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Evolution
A Unifying Theory of
Biology
I have a strong faith; I can’t believe
in this Evolution thing, right?
Wrong!
– Religion deals with faith issues and
supernatural forces
– Science deals with nature and natural forces
• Evolutionary Theory is science not religion
– Science will never prove OR disprove the
existence of God, or any supernatural being.
By definition, it can’t!
http://www.youtube.com/watch?v
=PKtamnmrNqs
Why is
Evolution
Controversial
Anyway?
What is science?
• Deals exclusively with the natural world and how
it operates
• Explains observed events in terms of natural
phenomena
• Is an ongoing process of observation about how
the world operates
• Collects and organizes information in a
systematic way
• Explanations (hypotheses) are “testable” and
subject to verification and disproof
• Explanations may be altered or rejected
according to available evidence
Yeah, we once believed this…
• The Earth is stationary
• The Universe, including the Sun, revolves around the Earth
– Disproved by Copernicus
• The Earth is flat
– Disproved by Galileo
• Flies arise spontaneously (spontaneous generation)
– Disproved by Pasteur
• Man can’t fly
– Disproved by the Wright Brothers
• Atoms can’t be broken down
– Rutherford, Thompson, Chadwick
• Space travel is science fiction
– Disproved by the Soviet Union
• No personal application for computers…
Why? These fit what was known at the time!
What is a Scientific Law?
• A Scientific Law is:
– A statement that describes what nature does
under certain conditions
– Explains an action or set of actions
– Very often mathematical
– Like a slingshot!
• Put a rock in the band, the one moving part, pull it back and
the rock will fly out at a predictable angle and speed
depending on how far back the band is pulled. It will work
the same way every time.
What is a Scientific Theory?
• A Scientific theory is:
– A synthesis of related natural phenomena
– A scientifically accepted principle
• supported by evidence
• used to provide an explanation of observed facts
• used as a basis for future discussion or investigation
– A system of ideas held as an explanation of a group
of facts or phenomena
– An explanation that encompasses general laws,
principles, or causes of what is known or unknown
– Very often non-mathematical
– Very complex and dynamic
Scientific Theories Continued….
• Scientific theories
are verified many
times by many
researchers.
• Scientific theories
are accepted as
true by the
scientific
community as a
whole.
Some Current Scientific
Theories
• Atomic Theory
• Big Bang Theory
• Cell Theory
• Theory of Evolution
• Gravity Theory
• Germ Theory of Disease
• Theory of Relativity
• Plate Tectonics Theory
• String Theory
• Quantum Theory
• Unified Field Theory
Scientific Theories are…
• Like a car!
– A car is a very complex mixture of parts that
function together to get people from one place
to another. Parts and systems may be
modified from year to year for improvements,
but the overall function of the car stays the
same.
• Components of a theory can be
changed without changing the overall
truth of the theory as a whole.
http://www.youtube.com/watch?
v=85diEXbJBIk
Isn’t
Evolution
Just a
Theory
And where do hypotheses fit in to
all this???
• A hypothesis is:
– An educated guess based on observation
– An explanation of a single event or
phenomenon based on what is observed but
not yet proved
– Supported or refuted by experimentation or
continued observation
The Story in the Rocks…
How do scientists know the Earth’s Age?
• Rocks exist in strata or layers
• Strata can be dated according to radioactive decay
– Radioactive emissions are constant and can be
measured using the half-life of an element which
decays into another element
– Different elements have different lengths of half life
varying from 4.5 billion years (U-238) to 5730 years
(C-14)
– Radioactive emissions are not affected by external
factors
• Amounts of the parent material are compared to
amounts of the daughter material
But There’s More!
• Rocks also explain historical Oxygen levels
– Geochemists use isotope geochemistry
– Compare rate of isotope accumulation (varies with amount of O2
or CO2 in atmosphere)
– Can read:
• Oxygen levels
• Air and ocean temperatures
• Extent and timing of ice ages
• These changes correspond with changing organism
types
– Organisms influence Environment
– Environment influences Organisms
• Combining this knowledge with fossils and fossil residue
(pollen levels) allows recreation of past landscapes!
