Theory question 102
Photosynthesis and Plant Nutrition(a) State four modes of nutrition in plants
(b) Outline the process involved in the light and dark reactions of photosynthesis
(c) Describe briefly the modifications and the mechanisms associated with the following feeding habits: (i) filter feeding in mosquito larva; (ii) parasitic feeding in tapeworm.
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(a) Any four: autotrophic/photosynthetic (green plants), chemosynthetic, parasitic (e.g. dodder, Cassytha), saprophytic, insectivorous/carnivorous (e.g. bladderwort), symbiotic (legume root nodules)
(b) Light stage (in grana): chlorophyll absorbs light; water is split (photolysis) into hydrogen and oxygen; oxygen is released; energy stored as ATP and hydrogen carried by NADP
Dark stage (in stroma): CO₂ is combined with a 5-carbon acceptor and reduced by the hydrogen using ATP to form sugars (glucose), then starch
(c)(i) Mosquito larva: mouth brushes beat to create a water current; small particles/organisms are swept into the mouth and filtered; it hangs from the surface film breathing through a siphon
(ii) Tapeworm: no mouth or gut; absorbs digested food through its body surface; scolex with hooks and suckers for attachment; thick cuticle resists host enzymes; produces anti-enzymes; huge numbers of eggs; hermaphrodite proglottids
Keep the light stage (needs light, splits water) and the dark stage (fixes CO₂) clearly separate.