesis.
Darwin in his
early years.
Opposition to Evolution
The upheaval surrounding evolution began
with publication of On the Origin of
Species and continues nearly 150 years
later.
Two (of many) arguments made against
evolution are:
Evolution is only a theory.
No one’s ever seen evolution.
An early disparaging
view of evolutionary
theory and its creator.
Evidence of
Evolution –
Genetic
Conservation and
Diversification
Why should
different
organism possess
related genes?
Why does the
degree of
relationship of
genes relate
perfectly to their
degree of
relationship
established by
other methods?
Organisms Change Over Time
Today’s Objective
(learning goal)
To identify how fossils are used as
evidence in changes within a species.
Clues to the Past
• About 95 percent of the species that have existed
are extinct—they no longer live on Earth.
• The oldest rocks that have been found on Earth
formed about 3.9 billion years ago.
• Among other techniques, scientists study fossils to
learn about ancient species.
• Fossils are evidence of organisms that lived long
ago that are preserved in Earth’s rocks.
TYPES OF FOSSILS
Fossils Types
Formation
A trace fossil is any indirect evidence
Trace fossils
Casts
left by an animal and may include a
footprint, a trail, or a burrow.
When minerals in rocks fill a space
left by a decayed organism, they make
a replica, or cast, of the organism.
A mold forms when an organism is
Molds
Petrified
fossils
Amber-Preserved
or
frozen fossils
buried in sediment and then decays,
leaving an empty space.
Petrified-minerals sometimes penetrate
and replace the hard parts of an organism
At times, an entire organism was
quickly trapped in ice or tree sap that
hardened into amber.
• Paleontologists, scientists who study ancient life,
are like detectives who use fossils to understand
events that happened long ago.
• They use fossils to determine the kinds of
organisms that lived during the past and sometimes
to learn about their behavior.
• Paleontologists also study fossils to gain knowledge
about ancient climate and geography.
• By studying the condition, position, and location of
rocks and fossils, geologists and paleontologists can
make deductions about the geography of past
environments.
• For example, if they find a fossil of a plant that
resembles a present day plant that can only survive
in mild weather, they can infer that the conditions
were mild when that plant was living as well.
• For fossils to form, organisms
usually have to be buried in mud,
sand, or clay soon after they die.
• Fossils are not usually found in other types of rock because of the ways
those rocks
form.
• Most
fossils
are found in sedimentary rocks.
rocksthe
form
at relatively
lowmetamorphic
temperatures
• These
For example,
conditions
under which
rocksand
form often
pressures
that may
damage
the organism.
destroy any fossils
thatprevent
were in the
originalto
sedimentary
rock.
• Few organisms become fossilized because, without
burial, bacteria and fungi immediately decompose
their dead bodies.
• Occasionally, however, organisms do become fossils
in a process that usually takes many years.
• Sediments from
upstream rapidly
cover the body,
slowing its
decomposition.
Minerals from the
sediments seep into
the body.
• Over time, additional
layers of sediment compress
the sediments around the
body, forming rock. Minerals
eventually replace all the
body’s bone material.
• A Protoceratops drinking at
a river falls into the water and
drowns
• Earth movements
or erosion may
expose the fossil
millions of years after
it formed.
• Scientists use a variety of methods to determine
the age of fossils.
• One method is a technique called relative dating.
• If the rock layers
have not been
disturbed, the layers
at the surface must
be younger than the
deeper layers.
• Thus, the fossils in the top layer must also
be younger than those in deeper layers.
• Using this principle, scientists can determine
relative age and the order of appearance of the
species that are preserved as fossils in the layers.
• To find the specific ages of rocks, scientists use
radiometric dating techniques utilizing the
radioactive isotopes in rocks.
• Radioactive isotopes are atoms that are unstable
and break down, or decay, over time, giving off
radiation.
• Because every radioactive isotope has a
characteristic decay rate, scientists use the rate
of decay as a type of clock.
• The half-life of an isotope is the time it takes for
half of the isotope in a sample to decay
• A radioactive isotope forms a new isotope after it
decays.
 If
you can know the amount of an
unstable isotope that was in a sample
 And
you know the rate at which that
isotope decays
 And
you can measure the amount of that
isotope presently in the sample
 You
can figure out how old the sample is
 14C
is used to date organic
samples like wood, hair, shells,
and other plant and animal products
Black dots represent carbon, grey dots carbon14

Atmospheric 14C is incorporated into organic
molecules by plants during photosynthesis

