Energy flows through an ecosystem in a one-way stream, from primary producers to various consumers. A food chain is a series of steps in which organisms transfer energy by eating and being eaten. 

The primary source of energy for almost every ecosystem on Earth is the sun. Primary producers use energy from the sun to produce their own food in the form of glucose, and then primary producers are eaten by primary consumers who are in turn eaten by secondary consumers, and so on, so that energy flows from one trophic level, or level of the food chain, to the next. 

The amount of energy at each trophic level decreases as it moves through an ecosystem. As little as 10 percent of the energy at any trophic level is transferred to the next level; the rest is lost largely through metabolic processes as heat.  

Trophic Levels

An ecosystem is divided into various levels called trophic levels. The trophic level of an organism is the position it occupies in a food web. Various trophic levels are as follows:

• First trophic level: This level is occupied by the producers which include green plants, phytoplankton and algae. These plants make their own food through photosynthesis. They are also called autotrophs. 

• Second trophic level: It is occupied by the primary consumers that consume plants (herbivores) and nothing else. 

• Third Trophic Level: This level is occupied by the secondary consumers (carnivores) .

• Fourth trophic level: Large carnivores that are also called tertiary consumers make up this level.

A heterotroph is an organism that consumes other organisms in a food chain. Primary, secondary and tertiary consumers can also be called hetrotrophs.

Decomposers (detritivores) break down dead plant and animal material and wastes and release it again as energy and nutrients into the ecosystem for recycling. Decomposers, such as bacteria and fungi (mushrooms), feed on waste and dead matter, converting it into inorganic chemicals that can be recycled as mineral nutrients for plants to use again.

A carbon sink is a natural or artificial reservoir that absorbs and stores the atmosphere’s carbon with physical and biological mechanisms. Carbon sequestration is the process of capturing and storing atmospheric carbon dioxide. 

As discussed in Activity 3, oceans are an important carbon sink but so too are forests. Forests like the bushland in Balls Head and Harbour Reserves are typically carbon sinks. This means that are places that absorb more carbon than they release. They continually take carbon out of the atmosphere through the process of photosynthesis. 

Ideally, the carbon cycle would keep Earth’s carbon concentrations in balance, moving the carbon from place to place and keeping atmospheric carbon dioxide levels steady. However, the carbon cycle is changing because of human activity. People are releasing more carbon into the atmosphere by using fossil fuels and maintaining large livestock operations. Deforestation is depleting Earth’s supply of carbon sinks. As a result, the amount of carbon in the atmosphere is rising. (Natural Geogrpahic: https://education.nationalgeographic.org/resource/carbon-sources-and-sinks/)