Theory question 103
Ecological Associations(a) Classify the following biological associations under the headings in the table below: (i) Remora and shark; (ii) Lichen; (iii) Cattle and white Egret; (iv) Tapeworm in the gut of humans; (v) Flowers and Honeybees; (vi) Mistletoe and Cacao plant.
Parasitism | Mutualism | Commensalism
(b)(i) State three adaptive features of parasites. (ii) State two effects of parasites on their hosts. (c)(i) What are saprophytes? (ii) Give four examples of saprophytes.
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(a) Parasitism: tapeworm in the gut of humans; mistletoe and cacao plant.
Mutualism: lichen; flowers and honeybees.
Commensalism: remora and shark; cattle and white egret.
(b)(i) Any three: hooks and suckers (or haustoria) for attachment; thick cuticle or anti-enzymes protect against digestion by the host; reduced or no digestive system, absorb digested food; produce very large numbers of eggs/spores; hermaphrodite (self-fertilising); resistant cysts or eggs; secondary hosts help spread them; reduced sense organs and locomotory organs.
(ii) Any two: deprive host of food, causing weakness and loss of weight; cause disease; damage tissues; cause anaemia (blood loss); produce toxins; may kill the host; reduce crop yield in plants.
(c)(i) Saprophytes are organisms that feed on dead and decaying organic matter, secreting enzymes onto it and absorbing the digested products.
(ii) Any four: Rhizopus (bread mould), Mucor, mushroom, yeast, Penicillium, saprophytic bacteria.
In commensalism one partner gains and the other is not affected.