Animals that eat the plants get 14C from the plants
they eat
• Scientists use carbon-14 to date fossils less than
70 000 years old.
• Carbon-14 (14C) is an isotope of carbon, that has 6
protons and 8 neutrons
•
14C
decays to 14N at a constant rate
• Every 5,730 years half the 14C in a sample will emit a
beta particle (electron) and decay to 14N
• Thus 5,730 years is called the half life of 14C
• For example, if the half-life of 14C (Carbon
14) is 5,730 years
and a sample today has 1,000 14C atoms
after 5,730 years 500
14C
atoms will remain
256 14C atoms
After 5730
years
or 1 half-life
128 14C and
128 14N atoms
After 11,460 yrs
or 2 half-lives
64 14C and
192 14N atoms
After 17,190 yrs
or 3 half-lives
32 14C and
224 14N atoms
After 22,920 yrs
or 4 half-lives
16 14C and
240 14N atoms
After 28,650 yrs
or 5 half-lives
8 14C and
248 14N atoms
After 34,380 yrs
or 6 half-lives
4 14C and
252 14N atoms
After 40,110 yrs
or 7 half-lives
2 14C and
254 14N atoms
• Scientists use potassium-40, a radioactive isotope
that decays to argon-40, to date rocks containing
potassium bearing minerals.
• Based on chemical analysis, chemists have
determined that potassium-40 decays to half its
original amount in 1.3 million years.
• Scientists always analyze many samples of a rock
using as many methods as possible to obtain
consistent values for the rock’s age.
• Errors can occur if the rock has been
heated, causing some of the radioactive
isotopes to be lost or gained.
• The fossil record indicates that there were several
episodes of mass extinction that fall between time
divisions.
• A mass extinction is an event that occurs when many
organisms disappear from the fossil record almost at
once.
• The oldest fossils are found in rocks that are
about 3.4 billion years old.
• Scientists found these fossils, in rocks found in
the deserts of western Australia.
• The fossils resemble the forms of modern species
of photosynthetic cyanobacteria (prokaryote).
Invertebrates
Eukaryotes
Major
Events
Prokaryotes
Major Life
Form
Life evolves
• About 1.8 billion years
ago, the fossil record
shows that more
complex eukaryotic
organisms, living things
with membrane-bound
nuclei in their cells,
appeared.
Period
Era
Precambrian
Million Years Ago
4000 3500 1800
• About 543 million years ago,
multicellular eukaryotes, such as
sponges and jelly-fishes, diversified
and filled the oceans.
• In the Paleozoic Era, which lasted until 248 million
years ago, many more types of animals and plants
were present on Earth, and some were preserved in
the fossil record.
Phylogenetics
The study of evolutionary relationships
among groups of organisms (species,
populations), which are discovered through:
1. Molecular sequencing data – DNA
sequencing and protein synthesis
2. Morphological data matrices – homologous
structures, analogous structures, and
embryonic development
Molecular Sequencing
Homologous Structures

Scientists Noticed Animals With
Backbones Had Similar Bone
Structure
– Same Structures Different Function
» Arms, Wings, Legs, Flippers
– Limb Bones Develop In Similar Patterns
– Help Scientist Group Animals
Homologous Structures
Homologous Body Structures

Not All Serve Important Functions
– Vestigial Organs
» Appendix In Man
» Legs On Skinks
Analogous Structure
Same function with different strutures
Similarities In Early Development

Embryonic Structures Of Different
Species Show Significant
Similarities
Divergent evolution is the
accumulation of differences
between groups which can
lead to the formation of new
species, usually a result of
diffusion of the same species
to different and isolated
environments that blocks the
gene flow among the distinct
populations. This allows
differentiation of
characteristics through
genetic drift and natural
selection.
Convergent
evolution is the
process by which
unrelated or
distantly related
organisms evolve
similar body forms,
coloration, organs,
and adaptations.
Adaptive radiation is the evolution of an
animal or plant group into a wide variety
of types adapted to specialized modes of
life.
Puncuated Equilibrium
A hypothesis in evolutionary biology which proposes that
most species will exhibit little net evolutionary change
for most of their geological history, remaining in an
extended state called stasis.
When significant evolutionary change occurs, the
hypothesis proposes that it is generally restricted to
rare and geologically rapid events of branching speciation
(the evolutionary process by which new biological species
arise) called cladogenesis.
Cladogenesis is the process by which a species
(organisms that breed and produce offspring that are
also fertile) splits into two distinct species, rather than
one species gradually transforming into another.
CLADOGRAMS
Morphological Change
Evolutionary Time Scales
Microevolution: Short time scale events (generation-togeneration) that change the genotypes and phenotypes of
populations.
Genetic drift -random fluctuations in the numbers of
allele differences in a population
*Takes place when the occurrence of alleles, increases and
decreases by chance over time.
*Typically occurs in small populations, where infrequently
occurring alleles face a greater chance of being lost
*Will continue until the involved allele is either lost by a
population or until it is the only allele present in a
population at a particular location
*Can cause a new population to be genetically distinct from
its original population, which has led to the hypothesis that
genetic drift plays a role in the evolution of new species.
Gene flow (also known as gene migration) is the transfer
of alleles or genes from one population to another.
Migration into or out of a population may be responsible
for a marked change in allele frequencies (the proportion
of members carrying a particular variant of a gene).
Immigration may also result in the addition of new genetic
variants to the established gene pool of a particular
species or population.
Mutations - when a DNA gene is damaged or changed
in such a way as to alter the genetic message carried
by that gene
Natural Selection the gradual process by which
biological traits become either more or less common
in a population as a function of the effect of
inherited traits on the reproductive success of
organisms interacting with their environment
Stabilizing Selection, extreme varieties from both
ends of the frequency distribution are eliminated.
The frequency distribution looks exactly as it did in
the generation before
Directional Selection - individuals at one end of the
distribution of beak sizes do especially well, and so
the frequency distribution of the trait in the
subsequent generation is shifted from where it was
in the parental generation
Diversifying (disruptive) Selection - both extremes are
favored at the expense of intermediate varieties. This is
uncommon, but of theoretical interest because it
suggests a mechanism for species formation without
geographic isolation
Evolution By Natural Selection
The Struggle for Existence
 Survival of the Fittest
 Descent with Modification

