Download Populations Close Notes Booklet - Morinville Community High School

Biology 30
Morinville Community
High School
Unit 6: Populations
Name: ______________
Populations Unit Outline
Key Concept A: Quantifying Gene Pools
A1. The Hardy Weinberg Equilibrium
Key Concept A: Quantifying Gene Pools
A1. The Hardy Weinberg Equilibrium
Key Concept B: Changes in a Gene Pool
B1. Hardy Weinberg Restrictions
B2. Founders & Bottleneck Effect
Key Concept C: Population Growth and Quantitative
analysis of populations
C1. Density & Population Distribution
C2. Population Growth & Growth Patterns
C3. Factors that Inhibit Growth: Density Dependent and
Density Independent Factors
C4. Life Strategies
Key Concept D: Population Interactions
D1. Intra and Interspecific Competition
D2. Predator Prey Relationships
D3. Defenses against consumers
D4. Symbiotic relationships
The Hardy-Weinberg formulas allow scientists to determine whether evolution
has occurred. Any changes in the gene frequencies in the population over time
can be detected. The law essentially states that if no evolution is occurring, then
an equilibrium of allele frequencies will remain in effect in each succeeding
generation of sexually reproducing individuals. In order for equilibrium to remain
in effect (i.e. that no evolution is occurring) then the following five conditions must
be met:
1.
2.
3.
4.
5.
There must be an infinitely large population
No migration of individuals into, or out of, the population.
Random mating must occur
No mutations can occur in the population
No natural selection can occur in the population
Obviously, the Hardy-Weinberg equilibrium cannot exist in real life. Some or all of
these types of forces all act on living populations at various times and evolution at
some level occurs in all living organisms. The Hardy-Weinberg formulas allow us
to detect some allele frequencies that change from generation to generation, thus
allowing a simplified method of quantifying genetic change.
Godfrey Hardy and Wilhelm Weinberg developed the following formula based on
patterns of genetic inheritance:
Key Concept E: Succession
E1. Primary & Secondary Succession
E2. Pioneer and Climax Communities
E2. Species Richness vs. Biomass
p2 + 2pq + q2 = 1
What do each of the terms represent in this equation?
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p = frequency of ____________________________ individuals
2pq = frequency of ___________________________ individuals
2
q = frequency of ____________________________ individuals
and…
p = frequency of the ______________________ allele
q = frequency of the ______________________ allele
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2. Sickle-cell anemia is an interesting genetic disease. Normal homozygous
individuals (AA) have normal blood cells that are easily infected with the
malarial parasite. Thus, many of these individuals become very ill from the
parasite and many die. Individuals homozygous for the sickle-cell trait (aa) have
red blood cells that readily collapse when deoxygenated. Although malaria
cannot grow in these red blood cells, individuals often die because of the genetic
defect. However, individuals with the heterozygous condition (Aa) have some
sickling of red blood cells, but generally not enough to cause mortality. In
addition, malaria cannot survive well within these "partially defective" red blood
cells. Thus, in Africa heterozygotes tend to survive better than either of the
homozygous conditions. If 9% of an African population is born with a severe
form of sickle-cell anemia (aa), what percentage of the population will be more
resistant to malaria because they are heterozygous (Aa) for the sickle-cell gene?
Hardy Weinberg Principle Practice Questions
1. You have sampled a population in which you know that the
percentage of the homozygous recessive genotype (aa) is 36%. Using
that 36%, calculate the following:
a) The frequency of the “aa” genotype: __________
b) The frequency of the "a" allele: __________
c) The frequency of the "A" allele. __________
d) The frequencies of the genotypes "AA" and "Aa."
AA: ________ Aa: ________
e) The frequencies of the two possible phenotypes if "A" is brown and
“a” is white.
Brown: __________
White: _________
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Hardy Weinberg Principle Practice Questions
3. Hip dysplasia is an autosomal recessive condition that affects 60% of
golden retrievers. Calculate
a)
the frequency of the recessive allele.
b)
the frequency of the dominant allele.
c)
the frequency of heterozygous individuals.
d)
the frequency of the homozygous dominant individuals
4. Within a population of butterflies, the color brown (B) is dominant
over the color white (b). And, 40% of all butterflies are white. Given
this simple information, which is something that is very likely to be on
an exam, calculate the following:
6. Cystic fibrosis is a recessive condition that affects about 1 in 2,500 babies in
the Caucasian population of the United States. Please calculate the following.
a)
The frequency of the recessive allele in the population.
b)
The frequency of the dominant allele in the population.
c)
The percentage of heterozygous individuals (carriers) in the population.
7. Huntington’s disease is an autosomal dominant disorder that affects 6.3
people per 100,000. Given this information, calculate the approximate number
of carriers per 1,000 people.
a) The percentage of butterflies in the population that are
heterozygous.
b)
The frequency of homozygous dominant individuals.
8. The ability to taste PTC is due to a single dominate allele "T". You sampled
300 individuals at MCHS, and determined that 273 could detect the bitter taste
of PTC and 27 could not. Calculate all of the genotype & allele frequencies.
