Biology · May / June 2023 · Paper 42 · Question 4

aquatic plants → midges → stoneflies → salmon → herons ; aquatic plants → mayflies → salmon → herons ;

aquatic plants → freshwater shrimps → salmon → herons ; all arrows drawn correct way from food to feeder and no additional wrong links and drawn as a food web ;

name of trophic level

organism in Fig. 4.1

producer

aquatic plants

mayflies / midges / (freshwater) primary consumer

shrimps and

secondary consumer

salmon / stoneflies ;

tertiary consumer and

salmon / herons ;

quaternary consumer and

herons ;

any three from:

primary consumers (tissues) contain chemical energy ;

energy is transferred to, secondary consumers / predator (from primary consumers / prey, that are eaten) ; ora

(named) food particles (of primary consumer) are digested (to make energy / glucose, available for respiration) ;

energy (released) is used for, growth / to make, more / new / larger, cells / mitosis ;

energy is used for, protein synthesis / reproduction / assimilation / storage as fat / storage as glycogen ;

any three from:

fewer herons (as less, food / salmon) ;

more, mayflies / stoneflies / (freshwater) shrimps (as less salmon to eat them) ;

fewer midges (as more stoneflies) ;

fewer / more, no change in, aquatic plants (as more,

mayflies / freshwater shrimps / fewer midges, feeding on them) ;

(organism) that gets its energy, from dead / waste organic, material ;

any four from:

as fewer trophic levels / plants are at a lower trophic level (than salmon / livestock) ; ora

idea that energy transfer along food chain is inefficient ;

(energy lost in) respiration / heat / (named) metabolic

process / movement / muscle contraction ;

ref to (more) material that is lost as, faeces / egested / inedible / not digestible (in longer food chains) ;

(energy lost in) excretion / urine ;