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Evolution
What is Evolution?
Evolution, or change over time, is the
process by which modern populations
have descended from preceding
populations of organisms.
Who is Charles Darwin?
Charles Darwin – born in England
 Joined the crew of the
H.M.S. Beagle
 Sailed around the world
 Made numerous observations
and collected evidence that
led him to propose his
hypothesis.

Hutton & Lyell:
ancient
earth
Lamarck:
acquired
traits
Early scientists:
past vs.
present
organisms
Malthus:
population
growth
Darwin
Natural Selection
What did Darwin observe during his voyage?
Patterns of Diversity:
•
Puzzled by distribution of different species (where they
lived and did not live)
•
He Asked (for example):
* Why were there no rabbits in Australia, despite the
presence of habitats that seemed perfect for them?
* Why were there no kangaroos in England?
* Why do they look so similar?
What did Darwin observe during his voyage?
Living Organisms & Fossils
•
Darwin collected and preserved fossils
•
Fossils: some resembled organisms that were still
alive – others looked completely unlike any creature
he had ever seen.
He Asked:
Why had so many of these species
disappeared?
Looks nothing like any living
species
Looks LIKE a Kangaroo
What did Darwin Observe?
The Galapagos Islands
•
Most influential place Darwin visited
•
Although islands were so close together, the islands had very
different climates.
•
Fascinated by the land tortoises, marine iguanas, & finches.
CatchIT Question:
Where are the Galapagos Islands?
D
A
C
B
What did Darwin observe on the
Galapagos Islands?
Click to zoom into Galapagos Islands
What did Darwin observe on the Galapagos Islands?
Galapagos Tortoises
* Domed shell w/ short neck
* Live on wetter islands
* Have short necks that
can reach grasses and
vegetation on the ground
What did Darwin observe on the Galapagos Islands?
* Flatter shell compared to
domed
* Live on slightly drier
islands
* Have longer necks than
domed to reach short
bushes and trees
What did Darwin observe on the Galapagos Islands?
* “Saddle” w/ VERY long necks
* Live on dry islands
* Dry climates have less
vegetation on the ground
* Long neck used to reach
vegetation up in bushes & trees
growing off the ground
Galapagos Tortoises
Click here for video
What did Darwin observe on the Galapagos Islands?
•
All tortoises resemble a species living in South America
•
Saw that giant tortoises varied in predictable ways from
one island to another.
•
The shape of a tortoise’s shell could be used to identify
which island a particular tortoise lived.
Natural Selection Questions
(Bill Nye)
1.
2.
3.
4.
5.
6.
7.
A young man that walked out was __ ___.
He quit medical school to become a ___.
How long did the Beagle stay in the Galapagos
Islands? __ days
Finches had different shaped ___: varied by
the environment they inhabited.
What was the mechanism that made evolution
occur? ___ ____
When did he publish his book?
Now, every where we look at today, we see
something that came from ___.
Natural Selection Clip
(Bill Nye)

Click here for video
Who influenced Darwin’s ideas?
James Hutton and Charles Lyell
(geologists)
 Recognized
that Earth is many millions of
years old.
 And the processes that changed Earth in
the past are the same processes that
operate in the present.
Hutton and Lyell
said…

Volcanoes release hot lava and gases now, just
as they did on an ancient Earth.

Erosion continues to carve out canyons, just as
it did in the past.

Also said that awesome geological features
could be built up or torn down over long periods
of time. (examples: earthquakes and volcanoes)
Wild/Crazy Idea: Earth changes over time
Hutton and Lyell
So……Because of Hutton & Lyell’s work…..
Darwin then asked:
If the Earth could change over time,
might life change as well?
Who else influenced Darwin’s Ideas?

Malthus (an economist) – Studied population
growth - observed that babies were being born
faster than people were dying.
He reasoned that if the human population
continued to grow unchecked, sooner or
later there would be insufficient living space
and food for everyone.

Who else was thinking about evolution?
Lamarck’s Theory of Evolution
Proposed that by selective use or disuse of
organs, organisms acquired or lost certain
traits during their lifetime.
Was he “right”?
These traits could then be passed on to their
offspring.
Lets break it down….
Over time, this process led to change in a species
How did Lamarck think organisms changed?
Fiddler Crabs: An Example
1. The male crab uses its small front
claw to attract mates and ward off
predators
2. Because the front claw has been
used repeatedly, it becomes
larger (acquired).
3. A larger claw, is then passed on to
the crab’s offspring.
He was WRONG! He did not realize
that the large claw traits were
inherited
Lamarck’s Theory
Another Example:
According to Lamarck's
theory, a given giraffe could,
over a lifetime of straining to
reach high branches,
develop an elongated neck,
which would then be passed
on to the next generation.
The long neck is ACQUIRED
What were Darwin’s arguments in his book?
Natural Variation and Artificial Selection
•
Argued that species were NOT perfect and
unchanging.
•
Natural Variation: There are differences
among individuals of a species.
What is Natural Variation?
White Version/Morph
Peppered moths
come in two
versions
Black Version/Morph
If trees in an area have dark bark, the
black version
blends in better
and is
home
message:
The
less likely to be eaten by predators.
Take
natural variation may give
certain members an
If trees in an area have white bark, the
advantage
over
white version
blends in better
and isothers.
less likely to be eaten by predators.
Darwin’s Book
On the Origin of Species

