State the significance of the statement: p<0.05.

Outline the trends in capillary density in the results of this experiment.

Describe how increased capillary density could affect the aerobic capacity of muscle.

State the time when the point of fatigue occurred in the Epi–exercise group.

Compare and contrast the results for the water–no exercise group and the Epi–no exercise group.

Discuss the effect of exercise on the results of the experiment.

Analyse the effect of exercise on the presence of the mitochondrial proteins in the leg muscle.

Mitochondria are essential for aerobic respiration. Suggest one possible role of the proteins that were studied.

The scientists concluded that Epi significantly increased aerobic capacity in leg muscle.

Evaluate the strength of the evidence provided by all of the data for dark chocolate improving the aerobic capacity of athletes.

there is a significant «statistical» difference between two experimental values
OR
there is a less than 5 % chance that the difference is random
OR
95 % or more probability that results are due to the experiment «IV» and not random/can reject the null hypothesis
OR
there is a relationship/correlation between doing exercise and capillary density

OWTTE

a. exercise «significantly» increased the density with both water and Epi 

“both” or OWTTE must be mentioned

b. Epi «significantly» increased the density with and without exercise 

c. Epi–exercise had the greatest increase in the density
OR
Epi increases the density more than exercise alone

a. increases amount of blood taken to the muscle 

b. increases the delivery of oxygen/glucose/nutrients for aerobic respiration 

c. increases the removal of carbon dioxide/wastes
OR
increased gas exchange

175 «seconds»

Accept 170 to 180 «seconds».

a. in both cases the tension decreased over time  

b. Epi–no exercise lasts longer/more time until «onset of» fatigue «than water–no exercise» 

c. the rate of decrease in tension is the same/similar in both 

d. Epi–no exercise has more contractions per second before fatigue point «than water–no exercise»

Do not accept numerical comparisons without justification.

a. «exercise with» water has no impact 

b. «exercise with» Epi promotes higher levels of tension for more time 

c. «exercise with» Epi increases the time to fatigue

a. exercise has no/very little effect with water 

b. exercise with Epi increased III/IV 

c. «it appears that» exercise with Epi has no/very little effect on II
OR
Epi relative to water increases all 4
OR
exercise has little/no effect on protein I/II 

d. exercise with Epi «appears to» decrease I

a. protein channels
OR
pumps in membranes of mitochondria
OR
hormone binding sites 

b. structural/integral/peripheral/glyco/surface proteins 

c. enzymes/catalysts  

Accept verifiable names of specific membrane enzymes.

d. electron transport chain proteins

Limitations:

a. study done on mice and may not apply to humans 

b. levels of Epi administered in experiment may exceed levels in a sample of dark chocolate
OR
levels of Epi administered in experiment may have different levels in a sample of dark chocolate
OR
chocolate may have other components with unknown effects on aerobic capacity 

c. mitochondrial proteins may not improve aerobic capacity 

Strengths:

d. data supports as dark chocolate contains EPI 

e Epi improves capillary density and would therefore increase aerobic capacity 

f. Epi improves fatigue resistance 

g. Epi in combination with exercise improves it further 

h. Epi increases mitochondrial proteins therefore/presumably increasing aerobic capacity

OWTTE

State the relationship between sloth body temperature and ambient temperature.

Explain how this relationship differs from that in humans.

Describe the trend in body posture as ambient temperature rises from 22 to 34 °C.

Suggest reasons for this trend.

The mean daily food intake fluctuated from day to day. State the month that contains the day on which the mean intake of food was highest.

Outline the relationship between ambient daily temperature and food intake in March.

Suggest, with a reason, how the activity of the sloth varies with ambient temperature.

State one feature of the sloth that would indicate it is a mammal.

body temperature increases with ambient temperature / positive correlation;

Since direct can be either –/+, no credit for direct correlation alone.

humans maintain/regulate a constant body temperature at different ambient temperatures/maintained by homeostasis;

As ambient temperature increases, the sloth spends more time with limbs spread
OR
as ambient temperature increases the sloth spends less time curled in a ball
OR
as ambient temperature rises, the posture changes from 1 to 6;

1. less surface area is exposed when curled up
   OR
   more surface area is exposed when all limbs spread;
2. curled position prevents heat loss/provides warmth
   OR
   stretched out position allows more heat loss/body cooled;

May;

1. food intake rises as daily temperature increases / positive correlation;
2. the lowest food intake corresponds to the lowest temperature;

1. the sloth will be more active at higher temperatures as it takes in more food for energy;
2. as temperature rises, the sloth uncurls to dissipate/lose heat;

Reason required.

1. mammals have mammary glands;
2. produce milk for their offspring;
3. bodies covered in hair/fur;

Characteristic must be exclusive to mammals.

If more than one answer, use the first one given.

Often steady or constant body temperatures for humans was given rather than homeostasis. Some candidates erroneously described humans as warming up in response to cold ambient temperatures.

There were a few beautiful responses where surface area was specifically incorporated into the answer achieving maximum marks.

