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EVOLUTION
Which one of these
animals is a fish?
Evolution is known as "the
unifying theory of biology"
What does that mean?
Create a list of statements regarding evolution (in your head).
Sort them into - Statements of Fact & Statements of Opinion
FACT
OPINION
The task is difficult.. partly because the word
"fact" is a tough word.
When something is a fact, it suggests it is absolute, and not
subject to change.
Science doesn't like absolutes.
Definition of fact: an observation that has been confirmed
repeatedly and is accepted as true
(although its truth is never final)
Scientists prefer to use the term OBSERVATIONS
Look at how it changes the tone of these sentences.
1. It is a fact that the sky is blue.
2. I observe the sky is blue.
(Is it?)
Animations like these perpetuate the myth that evolution
is a linear process.
While amusing to watch, the Simpsons video illustrates a
common myth about evolution.
Evolution isn't linear. Organisms aren't striving to become
anything, but rather changing due to their unique
environmental pressures.
More misunderstandings.....
1. If humans evolved into monkeys, why are there still
monkeys?
This is also related to the
misunderstanding that
evolution follows a linear
path...that everything is trying
to be human. - NOT SO There are many kinds of
primates, each adapted to its
own environment, just like there
are many kinds of felines
This picture is flawed, but commonly
used to illustrate human evolution.
None of
these
cats will
evolve
into a lion.
Myth 2: Scientists regularly debate whether
evolution occurs.
The only place debate occurs is in social settings, and is
philosophical in nature. If any debate occurs among
biologists, its often regarding specifics - such as timing, or
what animal is related to what, or when did a creature
evolve and what is its origins.
As a THEORY, evolution is supported by a large body of
evidence and is used to EXPLAIN new observations. It is
also useful for making PREDICTIONS
Myth 3: A person cannot be religious and
believe in evolution.
There are many
scientists who have
religious beliefs. One
does not necessarily
preclude the other.
To say that the two are
incompatible is unfair to
both scientists and
people of faith.
Another myth is that evolution
encourages the strong to destroy
the weak.
Remember, "strong" and "weak"
are relative. Organisms do not
have to be strong to survive and
cause evolution.
Cepahalopods aren’t the
strongest organisms in
the sea, but they do have
a unique survival skill.
There are many more
myths and
misunderstandings
about evolution. We
will hopefully tackle
those as we progress
through this unit.
E
V
O
L
V
E
On a notecard, write down a
question or statement you are
confused about regarding
evolution. You do not need to
put your name on this card. As
we cover evolution I will try to
address particular questions,
concerns and arguments.
Media sources that may be helpful:
PBS Evolution - many resources covering
the topic - videos, articles, activities and
more
Darwin's Dangerous Idea - 1st in a 7 part
series on evolution; begins with Darwin's
voyage on the Beagle and how he
established the Theory of Evolution by
Natural Selection
Nova: Intelligent Design on Trial - A recent covering of a trial in Dover,
Delaware, where the school board tried to establish "intelligent design"
as part of its science curriculum.
The Panda's Thumb - news archives about evolution and
society, focuses on debunking "creation science" and
"intelligent design"
Darwin and Evolution
“The Origin of Species”
Question: How did the giraffe get its
long neck?
Why are there 9 subspecies of giraffes?
17.1 History of Evolutionary Thought
In 1831, Charles Darwin, a 22-year-old naturalist, accepted a
position aboard the ship HMS Beagle that began a voyage
around the world; it provided Darwin with many observations.
Pre-Darwinian world-view was
determined by theological beliefs.
Rothchilds
Giraffe
1) The earth is young; ~10,000
years old
2) Each species was uniquely
created and did not change
3) Observations can only be
used to substantiate the
prevailing worldview, not
challenge it.
How would this worldview explain the giraffe’s neck?
How would it explain the 9 subspecies?
Mid-Eighteenth-Century Contributions
Carolus Linnaeus and Taxonomy
Taxonomy is the science of classifying organisms;.
Linnaeus developed a binomial system of nomenclature two-part names for each species
Homo sapiens
Canis lupus
Giraffa camelopardalis
* with 9 subspecies
Masai Giraffe (Giraffa camelopardalis tippelskirchi)
Thornicroft Giraffee
Giraffa camelopardalis thornicrofti
Biogeography
study of the distribution of species and ecosystems
in geographic space and through geological time
One of Darwin’s ancestors suggested the possibility of common descent.
The idea that species could
change was not Charles
Darwin’s original idea.
No one could propose a
MECHANISM for how these
changes could occur.
Paleontology was a new
field, uncovering fossils of
organisms that no longer
exist.
