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Study Questions #1


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Explain the 4 conditions required for evolution as a result of selection
I) Individuals vary w/respect to phenotypic traits
II) Offspring phenotypes resemble those of their parents (traits have a genetic basis, or are heritable).
III) Overproduction of offspring leads to a struggle for existence. "In a pop., typically more offspring are produced than can survive long enough to reproduce themselves b/c the resources necessary for survival and reproduction, s/a food, water and space, usually are limited. Since there are not enough resources to support everyone, the various members of the pop. compete for the resources necessary to stay alive and to have their own offspring
IV) Diffferent phenotypes exhibit differential survival & reproduction; "fitness MUST vary among individuals for Nat. Sel. to operate. This is b/c recources are limited, and in the struggle for existence certain phenotypes are more likely to survive & leave offsprin. Likewise, certain phenotypes are more likely to be detected &/or captured by predators than other phenotypes.
Directional Selection
occurs when Nat. Sel. favors phenotypes at one end of the distribution of all the possible phenotypes (imagine a bell curve, and selection favors survival & reproduction among individuals whose phenotypes fall at one of the tail ends of the distribution). Since the individuals w/the phenotype that gives them the highest relative fitness survive & pass their genes on, over gen. the entire distribution shifts in one direction.
Stabilizing Selection
occurs when Nat. Sel favors phenotypes in the center of the distribution (i.e., whose phenotypes fall at the center of the bell curve. The average phenotype is favored rather than either phenoype at the extreme tail ends of the distribution).
Disruptive/diversifying Selection
is a form of Nat. Sel. in which the mean phentype has the lowest fitness. (In this case, both tail ends of hte distribution have a higher fitness to the average phenotype. This causes the average phenotype to decrease in freq, and the phenotypes associated w/the tail ends of the bell curve become more common.
Characterize each as Directional or Stabilizing Selection:
a) peppered moth
b) sickle-cell anemia
c) eyespots on peacock tail
d) antibiotic cells in TB bacteria
e) human birth weight prior to 1900
a) peppered moth - direct
b) sickle-cell - stabil
c) peacocks tail - direct as a result of sexual selection
d) antibiotic TB - direct favoring proteins not affected by antibiotics
e) human birth weight - stab
What do you need to show in order to develop a sucessful breeding program of mustard plants to investors?
1) you need to show that the desired trait has a genetic basis and is an inheritable character that can be passed from parent to offspring. The step showing if the character in inheritable is to let the plant produce seeds, then grow the seeds in a controlled environment to see if the offspring in the next gen. resemble the parents. If they do, you would select the plants w/the best flavor that "BREED TRUE". you then would collect enough seeds to produce a large pop. of plants, and you would be on your way to developing a new mustard.
What kind of selection would a lizard egg eating snake impose on lizard egg size?
Directional Selection, favoring larger lizard egg sizes. So, the average egg size may increase, b/c large eggs are less likely to be eaten by snakes than are small eggs. If the survivorship of large eggs is higher, and egg size in inheritable, then you would expect the frequency of females who lay larger eggs to increase in the pop., over many gen.
Suppose the female lizards become egg bound and die when the egg size in larger than 3.5 cm in diameter, what type of selection would there be on egg size in lizards?
Stabilizing Selection would be imposed b/c smaller egg sizes are eaten and larger egg sizes injure of kill the mothers
Assume the gape size is a heritable character for snakes. What might be happen if these two coexist over a long period of time?
The snake gape size over a long period of time would likely increase.
Pesticides on Farm A vs. Farm B:
** What kind of selection force (directional, stabilizing, disruptive) do you think the pesticide represented for the larval moth pop in Farm B, resistant pop?
Strong Directional Selection for moth larvae resistant to this particular pesticide
Pesticides on Farm A vs. Farm B:
** From this example, what would you predict about heritability of pesticide resistance in this species of moth?
Pesticide resistance may be a highly heritable character
Pesticides on Farm A vs. Farm B:
** If there were no Nat. variation for pesticide resistance in the moth pop., would you expect the same response? Explain.
No, if there were no variation for pesticide resistance, all tha moths on Farm B would have dies, and htere would have been no phenotypic change in response to selection
Pesticides on Farm A vs. Farm B:
** Moth larvae grow up into adults, and adult moths can fly long distances. If adult moths flew from Farm B to Farm A, should Farm A worry, if so, what should Farm A worry about?
YES, Farm A should worry, b/c the Farm B moths could mate w/the moths on Farm A and introduce the pesticide resistant alleles to Farm A. B/C Farm A applied the pesticide very sparingly, and Farm A didn't select strongly for pesticide resistance, if the Farm B moth migrated to Farm A, then Farm A should worry about the GENE FLOW of pesticide residence increasing on their farm
Bacteria live almost everywhere, what would happen to the pop if a anti-bacterial guarantees to kill 99.9% of these bacteria:
1) What will happen to the bacteria pop size first?
2) Which bacteria will survive and produce offspring?
3) Why
