Outline how variations in specific molecules can lead to phylogeny.

Outline the value of classifying organisms.

a. phylogeny is the evolutionary line of descent;

b. the study of similar molecules in two different species; (e.g. mitochondrial DNA / hemoglobin / Cytochrome c)

c. the greater the differences, the longer the time span since the two species had a common ancestor;

d. variation can be due to mutations;

e. mutations are chance events so caution must be taken when interpreting these;

a. organization of data helps to identify organisms;

b. suggests evolutionary links;

c. suggests the closeness of a relationship the more similar the characteristics are;

d. allows prediction of characteristics shared by members of a group;

Candidates had trouble with the question regarding how variations in molecules can lead to phylogeny, confusing the study of evolutionary relationships with the actual development of the relationships themselves.

State a function of each of the following parts of the human brain.

(i)  Cerebellum

(ii)  Hypothalamus

Identify the two most closely related organisms.

Identify the species to which the Bonobo is most distantly related.

Describe one type of barrier that may exist between gene pools.

(i)  (coordinates) unconscious motor functions/balance and movement

(ii)  (maintains) homeostasis/thermoregulation/appetite/thirst / coordinates endocrine systems / secretes hormones/regulating factors

(common) chimpanzee and bonobo

gibbon

named barrier;
description of its action;
results in terms of gene pools;
e.g.:
behavioural barrier;
different populations mate at different times of year thus preventing interbreeding;
allele frequencies become different in the two gene pools/separates gene pools / sympatric speciation;

The vast majority of candidates provided correct answers.

This part presented a cladogram of larger primates and the two subparts were interpreted correctly by the vast majority of candidates.

This part presented a cladogram of larger primates and the two subparts were interpreted correctly by the vast majority of candidates.

This part required candidates to name a barrier that may exist between gene pools and describe its action and the results in terms of gene pools. Mixed results were obtained here, although many candidates gained all the marks. Some candidates confused between types of barrier and types of evolution (e.g. geographic vs allopatric), were vague about its action and could not relate to gene pools.

Define analogous characteristics using one example to illustrate your answer.

Outline two pieces of evidence that support the endosymbiotic theory for the origin of eukaryotes.

List two anatomical features that define humans as primates.

analogous structure similar in appearance/function but with different evolutionary history e.g. wing of bat and wing of bird;

smaller/70S ribosomes in mitochondria/chloroplasts (as in prokaryotes);

circular DNA in mitochondria/chloroplasts (as in prokaryotes);

mitochondria/chloroplasts have double membrane;

similar size/shape of mitochondria/chloroplasts to prokaryotes;

opposable thumb;

large range of shoulder movement;

good vision / stereoscopic vision / overlapping field view;

large brain relative to body size;

tailless primate;

Y-5 cusps of molars;

Those that knew the correct definition did well.

The main pieces of evidence supporting the endosymbiotic theory for the origin of eukaryotes seen were double membranes and the presence of circular DNA.

The most popular answers here were those of humans having an opposable thumb and stereoscopic vision. Many though only gained one mark point here with the answer of opposable thumb.

Distinguish between innate and learned behaviour.

Distinguish between analogous and homologous structures.

innate behaviour is independent of experience/environmental conditions/inherited
while learned behaviour is influenced by experience/environment / OWTTE

Many gave vague answers to this section and did not make reference to the role of the environment or experience in distinguishing between the two types of behaviour. Candidates should not describe "learned‟ behaviour as that which we learn.

The table was given so that candidates could easily distinguish between analogous and homologous structures clearly but some still did not compare like points.

Discuss the relationship between cladograms and the classification of living organisms.

classification traditionally based on morphology;
cladistics (strength) based on molecular differences/base sequences/amino acid sequences;
cladistics (weakness) is based on probability but improbable events do occur, so relationships can be wrong;
clade includes ancestral species/descendants from that species;
members of clade share set of features not found in more distant relatives;
cladogram is a tree-like diagram where nodes/branches represent the splitting of (two) new groups from a common ancestor;
different cladograms can represent same relationships in a group;
cladogram timescale not necessary;
classification based on cladograms is often same as traditional classification;
in some groups cladograms have led to revised classification;
Accept any of the above points shown in a clearly annotated diagram.