The actual title of his book is:
On the Origin of Species by Means of Natural Selection
•
The book proposed a mechanism for
evolution that he called natural selection.
•
He presented evidence that demonstrates
the process of evolution has been taking
place for millions of years. Darwin was 50 when it was
published!
What is Natural Variation?
Bessie
Elsie
* Elsie’s natural variation is to produce more milk than Bessie
* Which cow would the farmer use to reproduce offspring? Why?
What were Darwin’s
arguments in his book?
Artificial Selection: Nature provided the
variation among different organisms, and
humans selected those variations that they
found useful.
* Only the largest hogs, fastest horses, and the
cows that gave the most milk were selected to
breed and produce offspring.
Darwin’s Evolution by Natural Selection

The Struggle for Existence: members within
each species compete regularly to obtain food,
living space, and other necessities of life.

A predator that is the fastest or has a
specialized way of catching prey can catch
more prey.

Prey that are faster, better
camouflaged, or better protected
avoid being caught.
Darwin’s Evolution by Natural Selection

Survival of the Fittest: Process by which
individuals that are better suited to their
environment survive and reproduce most
successfully; also called Natural Selection.

Darwin called the ability of an individual to
survive AND reproduce in its specific
environment fitness.

An adaptation is any inherited characteristic
that increases an organism’s chance of
survival.
Darwin’s Discoveries Video Clip
Survival of the Fittest

The concept of fitness, Darwin argued, was
central to the process of evolution by natural
selection.
Example:
Baby birds compete for food in the nest. The
stronger bird may take food from the weaker
siblings. Then…how is this related to fitness?
Evolution by Natural Selection
Descent with Modification: Concept that each
living species has descended, with changes,
from other species over time.
•
Implies that all living organisms are related to
one another.
Common Descent: The principle that says all
species – living and extinct – were derived from
common ancestors.
Evidences of
Evolution
There are 4 categories
Evidence #1:
FOSSIL RECORD
What are some evidence of Evolution?
Fossil Record
Fossils that had formed in
the different layers of rock
were evidence of gradual
change over time.
One could view how a
species had changed and
produced different species
over time.
Evolution of Horses
Horses do not look
the same as they did
many years ago
-
- Fossil Record shows
evidence that animals
have changed over
time and that they
share common
ancestors based on
similarities in their
skeletons.
Evidence #2:
COMPARATIVE
ANATOMY
What are some evidences of Evolution?
Homologous Structures: Structures that have
different mature forms in different organisms but
develop from the same type of embryonic tissues.
These structures
provide evidence
for common
ancestry and
evolution.
Vestigial Structures
•
Vestigial Structures are structures that are the
reduced forms of functional structures in
different species.
Examples:
1. Snake Pelvis: The pelvis is the attachment
point for legs and is therefore nonfunctional in
an animal without legs
Vestigial Structures
2. Kiwi Wing: The wings of kiwis are too small to
be of any use in flight
3. Human Appendix: Important for digestion in
many mammals, but of limited use in humans &
some apes
What are some evidence of Evolution?
•
Analogous structures can be superficially
similar in construction, but are NOT inherited
from a common ancestor.
•
Example: The wing of an eagle & the wing of a
insect have the same function (both enable the
organism to fly) – but are constructed in
different ways & from different materials.
What are some evidence of Evolution?
* While analogous structures do not indicate
close evolutionary relationships, they do show
that functionally similar features can evolve
independently in similar environments.
Evidence #3:
COMPARATIVE
EMBRYOLOGY
What are some evidence of Evolution?
Similarities in Early Development
In their early stages of development, chickens,
turtles, and rats look similar, providing evidence
that they shared a common ancestry.
Evidence #4:
COMPARATIVE
BIOCHEMISTRY
What we know…

All cells rely on DNA to make proteins.

Using new technologies, biologists are able to
determine the amino acid sequences in proteins to
determine evolutionary relationships among various
species of organisms.