1) The pop size will be reduced by 99.9%
2) 100% of the surviving tiny pop will reproduce the resistance trait
3) The bacteria will be entirely immuned to this cleanser.
4) They use different cleansers b/c each cleanser kills some part of the pop, but b/c the agent of selection shifts continually the bacteria are not pushed toward resistance to any one cleanser. The pop will consist of many different genotypes, some of which will be vulnerable to each cleanser. It will be possible to reduce the bacteria pop size w/out putting the pop under strong directional selection.
Genetic variation among the individuals in a population arises by:
** List two ways that genetic varaition ARISES in a population?
a) Sexual reproduction (new combinations of genes occur in offspring).
b) Mutation (at several levels: genetic loci, chromosomes, etc).
c) Independent assortment (as part of sexual reproduction, it allows new genetic combinations in gametes).
d) cross over,recombination, during gamete formation makes new combinations of genes w/in chromosomes
Genetic variation can be MAINTAINED in a pop if:
** List two ways that genetic variation is MAINTAINED in a population?
a) selection favors different phenotypes at different tiems
b) assortative mating occurs (positive assortative mating = individuals w/the same phenotype mate w/each other, e.g., in a pop/ w/red & blue individuals, a red individual mates w/ another red; negative assortative mating = individuals mate w/a different phenotype, e.g., a red individual mates w/a blue).
c) environments are heterogeneous
d) there is a freq-dependent selection. (This means that whichever phenotype is more prevalent is selected against. For example, a phen is preyed upon more than another one season and then the other the next, this is an example of how GENETIC VARIATION remains in a perticular pop.
e) there is NO strong selection favoring any particular phenotype
Genetic variation can be INTRODUCED into a population via:
** List two ways that genetic variation can be INTRODUCED INTO a population?
a) GENE FLOW as a result of immigration of indiv. or dispersal of gametes (e.g. wind-blown pollen).
Using Hybridized seeds to farm the 1st year have high vegetable results, but if you use tradition methods of generating seeds, why do the vegetables produce less?
Hybrids produced by crossing 2 different homozygous paranta strains are heterozygous at many different loci. these heterozygous indiv at many loci are more vigorous than homoztgous indiv at many loci. However, if Hybrids cross (mate) in the field, many of their offspring will be homozygous at some loci. (For example, if AABBBCC parent strain crossed w/a aabbcc parent strain and then HYBRID OFFSPRING randomly mated w/one another, 1/2 of the offspring gen would be homozygous at each locus, this is an Ex. of Mendelian genetics. If the Hybrid plants grew well b/c they were heterozygotic at many different loci, then crosses BETWEEN HYBRIDS as a result of traditional farming methods will produce lower yields than were obtained from planting the pure hybrid seeds. The offspring of a cross BETWEEN HYBRIDS will be extremely varialbe (tall or short, thick stems of thin stems, flower early or late, cold tolerant of heat tolerant, etc) many will not do well.
DEFINE, 'agent of selection'
An Agent of Selection is a factor that favors one phenotype over other phenotypes in the same pop. In other words, it is the reason why one phenotype has higher reproductive success than other phenotypes.
Identify the agent of selection in each of the following examples:
a) changes in color in peppered moths
b) eyespots in peacocks tails
c) large body size in male elephant seals
a) Birds. Peppered moths that don't match their background suffer higher mortality b/c they are more conspicuous to avian predators
b) Female Peacocks. Females choose males w/moer eyespots, leading to higher mating success for males w/elaborate tails
c) Male Elephant Seals. Fights between males favored large mael body size, b/c large males won fights, and b/c the winners of male fights gained access to groups of females. (This will some up in class eventually)
Lizard eat birds, eggs, and small lizards and some eat toads. When poisonous toads were introduced to the population of toads, the lizard pop reduced,b ut recovered quickly.
** DESCRIBE the 4 conditions necessary for Nat. Sel. to act in this case a
a) Phenotypes vary: some lizards prefer to eat toads and other do not
b) PHENOTYPIC VARIATION is HERITABLE or has a GENETIC BASIS. Here we muct assume that preference for or dislike of toads as a food source is a HERITABLE character
c) OVERPRODUCTION of OFFSPRING. This condition typically is satisfied in nature, thus resulting in competition among individuals for resources that almost always are limited under natural conditions
d) PHENOTYPIC VARIATION results in differential survival and reproduction. Here, those lizards that did not like to eat toads had a higher relative fitness than those that did eat toads. The non-toad eaters left more offspring than those that preferred toads (most of these lizards died), and the genes for non-toad-eating spread in the population
Nmae factors that Limits Population Sizes
catastrophies, natural disasters, diseases, competition, predators, food & water supply, as well as shelter
Give an example of how Nat. Sel. operated by favoring individuals w/certain phenotypes over others
Ex. rabbits who have long legs have a better chance of escaping predators & passing on their traits to their offspring, across gen. this beneficial trait becomes more common in the pop
What are some KEY POINTS to Nat. Sel.
I) It operates on an individual basis
II) any trait that increases your relative fitness will be promoted by Nat. Sel.
III) results of Nat. Sel. are seen at the pop level
IV) Nat. Sel. ONLY operates on EXISTING variability