Many answers had content that did not match well with the markscheme, making this the hardest question in the exam, as very few candidates scored full marks. Often vague statements were given, not distinguishing between the fundamental differences between cladogram and traditional methods of classification. There was no clear idea about what/how/why cladograms were done, and the differences were between them and traditional classification. Many candidates believe that cladograms are the source of data, not their presentation.

State two characteristics that permit the classification of microbes into domains.

cell wall structure/composition / whether the cell wall contains peptidoglycan;
size of / 70S or 80S ribosomes;
(base sequence in) ribosomal RNA/rRNA;
whether there are introns;
whether there are histone proteins;
membrane structure / ether or ester bonds (in membrane lipids);

This posed few problems for well-prepared candidates, though (a) and (b) were not known by all.

Explain cladistics as a method of classifying organisms.

a. cladistics uses cladograms/tree diagrams;
b. show clades/branches (in parallel) that begin at a point/node;
c. each clade includes a (common) ancestral organism/node and all its descendents;
d. members of a clade share derived/inherited characteristics;
e. clades are nested/subsets of larger clades;
f. cladograms show evolutionary history/origin of organisms / phylogeny;
g. branch length (of clade) can indicate (relative) amount of genetic change/time;
h. clades based on (objective) molecular analysis/genetic evidence / differ in amino acid sequences/DNA base changes/mutations;
i. fewest number of differences/maximum parsimony determines branch separation;
j. predictability of DNA base changes/mutation rates suggests evolutionary timelines;
k. problems arise when gene change varies (greatly) from one gene to the next;
l. cladograms may not match traditional/Linnaean classification;
m. (mismatch) prompts re-examination of data / reclassification of a group;
Some of the above points may be included in a correctly annotated diagram clearly stating above points.

This was probably the most poorly answered of the longer response questions on this paper.  Candidates did not seem to have enough knowledge about cladistics to allow them to respond adequately and marks above 2 or 3 were rarely seen.  As they were unable to communicate ideas on clades clearly they waffled and were repetitive.  Better candidates were able to discuss cladograms to some degree.  Better teaching of this topic is required. 

Explain the biochemical evidence for the common ancestry of living organisms.

DNA/RNA found in all living organisms/genetic code is universal;

amino acids all L- not D- isomers;

same 20 amino acids/proteins found in all living organisms;

involves comparing similarities and differences in the amino acid sequence of the same molecule;

e.g. hemoglobin;

involves comparing base sequences of variable regions of DNA;

e.g. mitochondrial DNA;

the more similar the base/amino acid sequence, the more closely related;

comparing amino acid sequences that result in the phenotype/comparing DNA sequences that result in the genotype;

evidence for molecular evolution in drug resistance;

Discuss the use of cladograms in phylogenetic studies.

a. a cladogram is a diagram which shows shared characteristics/phylogenetic relationships;
b. phylogeny is the study of evolutionary origins/ancestry;
c. clade is a group of (all) organisms that evolved from a common ancestor;
d. evidence from biomolecules/DNA/RNA/protein/cytochromes;
e. cladograms can be compared with other representations of phylogenetic relationships/may confirm fossil/anatomical evidence;
f. organisms placed close together in a cladogram are closely related evolutionarily;
g. there may be more than one possible cladogram (for a particular group) raising questions about evolutionary relationships;
h. divisions between clades/nodes suggest the sequence in which groups diverged;
i. cladograms can be used to estimate time since groups diverged;
j. cladograms are often similar to classification based on other evidence/traditional methods;
k. cladograms may lead/have led to reclassification of a group;

Although this was a popular option, candidates did not do very well on it.

While some candidates had an idea that cladograms were used to show evolutionary relationships, they were not able to clearly indicate what clades were and how cladograms were used. Some candidates confused cladograms with dichotomous identification keys. Candidates seldom received more than 3 out of 6 marks for this question.