• The Present is the Key to the Past!
– Natural forces now changing the face of the Earth operated in
the past in the same way (Principle of Uniformitarianism)
Geologic Time
• Geologists divide Earth’s
history into Eons, Epochs
and Periods
• These divisions
correspond to rock strata
• Names vary according to
locality
• http://www.enchantedlear
ning.com/subjects/Geolog
ictime.html
• http://www.pbs.org/wgbh/
evolution/change/deeptim
e/index.html
Fossil Rock
• http://www.youtube.co
m/watch?v=ClJ5lwl_w
M0&list=PLvgILFwoR
X2luskEUC5XKfzCjm
aLnGUse&index=1
Fossils
• Fossils are found in
strata (Sedimentary
Rock layers)
– Similar fossils are found in
similar layers
– More complex fossils are
found in ‘younger’ rock
closer to the surface
• Fossils include:
–
–
–
–
Imprints (casts and molds)
bones
Wood
Actual remains
• Fossils formed only under specialized
conditions
–
–
–
–
–
–
–
0.1% of all organisms
Organism quickly covered with sediments
Anaerobic environment
Most often only hard parts survived
Replaced by dissolved minerals
Survive bending and folding by Earth’s processes
One bone in a billion
• Fossils show:
– Anatomy
• can reconstruct past
organisms
– Relationships between
modern and ancestral
forms
– Chronological order of
organisms
• Simplest forms in oldest
strata
• Similar organisms succeed
one another in time and
space
• Earliest forms are marine
– Environmental changes
• Major extinctions
– Environmental stability
Stromatolites in Australia
Fossils show transitions
• Whale Evolution
– Oldest ancestor, a
wolf-like mammal,
moved from the land
to the water
– Gradual changes over
a long period of time
produced our modern
whale
http://www.youtube.co
m/watch?v=xkwRTIKX
axg
How Do
We Know
Evolution
Works?
Plate Tectonics Theory
• Large plates of land
float on molten rock
– Convection currents
cause plate movement
– Plate movements
result in earthquakes,
volcanoes, mountains
– Continents fit together
like puzzle pieces
• continental shelves
Mountain Building by uplifting.
•
The uplifting forces of the Earth caused the rock strata to tilt, while erosion
exposed the layers which vary in composition and hardness.
Plate Tectonics Theory explains:
• How fossils from the
same organism are found
on different continents
– Glossopteris fern fossils
are found on four
continents, including
Antarctica
• The Geographical
distribution of various
species of organisms
– Marsupials, found in
Australia and South
America are linked through
Antarctica
You Mean To Tell Me We’re All Related?
Yes!
Unity of Pattern
•
Genetic code
– One basic code for all organisms
•
Cells
– Same cellular organelles and cell
cycle
•
Structure
– Limb patterns
•
Function
– Digestive system, nerve cells, etc.
– Can research various organisms
and apply results to other
organisms
•
Reproductive processes
– Meiosis → gametes
•
Developmental processes
– Fertilization
– Mitosis
– Embryonic development
What Went Before
(pre-history of Evolution)
• Comte de Buffon-stated that
living things change through
time (1700’s)
– Therefore, the earth had
to be older than 6000
years (as it was
commonly believed to be
at this time)
– Did not state these views
publicly, but buried them
in a 44 volume natural
history book series
• Jean Baptist Lamarck
(1744-1829) (French
Zoologist)
– did not believe life never
changed
– developed a hypothesis on
the inheritance of acquired
characteristics
• evolution occurs when an
organism uses a body part in
such a way that it is altered
during its lifetime and this
change is then inherited by its
offspring
– Lengthening necks of
Giraffes
– was later proven wrong, but
led to idea that all life is
connected
More Pre-History
• Evolution as an idea was proposed in early 1800’s
• Sir Charles Lyell (Father of modern geology)-popularized
idea of uniformitariansm including that the Earth is much
older than originally believed and changes continually
• Erasmus Darwin (Grandpa Darwin) wrote of Evolution
before Charles was born
• Patrick Matthew writes about principles of natural
selection in Navel Timber and Arboriculture in 1831
– No one notices!
