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Study Questions #2


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A Population of 2000 moths has the following geno freq: aa: 0.16
Aa: 0.04
AA: 0.80
Q) What is the freq of the a allele in this pop?
#a in aa =(2)(0.16)(N)=0.32N
#a in Aa =(1)(0.04)(N)=0.04N
Total #a allele = 0.36N

#A in AA = (2)(0.8)(N)=1.60N
#A in Aa =(1)(0.04)(N)=0.04N
Total #A alleles = 1.64N

So, f(a) = 0.36N/2N= 0.18 = q
and f(A) = 1.64N/2N= 0.82 = p
CHECK: 0.82 + 0.18 = 1.0 ,yes
so, f(a) = 0.18
Is the pop in HW? NO
0.18 x 0.18 = 0.324 =/ 0.16
If f(C) = p = 0.2
Q) what will the f(Cc) be?
If f(C) = 0.2 = p
then 0.2 + q = 1.0
So, q = 0.8
So, f(Cc) = (2)(p)(q)
f(Cc)=(2)(0.2)(0.8) = 0.32
If positive assortive mating is going on in a population, then what condition under the Hardy-Weinberg Equil would you expect a change in?
the genotypic frequencies, b/c Positive assortive mating mean Green-Green & Yellow-Yellow. The Gg freq will be fewer and the gg genotype will increase, but the # of g alleles or their freq won't change. So, the Gg reduces and the g's are later located in the gg phenotypes
Imagine a pop of birds living on an island near the mainland. If 6 birds from the mainland JOIN the island pop, which assumption of HW will be violated?
NO Migration/No GENE FLOW
If a population of condors was reduced to 13 birds and it then recovered to a normal pop, what differences would you expect to see between the initial large pop and the recovering pop of condors, IN TERMS OF NUMBERS OF ALLELES PER LOCUS?
B/C of the BOTTLENECK, the pop has lost some alleles at many loci. The modern pop would have a smaller number of alleles per locus. Overall, alelic freq will have changed.
What PROCESS are we concerned about in the condor example?
GENETIC DRIFT, this change in allele freq is not "DIRECTED"; it is due to chance and to sampling bias, the essence of genetic drift
Which ASSUMPTION of HW Equil is being violated when a pop goes through a bottleneck?
If the California condors choose to mate on the basis of tail length, which ASSUMPTION of HW equil would be violated?
A plant species has flowers in 3 colors - red, white and pink. Color is controlled by a single gene w/2 codominant alleles. Pollination is done by bees that prefer pink flowers. You are going to estimate the genotypic & allelic freq in the flower pop
HETEROZYGOTES have a higher relative fitness than other genotypes.
Positive assortative mating affects . . .?
affects genotypic freq, but not allele freq
General Formulas:
I) When you know the true allele freq:
If f(Y) = p & f(y) = q, then p+q=1.0 and
f(YY) = p^2
f(yy) = q^2
f(Yy) = 2pq

II) whne you know Genotypic Freq & that the pop is in HW, Large pop, then <
Potential VIOLATIONS of HW conditions:
Large Pop Size
freq = occurances-potential
So, Freq. vs. Probability (in the end these 2 mean the same thing)
** If & when you have a small sample size, then the freq. =/= prob. on every occasion
Potential VIOLATIONS of HW conditions:
Give 3 cases where Genetic Drift is likely to cause changes in allele freq?
a) when pop size is too small
b) when pop. bottlenecks, this means that when a large pop reduces and then recovers w/little diversity in alllelic freq. Ex. Northern elephant Seal pop about 30,000, hunted down to 20 and then recovered, leaving a small allele freq
c) Founder Effect or Founder Event occurs- a small # of indiv from one pop establishes a new pop. The allele freq from the parent pop tends to differ when a separation occurs & a new allele freq/ pop develops.
Potential VIOLATIONS of HW conditions:
Random Mating
A) Assortative mating - mates are chosen on the basis of some phenotypic trait, verses randomly
POSITIVE- selecting the same mate b/c they have the same phenotype as you
POSITIVE- changes Gen.Freq, but NOT Allelic Freq
NEGATIVE- mating w/someone w/a different phenotype
NEGATIVE- changes both, b/c some allelic freq are unable to mate at all
b) SELF FERILIZATION-happens in plants and some animals
Self Fert. doesn't produce identicle offspring since it is w/in your self. This does ALTER Gen. Freq, NOT Allelic Freq.
Ex. Hh x Hh -> 1HH:2Hh:1hh
HH x HH -> all HH
heterozygote deficiency happens from above.
Potential VIOLATIONS of HW conditions:
CLosed Population.
If you do have Gene Flow, then there is an increase in the freq of my alleles in this new pop
Potential VIOLATIONS of HW conditions:
They occur at low rates
Potential VIOLATIONS of HW conditions:
NO Advantages to individuals carrying particular alleles
Alleles carry your phenotypes