Explain the biochemical evidence for the common ancestry of organisms on Earth.

all organisms use DNA as genetic material;

same four (nucleotide) bases makes up DNA in all organisms;

number of mutations reflect differences between organisms;

all organisms use the same genetic code / minor differences;

genetic code is degenerate/OWTTE;

all organisms use the same 20 amino acids;

function of proteins constant between species;

protein/molecule examples; (eg hemoglobin, cytochrome, chlorophyll)

only left-handed amino acids have been observed in living organisms;

although right-handed amino acids will have been available;

only right-handed glucose/carbohydrates used in organisms;

similarities in glycolysis/metabolic pathways;

all use RNA/same enzymes in transcription/translation;

Candidates had more difficulty with this question than with questions requiring longer answers in the other options, but many nevertheless provided good answers and managed to gain all the marks; those who were less successful confused biochemical evidence with origins of life.

The table shows certain characteristics present (+) or absent (–) in six organisms.

Using the data, label the cladogram with the names of the organisms.

A species is often defined as a group of similar individuals that interbreed in nature and produce fertile offspring. Discuss some problems with the use of this definition.

Award [1] for the correct position of any two organisms.
Award [1 max] if the correct order is reversed horizontally (ie from cat on the left to Amoeba on the right).

a. not all organisms can be defined in this way / does not take into account hybrids/ microorganisms/plants;
b. (even if able to interbreed) may have differences in DNA/protein;
c. does not apply to bacteria/other organisms that reproduce asexually;
d. in sympatric/allopatric isolation members of the same species do not interbreed;
e. (in some species) significant differences in morphology can occur within the same species eg: sexual dimorphism/metamorphosis/ring species;
Accept any other correct answer.

The majority of candidates could label the cladogram correctly, although a certain number did it backwards.

Many candidates presented a good discussion about the use of species definition, but many others could not express their ideas clearly enough or only had a vague idea.  

Define the term clade.

Distinguish between analogous and homologous structures, giving an example of each.

The table below lists five animals along with four morphological characteristics. A plus sign (+) indicates that the animal has this characteristic while a minus sign (–) indicates that the characteristic is absent.

Based on the features above, a student constructed a cladogram. State the names of the organisms missing in the following cladogram.

a group of related organisms sharing a common ancestor / a group of organisms containing an ancestor and all of its descendants / OWTTE

homologous structures evolved from a common ancestor while analogous structures did not;
example of homologous and example of analogous; (both needed)

Two correct labels for [1].

Many were able to get mark for the definition of clade but others were omitting the idea of common ancestry.

This was fairly well done with many getting both marks. The most common example used for homologous structure was the pentadactyl limb with various examples for analogous structures such as insect and bird wings.

Virtually all candidates were able complete the cladogram for 2 marks.

State the year in which G. fortis had the greatest change in relative beak size.

Compare the trends in relative beak size of G. fortis and G. scandens.

Outline possible reasons for the trends in relative beak size in finches.

1977 / 1978
N.B. Some responses are interpreting this as a change between years.

both species increased (relative) beak size at the beginning of the study/ between the years 1973/1974 to 1977/1978;
no similarity in trend for both species after 1977/1978/1979 / no relationship between the two species in the years of increase and decrease;
more occurrence of decrease in (relative) beak size in G. fortis whereas G. scandens showed more increases in (relative) beak size;
G. fortis shows wider fluctuation in (relative) beak size than G. scandens;
Do not accept year by year comparisons.

changes in environment/rainfall/ocean currents/migration / drought;
change in food supply;
hybridization/crossbreeding between species;
natural selection / selection pressure;

N/A

The lack of sufficient explanation in the question, "mean beak size‟ for each species or for the two species together, led to a wide variety of answers that scored poorly. Many also quoted values for individual years which did not describe a "trend.‟  

Factors contributing to different beak size between species were stated (different food sources) instead of reasoning which factors cause that a given species change its size.

Calculate the percentage risk of bacteria becoming resistant to more than five kinds of antibiotics in turkeys and egg laying hens.

Turkeys:

Egg laying hens:

Compare the incidence of drug resistance in bacteria from chickens and egg laying hens.

Discuss the hypothesis that giving antibiotics increases antibiotic resistance in poultry bacteria.

Suggest how antibiotic-resistant bacteria are passed from animals to humans.

Outline the mechanism of the action of antibiotics.