• Thomas Malthus suggested related concepts in Essay
on the Principle of Populations
– Mathematically, food supplies are unable to keep up with
population growth (suggesting competition and unequal survival)
• 1844-Anonymous publication of Vestiges of the Natural
History of Creation –controversy abounds!
Great Men think alike…
• Alfred Russell Wallace
(1823-1913) (Naturalist)
– Wrote a paper about natural
selection in 1858 (one year
before Darwin published On
the Origin of Species)
– Sent the paper to Darwin for
his opinion
– Was part of a joint lecture
on the topic along with
Darwin the following year
– Did not receive credit for
natural selection
• Darwin’s had much more
research and natural history
examples
Who was Charles Darwin?
• Born Feb 12, 1809
• Father-physician, Motherdaughter of Josiah Wedgwood
(Wedgwood pottery)
• Lackluster academic
performance
• Studied medicine (couldn’t
handle blood!)
• Studied law (too dull!)
• Studied and obtained a degree
in divinity (religion!)
• Invited to sail on the HMS
Beagle at the age of 22
Who
Was
Charles
Darwin?
Sailing the Ocean Blue
• Five years (1831-1836) on the
HMS Beagle
• Discovered many ancient,
giant fossils
• Named new species
• Geological investigations in the
Andes
• Visited a lot of islands
– Species found nowhere else in
the world
– Noticed adaptations for
exploiting local resources
Why Islands?
Darwin Noticed:
• Species that were physically similar occupied adjacent areas
• Species were different from mainland species
Islands provide:
• Isolation
• Variable ecosystems and habitats within each Archipelago
• Opportunity for physically similar organisms to:
– Live on same or nearby islands
– Look and act in similar ways
– Use different resources
• Resources vary according to island
– Have different adaptations
• Extreme environmental changes
– Organisms unable to escape
Back in England…
• 1842-Darwin began to formulate his theory
– Darwin failed to note which finch came from which island
– Six years required to sort through and order specimens
• 1844-Darwin puts notes and thoughts aside for a while
– Fathered 10 children
– Studied barnacles for 8 years, variations in pigeons, and earthworms
– Pondered arguments for and against his theory
• 1858-Darwin receives a paper from Alfred Russel
Wallace
– Paper outlines a theory of natural selection very similar to Darwin’s
– Prods Darwin into action and publication
• July 1, 1858-Darwin’s and Wallace’s theory unveiled;
eventually credit is given to Darwin alone
• 1859-On the Origin of Species published
– Biology hasn’t been the same since!
Other Factoids
• On the Origin of Species published 22 years
after the voyage of the Beagle.
• Darwin struggled with his theory knowing it
would be controversial.
• “Survival of the Fittest” coined in 1864 (five
years after Origins published) by Herbert
Spencer in Principles of Biology
– Never used by Darwin
• “Evolution” not used until 6th edition of On the
Origin of Species
– Darwin preferred “descent with modification”
• Inheritance understood, but not mechanism
– No information about genes and DNA and how they
play a role in changes to species
Evidence since Origins Published
• Additional fossils
– Transitional species
• Natural experiments
– Peppered moth (Biston
betularia) in England
– Resistance in Bacteria
– Weed/Pest Resistance
• Current Field Work
– Galapagos Finches
• Genetics
• DNA Sequencing
– Shows degree of relatedness
Current Evolutionary Studies
• Peter and Rosemary Grant
– Galapagos finches - Several decades
• Measurable changes in beak size according to environmental
changes
– http://www.pbs.org/wgbh/evolution/library/01/6/pdf/l_016_01.pdf
• William Rice and George Salt
– Drosophila melanogaster – 35 generations
• Achieved two distinct fly populations adapted to different habitat
conditions
• Richard Lenski
– E. coli bacteria – Studied changes over 20,000 generations
All demonstrate that evolutionary change is very slow!