5. A very large population of randomly-mating laboratory mice
contains 35% white mice. White coloring is caused by the double
recessive genotype, "aa". Calculate allelic and genotypic frequencies
for this population.
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9. After graduation, you and 19 of your closest, none of which have
cystic fibrosis, charter a plane to go on a round-the-world tour.
Unfortunately, you all crash land (safely) on a deserted island. No one
finds you and you start a new population totally isolated from the rest
of the world. Two of your friends carry (i.e. are heterozygous for) the
recessive cystic fibrosis allele (f). Assuming that the frequency of this
allele does not change as the population grows, what will be the
incidence of cystic fibrosis on your island? Are there different answers
for this question? What does this scenario teach you about the
“theoretical” Hardy Weinberg model?
Key Concept B: Changes in a Gene Pool
B1. Hardy Weinberg Restrictions
The Hardy Weinberg formula only functions when 5 conditions or
parameters are upheld:
1. Larger populations are less likely to have significant changes in allele
frequencies. Small populations on the other hand may experience
genetic drift.
Genetic Drift:
10. What allelic frequency will generate twice as many recessive
homozygotes as heterozygotes? Show your proof to Mr. Malanchen
and see if he’ll give you a sucker of success.
2. The absence of migrations prevents a gene pool from changing.
Migration however can lead to gene flow.
Gene Flow:
3. If there are no mutations, there can be no new alleles or change in
alleles among individuals. If there are mutations however, than the allele
frequencies will change.
4. Natural selection increases the frequency of alleles that provide an
advantage and decrease the frequency of alleles that provide a
disadvantage.
5. Random mating ensure that each allele has an equal likelihood of
being passed on. Non-random mating on the other hand will favour
certain traits to be passed on instead of others.
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B2. Founders & Bottleneck Effect
Key Concept C: Population Growth and
Quantitative Analysis of Populations
Founders Effect:
C1. Density and Population Distributions
Density can be calculated using either of these two formulas:
Ex:
Dp =
Bottleneck Effect:
Where
N
A
or
Dp =
Dp
=
population density
N
=
population size
A, V =
area or volume
!
N
V
!
Ex:
Examples:
1. There is population of Morinville is estimated to be 7300. Morinvilleʼs
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estimated area is 10.6 km . Calculate Morinvilleʼs population density.
2. There are 5 fish in a 40 gallon aquarium. What is the population
density of the aquarium?
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Populations may be clustered in 3 main types of distribution
patterns:
Population growth growth rates can also be calculated using the following
two formulas:
Random Population Distribution:
gr =
Ex.
Where
!
Uniform Population Distribution:
Ex.
Clumped Population Distribution:
Ex.
"N
t
or
cgr =
"N
N
gr
=
growth rate
cgr
=
per
!capita growth rate
t
=
time (months, years etc)
"N =
change in population size
N
Initial population size
=
!
Examples
1. In 1980, the number of elephants in Kruger National Park (Africa) was
estimated to be 7,454. In 1999, it was estimated that population had
grown to 9,152 elephants.
What is the growth rate?
C2. Population Growth & Growth Patterns
There are four factors that you must take into consideration
when determining population growth / decline: births (B), deaths
(D), immigrations (I), and emigrations (E).
Write a formula for population growth using the terms above:
"N =
!
What is the per capita growth rate?
2. Albertaʼs woodland caribou population has steadily been declining due
to logging practices and loss of habitat. It was estimated that there were
9,000 caribou in Alberta in 1965 and an estimate from 2005 shows this
number has dropped to 3,000.
What is the growth rate?
What is the per capita growth rate?
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Growth rates & patterns usually follow one of two basic curves:
1. Exponential (J-Shaped) Growth Curve:
C3. Factors that Inhibit Growth: Density Dependant and
Density Independent Factors
Examples of Density Dependant factors that limit growth:
Examples of Density Independent factors that limit growth:
2. Logistic (S-Shaped) Growth Curve
C4. Life Strategies
Two factors govern the type of population growth a particular species will
exhibit:
Biotic Potential (r):
Lag Phase:
Carrying Capacity (k):
Carrying Capacity (k):
Environmental Resistance:
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Key Concept D: Population Interactions
Generally, organisms can be classified into one of two types of
life strategies depending on their growth and population patterns:
r-Strategists
k-Strategists
D1. Intra and Interspecific Competition
Intraspecific competition:
Interspecific competition:
D2. Predator-Prey relationships
Generally predator & prey populations follow a cyclic pattern:
Predators have evolved several adaptations to help them catch their
prey:
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D3. Defense against consumers & avoidance
mechanisms.
Mechanical Defense Ex:
Camouflage Ex:
Key Concept E: Succession
E1. Primary and Secondary Succession
Primary Succession:
Group Defense Ex:
Chemical Defense Ex:
Warning Colouration Ex:
Batesian Mimicry Ex:
Mullerian Mimicry Ex:
Secondary Succession:
D4. Symbiotic Relationships
Mutualism:
Ex:
Commensalism:
Ex:
Parasitism:
Ex:
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E2. Pioneer vs. Climax Species
E3. Species Richness vs. Biomass
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