Outline how and where energy is stored in plants. 

Ecologists sometimes display data from an ecosystem using a diagram called a  pyramid of energy. Describe what is shown in pyramids of energy.

Explain the control of body temperature in humans.

a. glucose (from photosynthesis) stored as starch;
b. starch stored (as granules) in chloroplast/in plastids;
c. (starch stored) in seeds/storage roots/stem tubers;
d. stored as lipids/oils;
e. (lipid/oils storage) in seeds;
f. lipids store twice as much energy per gram as starch;

a. pyramid of energy shows the flow of energy from one trophic level to the next (in a community);
b. units of pyramids of energy are energy per unit area per unit time/kJ m^–2 yr ^–1;
c. bar width is proportional to the energy stored (in the biomass) in that trophic level;
d. the first/lowest trophic level is producers;
e. second level is primary consumers/herbivores;
f. third level of secondary consumers/carnivores;
g. only a small amount (10 to 20 %) of energy of one level is passed to the next;
h. bar width/energy stored in the trophic level decreases (proportionally) as you go up each level;
i. pyramid shows that there is a limit to the length of food chains;
Award any of the above marking points to a correctly drawn and clearly labelled pyramid.

a. normal body core temperature constant/36.5 to 37.5°C; (accept single values within this range)
b. regulated by negative feedback/homeostatic mechanisms;
c. hypothalamus is the centre of thermoregulation;
d. hypothalamus sends impulses to the body to increase/decrease temperatures;
e. release of sweat (by sweat glands in the skin) if skin temperature rises;
f. evaporation of water cools the body; (concept of evaporation must be mentioned)
g. heat is transferred by blood;
h. transfer of heat from body core in blood to surface;
i. if temperature rises, increased flow of blood/heat to the skin/vasodilation of skin blood vessels/arterioles; (do not accept veins, arteries or capillaries)
j. if temperature drops, decreased flow of blood/heat to the skin/vasoconstriction of skin blood vessels/arterioles; (do not accept veins, arteries or capillaries)
k. shivering increases heat production (in muscles);
l. example of one behavioural mechanism; (eg reducing activity (to lower body temperature) / reducing exposed surfaces (to reduce heat loss)

This was a popular question among candidates.    

For part a, many did not earn full marks and this appeared to be due to a lack of knowledge of this part of the syllabus.

This was a popular question among candidates.    

For b, many candidates easily earned the marks for parts d, e and f requiring them to identify examples of organisms that occupy the various trophic levels of organisms. A number lost marks due to poorly constructed diagrams especially in relation to the bars not being drawn proportionately. Few correctly indicated the correct units for productivity of the various trophic levels.

This was a popular question among candidates.    

Part c was generally well done.  Most used the term homeostasis and negative feedback in their answers. A number have a misconception regarding vasodilation and vasoconstriction as they are writing that arterioles move toward and away from the skin surface. Few discussed the role of the hypothalamus in regulated body temperature.