– Thousands of generations required for speciation and
divergence into two species.
Top Common Misconceptions of
Evolution
• There hasn’t been enough time for all this to happen
– False! Modern geology has shown the earth to be ancient in
origin.
• Only microorganisms evolve
– False! Many recent studies have shown macroorganisms
changing in response to the environment; that is, evolving!
• Man evolved from monkeys/apes
– False! We share a common ancestor with characteristics of both
apes and humans. It was neither an ape or a human
Theories that set the stage
• Catastrophism—natural disasters happen
often during Earth’s history which shape
landforms and causes species to become
extinct (Cuvier)
• Gradualism—slow changes over long
periods of time (Hutton)
• Uniformitarianism—geological processes
that shape the Earth are uniform though
time.(Lyell)
What Allows Evolution to Work?
• Organisms make up Species
– Organisms that can mate and
produce fertile offspring
– Make up populations that live
in different areas
Mountain Lion
(Puma concolor)
• Mountain Lion (Puma,
Cougar, Catamount)
• Florida Panther
– tail crook, whorl of hair,
and white flecking
– Considered a subspecies
– Individuals have variations
Florida Panther
(Puma concolor coryi)
But Wait! How do you explain
Dogs?
• Dogs are the same
species despite looking
very different
• Variation has created
reproductive isolation
between the biggest and
smallest dogs
• Intermediate forms bridge
the gap
• Looks can be misleading!
– DNA is mechanism
– Variation is the key
So What Are Variations?
• Differences between
individuals of a
species
– Caused by mutations
– Can lead to speciationthe formation of new
species
• Occur in all sexually
reproducing
organisms
• Small or major
• Provide a survival
advantage for an
individual
– Allows beneficial
genes to be passed
on to offspring
• Must be passed on
for change to occur
in a population
But…Where do they come from?
Remember: Variations must be passed on
for changes to occur in a population.
• Two major sources
– Mutations
•
•
•
•
Changes in DNA sequence
Beneficial, harmful, neutral
1 per 1 billion per cell
Not always detectable
– Recessive
– Introns
• Create new genetic material
– Add to the gene pool (sum of all alleles in a population)
You Mean To Tell Me We’re All Related?
Yes!
Unity of Pattern
•
Genetic code
– One basic code for all organisms
•
Cells
– Same cellular organelles and cell
cycle
•
Structure
– Limb patterns
•
Function
– Digestive system, nerve cells, etc.
– Can research various organisms
and apply results to other
organisms
•
Reproductive processes
– Meiosis → gametes
•
Developmental processes
– Fertilization
– Mitosis
– Embryonic development
Second Source:
– Genetic Recombination
• Diploidy (adults have
two copies of
chromosomes)
– Shuffling of
chromosomes
– Only 4 alleles produces
64 trillion combinations
• Crossing over
– Within a gene sequence
– Unequal redistribution of
genetic material
So What is the Theory of Evolution
Really About?
Two main ideas:
• Historical evolution of
all species
– Common ancestor
• Natural Selection as the mechanism for
evolution
– characteristics that help an individual survive and
reproduce will be passed on to offspring
– Advantageous characteristics will replace less
advantageous characteristics in a population
– Characteristics are called adaptations
Natural Selection explains by
•
•
•
•
•
Variation
Adaptation
Overpopulation
Reproductive Isolation
Descent with modifications
Artificial Selection
• Breeding for specific, desirable
traits
– Domesticated animals
• Dogs, cats
• Cattle, sheep, pigs
– Domesticated plants
• Corn, wheat
• Takes a long time
– Hundreds of generations
– Only works with certain plants
and animals
• Can result in inbreeding and a
weakening of a species
– Hip dysplasia
Inspired Darwin to think of
Natural Selection
– If people could do this,
couldn’t it happen on it’s own
in nature?
What are adaptations?
• Anything that helps
an organism survive
and reproduce
– Polar bear
•
•
•
•
•
•
Hollow Hair
Wooly Undercoat
Feet
Sense of smell
Color
Black Skin
– Cactus
• Thorns
• Wax coating
• Roots
How does Natural Selection Work?
