Ecosystems, abiotic and biotic factorsEdexcel A-Level Biology A: Mind map

Exam questions on Ecosystems, abiotic and biotic factors

1. A school pond in a woodland contains common frogs, smooth newts, water beetles, dragonfly larvae, pondweed, algae and many microorganisms. The pond water has a pH of 6.8 and its temperature changes with the seasons.
   Explain why the pond is described as an ecosystem and not just as a community.2 marks
2. On a rocky shore two species of barnacle form separate bands. Chthamalus lives high on the shore, which is covered by sea water only at the highest tides. Semibalanus lives lower on the shore, which is covered by sea water for most of the time. Ecologists removed Semibalanus from the lower shore, and Chthamalus then settled and grew there. Semibalanus grows faster than Chthamalus and covers the rock. When the ecologists removed Chthamalus from the upper shore, Semibalanus still failed to survive there.
   Explain how both a biotic factor and an abiotic factor account for the distribution of the two species on the shore.2 marks
3. An ecologist is studying how the abundance of marram grass changes across a sand dune system, from the strand line (the top of the beach) to 200 m inland. She suspects that the water content and the salt content of the sand change across the dunes.
   Describe how she could use quadrats and a transect to measure the distribution and abundance of marram grass.3 marks