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The Theory of Evolution
Why do we say Theory?
What is Evolution?
• Evolution is a process by which modern
organisms have descended from ancient
organisms. It is a change in population (not
individuals) over long periods of time.
• Evolution is also called descent with
modification.
Evolution Videos
• Evolution of Dance
• https://www.youtube.com/watch?v=dMH0bH
eiRNg
• Evolution of Video Games
• https://www.youtube.com/watch?v=WYJoaV
MzQYc
• Evolution of Cell Phones
• https://www.youtube.com/watch?v=JcnXOhr
mDB8
• (look for pentatonix evolution of music)
Think Back
• Remember the videos?
• What did we see that evolved?
• Why is Pokemon a bad example?
Important Vocabulary for Evolution
Evolution = A change in populations and not individuals over
long periods of time.
Scientific Theory = well-supported, testable explanation of
phenomena that have occurred in the natural world.
Fitness= the ability for an organism to survive and
reproduce in its environment. It’s a result of adaptation.
Adaptation= any inherited characteristic that increases an
organism’s chances for survival.
Who is Charles Darwin?
• An English Naturalist and Geologist best known for his contributions to
the Theory of Evolution.
• In 1831, Darwin set sail from England about the H.M.S. Beagle for a
voyage around the world. At which time he made numerous
observations and collected evidence that led him to propose a
hypothesis about the way life changes over time based on natural
selection.
Darwin’s Pieces of Evidence
• Evidence that living things have been evolving for millions of
years includes:
• The fossil record
– Some of the fossils resembled organisms that were
still alive.
– Others looked completely unlike any creature he
had ever seen.
• Homologous, analogous, and vestigial structures
• Embryology
• Geographic distribution of living things
• Biochemistry
Darwin’s Theory of Evolution by Natural Selection
What is Natural Selection? (also known as Survival of the Fittest)
•
Process by which individuals who
are better adapted or most fit for
their environment will survive and
reproduce successfully.
• In the Galapagos Darwin notices
that there were variations among
members of the same species.
• Example: Finches, Giant
Tortoise
Example of Natural Selection – Peppered Moths
The evolution of the peppered moth over the last two hundred years has
been studied in detail. Originally, the vast majority of peppered moths had
light coloration, which effectively camouflaged them against the lightcolored trees and lichens upon which they rested. However, due to
widespread pollution during the Industrial Revolution in England, many of
the lichens died out, and the trees which peppered moths rested on
became blackened by soot, causing most of the light-colored moths, to die
off due to predation.
STOP! Moth Activity
• Color the two white moths you picked up on
your way into class.
• You are trying to camouflage (disguise) them
so they are well hidden from predators.
• I will pretend to be a bird and go hunting for
moths when the timer goes off.
• You will receive extra credit on the test if you
camouflage your moths well enough that I do
not find them.
Recap- Survival of the Fittest
• Process by which individuals who are better
adapted or most fit for their environment will
survive and reproduce successfully.
• Who had fit moths? How do you know?
Based on Darwin’s Theory, who would
be considered “fit”?
Tim Tebow?
Mama June?
Mama June
• Mama June is more fit
according to Darwin’s
Theory because she
produced multiple
offspring that survived.
• Tim Tebow did not
produce any offspring
to carry on his traits so
he is not considered fit
according to Darwin’s
Theory.
Beak Size Activity
• Get into groups of two.
• Watch demonstration.
• Design your own environment and record
what happens for 5 generations.
• You should write using detail. Minimum one
full page.
The Fossil Record
What are fossils? Remains of once living organisms
Like the hard parts of organisms (i.e. bones), impressions, or
casts.
Water carries small
rock particles to lakes
and seas.
Dead organisms are
buried by layers of
sediment, which forms
new rock.
The preserved remains
may later be discovered
and studied.
The Fossil Record:
– Portrayed by
remains of
ancient life
forms.
– When fossils are
discovered they
can be added to
the fossil record
based on age and
similarities.
– Found mainly in
Sedimentary
Rock
Homologous Structures
• Similar in structure but functions
differently
• Examples: flying, swimming, grasping etc.
Analogous Structures
• Structures that
have a similar
function, but
different
structures.
Example: Butterfly and bird
both use their wings for
flying, but wings are
structured differently, one
has bones, one has network
of veins.
Vestigial Structures
• Structures that serve no useful
purpose in an organism.
In whales, there is a
vestigial pelvis and
femur. In horses, there
is a vestigial toe. In
snakes, there are
vestigial hips
Can you name any
vestigial structures in
humans?
Human Vestigial Organs
•
•
•
•
appendix
tailbone
wisdom teeth
male breast tissue and nipples
Embryology: early stages in development align across species.
Share a common ancestor
Similarities in Embryology
In their early stages of
development,
chickens, turtles, and
rats look similar. This
provides evidence that
they shared a common
ancestor.
Biochemistry: DNA and Proteins
• Closely related
species share
common genetic
base sequences
BIOGEOGRPAHY (GEOGRAPHIC DISTRIBUTION)
•
a study in which scientists study the location and
distribution of plants and animals around the world,
particularly on islands.
For example: In Africa we find rhinoceroses,
hippopotamuses, lions, hyenas, giraffes, zebras,
chimpanzees and gorillas.
South America has none of these. Instead, it is
home to pumas, jaguars, raccoons, opossums and
armadillos.