Lamarck's Acquired Characteristics
Lamarck mistakenly saw "a desire for perfection" as inherent in all
living things; individuals could change their traits if they tried hard
enough. These newly acquired traits would then be passed on.
His view of giraffe evolution would have looked like this:
Experiments fail to uphold Lamarck's inheritance of
acquired characteristics
So….if that was wrong. How did giraffes come about?
Also, why are there so many subspecies of giraffes?
What We Know So Far
1. Taxonomy and classification emphasize similarities among
species (common descent)
2. Fossils show extinct species (paleontology)
3. Isolated species are distinct (biogeography)
4. Organisms have adaptations to help them survive
.........Enter Charles Darwin..........
The Voyage of the Beagle
Galapagos
●Islands off S. America
●Island species varied from mainland species
●Finches resembled mainland finches, but with more variation
●Tortoise Variations
Shells that flare up, long necks - feed on
tall plants
Figure 17.7a
Figure 17.7b
Darwin's Finches
a. Finches on the Galápagos Islands resembled a
mainland finch but there were more types.
b. Galápagos finch
species varied by
nesting site, beak size,
and eating habits.
Questions to Ponder:
Did the animals on the islands
descend from one mainland
ancestor?
What were the variations found on the finches?
Why were the island finches so different from
mainland finches?
Natural Selection and Adaptation
Natural selection was proposed by
both Alfred Russel Wallace and
Darwin separately, but at the same
time. It is simply that the
organisms best suited for their
environment will survive,
reproduce, and pass on their
desireable traits to the next
generation.
It is the MECHANISM by which
evolution occurs, and itt would
explain how giraffes got their long
necks, why finches have different
beaks, and why there are two
different varieties of tortoises.
There are three preconditions for natural
selection.
1. The members of a population have random but
heritable variations.
2. In a population, many more individuals are
produced each generation than the environment
can support.
3. Individuals have adaptive characteristics that
enable some to survive and reproduce better.
There are two consequences of natural selection.
1. An increasing proportion of individuals in succeeding
generations will have the adaptive characteristics.
2. The result of natural selection is a population adapted to its
local environment.
Natural selection can only utilize variations that are randomly
provided; therefore there is no directedness or anticipation of
future needs.
Pause and think: Thinking that evolution has a
direction is a common misconception.
Can you think of any statements you may have heard that
suggest people think that evolution is directional?
1. Why didn’t chimpanzees evolve the ability to talk?
2. Why aren’t other animals as intelligent as humans?
3. Why didn’t giraffes evolve in other places?
Extinction occurs when previous adaptations are no longer
suitable to a changed environment.
How Evolution by Natural Selection Works
1. Variations exist in a
population.
2. Every individual struggles to exist.
3. Individuals differ in FITNESS
a) fitness measures an organism’s reproductive success
b) it does not necessarily mean stronger.
Fully armored
stickleback (ocean)
Low armor (freshwater)
4. Survivors pass traits to offspring
Over time, the traits that provide the best chance of survival
and reproduction are the ones most prevalent in the
population - these are ADAPTATIONS
Apply these principles to the giraffes.
Procamelus (ancestor)
Be careful with that word…..
Adaptation is a trait, a noun.
It is dangerous to use it in verb form because it suggests that
an individual can adapt. They cannot.
***** POPULATIONS EVOLVE. INDIVIDUALS DO NOT.*****
Fix this sentence:
This Aye Aye has adapted to
a life of eating insects. Its
long digit is used to probe
wood.
ARTIFICIAL SELECTION
Dogs breeds were
developed by years of
breeding wolves
We chose the traits
most desirable, then
bred the organisms
with those traits.
Nature does the same
with “natural selection”
“On the Origin of Species” by Darwin
1. After the HMS Beagle returned to England in 1836, Darwin
waited over 20 years to publish.
2. He used the time to test his hypothesis that life forms arose
by descent from a common ancestor and that natural selection
is a mechanism by which species can change and new species
arise.
3. Darwin was forced to publish
Origin of Species after reading a
similar hypothesis by
Alfred Russel Wallace.
The Definition of Evolution
Evolution is the change in allele frequencies, or
a change in the gene pool, of a population.
Mythbuster:
“No one has ever seen one animal change into another,
therefore evolution isn’t true.”
How would you respond to this statement?
20 Points Extra Credit - a Scenario of Evolution.....
1. Choose a real or imaginary organism
2. Describe 2-3 variations in that organism’s population
3. Show how evolution would act on this population given a
change in the environment (climate, predators, food change,
etc.)
4. Note which variations are beneficial and which are harmful.
5. Show how reproduction changes the overall population
(with regard to these variations)
6. Be creative! You should draw and map your organism
through a few generations and write a short essay covering all
the requirements.