In the city of Chicago, it is illegal to
speak English
It is illegal to mispronounce the
name “Joliet” while in Joliet, IL
In Peoria, IL it is illegal to give
cigarettes to a monkey
In Indiana, you may not watch while a man
wearing a striped shirt throws knives
It Utah, all husbands are responsible
for crimes committed by their wives
In Iowa, kisses may last up to but
not more than five minutes
Pennsylvania
• When driving, the man must run in front of the
car when the woman is driving, firing a rocket
every mile, phoning the chief of police when they
enter a town and disassembling the car and
hiding it under a bush should they pass a horse
Are there biological “laws” that you
cannot obey?
POPULATIONS DO NOT
HAVE TO EVOLVE
Neo-Darwinism
• Nature selects not only
for certain phenotypes,
but for the alleles that
produce those
phenotypes
• Populations whose
allele frequencies
change over time are
said to be evolving.
Gene Pool & Allele Frequency
• Gene Pool = all of the
different alleles in a
naturally reproducing
population
• Allele Frequency: the
% of a given allele
form for a trait
present in the gene
pool
Natural Selection & Alleles
• Since “selected”
individuals have higher
differential reproduction,
their alleles become more
frequent in the gene pool
• As a population shifts in
terms of allelic
frequencies, the
phenotypic frequency may
also change
Hardy-Weinberg Equilibrium
• If the allele frequencies
of a gene pool do not
change over time, the
gene pool does not
undergo evolution.
• KEY POINT: Individuals
DO NOT EVOLVE;
populations DO
Requirements of Populations At
Hardy-Weinberg Equilibrium
• No selective pressures (all must have
equal chance of surviving)
• No differential reproduction
• No mutations
• No immigration or emigration
• No changes in allele frequencies
Why don’t populations exhibit
Hardy-Weinberg Equilibrium?
Back In The Real World…
• Populations rarely
ever exhibit many of
the characteristics of
HW Equilibrium
• Mutations and
environmental change
are random
• Alleles that code for
adaptations may be
reduced to variations
in a new environment
Microevolution
• Most changes
in allele
frequency are
small and
occur over
long periods
of time
Sickle Cell Anemia
Genetics of Sickle Cell Anemia
• Sickled red blood corpuscles caused by
incompletely dominant allele (s).
• Individuals with ss genotype have terminal sickle
cell anemia
• Individuals with As genotype have sickle cell
anemia but do not die from the disease. In
addition, they will not contract Malaria
• Individuals with AA genotype do not have sickle
cell anemia, but will die from Malaria if infected
Setup
•
Obtain five (5) containers and label
1.
2.
3.
4.
5.
Population
AA non-sickle cell & non-Malarial
As sickle cell
ss sickle cell, terminal
Non-surviving Alleles
Place 150 white/red beans and 50 black beans in the
first container. These beads represent the
following alleles
-White or Red = A
Black = s
Natural Selection
• Have one partner randomly remove 2
beans at a time. These two alleles
represent an individual and their
phenotype/genotype.
• It will take 100 turns to apply the selective
pressure to each individual in the pop.
• For groups 4-6, apply the selective
pressure of Malaria of 40% (i.e. 40 of 100
turns)
Applying The Selective Pressures…
• If two white/red beans (AA) are selected
during a non-Malarial season, place both
beads in the first cup, representing
surviving alleles
• If two white/red beads (AA) are selected
during a Malarial season (Africa ONLY),
place both beans in the Non-Surviving
Container
• If two black beans (ss) are selected at any
time, place them in the fourth (“ss”) cup.
• If a white/red and a black are
simultaneously selected, place both beads
rd
Totaling The Survivors
• After 100 pairs of alleles have been selected, kill
off the “ss” terminal sickle cell alleles by pouring
cup #4 into cup #5
• Tally the number of white/red beans (A allele)
and the number of black beans (s allele) from
cups #2 & 3 combined
• Using the formulas in the lab (under data table
1), calculate the allele frequencies (i.e. how
many A or a alleles/total number of alleles in
survivors) for the A and s alleles
Successive Generations
• Take the surviving A and s alleles from cups 2 &
3 and recombine them in cup #1
• Repeat the selection process, pulling out pairs of
alleles/beans and applying the Malarial selective
pressure at the same 40% infection rate
(AFRICA ONLY).
• As in the first trial, discard the alleles for the nonsurviving and ss individuals (cups #4&5) and
tally the combined # of white/red (A) and black
(s) beads.
• Calculate the new allele frequencies using the
formulae under data table #2
• ADD SPACE IN YOUR DATA TABLE FOR A
THIRD and FOURTH TRIAL. Repeat this
process through four generations
CALCULATING & SHARING
• Calculate the allele frequencies for the
dominant (A) allele and the recessive (a)
allele for each generation.
• Share your data with the other side of the
room.
• Answer the analysis questions, citing
specific detail.
REPLACEMENT/ADDITIONAL
ANALYSIS QUESTIONS
• #4) Replace Birgus latro with Trinidadian
Guppies
• #6) Did the rate of change in either
population increase/decrease more
dramatically as you went through
successive generations? Why do you
think this was/was not happening?