Goal 3.05d: Applications of Evolution through Natural Selection

The process through which natural selection occurs varies according to

the environment and the organisms involved.

Divergent Evolution = when species develop from a common ancestor

evolutionarymodel.com

Convergent Evolution = when species develop similar traits but are not evolutionarily connected.

pbs.org

Parallel Evolution = when species develop from common ancestor along a parallel path without diverging.

biologie.uni-hamburg.de

Coevolution = a change in the genetic composition of one species (or group) in response to a genetic change in another.

sdakotabirds.com

Three Types of Natural Selection

Stabilizing Selection = maintains an already existing system.> eliminates organisms that deviate from the norm.> environment must remain unchanged.> explains why there are “living fossils.”> as long as environment doesn’t change, organisms

won’t change.

Horseshoe CrabGinkgo Tree

Directional Selection = favors one extreme or the other.> eliminates organisms that are not in that extreme.> eventually leads to changes in the population.> occurs when organisms must adapt to a change in

their environment.> may develop into a RESISTANCE (the ability of an

organism to withstand a harmful agent).

MALARIA

Directional Selection: PESTICIDE Resistance

Pesticide = kills insects (pests)

Insects with resistance live to reproduce…Resulting in a new population of resistant insects.

This insect was born with resistance.

This insect was not.

• Malaria is a bacteria transported by mosquitoes.

• DDT (toxic pesticide) was used to kill mosquitoes.

• India 1959 DDT-resistant mosquitoes were detected.

• When directional selection occurs, the resistant mosquitoes survive to produce a new resistant population.

Resistance is amplified by directional selection.

• The directional selection of malaria has led to a change in the gene pool of persons living in malaria-infested areas.• Sickle-cell anemia is a disease of the blood in which the hemoglobin does not develop properly and the red blood cell is sickle-shaped.• HEMOGLOBIN is the part of the red blood cell that carries oxygen throughout the body.

Some bacteria are naturally resistant to antibiotics and must be killed by your body.

Strep Throat!

Streptococcus bacteria

Normal

Resistant

Your doctor gives you antibiotics to help your body kill the normal bacteria. This allows your body to concentrate on the RESISTANT bacteria.

Directional Selection: ANTIBIOTIC Resistance

Antibiotics = kill bacteria

Your doctor gives you antibiotics to help your body kill the normal bacteria. This allows your body to concentrate on the RESISTANT bacteria.

Directional Selection and the Peppered Moth.> Before industrial revolution = moths are peppered.> After industrial revolution = moths are black.> After pollution controls = moths are peppered.

Disruptive Selection = favors two extremes at one time.> eliminates organisms that are more common.> eventually leads to changes in the population.

African butterflies can range from red to blue.

The red and blues are foul-tasting to predators.

The other colors are eaten more often resulting in a selection in favor of the extreme colors.