1. Ch 4, Section 2: Evolution
Standards: SEV2a, SEV3a, SEV3b, SEV3d

2. 
What is Evolution?
 Change in the traits of a
population over a long
period of time.
 Evolution DOES NOT
happen to an
individual organism.
 Evolution is the end
result of natural
selection.

3. 
What is natural
selection?
 Darwin’s came to the conclusions:
 All living things overproduce
 There is variation among the
offspring.
 Variations in offspring and
limited resources create struggle
for existence.
 Those with advantageous traits
survive and pass on
advantageous trait to offspring.
 Those with negative traits die
and take those traits out of the
population.
 Nature selects those that are most
fit for the environment to survive.

4. 
What is an adaptation?
 Trait (physical or
behavioral) that enables
an organism to better
survive in a particular
environment.
 Organisms are BORN
WITH adaptations.
Adaptations are
GENETIC.
 Organisms DO NOT
acquire adaptations
throughout their life.

5. 
What is coevolution?
 When two populations evolve
due to a long-term interaction
with each other.
 EX: Lobelia flower has evolved
pollen structures that rub the
honeycreepers head as it feeds
from the long curved flower with
its long curved beak.
 EX: Gazelles are fast to escape
cheetahs. Only the fastest
cheetahs will catch gazelles, eat,
survive and pass on fast trait to
offspring. Only the fastest
gazelles will survive fast cheetahs
and pass that onto their offspring.

6. 
Can evolution happen by artificial
selection instead of natural selection?
 Yes!
 This is how domesticated
animals and plants have
been “created.”
 By selectively breeding two
species with desirable traits
we can get a different
species.
 Ex: We’ve bred corn to be
larger, sweeter, easier to
harvest. Teosinte was
ancestral corn- look how
selective breeding has
changed it!

7. 
Why should you care about
evolution now?
 Evolution of resistance is
occurring with organisms
that are able to create
many new generations in
a short period of time
 Ex: bacteria & insects
 Resistance makes an
organism able to tolerate
a chemical specifically
designed to kill it.

8. 
Is there a way to prevent
insect resistance?
 Typical scenario (diagram on left)
 Pesticide sprayed on crop.
 Most insects killed. Some are
genetically adapted to resist
pesticide.
 These resistant insects survive &
pass on resistance to offspring.
 After many generations of
reproduction the entire population
is resistant.
 If a farmer sprays most of his field
and leaves a section unsprayed (a
refuge) then more of the
nonresistant will survive & breed
with resistant and keep the
population from becoming
completely resistant. (diagram on
right)