Labs

Question 1

Great Lakes fishery populations

Answer 1

• overexploitation and invasion by exotic species has placed severe stress on native fish species
• many commercially valuable species have been eliminated/reduced

Question 2

what evolutionary forces have had a significant impact on the genetic variation of Great Lakes fishery populations?

Answer 2

• selection forces of humans reduce genetic diversity (eg size-selective fishing gear, habitat elimination, alteration of prey species, pollution stresses)
• gene flow; the greater the rate of gene flow, the more homogeneous two populations become. any activity which changes the population densities affects the distance between populations
• genetic drift

Question 2

what did managers have to do to combat the Great Lakes problem?

Answer 2

• stock the lakes with fish that would eventually begin to reproduce and replenish species
• cultivated in hatcheries

Question 3

issues with cultivating fish in hatcheries then releasing them into the wild

Answer 3

• genetic diversity is low
• locally adapted populations may be replaced with genetically homogeneous populations which limits adaptive potential
• may increase competition or introduce diseases

Question 4

why are traditional Mendelian methods of making crosses/scoring phenotypes insufficient for a detailed estimate of genetic variation within a population?

Answer 4

• restricted primarily to phenotypic characters
• too time consuming to wait for future generations
• does not always yield precise information on genotype (homozygous dominant vs heterozygote)
• too many gene loci in most organisms for this process to yield reliable estimates of genetic variation

Question 5

protein electrophoresis

Answer 5

• tissue sample homogenised to release enzymes
• drop of each sample placed in a straight row near the edge of a rectangular sheet of cellulose acetate gel
• electrodes attached to filter paper wicks soaked in buffer solution at the end of each gel
• electrical current applied across the gel for 20/30 mins
• gel stained for a particular enzyme by pouring over it a solution containing a substrate along with a dye that precipitates where the reaction occurs
• dark bands appear

Question 6

why do different allonyms move through the gel at different rates?

Answer 6

enzymes of the same size and shape move at a rate determined largely by the ratio of positively charged to negatively charged amino acids

Question 7

allozymes

Answer 7

differ in their amino acid sequence and are the product of a single genetic locus

Question 8

diagram for allozyme gel analysis

Question 9

monomeric enzyme

Answer 9

produces one polypeptide chain which is a fully functional protein

Question 10

dimeric enzyme

Answer 10

single polypeptide chain is produced by each allele, but these remain inactive until they form dimers

Question 11

it is necessary to screen at least —— enzyme loci to get a representative sample of the variation in populations

Answer 11

12 to 15

Question 12

two measures of genetic variation

Answer 12

polymorphism (P)
heterozygosity (H)

Question 13

variation as measured by the average heterozygosity represents

Answer 13

the adaptive potential of the species and is a powerful evolutionary mechanism

Question 14

two statistics to quantify genetic differentiation between populations

Answer 14

1. genetic identity, I, which estimates the proportion of genes that are identical in the two populations being compared
2. genetic distance, D, which estimates the accumulated number of gene differences per locus that have occurred over evolutionary time

Question 15

advantage of statistical measures of genetic differences

Answer 15

• they apply to any population, whether they be haploid, diploid, tetraploid or selfing
• definitions depend solely on allele frequencies rather than on the genotype frequencies used in the HW equation

Question 16

look over the method for the experiment

Question 17

aim of the experiment

Answer 17

to analyse differences in allosyme variation between two species using electrophoresis

Question 18

zebra mussels

Answer 18

benthic (live on the bottom of the lake)
sessile (fixed to a substrate)
bivalves (mollusc with two shells)
males and females can only be distinguished based on microscopic examination of gonad tissue

Question 19

phylogenetic systematics

Answer 19

• method for reconstructing evolutionary relationships
• clusters organisms into groups based on modified characters that are shared by members of the group

Question 20

3 characteristics of the method of phylogenetic systematics

Answer 20

quantitative (characters can be enumerated), reproducible (data are not subjective), and testable

Question 21

assumptions of phylogenetic systematics

Answer 21

1. evolution occurs
2. there is a singly phylogeny of life, a result of evolutionary descent
3. characters are passed from generation to generation, modified or unmodified, during evolutionary descent

Question 22

steps in constructing a phylogenetic tree

Answer 22

1. identify homologous characters
2. code the characters as ancestral or derived and construct a matrix
3. group by shared derived characters to produce a phylogenetic hypothesis

Question 23

character

Answer 23

observable trait of an organism

Question 24

character reversal

Answer 24

a form of homoplasy, where a species re-evolves the ancestral character state

Question 25

unique vs shared derived character

Answer 25

unique - found in one taxon shared - found in more than one taxon

Question 26

it is ------ ------ ----- that are used to infer evolutionary relationships

Answer 26

shared derived characters

Question 27

binary vs multistate characters

Answer 27

binary: present or absent (coded 0 and 1) multistate: in more than two different states (coded as 0, 1, 2)

