Although there are many kinds of organisms in the ecosystem and they play different roles in the ecosystem, they can be divided into three categories according to their roles in energy and material movement: producers, consumers and decomposers.
Producers are mainly green plants, which can make nutrients from inorganic substances. This function is photosynthesis, including some chemotactic bacteria (such as nitrifying bacteria). They can also synthesize organic matter from inorganic matter. The role of producers in the ecosystem is primary production or primary production, so they are primary producers or primary producers. The biomass they produce is called primary production or primary production. The producer's activity is to obtain carbon dioxide and water from the environment and synthesize carbohydrates (mainly glucose) under the action of solar light energy or chemical energy. Therefore, only through producers can solar radiation be continuously input into the ecosystem and transformed into chemical energy, that is, biological energy, which becomes the only energy in the life activities of consumers and decomposers.
Consumers belong to heterotrophs, referring to those animals that feed on other organisms or organic matter, and they directly or indirectly feed on plants. According to different feeding habits, it can be divided into herbivores and carnivores. Herbivores are called first-class consumers. They devour plants to get the food and energy they need. This kind of animals, such as some insects, mice and wild boar, walk all the way to the elephant. Herbivores are also preyed by carnivores, who are called second-class consumers. For example, ladybugs feed on aphids and weasels feed on mice, so ladybugs and weasels can also be called first-class carnivores. There are also some large carnivores that prey on small carnivores, such as foxes, wolves and snakes, which are called third-class consumers or second-class carnivores. There are other carnivores, such as lions, tigers, leopards, eagles and vultures, which feed on second-class carnivores, that is, fourth-class consumers or third-class carnivores. In addition, parasites are special consumers and can be regarded as herbivores or carnivores according to their feeding habits. However, some parasitic plants, such as mistletoe and mistletoe, belong to producers because they can make their own food. Omnivorous consumers are between herbivores and carnivores, eating both plants and animals, such as carp and bears. Human food is also omnivorous. These different levels of consumers get food from different organisms, forming a "nutrition level"
Because many animals not only get food from one trophic level, for example, tertiary carnivores not only prey on secondary carnivores, but also prey on primary carnivores and herbivores, so they belong to several trophic levels. In the end, human beings are the most advanced consumers. He is not only a carnivore at all levels, but also feeds on plants. So the boundaries between different trophic levels are not obvious.
In fact, in nature, each animal does not eat only one kind of food, thus forming a complex food chain network.
The decomposer is also heterotrophs, mainly various bacteria and fungi, including some protozoa and saprophytes such as beetles and termites that feed on dead wood, as well as earthworms and some mollusks. They decompose complex animal and plant residues into simple compounds, and finally into inorganic substances, which return to the environment and are reused by producers. Decomposition is of great significance in material circulation and energy flow, because about 90% of the primary production on land must be returned to the earth through decomposition, and then transferred to green plants for photosynthesis. So decomposers can also be called reducers.
The biological chain cannot be changed according to one's own wishes. If it is not changed properly, it will have a great impact on biology.