Outline the mechanism of the action of antibiotics.

turkeys: 33/32.6/32.56 %

egg laying hens: 0 %

Both needed to award the mark.

a. none of the egg laying hens have bacteria resistant to 5 or more antibiotics while (10) chickens have bacteria resistant to 5 or more antibiotics;

b. 13/65 % of the egg laying hens have no resistant bacteria while 9/20 % of the chickens have no resistant bacteria;

c. both have approximately same percentage/number of E. coli resistant to 1 or 3 antibiotics;

d. egg laying hens have less incidence of antibiotic-resistant bacteria than chickens;

a. hypothesis supported for poultry raised for meat but not for egg-laying;

b. turkeys and chickens always have bacteria resistant to more antibiotics than egg laying hens;

c. antibiotic-resistant bacteria are still found in egg laying hens even though antibiotics are rarely given;

d. antibiotic-resistant strains (of bacteria) may have arisen by other means/other than by poultry being given oral antibiotics;

from fecal matter to man handling the chickens / by accidental hand to mouth contact / contaminated dust / eating raw meat;

a. inhibition of synthesis of walls;

b. inhibition of protein synthesis;

c. inhibition of nucleic acid synthesis;

a. inhibition of synthesis of walls;

b. inhibition of protein synthesis;

c. inhibition of nucleic acid synthesis;

Many could calculate the percentages correctly, but demonstrated a total lack of understanding of the data. There was quite a bit of confusion about the poultry being resistant to bacteria rather than the bacteria found in the poultry being drug resistant.

Many could calculate the percentages correctly, but demonstrated a total lack of understanding of the data. There was quite a bit of confusion about the poultry being resistant to bacteria rather than the bacteria found in the poultry being drug resistant.

Many could calculate the percentages correctly, but demonstrated a total lack of understanding of the data. There was quite a bit of confusion about the poultry being resistant to bacteria rather than the bacteria found in the poultry being drug resistant.

Many could calculate the percentages correctly, but demonstrated a total lack of understanding of the data. There was quite a bit of confusion about the poultry being resistant to bacteria rather than the bacteria found in the poultry being drug resistant.

Many could calculate the percentages correctly, but demonstrated a total lack of understanding of the data. There was quite a bit of confusion about the poultry being resistant to bacteria rather than the bacteria found in the poultry being drug resistant.

Many could calculate the percentages correctly, but demonstrated a total lack of understanding of the data. There was quite a bit of confusion about the poultry being resistant to bacteria rather than the bacteria found in the poultry being drug resistant.

State which butterfly (sub)family contains the species with the greatest escaping ability.

Suggest one feature of butterfly wings that might help a butterfly to escape from a predator.

Explain how the ability of a butterfly to escape from predators could increase by natural selection.

The graph shows that distasteful butterflies tend to have a lower ability to escape from predators than palatable butterflies. Suggest reasons for this trend.

Limenitidinae

large wing size / camouflage/cryptic coloration / warning coloration / mimicry / powerful wing muscles / high flight speed / erratic flight pattern / OWTTE

natural selection favours survival of better-adapted individuals;
better-adapted butterflies have greater ability to escape predation;
and survive to reproduce;
allowing them to pass their characteristics/alleles/genes to offspring;
over generations, the number of butterflies with best-escaping ability increases in the population / frequency of alleles/genes for better
escaping ability increases in the population/gene pool;

palatable butterflies with high escaping ability can survive to pass on genes / palatable butterflies with low escaping ability are eaten and their genes are lost;
unpalatable/distasteful butterflies, regardless of escaping ability, are not eaten/are avoided by predators;
such butterflies survive to pass on their genes to the next generation;

This part required candidates to read the highest escaping ability correctly, which was done by the vast majority of candidates.

The vast majority of candidates suggested a plausible feature that could increase the escaping ability among butterflies, most mentioning camouflage.

This part seemed more challenging for candidates who nevertheless managed to gain marks. In (i), stating the principles of natural selection clearly in terms of adaptation, survival, reproduction and relating to populations and/or gene pools was the most difficult part, with many answers failing to include the words adaptation, population and gene pool.