The more closely related two species are, the greater
the similarity in amino acid sequences of their
proteins.
For example:
Evolution Video
Click here for video clip:
Darwin, the Beagle, and Finches: Darwin
Discovers Evidence of Natural Selection
Types of Evolution
There are 5 main types
Divergent Evolution:
When two species move away from the traits
that they share with a common ancestor as
they adapt to their own environments
Also called
Adaptive Radiation…
Produces
homologous structures,
And are more
CLOSELY related!
Convergent Evolution:
When two distinct species with differing
ancestries evolve to display similar features.
Sugar Glider:
Australian marsupial
Produces
analogous structures,
Flying Squirrel
A GA squirrel
And are NOT
closely related!
**Coevolution**
Coevolution
 Pollenation

Geographic Distribution of Living Species
- Species now living on different
continents had each descended from
different ancestors.
- Because some animals on each
continent were living under similar
ecological conditions, they were
exposed to similar pressures of natural
selection.
• They ended up evolving certain
striking features in common…
but are NOT related!
• This is called Convergent Evolution
Punctuated Equilibrium
Evolution that has long periods of stability or
“unchange” followed by short periods of rapid
change.
Gradualism
A change that is very slow over time. It’s
hard to notice a difference over a short
period of time…it is slow and gradual.
5. Biological Resistance
Some organisms obtain a mutation that makes
them resistant to a toxin (antibiotic or pesticide).
Overuse of antibiotics & pesticides create
populations of “super bugs”.
This is why you need to take your
antibiotics for the entire time…
You expose the bacteria to the toxin;
but if you don’t kill them all (take all
your medicine), then you “taught
them” how to resist the antibiotic!
Resistance
Explanation of how resistance happens:
http://www.sumanasinc.com/scienceinfocus/sif_antibiotics.html
Explanation of how bacteria transmit resistance:
http://survivalrivals.org/the-x-bacteria/animation
Video about antibiotic resistance:
http://www.youtube.com/watch?v=W-WumllRPLI
5. Other patterns of selection
Frequency of Phenotype
Generic Bell Curve for Natural Variation
Remember
the graph…?
in a Complex
Trait
5. Other patterns of selection
a. Stabilizing Selection
Stabilizing Selection
Key
Low mortality,
high fitness
High mortality,
low fitness
Selection
against both
extremes keep
curve narrow
and in same
place.
What good
reasons can you
come up with for
this trend?
Human babies that have
a really low birth
weight…
Human babies that have
a really high birth
weight…
Birth Weight
 In
stabilizing selection, the bulk
portion of the bell-shaped curve is
favored;
 The
average phenotype is favored
b. Directional Selection
Key
Directional Selection
Food becomes scarce.
Low mortality,
high fitness
High mortality,
low fitness
 In
directional selection, the one
side of the bell-shaped curve is
favored;
 The
one extreme phenotype is
favored over the other, over the
average
c. Disruptive Selection
Disruptive Selection
Low mortality,
high fitness
High mortality,
low fitness
Population splits
into two
subgroups
specializing in
different seeds.
Beak Size
Number of Birds
in Population
Key
Number of Birds
in Population
Largest and smallest seeds become more common.
Beak Size
 In
disruptive selection, both end
portions of the bell-shaped curve
are favored;
 Both
extreme phenotypes are
favored over the average
Adaptation:
body parts, body coverings, or
behaviors that help an organism
survive its environment or
reproduce more effectively
Adaptations:

Mimicry: Adaptation in which one species
evolves to resemble another species for
protection or other advantages.
Adaptations:

Camouflage: Adaptation
that allows organisms to blend
into their surrounds.
Adaptations:

Imprinting: a form of learning in which a very
young animal fixes its attention on the first
object experience and then follows that object
Plants:
Tropisms (Growth Responses):
1) Phototropism: Responds to light
Plants:
Tropisms (Responses):
2) Thigmotropism: Responds to touch
Plants:
Tropisms (Responses):
3) Gravitropism: Responds to gravity
Click here for link to cool videos online.
Plants:
Tropisms (Responses):
4) Hydrotropism: Responds to water
Cactus
Ridges:
Expand to store more water
when it rains
Thorns:
Flowers:
Waxy Covering:
Can reproduce Sexually
as well as asexually Prevent water loss
Protect against
being eaten
No Leaves:
Prevent water loss
Polar Bear
Short/small Ears:
Thick Blubber:
Save Heat
Keep warm
Large Paws:
Walking on snow
White/clear Fur:
Blend in with snow
Long Claws:
Catching prey/digging
Adaptation Prompt
Draw an organism and describe the adaptations that
make it “fit” (as in ‘fitness,’ ‘survival of the fittest’).
1.) Organism must be drawn, in color, & neat
2.) Must include background environment
3.) Must have at least 3 adaptations w/ explanation of
advantage for survival/reproduction
Not adaptations: How long they live, where they
live, what they eat
Adaptation examples:
* Large paws, thick beak, bright colored feathers, skinny
legs, large ears, sharp teeth, fur thickness….
Hint: Must be clearly related to survival or reproduction!!
Another example to demonstrate these
selection patterns:
http://bcs.whfreeman.com/thelifewire/
content/chp23/2302001.html
http://devour.com/video/theevolution-of-life-on-earth/