Presentation going over the patterns of evolution, the forces of evolution, and the different types of selection. Relevant for freshman level High School Biology.

1. Types of Evolution

2. Essential Question
How do we organize the different ways in
which animals evolve?

3. Patterns of Evolution
● Coevolution
● Convergent Evolution
● Divergent Evolution
● Artificial Selection
● Natural Selection

4. Coevolution
● When the evolution of two or more
species influence each other.
● Examples: Flowers have coevolved
with their pollinators. They are both
reliant on each other for survival.

5. Convergent Evolution
● When organisms evolve similar
adaptations despite not being
closely related to each other.
● Examples: Wings have evolved
independently several times
throughout history.

6. Divergent Evolution
● When similar species start to differ
due to pressure from the
environment.
● Examples: Darwin’s finches
evolving different beaks from the
mainland finches.

7. Artificial Selection
● Breeding of organisms for specific
desired traits.
● Examples: Domestic dog breeds or
crops.

8. Natural Selection
● Process of evolution where
organisms with higher fitness
reproduce more often.
● Development of long necks in
giraffes.

9. Discussion
Driver - Try to think of another example of coevolution. Why do you think it was
coevolution?
Passenger - Try to think of another example of convergent evolution. Why do you
think it was convergent evolution?
Rear Driver Side - Try to think of another example of divergent evolution. Why do
you think it was divergent evolution?
Rear Passenger Side - Try to think of another example of artificial selection. Why
do you think it was artificial selection?

10. Evolutionary Forces
● Mutation
● Gene flow
● Genetic drift
● Selection
Use the force Luke

11. Mutation
● The ultimate source of new
variation. Mutations are changes in
DNA. These accumulate to form
changes in alleles over time.
● Example: Sickle cell anemia in
humans is the result of a single
mutation.

12. Gene flow
● Exchange of genetic material
between two or more populations.
Primarily increases genetic
diversity and reduces inbreeding.
● Migration or pollen being blown
long distances.

13. Genetic Drift
● Changes in allele frequencies due to
random chance.
● Smaller populations are more
affected.
Bottleneck Effect
● Mass dying off of original population
changes allele frequency.
Founder Effect
● Small portion of population moves
away and changes allele frequencies.

14. Selection
● More fit individuals will leave
behind more offspring on
average.
● Two types
○ Artificial selection
○ Natural Selection

15. Math of Selection
● Selection is a statistical concept.
○ One cannot predict the fate of any single individual
○ But it is possible to predict which kind of individual will
tend to become more common in a population
● Three types of natural selection have been identified
○ Stabilizing selection
○ Disruptive selection
○ Directional selection

16. Stabilizing Selection
● Eliminates both extreme
phenotypes. Average individuals
are the most fit.
● Example: The weight of infants at
birth.

17. Disruptive Selection
● Intermediate/Average
phenotypes are not favored.
● Example: Bird beaks
○ Larger beaks are better suited
for crushing large seeds
○ Small beaks are better suited
for grabbing small seeds

18. Directional Selection
● One of the extreme
phenotypes are favored.
● Example: Hummingbird Beaks
○ Thinner beaks are favored
for collecting nectar from
flowers.

19. Discussion
Rear Passenger Side - Why is stabilizing selection helpful for keeping animals
well-adapted to their environment?
Driver - What kinds of places might make disruptive selection more likely, and how
are they different from other places?
Rear Driver Side - How might disruptive selection affect the appearance of
individuals in a population?
Passenger - What do you think will happen as a trait gets more common due to
directional selection?

20. Get Ready for Next Week
● You will have quiz on Monday for this lecture.
● Circle any concepts learned today that you might
struggle with.
● Star any concepts you feel strong about.
● No workbook will be due today.
● Have a good weekend!