IB Biology Sub-topic C4.2 Notes

A huge focus on Topic 4 is ecology, defined as the study of ecosystems, and you are expected to know them in detail. An ecosystem is the interaction of a community with its abiotic environment. Within this:

1. The nutrient supply is maintained via cycles, making it extremely sustainable. 
2. The energy supply is not maintained, as energy is able to pass in as sunlight and pass out as heat.

By definition, this makes ecosystem closed systems, as energy is able to move in or out, but matter is not (for the most part). Remember that sunlight is the principal source of energy that sustains each ecosystem on the planet, with exception of:

1. Caves - deep enough, sunlight is unable to reach and provide energy for the ecosystem. Energy thus enters in the form of entering animals or debris that has washed in.
2. Deep water - deep enough, sunlight does not penetrate either and thus it does not provide energy. Energy thus enters in the form of dead animals that have sunk into the deep ocean.