What is the food chain?

The sequence of food relationships among various organisms in the food chain ecosystem is linked by a series of relationships between eating and being eaten. Eagles eat snakes, snakes eat frogs, frogs eat locusts, and locusts eat grass. This is a food chain with five links. Generally, it can be divided into three categories: raw food chain, or predation chain, starting from plants and passing through herbivores to carnivores; Fragrant rot chain, also known as debris chain, starts from animal and plant carcasses, such as litter → decomposer bacteria → bacteria eater → predator; Parasitic chains start from living animals and plants and pass through parasites at all levels, such as weasels → fleas → bacteria → bacteriophages. The proportion of energy flow in various food chains in the ecosystem varies greatly, which can be used as an indicator of the functional characteristics of the ecosystem. In the highly grazing grassland ecosystem, the food chain is mainly raw; In shallow water and forest ecosystems, saprophytic chains are dominant, and the proportion passing through parasitic chains is generally small. The food chain in the ecosystem is not fixed. For example, the eating habits of frogs change at different stages of individual development, and the eating habits of omnivores are also different in different seasons. If a link in the food chain changes, it may affect the structure and function of the ecosystem. Generally, the food chain does not exceed five or six trophic levels, because each level will lose a large part of energy, so the longer the food chain, the more the flow loss. Shorten the food chain. If food is mainly produced by producers, limited land can feed more people.