V) Nat. Sel. leads to ADAPTATION, this only makes sense in local environment
having multiple alleles of a gene within a population, usually expressing different phenotypes
Examples of Nat. Sel
peppered moth, in the 1800 was grey, but by the 1900 the pop was mostly black, b/c an agent of selection, birds, w/out the change in phenotype the pop might have been eliminated by the birds
What are the 3 forms of Natural Selection?
Give an example of:
a) Directional Selection
b) Stabilizing Selection
c) Disruptive Selection
a) elephant seals weight/larger size = more seals w/a higher relative fitness
b) human birth weight/mortality
c) African Seed-cracker finches bill size/seed size
Name the two types of TISSUE we have covered?
I) Epithilial Tissue - has three shapes of cells
a) squamous cells, which are flat and elongated
b) Cuboidal Cells, which are box shaped
c) Columnar Cells, which are tall cells
** Stratified is multiple layers of cells, an example, an area of squamous, cuboidal and columnar cells in stacked ontop of one another
Name all types of Connective Tissue?
I) Loose connective tissue
II) Dense fibrous connective tissue
III) Adipose Tissue
IV) Hyaline cartilage
V) Bone
VI) Blood
What is, Loose Connective Tissue?
it is a matrix of loosely packed COLLAGENOUS FIBERS and ELASTIC FIBERS (both made of protein), embedded in gelatinous GROUND SUNSTANCE. The darkly stained cells are the nucleus of FIBROBLAST cells, which they secrete the matrix described above.
it is a matrix of densely packed collagenous fibers, w/little ground substance. The parallel rows of cells are the NUCLEI of FIBROBLASTS, they are squeezed between the bundles of fibers
adipocyte = tightly packed cells that store fats w/in fat vacuoles. A close up of an adipocyte has an outer PLASMA MEMBRANE, the middle location is the FAT VACUOLE and located on the outside is the NUCLEUS
What is, Hyaline Tissue?
it is a connective tissue, matrix of COLLAGENOUS FIBERS and Chondrin (gelatinous ground substance), secreted by chondrocytes
The cells w/in are the LUCANAE = small cavity that contains chondrocytes
CHONDROCYTES = cells that secrete the matrix (the nucleus is stained in the center)
What is, BONE?
it is a connective tissue, HAVERSIAN CANAL is located in the CENTER and it holds blood vessels & nerves that supply the bone
LAMELLAE is a bony matrix of concentric rings around the HAVERIAN CANAL
LACUNAE is the outer most part of the cell, they house the OSTEOCYTES which are the cells that lay down the bony matrix.
CANALICULI are perpendicular tiny canals connecting osteocytes to each other & to the HAVERSIAN CANAL
What is, BLOOD?
it is a connective tissue, that has two types:
I) Erthrocytes (red blood cells, RBC), which are smaller in size
II) Leucocytes (white blood cells), much larger than RBC
a group of individuals w/in a species that breed w/each other
any genetic change in allele freq & resulting phenotypic change in a pop of organisms from one gen to the next (NO CHANGE = NO EVOLUTION)
how often an event occured divided by the the total # of possible occurences,
(#Occurred)/(Total # Possible in Occurances)
goals is to understand changes in (allelic & genotypic) freq from one gen to the next
What are the 5 conditions in the Hardy-Weinberg Equil that specify when evolution should NOT occur if in HW?
I) Pop. size is LARGE
II) Mating is RANDOM w/ regards to the phenotypic trait (NO PREFERENCE to color, shape, size or dances)
III) NO GENE FLOW (closed/ discrete pop, this keeps the alleles from changing)
IV) MUTATIONS are in equilibrium (*the likely hood of allele R->r or r->R
V) NO ADVANTAGE to individuals carrying particular alleles at a given locus
(** PHENOTYPES do not declare whether you live or die or reproduce)
any observable trait of an individual, color, height, weight, etc
All of the alleles of every gene present in a given individual, (Ex. YY, Yy, yy)
Having one set of chromosomes. (Symbolized by N) Ex. animal gametes
with two sets of chromosomes (Symbolized by 2N) Ex. most animals and many plants
is a cell or organism that carries two identicle copies of a specific gene for a given trait on two corresponding chromosomes. These cells are diploid or polyploidy and have the same alleles at a locus (center position) on homologous chromosomes. Ex. when the genotype is AA or aa
An allelethat determines the phenotype of a heterozygous individual. Ex. is one that can hide the presence of a recessive allele
Property of an allele whereby its influence on phenotype can be entirely hidden by the presence of another, dominant allele
Occurs when a single gene influences multiple phenotypic traits. Consequently, a new mutation in the gene will have an effect on all traits simultaneously. Aproblem cna happen when one trait prefers another mutant, while the selection at the other trait favors another mutant
is an organism for a gene of trait that has different alleles at the gene's locus for each homologous chromosome. THis organism must have two homologous chromosomes in each cell, or polyploidy, having more than homologous chromosomes. In a diploid organism, the two different alleles were inherited from the organiosms two parents
a section of DNA (or RNA, or some viruses) that encodes info for building a polypeptide or a functional molecule of RNA
A genes physical location on a chromosome (plural=loci)
a particular version of a gene
Expected Genotypic Freq in F1 are:
f(YY) = 0.8 x 0.8 = 0.64
f(Yy) = 2 x 0.8 x 0.2 = 0.32
f(yy) = 0.2 x 0.2 = 0.04
* what are the phenotypice freq?
Phenotypic Freq:
f(green) = 0.64 + 0.32 = 0.96
f(blue) = 0.04
Total = 0.96 + 0.04 = 1.0
True Allele Freq:
is when you use known genotypic freq to calculate TRUE ALLELE FREQ, this is the "Counting Method"
EXAMPLE: Field work shows that the genotypic freq are:
f(YY) = 0.64
f(Yy) = 0.32
f(yy) = 0.04