Good reasoning was not seen often, best answers needed some of the elements in this linkage: higher temperature led to uncurling which led to movement which led to eating because of energy needs; "sloth prefers staying curled up so cold does not affect them" or "sloth enjoys staying curled up" were not acceptable

Have hair/fur or feed young with milk were the best answers. Many students wrote "give birth to live young;" While this is true of most mammals, monotremes lay eggs. Furthermore, some other animals give birth to live young (ovoviviparous) such as some reptiles and some groups of fish. We credited only characteristics exclusive to all mammals.

Identify which organism has the highest percentage of edible mass.

Calculate how much more feed is required by cattle than chickens to produce 1 kg of live mass.

Identify which organism requires the least feed to produce 1 kg of edible mass.

Distinguish between the amino acid contents of yellow mealworms and cattle.

Predict, with a reason, whether the amino acid composition of yellow mealworms or cattle is more suitable for a human diet.

Outline the differences between the environmental impact of using mealworms and traditional farm livestock for protein production.

Birds and mammals maintain constant body temperature despite considerable losses of body heat to the environment. In insects such as mealworms, body temperature is variable and is often the same as the temperature of the environment or only slightly above it. Analyse the data in the bar charts, using this information.

Using all the relevant data in this question, discuss the use of insects as a major food source for humans.

cricket

25 − 4 = 21kg «more required for cattle»

Must state unit kg.

cricket

a. mealworms have more isoleucine/leucine/valine than cattle 

b. cattle have more lysine/methionine/phenylalanine/threonine 

c. the total proportion of these amino acids is «slightly» greater in cattle (188 to 176) 

a. cattle as they are more closely related to humans 

b. cattle as they are more likely to have proteins with a similar amino acid composition to humans OWTTE.

c. cattle as they contain a «slightly» higher proportion of «essential» amino acids required in human diet (188 to 176)

OWTTE

a. mealworms contribute much less to global warming than other traditional farm livestock for protein production 

b. mealworms require less land use than other traditional farm livestock for protein production

Accept converse or OWTTE.

a. cell respiration required to generate heat (lost to environment) to maintain body temperature 

b. birds/chickens and mammals/cattle carry out cell respiration at higher rate than insects 

c. «chickens/cattle therefore» generate more CO₂ per kg protein produced 

d. «chickens/cattle» need more food/land area to produce body mass 

e. feed conversion ratios are lower in mealworms/insects/cold blooded animals as they do not need to maintain a constant body temperature (accept converse)

a. insects/crickets have the highest edible percentage 

b. insects have the lowest feed conversion ratio/produce the most edible mass per kg of food they eat 

c. insects supply amino acids required in the human diet 

d. insects cause less global warming/use less land area per kg of protein produced 

e. in western countries, there is a disgust factor/cultural factors about eating insects which would need to be overcome before they could be used as a significant food source 

f. insects may supply less proportions/content of amino acids required in human diets

Describe the effect of neonicotinoid pesticides on the nervous system of insects.

State the cumulative increase in the mass of control colonies at 7 weeks.

Compare and contrast the cumulative increase in mass of the three groups of colonies once they were placed in the field.

Suggest a reason for the changes in mass in the colonies between weeks 6 and 8.

Using the data in the graph, predict how the use of neonicotinoid pesticides will affect bumblebee populations.

Identify the species whose eggs are most affected by a high dose of neonicotinoid.

Describe the overall effects of low and high doses of neonicotinoid on the egg lengths of all four species.

Deduce, based on the data presented, whether the levels of neonicotinoids used in agriculture cause direct harm to B. terrestris.

1. blocks synaptic transmission at (cholinergic synapses);
2. binds to (acetylcholine) receptors;

230 g;

Accept range of 215 – 265. This takes into account the beginning and end of week 7.
Unit required.

1. all increased in (cumulative) mass gain up to 5–6 weeks
   OR
   all decreased (in cumulative mass gain) after 6 weeks;
2. both with neonicotinoids have significantly lower (cumulative) mass than the control colonies (at all periods)
   OR
   colonies exposed to high concentration always had the lowest (cumulative) mass gain;

Accept vice versa.

1. less production of honey/wax;
2. fewer bees/dispersal of bees/queens;
3. bad weather/environmental change/predators/disease/pests;

1. number of populations may/will decrease;
2. both treatments decreased very significantly the number of queens;
3. low treatment had (almost) the same effect as the high
   OR
   even low levels have as toxic/lethal effects as high levels;
4. without new queens, new colonies cannot be founded;
5. no/less/little reproduction (as only queens lay eggs);
6. new colonies are essential to maintain bumblebee populations;

B. lucorum;

1. low doses caused (slight) decrease in (average) egg lengths in 3 species/most species
   OR
   low doses caused a slight increase in 1 species/B. pascuorum;
2. high doses caused (slightly) lower (average) results in all 4 species (compared to control);
3. in only one species/B. pratorum, the high doses caused larger lengths than the low doses;

Accept any other valid comparison.

