Download Genetic Variation in Natural Selection

Warm-Up (2/3)
On the piece of white paper from the back, answer
the following question.
Explain how a retrovirus can acquire genetic
variation.
Name
Date
Period
1C.3b: Scientific evidence supports the idea that evolution continues to occur.
Illustrative example: Emergent diseases
1A.1c: Genetic variation and mutation play roles in natural selection. A diverse
gene pool is important for the survival of a species in a changing environment.
1A.1d: Environments can be more or less stable or fluctuating, and this affects
evolutionary rate and direction; different genetic variations can be selected in each
generation.
1A.1e: An adaptation is a genetic variation that is favored by selection and is
manifested as a trait that provides an advantage to an organism in a particular
environment.
1A.2b: Phenotypic variations are not directed by the environment but occur through
random changes in the DNA and through new gene combinations.
Genetic Variation in Natural Selection
Healthy populations have
much genetic variation.
% of DNA
identical to
Fleenor’s:
Genetic Variation in Natural Selection
Healthy populations have
much genetic variation.
% of DNA
identical to
Fleenor’s:
DNA differences caused
by mutations.
Genetic Variation in Natural Selection
Variation caused by
mutations in gametes.
Changed cell
Changed seed
DNA differences caused
by mutations.
Genetic Variation in Natural Selection
Environments can be
stable or fluctuate.
Generation after
generation, different
phenotypes can be
selected.
Change in Winter Temperatures from Average
*
Hairless
mutant
sperm
*
Furry
mutant
sperm
Genetic Variation in Natural Selection
Healthy populations have
much genetic variation.
Selection is only possible
with a diverse gene pool.
Genetic Variation in Natural Selection
Healthy populations have
much genetic variation.
The selected
trait is an
adaptation.
Selection is only possible
with a diverse gene pool.
Genetic Variation in Natural Selection
Case in Point: the Zika Virus
Infects humans
Infects monkeys
Pre-2014
Genetic Variation in Natural Selection
Case in Point: the Zika Virus
Infects humans
Infects monkeys
Post-2014
Critical Thinking Question #1&2
The Zika virus is a retrovirus which, historically, has been endemic to
Brazil and has almost exclusively infected monkey populations
(infection of human populations has been rare; see table below). In the
past ten years, Brazil has experienced significant deforestation and
expansion of its cities.
State the point in time at which a mutation formed that causes easier
infection in humans, and predict how the virus carrying this mutation
had a selective advantage in a changing environment.
Human, Monkey, and Zika Population Levels in a Deforested Region of Brazil,
(1985–)*
Time
Human Population
(millions)
Monkey
Population
(thousands)
Human Zika
Infections
(thousands)
1985Jan
3.6
1995Jan
4.0
2005Jan
4.6
2015Jan
5.4
2015May
5.4
2015Aug
5.5
2016Jan
5.5
12.5
11.9
11.0
6.2
6.0
5.9
5.8
0.003
0.004
0.002
0.005
0.150
12.0
20.0
Closure
On the piece of white paper from the
back, answer the following question:
Explain the importance of
genetic variation in a changing
environment.
Name
Date
Period
Scale
1 – 10