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AP Biology Discussion Notes

Wednesday 12/20/2017

Goals for the Day

1. Be able to describe & explain

natural selection & biological

fitness

Two Requests:

• Keep an open mind about the content that is

presented & be respectful of your classmates

views/questions/opinions

• If you have questions:

ASK THEM!

Evolution is a Big Idea….Literally

• Big Idea 1: The process of evolution

drives the diversity and unity of life.

• So….if you have questions you should….

ASK THEM!

12/20 Question of the Day

• Explain whether modern day catastrophes,

such as severe hurricanes provide evidence

for Cuvier’s idea of catastrophism.

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.

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?

What kind of things could affect them?

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?

So what makes a SPECIES?

Common Grackle

- Quiscalus quiscula

European Starling

- Sternus vulgaris

So what makes a SPECIES?

Common Grackle

- Quiscalus quiscula

Great-tailed Grackle

- Quiscalus mexicanus

Biological Species Concept

• Reproductively isolated from other such

groups

– Produce fertile offspring

• Works well for ANIMALS

• Doesn’t work well for PLANTS

Figure 24.4Grizzly bear (U. arctos)

Polar bear (U. maritimus)

Hybrid “grolar bear”

Types of Isolation

• Pre-Zygotic – before the zygote

– Mating or fertilization is inhibited

• Post-Zygotic – after the zygote

– Mating/Fertilization can occur but the resulting

offspring is less fit

Reduced Hybrid

Viability

Reduced Hybrid

Fertility

Hybrid

Breakdown

FERTILIZATION

VIABLE,FERTILE

OFFSPRING

Postzygotic barriers

(k)

(h) (i)

(j)

(l)

Figure 24.3_c

Types of Post-zygotic Isolation

• Reduced Hybrid Viability

• Reduced Hybrid Fertility

• Hybrid Breakdown

What could prevent these 2

groups from breeding? (Even if

they got back together?)

Figure 24.3_b

Prezygotic barriers

Habitat

Isolation

Temporal

Isolation

Behavioral

Isolation

Mechanical

Isolation

Gametic

Isolation

Individuals of

differentspecies

MATINGATTEMPT

FERTILIZATION

(a) (c) (e) (f)

(b)

(g)

(d)

Behavioral Isolation