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?
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….
By now you must be feeling
pretty sick!
…….time for some medicine........ How about
some Antibiotics!.........
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?
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?
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
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
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)