In (ii), many candidates managed to state that unpalatable butterflies were not eaten by predators, but had much difficulty to figure out that it was regardless of escaping ability; many answers had a lamarckian connotation, stating that butterflies who could not escape had to evolve to become unpalatable, which is incorrect. Furthermore, candidates largely failed to explain palatable butterflies here. Very few marking points were awarded for “palatable butterflies with high escaping ability can survive to pass on genes / palatable butterflies with low escaping ability are eaten and their genes are lost.”

Identify the year with the highest frequency of the melanic form of O. bidentata.

Estimate the percentage of non-melanic forms of A. crenata in 1978.

Compare the trends for the three moth species during the study.

Suggest reasons for the differences in trends.

1972

32 (units not required) (Allow answers in the range 31–33)

Award [2 max] if at least 1 similarity and 1 difference not given.

Similarities:
in all species, melanics show a decline / non-melanics an increase in frequency;
up to 1987 percentage of melanics stable/slight decline for all three species;

Differences: Both parts of comparision required for [1].
after 1987 percentage of B. betularia melanics declines sharply whereas percentage for the other species declines slowly;
at start of investigation/1969/up to 1987 (very) few (less than 10 %) non-melanic forms of B. betularia whereas the percentage much higher (more than 20 %) for the other two species / converse;
melanic forms of B. betularia and O. bidentata drop below 50% (by 1996) but A. crenata does not;

change from polluted (industrial) environment to clean (post-industrial);
change in tree species allowing different habitats for resting moths;
change in predators as climate/habitats change;
changing selection pressures/mutation/migration/genetic drift;
grass grows quickly/colour not influenced by pollution so least change in/less selection pressure on A. crenata;

Almost every candidate was able to identify 1972 as the year with the highest frequency of the melanic form of O. bidentata.

Many obtained one mark for correctly estimating the percentage of non-melanic moths in 1978.  

This part proved more discriminating. For (i), many candidates obtained one mark for indicating that in all species, melanics showed a decline. However, most did not compare the trends but simply stated what was happening for each of the three moth species over time. They also did not connect the fall in percentage melanics with a rise in percentage of nonmelanic forms of the species but instead incorrectly stated that the species number fell. .  

Many were able to suggest the trends were due to a change from the polluted environment to a cleaner one for one mark but did not get a second point.

Calculate the percentage of the total body mass made up by the human brain.

Compare the mass of human organs with the mass of other primate organs.

Using information from the table and the graph, identify the human organ which uses the greatest amount of energy per kilogram of body tissue.

Explain the differences between the organ size of humans and other primates in terms of trends in human evolution and their causes.

a. total organ mass (approximately) same for both;

b. very little difference in mass in heart/kidney/liver;

c. human brain has greater mass than the primate brain;

d. human gut has lower mass than the primate gut;

heart

a. brain size increased during hominid evolution / OWTTE;

b. change in diet from mostly vegetarian to more protein-rich/meat eating diets;

c. eating meat/protein allows larger brain growth / change in diet corresponds to the start of increase in hominid brain size;

d. larger brains require more energy;

e. larger gut necessary for plant material digestion;

f. smaller gut is sufficient for meat/cooked food;

The majority of candidates could interpret the data correctly, although there were some erroneous calculations and identifications of liver instead of heart as the organ using the greatest amount of energy per kilogram of body tissue (due to calculation issues). Most candidates displayed some knowledge when explaining the different organ sizes, but their understanding of cause and effect was sometimes not that clear.

The majority of candidates could interpret the data correctly, although there were some erroneous calculations and identifications of liver instead of heart as the organ using the greatest amount of energy per kilogram of body tissue (due to calculation issues). Most candidates displayed some knowledge when explaining the different organ sizes, but their understanding of cause and effect was sometimes not that clear.

The majority of candidates could interpret the data correctly, although there were some erroneous calculations and identifications of liver instead of heart as the organ using the greatest amount of energy per kilogram of body tissue (due to calculation issues). Most candidates displayed some knowledge when explaining the different organ sizes, but their understanding of cause and effect was sometimes not that clear.