Question 28

multistate characters can be considered to be

Answer 28

ordered or unordered

Question 29

ordered characters

Answer 29

follow a logical evolutionary path (eg small size beak to medium to large)

Question 30

unordered characters

Answer 30

do not follow any logical evolutionary progression (eg colour of coral reef fishes)

Question 31

go through the process of making a phylogenetic tree

Question 32

parsimony

Answer 32

a principle in phylogenetic which forces one to accept the shortest tree that explains all the character states

Question 33

polytomy

Answer 33

an unresolved group of three or more taxa

Question 34

measurement error

Answer 34

reflects the discrepancy between our repeated measurements and the true value of the object being measured

Question 35

precision

Answer 35

the repeatability of the measurement

Question 36

accuracy

Answer 36

the tendency for the measured value to be close to, or approximate, the true accepted value

Question 37

sample size is abbreviated by

Answer 37

n

Question 38

population size is abbreviated by

Answer 38

N

Question 39

title for a graph

Answer 39

placed at bottom of a graph

Question 40

interpolation

Answer 40

a line of best fit through the data that allows you to predict values of the dependent variable for which you do not have actual data points

Question 41

extrapolation

Answer 41

the process of extending the line beyond the existing data, maintaining the trend shown by interpolation, and provides a basis for prediction

Question 42

bar graph

Answer 42

used for discrete quantitative variables which are similar but not necessarily related

Question 43

histogram

Answer 43

used exclusively for showing the distribution of data that are continuous

Question 44

statistics of location

Answer 44

describe the position of a sample along a given dimension - most common statistics of location are the mean, median and mode; these are called measures of central tendency

Question 45

statistics of dispersion/variability

Answer 45

describe the distribution of observations. - simplest is the range, and most common are the variance and standard deviation and standard error

Question 46

variance

Answer 46

measure of how much scatter there is around the mean

Question 47

(n-1)

Answer 47

degree of freedom. adjustment to have an unbiased estimate of the variance from a sample

Question 48

standard deviation, s

Answer 48

average size of the deviation from the mean

Question 49

standard error

Answer 49

measure of how reliable the sample mean is as an approximation to the population mean

Question 50

test of significance

Answer 50

evaluates the probability of rejecting the null hypothesis when it is actually true

Question 51

student's t-test

Answer 51

statistical test that compares the means of two samples and assesses whether or not they differ enough to represent samples from different populations

Question 52

significance level

Answer 52

the probability of mistakenly rejecting the null hypothesis when it is true

Question 53

draw graph for t test acceptance/rejection region

Question 54

chi square test / goodness of fit /contingency

Answer 54

used to test a hypothesis in an experiment in which the data are frequency data rather than continuous date - tests difference between observed and expected frequencies and is used for data that can be arranged into classes such as habitat, genotype, percentage

Question 55

assumptions of a chi square test

Answer 55

1. data must consist of samples taken at random from a large population 2. for each sample taken there is a restricted number of outcomes that can be divided into distinct categories 3. probabilities for each of the outcomes are independent from each other and do not change from one sampled individual to another

Question 56

draw graph for acceptance/rejection region for chi squared distribution

Question 57

when would you use a 2 x 2 contingency table?

Answer 57

when an analysis is concerned with two variables

Question 58

what did Hardy and Weinberg realise?

Answer 58

that the genotype frequencies of a population could be predicted from the frequency of the alleles, represented as p and q, using the binomial equation: p^2 + 2pq + q^2 the above equation describes a single locus with two alleles

Question 59

what is necessarily true for the HW equation?

Answer 59

frequencies of the two alleles (p + q) must equal 1 and the frequencies of the genotypes (p^2 + 2pq + q^2) must also equal 1.

Question 60

two functions of HW equation

Answer 60

- calculate genotype frequencies of a pair of alleles at a gene locus - predict genotype frequencies of the next generation as long as there have been no changes in the gene pool

Question 61

when there have been no changes in the gene pool, genetic equilibrium will only occur when:

Answer 61

1. population is large enough to be unaffected by random gene changes (i.e. genetic drift) 2. there is no gene flow (immigration or emigration) 3. no mutations occur or there is mutational equilibrium 4. reproduction is random (independent of genotype) 5. natural selection is not acting on a particular phenotype

Question 62

why is the concept of genetic equilibrium an important concept if in natural populations all of the conditions are almost never met?

Answer 62

significant deviations from the expected HW values provide evidence that some evolutionary force is in action. We can think of the expected HW values as a null hypothesis (no evolutionary force is acting on the population)