The basic level of any ecosystem is called the producer, and this level mainly consists of autotrophic plants (the ones capable of photosynthesis). These plants absorb nutrients from the soil, and with the help of sunlight synthesize carbohydrates to form glucose molecules. These compounds are further used for energy generation, along with water and carbon dioxide. The next levels consist of primary, secondary, and tertiary consumers, each of which depend on the lower ranks for food and energy. Apart from this, another class of organisms called detritivores (for example, fungi, and bacteria) exist in every ecosystem, which help in the decomposition and degradation of dead organisms. This helps in releasing nutrients back to the Earth's surface, wherein the cycle starts again. Energy is transferred from the lower to the higher levels, as the complexity goes on increasing.
Differentiating the various environment of habitation is possible if one has the basic knowledge of all the relevant parameters. The 12 types of ecosystems and their characteristics are described in brief, in the following sections.