evolution - henry county public schools

EVOLUTION

Which one of these

animals is a fish?

Evolution is known as "the

unifying theory of biology"

What does that mean?

FACT OPINION

Create a list of statements regarding evolution (in your head).

Sort them into - Statements of Fact & Statements of 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. (Is it?)

2. I observe the sky is blue.

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.

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?

Rothchilds

Giraffe

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.