AP Biology Discussion Notes

Friday 11/07/2014

Goals for the Chapter1. Learn about the Theory of Evolution and

evidence that is used to support this theory

2. Understand the development of this theory in the context of a historical timeline

3. Develop critical thinking skills that help us examine evidence for ALL theories.

Question of the Day

• What does the process of Natural selection act on?

• What evolves?

Descent with Modification

• Descent -the fact or process of originating by generation from an ancestor

• Descent with modification all life comes from a common ancestor.

Evidence for EvolutionThe Tree of Life

• Is this theory saying that everything can be traced back to one common ancestor?

Evidence for Descent with Modification

• Fossil Record• Homologies

– Tree of Life– (Not chain of being)

The Fossil Record• Fossils provide an actual record of Earth’s

past life-forms and gives evidence that:

1. Earth is about 4.5 billion years old.

2. Organisms have inhabited Earth for most of its history.

3. All organisms living today share common ancestry with earlier, simpler life-forms.

Evidence for Natural Selection

• Fossil Record shows the– Succession of

Fossil forms

– Chronological appearance of vertebrates and other groups

Formation of Fossils

Why isn’t the fossil record complete?

Evidence for Descent with Modification

• Fossil Evidence– Cetaceans (Whales)– Whales are mammals,

unlike sharks which are fish !

• Tree of Life– Not chain of being

Evidence for Descent with Modification

• Homologies – characteristics resulting from common ancestry

– Anatomical Homology– Embryological Homology– Molecular ( __ __ __ )Homology

How & why collect all of those animals?– To compare their structure and describe them.

Evidence for Descent with Modification• Anatomical Homologies – fore limbs of mammals have

the same bones, which have changed over time to adapt to different lifestyles of different organisms

Evidence for Descent with Modification• Embryological Homologies – development of vertebrates

is very similar in early stages

Evidence for Descent with Modification• Molecular Homologies

– All species of life use the same basic machinery (DNA & RNA)

• Used to build Molecular Phylogenies

Evidence for Descent with Modification

Used to build Molecular Phylogenies

Evidence for Descent with Modification

Used to build Molecular Phylogenies

Evidence for Evolution

Molecular Homologies

Used to build Molecular Phylogenies

Evidence for Natural Selection• Artificial Selection – provides

evidence of how many small changes can amount to a large change over time.

Are dogs really descended (come from) wolves and why do scientists believe that?

Evidence for Natural Selection• Vestigial Structures - Structures present in an

organism, but reduced in size and either have no use or have a less important function than they do in other, related organisms.

Evidence for Natural Selection• Vestigial Structures - Structures present in an

organism, but reduced in size and either have no use or have a less important function than they do in other, related organisms.

Evidence for Natural Selection

Evidence for Natural Selection

Evidence for Natural Selection

Evidence for Natural Selection

Evidence for Natural Selection• What kind of creatures did scientists think

whales descended from?

Evidence for Evolution

• A good theory not only explains, but PREDICTS.

• Prediction #1:• There should be

intermediate forms between major groups of organisms.

According to Darwin…..• Evolution’s Mechanism/driving force/cause is

____________ ___________ or an organism’s __________________.

• What needs to be present for evolution(change over time) to occur?

According to Darwin…..• What needs to be present for

evolution/change over time to occur?

–VARIATION• What must be true of this variation that is

present?

According to Darwin…..

What are Sources of GENETIC VARIATION?

– Sexual Reproduction:• Crossing over in Meiosis• Recombining of DNA (½ from Mom and ½ from Dad)

– MUTATION!• A ____________ in an organism’s __________

According to Darwin…..

What ENVIRONMENTAL factors could have affected the kiwi ancestors?

According to Darwin…..

Why could it be an advantage for a kiwi to have a smaller wing?

Microevolution

The changes that occur within a species over time.

Typically happens over short periods of time, and can therefore be more easily observed.

Antibiotic Resistance in Bacteria….

….Let’s say you have one little pathogenic bacteria in your body….

Antibiotic Resistance in Bacteria….

….Let’s say you have one little pathogenic bacteria in your body….

….which becomes 2….…. which becomes….

Wait….what happened here?

Wait….what happened here?

It appears we have some variation!

How could that have occurred?

By now you must be feeling pretty sick!

…….time for some medicine........ How about some Antibiotics!.........

Did we get them all?

What can this bacteria do now?

You guessed it!

You guessed it!

You guessed it!

You guessed it!

You guessed it!

You guessed it!

You guessed it!

Seems like you’re not feeling well again

…….time for some more medicine........

You guessed it!

You guessed it!

Antibiotic Resistance in Bacteria….

Now what?

If this represents a change WITHIN a species, than this is also an example of what type of evolution?

Lets get back to our Kiwis…..

Macroevolution

Changes that lead to the formation of an ENTIRELY NEW SPECIES!

USUALLY difficult to observe since it typically happens over a LONG period of time

So what makes a species?

Biological Species Concept

• Reproductively isolated from other such groups– Produce fertile offspring

• Works well for ANIMALS• Doesn’t work well for PLANTS

What could prevent these 2 groups from breeding? (Even if

they got back together?)

If we stopped walking, would our legs eventually shrink and

become useless?• What does Darwin say has to be present

for evolution to occur?

• What would need to be true of that variation?

If we went back into the water, would we eventually develop

gills?• What does Darwin say has to be present

for evolution to occur?

• What would need to be true of that variation?

What if there is trouble in Paradise?

Can the Kiwi’s get their wings back?

Unfortunately Evolution is not forward thinking!

• ………maybe because its not “thinking”

• Things that were beneficial in the past may not be of benefit in the future.

• What is done is hard to undo!

What would need to be present for Evolution to occur?

• What has to be true of that Variation?

• What happens if there aren’t any Kiwi’s that had a longer wing?

• How long would this take to happen if it could?

Testing the testable components