The majority of candidates could interpret the data correctly, although there were some erroneous calculations and identifications of liver instead of heart as the organ using the greatest amount of energy per kilogram of body tissue (due to calculation issues). Most candidates displayed some knowledge when explaining the different organ sizes, but their understanding of cause and effect was sometimes not that clear.

The diagram below represents the human eye. State the names of structures I, II, III and IV.

I. ..................................................................

II. ..................................................................

III. ..................................................................

IV. ..................................................................

Outline the evidence provided by DNA for the common ancestry of living organisms.

The cladogram below shows the classification of species A to D. Deduce how similar species A is to species B, C and D.

Suggest two reasons for using cladograms for the classification of organisms.

I. cornea;
II. lens;
III. vitreous humour;
IV. choroid; (Accept sclera as line is on the border between these two)
Two correct for [1] and four correct for [2].

all living organisms use DNA as genetic/hereditary material;
genetic code is (almost) universal;
idea that mutations accumulate gradually in DNA;

A is most similar to B;
A is equally similar to C and D;
A is least similar to both C and D;

methods used to prepare cladograms use a different approach from traditional classification/taxonomy;
show ancestral relationships;
reflect how recently two groups shared a common ancestry;
cladograms are (objective/accurate because they are usually) based on molecular differences;
they should be considered as a good complement to traditional classification;

Candidates did surprisingly poorly on this simple task of naming the structures of the eye. The label line for IV was on the border of the choroids and the sclera, and thus either one was accepted as correct.

This was poorly done.  Some correctly indicated that DNA was the genetic or hereditary material for all living organisms and that the genetic code is universal. Many wrote about pentadactyl limbs, DNA being made of 20 amino acids or about chimps and humans which did not get marks. 

Many candidates correctly interpreted the cladogram, deducing that A and B were most similar. Some were able to get a second point.

Many were able to get one mark for indicating that cladograms showed ancestral/evolutionary relationships but only a few got the second mark for another reason for using cladograms.

State the effect of the presence of the helpers on mean chick mass.

Calculate the percentage decrease in mean egg volume found in the presence of helpers as compared to the parents only. Show your working.

With reference to the data, suggest why the activity of the helper affects the probability of survival of the breeding female until the next breeding season.

Cooperative breeding is an altruistic behaviour. Outline the evolution of altruistic behaviour.

(mean) chick mass increases in presence of helpers

with helper, smaller egg volume;

less resources from mother to produce egg/rear young;

more resources toward survival of mother;

(altruistic) behaviour is inherited;

adaptations/behaviours that help the colony survive at expense of individual;

selected for (natural selection);

will be more likely to be passed on;

Most candidates correctly identified an increase in the mean mass of the chicks in the presence of the helpers.

Many candidates correctly stated the percentage decrease in mean egg volume. Some were reluctant to round up to one decimal point. A few used an alternative method for this calculation.

No candidate used all the data. That is, no candidate used the smaller mean egg volume to explain that this may mean that the breeding female would be using less resources as the egg volume was smaller. Many incorrectly wrote of helpers protecting the breeding female from predators- as this did not use the data in any way. Marks were awarded if data was used, and most did suggest that with the helper the female may use less energy and that this may increase survival.

Very few candidates applied the theory of natural selection here. Although many did correctly state the meaning of altruistic behaviour, which was the starting point leading towards the idea of selection pressure.

Outline how open reading frames are identified in DNA. 

Explain what the branching off points represent in the cladogram of these fungi.

There are several methods of introducing DNA into a cell in the laboratory. Outline the introduction of recombinant DNA in plant cell protoplasts.

a. identify a start codon and stop codon 

b. identify base sequences for a gene/that could code for a polypeptide 

c. possible correlation with existing open reading frames in databases

a. represent common ancestors shared by the organisms that emanate from the point 

b. indicates time since divergence 

c. indicates number of differences in DNA

a. plant cells made into protoplasts by removing their cell wall / use cellulase to produce protoplasts

b. physical methods such as electroporation /microinjection/biolistics

c. chemical methods such as liposomes/calcium chloride/polyethylene glycol «PEG»

d. vectors such as Agrobacterium/tobacco mosaic virus

On the cladogram, label with the letter C the point that shows the most recent common ancestor of Pambdelurion and Fuxianhuia.

