Fig. 1 shows plants and animals observed on a rocky hot desert slope in northern Chile. Rain falls only occasionally, yet a cactus, a small lizard and an in...
Question 1 Report
Fig. 1 shows plants and animals observed on a rocky hot desert slope in northern Chile. Rain falls only occasionally, yet a cactus, a small lizard and an insect are present. The researcher recorded that the cactus has a thick stem and shallow spreading roots. The lizard was seen sheltering below a rock during the hottest part of the day. This case study is being used to investigate adaptation to water shortage and extreme temperature.
(a) Outline three adaptations of the cactus shown in Fig. 1. [3]
(b) Explain how the lizard can reduce water loss and avoid overheating. [4]
(c) Draw an annotated food web for this hot desert using the organisms in Fig. 1 and two suitable additional organisms. Explain how the web could be affected by a prolonged drought. [8]
Answer Details
(a) Any three: thick succulent stem stores water [1]; spines reduce leaf surface area [1]; spines deter grazing [1]; shallow widespread roots absorb brief rainfall [1]; waxy surface reduces evaporation [1]. (b) Shelters in shade/burrow during hottest hours [1]; avoids direct solar heating [1]; may be active at cooler times [1]; reduced activity lowers water loss/respiration [1]. (c) Award up to [8]: at least five organisms including cactus, insect and lizard [1]; arrows correctly show energy transfer [1]; cactus correctly shown as producer [1]; insect correctly shown as primary consumer [1]; lizard correctly shown as consumer of insects [1]; two plausible extra organisms, for example seed-eating rodent and hawk [1]; drought reduces plant productivity/food [1]; linked population decline or increased competition/predation [1].
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