Ecosystems Questions Essay Example

[Total 8 marks] 6.

Chalk grassland communities are found in areas of southern England such as the South Downs. Woodland rather than grassland is the climax community for this habitat. Grazing by sheep and rabbits maintains the grassland. (I) Define the term climax community. Suggest how grazing by sheep and rabbits could prevent a woodland climax community from developing. Littoral 2 marks] 7. (a) Plants rely on the cycling of nitrogen to supply them with nitrogen in a form that they can absorb. Select, from the list, the most suitable word or term that matches the statements I) to (v) below. Active transport nitrogen fixation demagnification Interrogate identifying bacterium Interactions differentiations endometriosis Rhizome nitrification (I) The conversion of nitrate ions into nitrogen gas. A bacterium that fixes nitrogen. (iii) A method by which nitrate ions pass into root hair cells.. ? (iv)The conversion of ammonium ions into nitrite ions. (b) Before the widespread use of artificial fertilizers, farmers used a variety of methods to improve the fertility of the soil and so improve the yield of their crops.

Two of the methods in common use were: Plugging-in In which legumes, such as beards, alfalfa or clover, were grown in a field and then harvested. The roots were then ploughed back into the soil rather than being dug up or burnt. Crop rotation In which different crops were grown in a field in each year for three years. In the fourth year, the fallow year, the field was not used for crops. In the following year the crop cycle was started again. Explain how plugging-in and crop rotation are able to improve the fertility of the

soil.