• Process:
– Variations provide the raw material for change.
• Genetic mutations expressed in phenotype
– Constant struggle for existence occurs among organisms.
• Competition for resources
– Certain individuals survive and reproduce.
• Survival of the fittest
– Genetic changes occur in a population
• Change in the gene pool
– Organisms are better adapted to the environment.
• Better able to compete
• Environmental changes affect populations
– Natural and man-made disasters
– Climate change
• Populations affect environment
– overgrazing
How does
Evolution
Really
Work?
What Else Allows Evolution To
Work?
• Reproductive
Isolation
– Maintains distinctness
– Prevents interbreeding
– Allows formation of
new species
(speciation)
Ways to Achieve Reproductive
Isolation
• Prevent Mating
– Geographical
• Live in different areas
(Physical and Ecological
Barriers)
• Formation of subspecies
• Leads to speciation
– Behavioral
• Different mating rituals
– Tree and Meadow Pipit
– Physical
• Size difference
• Chromosome
Incompatibility
– Death of Offspring
• Leopard and Bullfrog
→Embryos fail to develop
– Sterile Offspring
• Horse + Donkey → Mule
Other Factors…
• More individuals are
born than can survive
• Excess population
growth drives
competitive struggle
for resources
– More successful=more
surviving offspring
– Less successful=fewer
surviving offspring
Mechanisms affecting Populations
• Allele frequencies generally stay stable in
a population
– Population is in equilibrium
• Frequency can be changed
– Mutation
• Expressed in phenotype
– Artificial or natural selection
• Strong selection pressure=faster changes
• Weak selection pressure=slow change
• Changes in allele frequency cont.
– Migration
– Random Change
• Genetic Drift
– Affects small populations most (small gene pool)
• Natural Forces
– Nonrandom mating of individuals
• Sexual Selection
• Changes can lead to Reproductive
Isolation
– Speciation
Speciation
• Development of a new
species based on a
natural selection and
variations
Mountain Lion
(Puma concolor)
– Subspecies occur first
• Occurs via adaptive
radiation
– offspring of a species
disperses
– Adaptation to the new area
occurs over time
– New traits are bred into
future generations
– Process continues
Florida Panther
(Puma concolor coryi)
Evolutionary Patterns:
Parallel Evolution
• After divergence, closely
related organisms evolve in
the same direction
• live in different places with
similar environmental
selection pressure
– Large flightless birds
• Emu
• Rhea
• Ostrich
Evolutionary Patterns:
Convergent Evolution
• Similar features evolve
independently in
unrelated organisms
living in similar habitats
• similar environmental
selection pressure
– Dolphins and sharks
– Bats and birds
Evolutionary Patterns:
Co-evolution
• Two unrelated groups
of organisms evolve
adaptations to each
other
– Depend on each other
for survival
• Yucca and Yucca Moth
• Ants and Acacia trees
Vestigial Structures
• Remnants of
organs or
structures that had
a function in an
early ancestor
Vestigial Structures
• Left over body parts with
no current function
– Snakes
• pelvis
– Humans
– Flightless beetles
• wings
– Whales
• Pelvis and back legs
• Show common ancestry
Homologous Structures
• that are similar in
structure but
appear in different
organisms and
have different
functions
Analogous Structures
• Structures that
perform a similar
function but are not
similar in origin
Fossils provide a
record of evolution
• Paleontology—
study of fossils or
extinct organisms
• DNA sequence
analysis
• Pseudogenes
(sequences of DNA
• Molecular &
Genetic evidence
supports fossil &
anatomical
evidence
nucleotides)
• Homeobox genes
(controls development of
specific structures)
• Protein
Comparisons
Why does Evolution Matter Now?
• Drug resistance
– Bacteria
• Tuberculosis
– Viruses
• HIV
• Pesticide/Herbicide
resistance
– Insect pests
• Mosquitoes
– Noxious weeds
• Sericea Lespedeza
Why Does
Evolution
Matter
Now?