#Y in YY = (0.64)(2)(N)=1.28N
#Y in Yy = (0.32)(1)(N)=0.32N
Total #Y allele in F1 = 1.60N

So, f(Y) = 1.6N/2N = 0.8 = p

#y in yy = (0.04)(2)(N)=0.08N
#y in Yy = (0.32)(1)(N)=0.32N
Total #y allele in F1 = 0.40N

So, f(y) = 0.4N/2N = 0.2 = q

So, f(Y)+f(y)=0.8 + 0.2 =1.0
Compare Parental to F1
p = 0.8 <-> 0.8 , yes
q = 0.2 <-> 0.2 , yes
Chi Square Test
Compares the ratio of OBSERVED to EXPECTED
Ex. coin toss
H:T 100 tosses -> 50:50 expec
suppose it was 55:45
T/T the ratio is 1:2:1

Chi Sq Test = Sum((Observed - Expected)^2 /Expected)
Degree of freedom:
# of data classes - 1
so, if YY, Yy, yy are the data classes then the degrees of freedom are 3-1 = 2, so refer to line number 2 for results, if p<0.5 then we reject the null hypothesis and evolution has taken place,
If p > 0.5 then we accept the nul hypothesis and no evolution has occurred
group of similar cells that share a common embryonic origin & are specialized to perform a certain task
For example, Tissues get organized into organs and organs into systems and sytems into organisms
I) Epithelial Tissue - covers & lines surfaces of internal organs, blood vessels, skin, forms glands, regulates passage of materials across surfaces, tightly packed cells (allow to be an effective barrier)
II) Connective Tissue - supporting your body tissue, to connect, protect & support organs & other tissues, the cells are spaced much more widely w/gelatinous matrix in between
III) Muscle Tissue
IV) Nervous Tissue
Name the 5 conditons required for Hardy-Weinberg equilibrium are:
1) Large pop. size
2) Mating must be Random w/respect to the phenotypic trait
3) NO Migration
4) No net change in allel freq as a result of Mutation
5) NO advantage to individuals carrying particular alleles at a locus

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