Homework two. 2016 Questions one, five, seven and eight are to
be handed in as written proof that you did the homework. All
questions will be discussed in class this week.
A classic example of natural selection:
1: Please read the paper on industrial melanism.
a. State Kettlewell’s Hypothesis
b. List the different ways Kettlewell tested his hypotheses
c. Determine which type of evidence, frequency distributions
(correlations), mark-recapture work, experiments on
predation or modeling you feel best supports Kettlewell
hypothesis. Justify your answer.
2. Go to the following website:
http://www.hhmi.org/biointeractive/making-fittest-natural-selectionhumans
a. What is sickle cell anemia?
b. How was the correlation between sickle cell and malaria
deduced?
c. What does the sickle cell mutation tell us about how natural
selection works?
d. The union of genetics and evolutionary theory has been
termed the grand synthesis. Can you use the story of sickle
cell anemia to illustrate why this term is appropriate for this
union?
A bit on correlation
To examine medicine with an evolutionary focus requires a good
understanding of trend analysis and the comparative method. We will
do more on the comparative method under the topic of phylogeny.
Many studies in evolutionary medicine will relay on correlations rather
than experimentation.
The experiment has long been accepted as a way to gather evidence
for or against hypothesis. Yet often it is impossible to conduct the
appropriate experiments to examine major evolutionary questions.
Making more observations has always been a legitimate way of
testing scientific hypotheses.
Example: Every time the sun sets in the west and rises in the east I
am more convinced that it will continue to do so. (reason for the sun
rising----http://www.universetoday.com/18117/why-does-the-sun-risein-the-east-and-set-in-the-west/)
Correlations are trends, collections of observations, measured by the
tightness of fit between two variables. Statistics is often used to
determine how closely data points fit to a straight line drawn between
them (linear regression).
Three relationships with the same slope, but different amounts of
“scatter” around an imagined best fit line.
Lately non-experimental science has been dubbed discovery science.
This seems a humble name for methods that have given use major
theories in biology such as "the cell theory" and "the grand synthesis
or evolutionary theory".
3. Dr. Snow used observations and correlations to determine
the cause of cholera.
An observation based on interviews and city medical records.
"The most terrible outbreak of cholera which ever occurred in this
kingdom, is probably that which took place in Broad Street, Golden
Square, and the adjoining streets, a few weeks ago. Within two
hundred and fifty yards of the spot where Cambridge Street joins
Broad Street, there were upwards of five hundred fatal attacks of
cholera in ten days. The mortality in this limited area probably equals
any that was ever caused in this country, even by the plague: and it
was much more sudden, as the greater number of cases terminated
in a few hours.
The mortality would undoubtedly have been much greater had it not
been for the flight of the population. Persons in furnished lodgings left
first, then other lodgers went away, leaving their furniture to be sent
for when they could meet with a place to put it in."
A correlative map put together by Snow.
a. How do you think Snow used observation and mapping to
pinpoint the source of cholera.
b. Read the following passage from Snow's work. Why did
Snow feel it important to investigate individuals in the area of the
outbreak that did not get cholera?
“There are certain circumstances bearing on the subject of this
outbreak of cholera which require to be mentioned. The Workhouse
in Poland Street is more than three-fourths surrounded by houses in
which deaths from cholera occurred, yet out of five hundred and
thirty-five inmates only five died of cholera. . . . The workhouse has a
pump-well on the premises, in addition to the supply from the Grand
Junction Water Works, and the inmates never sent to Broad Street for
water. If the mortality in the workhouse had been equal to that in the
streets immediately surrounding it on three sides, upwards of one
hundred persons would have died. “
“ There is a Brewery in Broad Street, near to the pump, and on
perceiving that no brewer's men were registered as having died of
cholera, I called on Mr. Huggins, the proprietor. He informed me that
there were above seventy workmen employed in the brewery, and
that none of them had suffered from cholera--at least in a severe
form--only two having been indisposed, and that not seriously, at the
time the disease prevailed. “
“ The men are allowed a certain quantity of malt liquor, and Mr.
Huggins believes they do not drink water at all; and he is quite certain
that the work-men never obtained water from the pump in the street.
There is a deep well in the brewery, in addition to the New River
water. “
4. More recent examples of natural selection in action:
a, Examine the examples on this web site. Briefly explain why the
first two examples are good examples of natural selection directing
the changes observed.
http://evolution.berkeley.edu/evolibrary/article/microexamples_01
b. Carl Bergstrom’s work on modeling antibiotic resistance
http://evolution.berkeley.edu/evolibrary/article/0_0_0/bergstrom_03
to
http://evolution.berkeley.edu/evolibrary/article/0_0_0/bergstrom_05
More on genetic drift:
5. Examine the examples on these two websites.
http://evolution.berkeley.edu/evolibrary/article/samplingerror_01
and
http://evolution.berkeley.edu/evolibrary/article/bottlenecks_01
Briefly compare founder effects to bottlenecks.
6. Go to following site for Huntington’s chorea.
http://evolution.berkeley.edu/evolibrary/article/medicine_05
Why is Huntington’s chorea so prevalent in the lake
Maracaibo community? You should consider all
evolutionary factors that affect the persistence of this
disease.
7. A simulation on genetic drift.
Please visit these web pages and answer questions 7a and 7b. 7a
http://pages.ucsd.edu/~dkjordan/resources/clarifications/Mitochondria
lEve.html
and
7b
http://www.cals.ncsu.edu/gn/ex/mit-eve.html
a. Who is mitochondrial eve?
b. Run the simulation 5 times until only one Eve remains. What is
the smallest number of generations it took to fix mitochondrial type?
What was the longest number of generations it took to fix
mitochondrial type?
8, Go to
http://evolution.berkeley.edu/evolibrary/news/131211_bottlenecks
a. What can evolutionary history tell us about the evolution of the
BRCA gene?
b. Read an article expression an alternate explanation. You must
download it from the web. The link is on the course schedule. Try
simply to understand the hypothesis and how the authors tested it.
Assume the authors use of statistics is legitimate, although we may
ask Dr. Thorne’s opinion of their methods.
c. Which explanation in your mind is best supported by the evidence
presented?