Theory question 105
Feeding Relationships and Energy FlowSection B
(a) Explain briefly the reason why energy flow in an ecosystem is non-cyclic.
(b) Make a drawing of a pyramid of energy using the information below.
Primary consumer - 1000kJ
Tertiary consumer - 200kJ
Secondary consumer - 500kJ
Producer - 3000 kJ
(c) State three differences between pyramid of energy and pyramid of numbers.
Table columns: Pyramid of energy | Pyramid of numbers
(d) State the: (i) first law of thermodynamics (ii) second law of thermodynamics
(e) State three adaptations of a tapeworm to its mode of feeding.
(f) Two organisms A and B live in different habitats within a rural area. Organism A possesses gills while organism B possesses lungs for gaseous exchange.
(i) Name the habitats of each of organisms A and B
(ii) Give two abiotic factors that are unique to the habitats of each of organisms A and B.
Show the model answer
(a) Energy enters as sunlight, passes one way from producers to consumers, and at each level some is lost as heat (respiration, movement) and cannot be reused by producers, so it does not cycle back.
(b) A pyramid of four stacked bars, widest at the base: Producer 3000 kJ (bottom), Primary consumer 1000 kJ, Secondary consumer 500 kJ, Tertiary consumer 200 kJ (top); bar widths in proportion, each level labelled, with a title.
(c) Any three: pyramid of energy is always upright, pyramid of numbers may be inverted; energy pyramid shows energy (kJ) at each level, numbers pyramid shows the count of organisms; energy pyramid takes account of the size of organisms and time, numbers pyramid does not; energy pyramid allows comparison between ecosystems, numbers pyramid does not.
(d)(i) Energy can neither be created nor destroyed, but can be changed from one form to another.
(ii) In every energy change some energy is lost as heat (unusable energy), so no transfer is 100% efficient.
(e) Any three: hooks and suckers on the scolex for attachment to the host's gut; thick cuticle resistant to digestive enzymes; secretes anti-enzymes; no mouth or gut - absorbs digested food over its whole body surface; flat body with large surface area; can respire anaerobically; produces very many eggs.
(f)(i) A - aquatic habitat (e.g. pond, stream, river); B - terrestrial habitat (land).
(ii) A, any two: turbidity; salinity; dissolved oxygen; water current/waves; depth/pressure of water. B, any two: relative humidity; wind; soil/edaphic factors; topography/altitude; rainfall.
In (b) the bars must decrease in width from the producer to the tertiary consumer.