A local museum is preparing a display called “Hidden variety in a compost heap”. A student has described four unknown specimens. Organism A is multicellular...
Question 1 Report
A local museum is preparing a display called “Hidden variety in a compost heap”. A student has described four unknown specimens. Organism A is multicellular, green in light and has chloroplasts and cellulose cell walls. Organism B is made of branching filaments with chitin cell walls and absorbs dissolved food after releasing enzymes. Organism C is a single cell with a cell wall but no nucleus. Organism D consists of genetic material inside a protein coat and was detected only inside cells of a diseased plant.
(a) Complete the display labels by naming the group of organisms A, B, C and D. [4]
(b) Explain why B and A are placed in different groups, even though both have cell walls. [4]
(c) Describe how the student could use evidence about DNA or protein to improve the classification of two closely related organisms. [4]
(d) Explain why maintaining a wide variety of organisms in compost is useful to gardeners and to the wider environment. [4]
Answer Details
(a) A is plants, B is fungi, C is bacteria, and D is a virus. [4]
(b) Both A and B have cell walls, but B has chitin walls while A has cellulose walls. A has chloroplasts and makes food by photosynthesis. B lacks chloroplasts, is made of hyphae or filaments, releases enzymes for external digestion, and absorbs dissolved food. [4]
(c) Extract DNA or protein from each organism, then compare DNA base sequences or amino-acid sequences in proteins. Organisms with more similar sequences are likely to be more closely related. Combine this evidence with visible structural features to place organisms in groups or construct a classification tree. [4]
(d) Bacteria and fungi decompose dead material. This returns mineral ions to soil for plant growth. A range of organisms also provides food for different animals in food chains. Greater diversity makes the compost ecosystem more stable if one population falls and supports biodiversity. [4]
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