91Èȱ¬

Organisms depend on each other for survival. This is called interdependence. Both living and non-living factors will affect the abundance and distribution of organisms in a habitat.

The feeding relationships between organisms in an ecosystem can be seen in food chains. Sampling allows us to measure the abundance and distribution of these species.

Biodiversity is a measure of how many different species live in an ecosystem. Human activities like changing land use, deforestation and peat bog destruction reduce this.

Factors such as the increase in human population, new pests and pathogens and armed conflict, can result in food scarcity. Improved farming techniques and sustainable fisheries can help increase supply.

Materials such as carbon, nitrogen and water are recycled in the ecosystem. When organisms die, decomposition will recycle minerals and nutrients back to the environment.

Understanding how to approach exam questions helps to boost exam performance. Question types will include multiple choice, structured, mathematical and practical questions.