Identify which two species evolved most recently.

Leanchoilia and Euarthropoda

A large number of candidates had some difficulty labelling the common ancestry in the cladogram correctly, either because their label was not precise enough, even if they understood it (e.g. label at the right of Pambdelurion), or because they could not interpret it at all. It was easier for them to identify the two species that evolved more recently at the bottom of the cladogram, although some might have done it by chance due to their position on the cladogram.

A large number of candidates had some difficulty labelling the common ancestry in the cladogram correctly, either because their label was not precise enough, even if they understood it (e.g. label at the right of Pambdelurion), or because they could not interpret it at all. It was easier for them to identify the two species that evolved more recently at the bottom of the cladogram, although some might have done it by chance due to their position on the cladogram.

Outline the trends in proboscis length in soapberry bugs shown in the graph.

Suggest, giving a reason, the expected trend in the proboscis length of the soapberry bug in the South Central United States over the past 70 years.

proboscis length has decreased;

proboscis length has become less variable;

introduced fruit has a thicker flesh;

expect proboscis to get longer;

The trend required was often seen, the change in the variation of the data however, was rarely stated.

This was mostly very well answered with many students successfully suggesting that the proboscis length would increase over time due to the distance of the seeds from the outside of the fruit.

Identify the relationship between wing size and latitude shown by D. subobscura in Europe.

Compare the data for wing size of D. subobscura in North and South America with wing size in Europe.

Suggest one reason for the differences.

Predict, with a reason, what might happen to D. subobscura in the future as a result of its introduction to new areas.

as latitude increases so does wing size / direct relationship / positive correlation
(do not accept directly proportional as line does not pass through the origin)

at higher latitudes/above 45° European species have larger wings than American species/largest wing sizes seen in European flies;
European flies show more variation than American flies (steeper curve);
at lower latitudes/below 45° North American flies have larger wings than European species;
South American flies have smaller wing size than European/ N. American flies;

American species show less variation because they have had less time to diverge / evolve;
size of American flies closer to that of flies recently introduced/founder effect / European founder population from low latitudes;
American flies exposed to different selective pressures;

isolated populations diverge (genetically) / separation of gene pools;
may become a new species / allopatric speciation;
wing size will follow same trend as in Europe as population spreads (to higher latitudes because larger size favored by higher latitudes/colder climate);
wing size may stay small due to smaller gene pool/different climate;

Almost every candidate was able to identify the relationship shown in the graph. Candidates sometimes confused latitude with altitude which caused problems when answering the other sections of D1.

Many obtained one mark for correctly indicating that the European flies showed more variation than the American flies but few were able to get a second point in (i) or to suggest an acceptable reason for this in (ii).  Those that did answer (ii) got a mark for understanding the role of selection pressures. Candidates need to be sure to make comparisons when asked rather than write descriptions.

Many obtained one mark for correctly indicating that the European flies showed more variation than the American flies but few were able to get a second point in (i) or to suggest an acceptable reason for this in (ii).  Those that did answer (ii) got a mark for understanding the role of selection pressures. Candidates need to be sure to make comparisons when asked rather than write descriptions.

Many were able to get one mark for indicating that a new species may form and some indicated this was a result of separation of gene pools due to geographic isolation.

Determine the greatest genetic distance between any pair of colonies of V. squamosa.

Identify the greatest geographic distance between any pair of colonies of V. maculifrons.

Describe the relationship between the geographic distance and genetic distance in the two species.

Compare the two species in terms of genetic distance between the pairs of colonies.

0.26 (arbitrary units) (units not required)

123 km (accept answers in the range of 122 km and 124 km)

none / low correlation / non-significant / OWTTE;
less data/fewer results/less variation at 60/70 km distance;

both show genetic differences (between all pairs of colonies);
both have (highly) variable/wide range of genetic distance;
similar mean/average genetic distance;
V. maculifrons has a greater range than V. squamosa; (vice versa)

Parts (a) (i) and (ii) were intended to key the candidates in to the data and give two relatively easy marks. Most scored them, but those that did not often then scored poorly on the rest of this question. 

Parts (a) (i) and (ii) were intended to key the candidates in to the data and give two relatively easy marks. Most scored them, but those that did not often then scored poorly on the rest of this question. 

Part (b) was perhaps slightly misleading, given that the expected answer is that there is not clear relationship between genetic and geographic distance in the pairs of colonies.

Some candidates overcomplicated their answers to (c) by including differences in geographic distance. This was not intended and the two available marks could be scored relatively easily by giving similarities and differences between the two species in the genetic difference between pairs of colonies. 

State the range of the time of spawning for the male M. cavernosa.

State how many amino acids are in the same position in the E. coli (Fe), E. coli (Mn) and the mitochondrial dismutase sequences shown.

State the amino acids which are present in the same position in at least one bacterial dismutase and in both eukaryotic dismutases.

Compare the E. coli (Mn) and the mitochondrial dismutases.

The sequences of the two bacterial dismutases and the mitochondrial dismutase show a high degree of homology. Discuss how this supports the endosymbiotic theory for the origin of mitochondria.

from 60 to 105 minutes (post-sunset) / 45 minutes

11

Ile and Glu (both needed to award the mark)

a. share 17 (out of 29) amino acids in common / more amino acids similar than different;

b. both have Mn in the enzyme (as cofactor);

c. greatest difference between them is from amino acid 18 to 22;

d. mitochondrial has Gly (position 12) while E. coli (Mn) never has Gly;

e. Leu is most common amino acid in both appearing four times / other valid comparison;

a. endosymbiotic theory states bacteria were engulfed by organisms to become mitochondria;

b. sequence comparison between mitochondrial and bacterial dismutase supports this hypothesis;

c. more similarity in the amino acid sequence between mitochondrial and bacterial dismutase than between mitochondrial and cytoplasmic dismutase;

Most candidates performed well in the data analysis with (e) being the best discriminator of the better candidates.

Many candidates responded correctly to (a).

Many candidates responded correctly to (a) and (b), although some candidates only stated one of Ile and Glu.

Many candidates were familiar with the endosymbiotic theory and gained marks in (e).

State the greatest angle from the vertical of the scratch marks on the tool used on termite mounds.

Calculate the difference in the angle between the mean values for the Swartkrans tool and the tool used to dig for plant bulbs.

Compare the width of scratch marks on the tool used to dig for larvae with the Swartkrans tool.

Using evidence from the photographs and the graphs, suggest what the researchers’ main conclusion was.

A. robustus was thought to have coexisted with Homo habilis, both becoming extinct at the same time. State approximately how many years ago A. robustus became extinct.

11° (accept answers in the range of 10.5° to 11.5°)

6° (accept answers up to 7° ) (working not required)

a. mean/average of Swartkrans less than larvae;
b. range of Swartkrans less than larvae;
c. no overlap between the two in terms of widths of scratch marks / widest Swartkrans less width than the narrowest larvae;
Do not accept answers stating numerical values only.

from the photograph:
a. (A. robustus) ate termites because the pattern of scratch marks on the tool are of similar angle;

from the graph:
b. (A. robustus) ate termites because the ranges of widths/means of angles/widths are more similar;

1.4 to 1.8 million years ago (accept answers within this range)

Many candidates had difficulty to relate to the means when comparing the tools. References to photographs, if any, remained too vague to earn any mark in most cases. The vast majority of candidates ignored the approximate date of extinction of H. robustus.

Many candidates had difficulty to relate to the means when comparing the tools. References to photographs, if any, remained too vague to earn any mark in most cases. The vast majority of candidates ignored the approximate date of extinction of H. robustus.

Many candidates had difficulty to relate to the means when comparing the tools. References to photographs, if any, remained too vague to earn any mark in most cases. The vast majority of candidates ignored the approximate date of extinction of H. robustus.

Many candidates had difficulty to relate to the means when comparing the tools. References to photographs, if any, remained too vague to earn any mark in most cases. The vast majority of candidates ignored the approximate date of extinction of H. robustus.

Many candidates had difficulty to relate to the means when comparing the tools. References to photographs, if any, remained too vague to earn any mark in most cases. The vast majority of candidates ignored the approximate date of extinction of H. robustus.