Environmental Science
Environmental Science
This domain tests ecosystems, food chains and webs, energy flow, biogeochemical cycles, natural resources, pollution, biodiversity and conservation.
Core rules
- An ecosystem includes biotic communities and abiotic factors interacting in a defined area.
- Producers make food by photosynthesis; consumers eat other organisms; decomposers break down dead matter and recycle nutrients.
- A food chain shows one path of energy transfer; a food web shows interconnected chains.
- Energy flow is unidirectional and follows the 10% law: only about 10% passes to the next trophic level; most is lost as heat.
- Nutrients such as carbon, nitrogen and oxygen cycle through biotic and abiotic components; energy does not cycle.
- Pollution can be air, water, soil or noise; biomagnification concentrates non-biodegradable pollutants along food chains.
- Biodiversity conservation includes protected areas, afforestation, recycling and reducing pollution.
Worked example
If producers contain 10,000 J of energy, herbivores receive about 1,000 J and carnivores about 100 J under the 10% law. The remaining energy is lost mainly as heat through respiration and in uneaten parts and wastes. This is why food chains rarely have more than four or five trophic levels: too little energy remains to support higher consumers.
Traps
Do not say energy is recycled; nutrients cycle, energy flows. Decomposers are not a trophic level of predators. Ozone depletion and global warming are different problems: CFCs deplete ozone, while greenhouse gases trap heat. A longer food chain does not mean more energy.