Omnivores are organisms that have a diet that includes of the ingestion of both plant and animal tissues. They have also been known to ingest bacteria and fungi.

Decomposition has been classified into the following three types: leaching, fragmentation, and chemical breakdown. Leaching is described as the flow of water through tissue, allowing it to be dissolved by the water solvent. Fragmentation is the physical breakdown of tissue to increase surface area exposure to microbes. Finally, chemical breakdown is defined as an enzymatic digestion of tissue.

The food web presents a graphical representation of the interconnected food chains within an ecosystem. In other words, food chains illustrate the trophic levels of a particular ecosystem.

Both detritivores and decomposers play important roles in the food chain and energy exchanges within an ecosystem. Detritivores consume decomposing plant and animal tissue (i.e. vultures). Decomposers break down decomposing tissue using biochemical reactions rather than ingestion (i.e. fungi).

The relationship that is occurring between the frog and the mite is known as commensalism because although the mite is benefitting from the frog, the frog is neither harmed or benefitting. Commensalism occurs when one organism benefits and the other is neither harmed or helped in any way. Parasitism benefits one organism at the expense of another. Mutualism benefits both organisms. Symbiosis is the general term for a specific interaction between species.

Both cellular respiration and photosynthesis are involved in the carbon cycle and the oxygen cycle. They both require carbon and oxygen in order to complete their mechanisms of action.

During photosynthesis, carbon is taken by the plant and converted into energy. As a result, oxygen is released. This oxygen can be used by cellular respiration to generate energy, which produces a carbon dioxide product. This carbon dioxide product can be recycled and eventually used for photosynthesis.

Energy, in an ecological context, refers to its flow in an ecosystem. Energy is passed from trophic level to trophic level; however, each time this occurs about ten percent of this energy is lost to the environment or as digested food. Energy is thus not recycled in this context.

In contrast, water, carbon, oxygen, nitrogen, and hydrogen are passed from one organism to another as organic material. This material is digested and incorporated into the organism's own biology, or released back into the ecosystem for continued use by other organisms in the environment. Energy can be passed from one organism to another in the form of chemical bonds and is released in the form of heat, but cannot be used by other organisms once it is returned to the environment and does not follow an ecological cycle.

Water, carbon, nitrogen, sulfur, and phosphorus have cyclic pathways that allowing them to flow within an ecosystem. Iron is not involved in very many ecological processes, and does not follow a defined chemical cycle.

Nitrogen makes up most of the Earth’s atmosphere; however, this reserve of nitrogen is limited for biological use. Nitrogen exists in diatomic forms in the atmosphere and the process of nitrogen fixation frees atoms for biological use. As a result, nitrogen is a limiting resource in many ecosystems.

In Earth’s atmosphere, carbon can be found in two forms: carbon dioxide and methane. Both are responsible for the greenhouse effect as they absorb and retain heat.