1. yes, as even low/both doses (of first neonicotinoid) affect the (overall) development of colonies negatively; (From Graph 1)
2. yes, as decreased numbers of queens (likely) affect reproductive capabilities; (From Graph 2)
3. the second neonicotinoid (likely) had less/little/no effect on the bees as it had little effect on egg size; (From Graph 3)

OWTTE

A pleasing number were able to correctly describe the effect of the pesticides on the synapses and state the cumulative increase correctly in ai and aii. However, in aiii, many did not see the similarity in pattern for the compare mark. In part b stronger candidates commented on the fact that even at low doses the pesticide had a great effect and that the difference between high and low doses was negligible. Many examiners were bemused by the answers to c(i) where about half of the candidates failed to identify B. lucorum as the most affected species. B. pascuorum and B. terrestris were often incorrectly given. In cii. Better candidates described the overall effects as asked, with weaker candidates just describing each species in turn. In 1d the top candidates looked at all of the data, but those who just stated that the effect was not noticeable as the egg length was not significantly smaller gained the mark.

State the approximate value of the membrane potential at X.

Y is the threshold potential. State what happens when the threshold potential is reached.

Describe the movements in ions that occur during time t.

Explain how a nerve impulse is passed on to other neurons.

0 mV; (accept answers in the range of – 10 mV to +10 mV) (Units required)

sodium channels (start to) open
OR
depolarization/axon begins to depolarize
OR
action potential occurs;

Reject pumping of ions.

Na⁺/sodium ions diffuse into the axon (in the first part/half of t);
K⁺ /potassium ions diffuse out of the axon (in the second half/part of t)

Do not accept the name of the element without indication that it is an ion.

1. impulses pass to another neuron at a synapse/across synaptic gap/cleft;
2. (depolarization causes) Ca²⁺/calcium ions to diffuse into the (presynaptic) neuron/axon;
3. depolarization (of presynaptic neuron) causes release of a neurotransmitter
   OR
   neurotransmitters diffuse across the synapse;
4. (neurotransmitters) bind to receptors on postsynaptic neuron/membrane;
5. (if the threshold potential is reached) an action potential occurs/sodium gates open (in the postsynaptic neuron);

There were some truly brilliant answers to Question 5. However, the weakest answers in the examination were also found here. Of the questions, these were the most commonly left blank.

Candidates were often unable to approximate X. Missing units resulted in no marks awarded.

Fundamental terms such as action potential or depolarization were not used in Q5(b) and (c). Some candidates failed to distinguish between elements and ions.

Some candidates talked about ion movement but with no reference to a specific ion; some described the Na⁺/K⁺ pump here and received no marks.

Use of term "synapse" was often missing; involvement of the brain was sometimes built into the passage of a nerve impulse to another neuron.

State the level of COPD that has the lowest FEV.

Explain how a low FEV can be used to indicate emphysema.

State the disease severity group that has the highest range of plasma desmosines.

Evaluate which of the two biomarkers would be the most useful indicator of COPD severity.

Elastin is also an important component of other tissues such as arteries and ligaments. Evaluate how these other sources of elastin could affect the interpretation of the biomarker as an indicator of COPD.

State the relationship between diffusion capacity and urine desmosines.

Other studies on pulmonary diseases have shown a wide variety of results. Apart from age, sex and severity of COPD, list two other factors that may explain the inconsistent results between studies.

Discuss whether measurements of desmosine concentration would be useful for monitoring changes in the health of a patient.

Severe

a. low FEV indicates inability to force out air/adequate volume of air

    OWTTE

b. airflow limitation is the reason for inability to force out air/shortness of breath

c. inability to force out air/shortness of breath indicates emphysema

d. emphysema causes/involves breakdown of alveoli walls «so less elastin»

    The idea that there are fewer alveoli to “push”

[Max 2 Marks]

No disease

a. plasma desmosines

b. neither is very good due to large overlaps of ranges

    OWTTE

    OR

    the range of data for each category is less for plasma desmosines

    OR

    data are more reliable

c. the level of plasma desmosines increases with disease severity

d. easier/less invasive to take urine sample rather than a plasma sample

[Max 2 Marks]

a. degradation of elastin from other tissues may have contributed to the results

b. there is no guarantee that the concentrations of desmosines measured came from the lungs

    OR

    difficult to assess how much lung elastin constitutes the total

c. overlapping ranges makes interpretation difficult

[Max 2 Marks]

inversely correlated

OR

negative correlation

OR

the higher the «urine» desmosine concentration, the lower the diffusion «rate»

a. «small» sample size

    OR

    only studied in one country

b. methods used

c. environment/pollution/workplace exposure

d. race/genetic factors

e. health status/fitness/BMI of volunteers

[Max 2 Marks]

a. positive correlation with COPD severity «as seen in the table»

    OR

    negative correlation with «CO» diffusion capacity «as seen in the graph»

b. not directly proportional/other factors affect it

c. «but» if other factors stay the same in a patient it could be an effective indicator of change

d. because the ranges are high, only change in an individual is useful

e. the measurements may be more useful for one gender than the other as differences seen in the graph

[Max 3 Marks]