What About Us?
Lucy
• Discovered by Dr.
Richard Leakey and
Mary Leakey
• Africa
• Most complete fossil
skeleton found
• bipedal
• Australopithecus
afarenisis
Dr Leakey
Reproduction
of Lucy’s
completed
skull
What else?
• Similarities between
primates
– Eyes directed forward
• View 3-dimentionally
• Depth perception
– Opposable thumb
– Large brain
– Single offspring
• Extended maternal care
• Teaching of offspring
– Social groupings
– DNA
• Chimpanzees and
humans share 98.5% of
their DNA
Modern Human Ancestry
3.were
3 mya:
Australopithecus
afarensis
1.5
mya:
Hand
axes
used.
Also,
hominids
1. Before
56)
mya:
In
Africa,
our
ancestral
lineage
and
the
chimpanzee
8) 50,000
7)
100,000
years
9)
25,000
ago:
years
Human
years
ago:
Human
cultures
ago:
Other
brains
produced
Homo
reached
cave
species
more
paintings
had
orhad
less
gone
and
5)
2
mya:
The
first
members
of
the
Homo
clade,
(“Lucy”)
lived
in
Africa.
2.
Before
4
mya:
The
hominid
Australopithecus
4)
2.5
mya:
Some
hominids
made
tools
by
chipping
stones
to
form
a
spread
out
of
Africa
and
into
much
of
Asia
and
Europe.
the current
extinct,
range
and
leaving
constructed
of
sizes.
onlyEarly
modern
elaborate
Homo
humans,
burials.
sapiens
Homo
Also,
lived
some
sapiens,
in groups
lineage body
split. adornment,
with
their
relatively
large
brains,
lived
in
Africa.
anamensis
walked
around
what
is
now
Kenya
cutting
edge.
There
were
perhaps
four
orWorld.
more species
of
hominid
These
hominids
included
the
ancestors
of
Neanderthals
of modern
Africa.
humans
At
spread
the
same
extended
throughout
time,their
Homo
the
range
Old
neanderthalensis
beyond
Africa.
and
Homo
on
its
hind
legs.
living
in
Africa.
erectus
lived in other parts
of Europe
theisOld
World.
(Homo
neanderthalensis)
in
and Homo
erectus that
in
•A clade
a group
of organisms
Asia.
Did
include all the decedents of a common
Humans
Evolve?
ancestor and that ancestor.
• Classification comparison:
– more similar categories show closer relationship
Humans
Chimpanzee
Mouse
Maize (corn)
Kingdom:
Animalia
Animalia
Animalia
Plantae
Phylum:
Chordata
Chordata
Chordata
Angiospermae
Subphylum:
Vertebrata
Vertebrata
Vertebrata
***
Class:
Mammalia
Mammalia
Mammalia
Monocotyledons
Order:
Primates
Primates
Rodentia
Poales
Family:
Hominidae
Pongidae
Muridae
Poaceae
Genus:
Homo
Pan
Mus
Zea
Species:
Homo sapiens
Pan troglodytes
Mus musculus
Zea mays
100%
91.3%
66.7%
Cytochrome C is a
protein sequence
found in almost all
living organisms.
% Cytochrome
C Shared
Summary
• Individuals have variations
• Variations allow for differential survival in
response to the environment
• Beneficial variations are passed on to offspring
• Genetic changes occur in a population over time
• Speciation
• Occurs in all populations
• Takes a very long time
To learn more…
•
•
•
•
•
•
•
•
•
•
www.pbs.org/wgbh/evolution
http://www.talkorigins.org/
http://www.madsci.org/FAQs/evolve.html
http://www.actionbioscience.org/evolution/index.html
http://www.evolutionhappens.net/
http://www.ucmp.berkeley.edu/historyoflife/histoflife.
html
http://mcb.harvard.edu/BioLinks/Evolution.html
http://www.bbc.co.uk/education/darwin/index.shtml
http://www.becominghuman.org
http://evolution.berkeley.edu//evosite/evo101/index.s
html