The Struggle for Existence

Malthus’ Influence
– High Birth Rates & Limited Resources
Would Force Life & Death Competition

Each Species Struggles For:
– Food
– Living Space
– Resources
Survival of the Fittest

Fitness
– Ability of an Individual To
Survive &
Reproduce

Adaptation
– Inherited Characteristic That
Increases an Organisms Chance
for Survival
Survival of the Fittest
 Adaptations
Can Be:
– Physical
»Speed, Camouflage, Claws,
Quills, etc.
– Behavioral
»Solitary, Herds, Packs,
Activity, etc.
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
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
Natural Selection
 Cannot
Be Seen Directly
 It Can Only Be Observed As
Changes In A Population Over
Many Successive Generations
– Radiation
– Fossil Record
Population Growth

Thomas Malthus, 1798
– Economist
– Observed Babies Being Born Faster Than
People Were Dying
» Population vs. Food Supply
Population Growth

Key Concept
– Malthus Reasoned That If
The Human Population
Continued To Grow
Unchecked, Sooner or Later
There Would Be Insufficient
Living Space & Food For
Everyone
» Famine, Pestilence
» Political Instability, War
» Death Rate Will Increase To
Balance Population & Food
Supply
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
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?
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

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
Publication of “On The Origin of Species”
Darwin Presented Wallace’s Essay &
Some Of His Work At A Scientific
Conference of the Linnean Society
in July of 1858
 Then He Started On “Origin of
Species”

– It Took Darwin 18 Months To
Complete The Book
Natural Variation & 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
(Selective Breeding)

Natural Variation & Artificial Selection
 Natural
Variation
– Differences Among Individuals Of
A Species
 Artificial
Selection
– Selective Breeding To Enhance
Desired Traits Among Stock or
Crops
Natural Variation & Artificial Selection
Key Concept
In Artificial Selection, Nature
Provided The Variation Among
Different Organisms, And
Humans Selected Those
Variations That They Found
Useful
Evidence of Evolution
Key Concept
Darwin Argued That Living Things Have Been
Evolving On Earth For Millions of Years.
Evidence For This Process Could Be Found In:
– The Fossil Record
– The Geographical Distribution of Living Species
– Homologous Structures of Living Organisms
– Similarities In Early Development
Geographic Distribution of Living Species

Different Animals On Different
Continents But Similar Adaptations
To Shared Environments
Darwin's Theory
1.
2.
Individual Organisms In Nature
Differ From One Another. Some
Of This Variation Is Inherited
Organisms In Nature Produce
More Offspring Than Can Survive,
And Many Of These Offspring Do
No Reproduce
Darwin's Theory
3.
4.
Because More Organisms Are
Produced Than Can Survive,
Members Of Each Species Must
Compete For Limited Resources
Because Each Organism Is Unique,
Each Has Different Advantages &
Disadvantages In The Struggle For
Existence
Darwin's Theory
5.
6.
Individuals Best Suited To Their
Environment Survive & Reproduce
Successfully – Passing Their Traits To
Their Offspring.
Species Change Over Time. Over Long
Periods, Natural Selection Causes
Changes That May Eventually Lead To
New Species
Darwin's Theory
7.
8.
Species Alive Today Have
Descended With Modifications
From Species That Lived In The
Past
All Organisms On Earth Are
United Into A Single Tree Of Life
By Common Descent