Download Evolution Exam Review

Evolution Exam Review
Take out a piece of paper and answer the following questions
1. What is evolution?
2. What causes evolution?
3. Where does genetic variation come from?
4. What is Natural Selection?
5. What method is used to determine evolution in a population?
6. How do we determine evolutionary relationships between
species?
What is evolution?
• The theory of how organisms have changed over
time.
• Change in the genetic makeup of a population over
time. *Remember – individuals don’t evolove
• Descent with modification
• Evolution only occurs when there is a change in gene
frequency within a population over time. These genetic
differences are heritable and can be passed on to the
next generation — which is what really matters in
evolution: long term change.
What causes evolution?
• Genetic variation
Where does genetic variation
come from?
•
•
•
•
•
Mutation
Sexual reproduction
Migration
Gene flow
Genetic drift
• Founder effect
• Bottleneck
• Natural Selection
What is Natural Selection?
• The mechanism by which evolution takes place
• It does not attempt to explain how life began
How does Natural Selection work?
Mutation creates variation
Unfavorable mutations selected against
Reproduction and mutation occur
Favorable mutations more likely to survive
……. And reproduce, changing genetic
frequencies
What method is used to determine
evolution in a population?
• Hardy-Weinberg Theorem, which says…
• if a population is NOT evolving then the
frequencies of the alleles in the
population will remain stable across
generations - it is in equilibrium.
Hardy-Weinberg problem
Allele T, for the ability to taste a particular chemical, is
dominant over allele t, for the inability to taste the chemical.
Four hundred university students were surveyed and 64 were
found to be nontasters. Calculate the genotypic percentage of
this population. Assume that the population is in H-W
equilibrium.
p+q=1
p2 + 2pq + q2 = 1
p+q=1
p2 + 2pq + q2 = 1
Calculate the percent of homozygotes recessive individuals
64/400 = 0.16 = or 16%
0.16 = tt = q2
q = √q2 = 0.4, which is the allele frequency of t
p + q = 1, so p= 1 – 0.4 = 0.6, which is the allele frequency of T
Homozygous (TT) = p2 = 0.62 = 0.36 or 36%
Heterozygote (Tt) = 2pq = 2(0.6)(0.4) = 0.48 or 48%
Homozygous (tt) = q2 = 0.42 = 0.16 or 16%
How do we determine evolutionary
relationships between species?
By drawing a cladogram or phylogenetic tree
Draw a phylogenetic tree based on the data
below. Draw hatch marks on the tree to indicate
the origin(s) of each of the 6 characters.
Answer: