Exposure of cells to certain chemicals and radiation increases mutations and thus increases the chance of cancer. At times, environmental conditions are such that plants and marine organisms die faster than decomposers can recycle them back to the environment. Layers of energy-rich organic material have been gradually turned into great coal beds and oil pools by the pressure of the overlying earth. By burning these fossil fuels, people are passing most of the stored energy back into the environment as heat and releasing large amounts of carbon dioxide. The amount of life any environment can support is limited by the available energy, water, oxygen, and minerals, and by the ability of ecosystems to recycle the residue of dead organic materials.
Human activities can change the flow and reduce the usability of earth's resources.
Predict future impact if trends are consistent. The chemical elements that make up the molecules of living things pass through food webs and are combined and recombined in different ways. At each link in a food web, some energy is stored in newly made structures but much is dissipated into the environment as heat and becomes unusable by living organisms. Continual input of energy from sunlight keeps the process going. Construct a model of an ecosystem that illustrates the transfer and conservation of energy and matter as it flows through the biotic and abiotic environment.