IN-CLASS ACTIVITY 5 Microevolution RUBRIC
Group Name ___________________ _____________________
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1. What is meant by genetic variation in a population?
Variation among alleles and genotypes within the gene pool of a population.
2. What is the ultimate source of new genetic variation in a population? (no migration)
mutation (n.b. new alleles)
3. What two major components of sexual reproduction recombine genes to yield new
genotypes?
A. meiosis
B. fertilization (n.b. both aspects of sexual reproduction create new genotypes)
3. Define evolution.
a change in allele (genotype) frequency in a population through time
4. Define natural selection.
Process whereby environmental forces (agents) cause differences in survival/
reproduction among individuals in a population
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X (M rarely + at very slow rate)______________mutation
D R X______________natural selection (not disruptive)
R X______________founder effect
R X______________population bottleneck
R X______________genetic drift
H M X ______________gene flow
XR______________inbreeding
M (possible X if mating not random)______________outbreeding
M X______________varying selection pressures in time and space
5. Put an X in front of those forces causing changes in genotype frequency in a
population.
6. Put an R in front of those that remove genetic variation from the population.
7. Put an M in front of those that maintain genetic variation in the population.
8. Put a D in front of the one primary force differentiating subpopulations.
9. Put an H in front of the one primary force homogenizing subpopulations.
N.B. a term can have more than one letter in front of it.
10. Fitness
Genetic variation
Natural selection
Pre-adaptation
Phenotypic variation
Evolution
Adaptation
Write a paragraph that incorporates these seven words to describe steps required for
the evolution of earlier breeding by Yukon red squirrels. The squirrels are growing in
an area that has experienced elevated temperatures that caused squirrel food (spruce
cones) to be available earlier. Prior to this climate change, the squirrel population was
living in the area.
First, write a topic sentence.
Then, develop the steps BEFORE mining.
Finish with the steps AFTER mining.
Student 1.Climate change has led to the evolution of earlier breeding by Yukon red
squirrels. Prior to climate change, genotypic and phenotypic variation existed in the
population of squirrels, so the frequency of alleles was different. Some squirrels have
genotypes that results in a phenotype of early breeding. These squirrels have a preadaptation that will allow them flourish with climate change; other genotypes have
phenotypes with late breeding. After climate change begins, natural selection resulted in
the pre-adapted squirrels to have higher fitness than those lacking that trait; i.e. early
breeding individuals had greater survival and left more offspring than those breeding
later. The high fitness genotypes have an adaptation that results in early breeding
squirrels to flourish with climate changes. Over time, the frequency of alleles for early
breeding increases while the frequency of alleles for late breeding decreases. Genotypic
and phenotypic variation declines. Thus the population experiencing climate change
undergoes evolution toward earlier breeding.
Student 2. Climate change caused squirrel food source to be available earlier which
caused evolution of earlier breeding. Before climate change, the squirrel population had
great genetic and phenotypic variation. An individual in the population pre-adapted (due
to a random mutation) a trait that allowed it to breed earlier. After the climate change,
the fitness of the individual with the mutation was higher (because it could breed earlier).
Natural selection occurred, and as the mutation was passed to more and more offspring
in the new generation, they adapted to the new earlier food source. As a result,
phenotypic (and genetic) variation was reduced from that of the original population.
The population evolved to include more early breeding individuals with the mutation than
the original population had.