Fig. 1 shows a simplified food web observed in a saltmarsh field. Arrows show the direction in which food energy moves between organisms. A student is inves...
Question 1 Report
Fig. 1 shows a simplified food web observed in a saltmarsh field. Arrows show the direction in which food energy moves between organisms. A student is investigating the effect of a disease that reduces the number of shore crabs in this natural habitat.
(a) Name the producer and one primary consumer in Fig. 1. [2]
(b) Complete this food chain using organisms from Fig. 1: marsh grass → ________ → shore crab → heron. [2]
(c) Explain how a large decrease in the number of shore crabs could affect both snail numbers and the amount of marsh grass. [4]
Answer Details
(a) The producer is marsh grass. A primary consumer is a snail or a worm, because it feeds on the producer. [2]
(b) The completed food chain is marsh grass → snail → shore crab → heron. [2]
(c) If shore crab numbers decrease, fewer crabs eat snails. Snail numbers therefore increase. More snails feed on marsh grass, so the amount of marsh grass decreases. This is an indirect effect through the food web. [4]
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