When describing an ecosystem, you are essentially describing all of the elements of nature in a specific local environment. Types of ecosystems you might describe include woodlands, grasslands, lakes, marshes and even underwater environments such as coral reefs. Regardless of the type, all ecosystems consist of a mixture of various living and non-living components.
An important part of most ecosystems are the primary producers. When describing primary producers, you basically are describing green plants. These plants, including trees and flowers, manufacture the bulk of their food through a process known as photosynthesis. During photosynthesis, plants turn sunlight into nutrients--specifically, sugars. Primary producers get their name because they provide nourishment to another very important part of the ecosystem--consumers.
Usually when people talk about consumers in an ecosystem, they are referring to animals, from insects to fish to humans. Unlike primary producers, which obtain their energy from non-living parts of the ecosystem, consumers get most of their energy from producers or other consumers. You can describe the different consumer species of an ecosystem by placing them into three main categories: carnivores, herbivores, and omnivores. Carnivores mainly subsist on other animals, herbivores consume only plants, and omnivores eat a combination of plants and animals.
When describing the parts of an ecosystem, it is helpful to also describe the relationships among the different parts. Producers and consumers inevitably die, and when they do, organisms known as detritivores feed on their remains. This process is called decomposition. During decomposition, detritivores convert dead plant or animal material into non-living, inorganic matter, which is eventually reused by producers. Many detritivores are microorganisms, such as bacteria, but fungi and larger creatures like earthworms and crustaceans also act as decomposers.
In descriptions of ecosystems, the non-living elements--also known as abiotic or inorganic compounds--may often be overlooked. Rocks, minerals, soil, water and the atmosphere itself are examples of abiotic parts of ecosystems. When describing an ecosystem, it’s imperative to also describe the abiotic parts, because they essentially enable the rest of life to exist in the ecosystem. For example, sunlight provides the energy plants need for photosynthesis, and the air or water provides the oxygen that mammals need to breathe. It is through such processes that energy flows through different parts of the ecosystem.