Marsupials are found in Australia and South
America, but not in Europe
Let’s take a break- Island Activity
• Today you will be finches. I will read you a
story and you will act it out.
• Everyone to the back of the room please.
• This activity will be very similar to the beak
size activity.
Who influenced Darwin?
• Darwin’s thoughts over Evolution were influenced by
numerous people such as James Hutton and Charles
Lyell (geologists)Thomas Malthus (an economist), and
Jean-Baptiste Lamarck (a naturalist, like Darwin).
Thomas Malthus
Jean-Baptiste LaMarck
Lamarck’s Idea of Acquired Traits:
• He proposed that by selective use or disuse of organs,
organisms acquired or lost certain traits during their lifetime. He
believed that these acquired traits could then be passed on to
their offspring which led to a change in a species.
You’ve Heard the Facts
• Take 5 minutes to discuss Darwin’s 5 pieces of
evidence with your elbow partner.
• Which piece is the most convincing?
• Come up with three strong arguments for your
piece of evidence.
• What questions do you still have?
We know the evidence…
What do we see?
Types of Adaptations
Adaptation: any inherited characteristic that
increases an organism’s chances for survival.
Hummingbirds have adapted to their
environment in two ways:
1.Very fast flight to keep them steady.
2.Long beak and tongue to reach into flowers
and extract nectar.
REMEMBER…
Fitness: the ability for an organism to
survive and reproduce in its environment.
It’s a result of adaptation.
Types of Adaptations
CAMOUFLAGE: An adaptation that allows organisms to blend into their
environment. Example: ghekko blending in to avoid predation.
Remember you camouflaged
your moths so the bird wouldn’t
eat them.
Types of Adaptations
MIMICRY: An adaptation that allows one species to evolve into resembling
another species which often results in the species to often increase their
fitness ability while also allowing them to escape possible predation.
Example: Eastern Coral Snake/Scarlet King Snake or the Monarch/Viceroy
Butterflies
STOP! Chocolate!
• If you want a piece of chocolate, take a piece
as the bin is passed around. Do not eat it yet.
• We will all eat the chocolate when I count to
3.
Now that everyone has water…
•
•
•
•
What was this an example of?
All the chocolate looked the same.
Did it all taste the same?
Why did some of you run for the trash?
Why is mimicry useful?
• This is what happens when predators eat
certain prey. They taste bad. It’s advantageous
for a yummy prey to look like the nasty prey.
Then the predators won’t want to eat them.
Genetic Variation
Based on modern knowledge of genetics, we NOW know that
natural selection is dependent on genetic variation within
the gene pool. Genetic variation allows diversity within a
population.
Gene Pool: consists of all the genes including all the different
alleles that are present in a population.
A population is a group of individuals
that inhabit the same area.
A species is a group of similar
organisms that can breed and produce
fertile offspring.
Speciation: the formation of a new and distinct species in the
course of evolution.
Geographic Isolation:
• When two populations of a species becomes separated by
geographic barriers such as rivers or mountain ranges
resulting in the formation of 2 separate gene pools.
• Allopatric Speciation
• Ex: Abert Squirrels
vs. Kaibab Squirrels.
MECHANISMS OF EVOLUTION
Although natural selection remains a
central theme in evolution, scientists
NOW know that natural selection is NOT
the only mechanism for evolution.
One of those mechanisms is called the
HARDY-WEINBERG PRINCIPLE which states that when an
allele frequency remains constant, a population is in genetic
equilibrium.
Hardy (mathematician) and Weinberg (physician) both
showed mathematically that evolution will not occur in a
population unless allele frequencies are acted upon by
forces that cause change. There are 5 conditions required to
maintain genetic equilibrium: (1). Random mating (2) must
have very large population (3) no movement into or out of
population (4) no mutations and (5) no natural selection.
Poker Chip Activity
• Look at your hand outs and work with your
group to complete the activity.
• Please raise your hand to ask questions.
Another mechanism is called Genetic Drift
• a change in allele frequencies that occur in small
populations. These changes are associated with
random events .
• There are 2 types of genetic drift:
– founder effect
• small group splinters off & starts a new colony
– bottleneck
• some factor (disaster) reduces population to
small number & then population recovers &
expands again
Bottleneck
Bottleneck Effect Example:
A Diverse Population  “Catastrophic Event”
(hunting, earthquake, volcanic eruption, etc.)  A
Small % of the Original Population Remains & RePopulates  A Less Diverse Population
Genetic Drift by way of
Founders Effect
• Small population gets
separated by chance (storm,
earthquake, etc.)
• Develop different adaptations
over many generations
• If they come in contact later,
they are too different to
interbreed
• Ex. Galapagos finches fly to
nearby island
Gene Flow: the transfer of genes or alleles from one
population to another.
Gene Flow
• Movement of individuals &
alleles in & out of populations
– seed & pollen distribution by
wind & insect
– migration of animals
• sub-populations may have
different allele frequencies
• causes genetic mixing
across regions
• reduce differences
between populations
Human Evolution Today
• Gene flow in human
populations is
increasing today
– transferring alleles
between populations
Are we moving towards a blended world?
Tiger Survival
• Get into groups of two.
• Make sure you have a work sheet, directions,
and a bag of beans.
Goldfish Genetic Drift
• Get into groups of two.
• Make sure you have a worksheet and a paper
towel.