** This is the assumption that is MOST OFTEN VIOLATED & is likely to have caused the changes you have seen
Define: Fundamental Asymmetry of Sex
Women select a mate & males compete for mating
3 key observations to women choosing a mate
1) bright colored feathers
2) long tails
3) specific mating dance or rituals are done right
4) beak color is bright from caratenoid, which means the bird is a healthy eater and has a strong immune system
a group of organisms that are related to each other by a descent from a common ancestor, sometime known as a blob of alleles represented by everyone that was once alive at one point.
is best defined by the Biological Species Concept, which is a species of group of naturally or potentially interbreeding pop. that are reproductively isolated from other such groups.
Name 4 Mechanisms that shift allele freq in populations
1) Natural Selection
2) Genetic Drift
3) Gene Flow
4) Mutation
Natural Selection
The process by which indiv w/certain heritable traits tend to produce more survivng offspring than do indiv w/out those traits, resulting in a change in the genetic make-up of the pop
* A major mechanism of evolution
** Natural Sel increases the freq of certain alleles - the ones that contribute to improve reproductive success
Genetic Drift
The LARGER the pop the longer the genetic drift to Fixation or Lost
Gene Flow
The movement of alleles between populations

* Gene Flow occurs when indiv immigrate into (enter) or emigrate from (leave) a population. Allele freq may change when gene flow occurs, b/c arriving indiv introduce alleles to their new population and emigrating indiv remove alleles from their old pop.
Any change in the heriditary material of an organism (DNA in most orgoanisms, RNA in some viruses)
* Mutation modifies allele freq by continually introducing new alleles. The alleles created by mutation may be beneficial, detrimental, or have no effect on fitness.
Name the 3 criteria for identifying species that are in common use:
1) The Biological Species Concept
2) The Morphospecies Concept
3) The Phylogenetics Species Concept
Biological Species Concept
The concept that species are best identified as groups that area reproductively isolated from each other; thus, different species cannot cross breed in nature to produce viable and fertile hybrid offspring
Morphospecies Concept
The concept that species are best idnetified as groups that have measurably different snatomical features
Phylogenetic Species Concept
HAS 2 distinct advantages:
1) It can be applied to any pop (fossil, asexual, sexual)
2) It is logical, b/c pop are mono-phyletic only if they are independent of one another and isolated from gene flow
** The concept that species are best identified as the smallest mono-phyletic group in a PHYLOGENETIC TREE, which is a diagram that depicts the evolutionary history of a group of organisms
Name the 4 possible fates of a lineage over time
1) statis
2) anagenesis
3) extinction
4) cladogenesis
this happens due to reproductive isolation & subsequent divergence
Name the 3 mechanisms of Cladogenesis?
1) allopatric speciation
2) parapatric speciation
3) sympatric speciation
Allopatric Speciation
allopatric pop have non-overlapping ranges, this says that these 2 or more pop living in differnt areas mix their genes until something divides one of two or all pop from one another
** For cladogenesis to happen then ALLOPATRIC Speciation has occurred.
Ex. Galapagos Island Finch Pop. is an evample of a Founder Event for genetic drift to happen and Adaptation, which overall lead to 14 different speciese of finches.
adjacent but non-overlapping ranges, what prevents them from breeding is b/c they become adapted to separate locations but they do NOT trade genes
*EX: Pop A & Pop B belong to a group of Species I, these two groups can ONLY breed w/themselves NOT each other. Pop A lives in the meadow & Pop B is tolerant to the heavy metals from this mine.
When Species I breeds with those from another Species II, the Gene Flow STOPS HERE.
Sympatric Speciation
Sym Pop have overlapping ranges, but due to specialization on different resources w/in same habitat one fashion specialized on one resource and the other fashion specailized on another resource
EX: Fruit maggots, some like Hawthorn fuit and others apples.
1) Fruit maggots life cycle is completed on the fruit
2) Some fruit maggots shift apples & stay
3) gene flow stops between sympatric pop and this leads to genetic divergense & speciation, for they do not share the same fertilization cycle, for one fruit maggot lays their eggs on apples in about 40 days and the other lays their eggs on Hawthorne fruit in about 55-60 days.
** In an infinitely LARGE POP, there should be NO GENETIC DRIFT, but there are some chance changes in the Frequencies.
Genetic Drift:
Q) How big must a pop be to maintain the Hardy-Wein Eq?
A) about 10,000
Selective Simulation: In the peppered moth example did either the A or a allele ever go to fixation? If not, why?
Yes, every time when the aa was ... look up
What is the heterozygote advantage, and how does it help maintain genetic diversity in a pop?
Heterozygous genotype has highest relative fitness

e.g. sickle-cell anemia: if Hb^s/Hb^s- homozygpus recessive for sickled erythrocytes, then these get stuck in your blood and the cells cannot work properly & then it shuts down & you die
** If Hb^A/Hb^A- homozygous dominant for normal RBC- then these people may die from Malaria
*** If Hb^A/Hb^s-heterozygous, which has both forms of hemoglobin and it is NOT likely to die from either disease, which is a PLUS...
Extant taxa
whatever is at the TOP is the extant taxa, thus meaning that it is the only species still alive
What is an Outgroup?
It is distantly related to the taxaof interest and it tells us about the ancestral states of character...

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