Food chain: the food chain refers to the order of food nutrition supply and demand between biological members in the ecosystem through eating and being eaten. For example, in the grassland ecosystem, rabbits eat grass, foxes eat rabbits, and wolves eat foxes, forming a "grass-rabbit-fox-wolf" food chain. As the basic unit of the nutritional structure of ecosystem, food chain is the main channel of material circulation, energy transformation and information transmission in the system. Every feeding level in the food chain is called trophic level. In the above example, grass is the first trophic level, rabbit is the second trophic level, and so on, which are represented by symbols T 1, T2, T3, etc.
Due to different food habits, food chains are often divided into the following four types: ① Predatory food chain, also known as living food chain or herbivorous food chain, which is characterized by direct consumption of living organisms or their tissues and organs. For example, the algae-crustacean-small fish-big fish food chain existing in lakes belongs to the predatory food chain type. ② The food chain of scavengers, also known as the food chain of scraps or scraps, is a food chain that decomposes organic matter into inorganic matter through decomposition. For example, the litter in the forest is transformed into organic particles or debris by earthworms, then into simple organic matter by fungi and actinomycetes, and finally decomposed into inorganic matter by bacteria, which belongs to the type of scavenger food chain. (3) Mixed food chain, also known as omnivorous food chain, is characterized by the existence of both living food chain and scavenging food chain in many links of the food chain. For example, the plant-herbivore-feces-earthworm-bird food chain on grassland belongs to the mixed food chain. (4) Parasitic food chain is a food chain formed by feeding on living tissues or organs in a parasitic way. For example, the food chain of mammals or birds-flea-protozoa-bacteria-virus belongs to parasitic food chain type. In addition, there are many kinds of plants that can prey on animals in nature, such as pitcher plants, pitcher plants, flycatchers and so on. They can catch small beetles, moths, bees and even frogs. These plants decompose trapped animals, produce amino acids and then absorb them. This is a very special food chain.
Food web: Food web refers to the network relationship between food supply and demand formed by connecting multiple food chains. In the ecosystem, the relationship between eating and being eaten by various organisms is often not single, and the trophic level is often complex. The formation of food webs is due to the fact that one organism often feeds on a variety of foods, and the same food is often eaten by many organisms.
The revelation of food web phenomenon and its laws has the following ecological significance: ① Food web is ubiquitous in nature, which directly or indirectly connects various biological components in the ecosystem. ② There are many kinds of food webs with complex components, which means that the composition and structure of food webs are often diverse and complex, which is very important for increasing the stability and sustainability of ecosystems. (3) Food web essentially reflects a series of relationships between repeated eating and being eaten among organisms in the ecosystem. It not only maintains the relative balance of the ecosystem, but also is a powerful driving force to promote biological evolution and the continuous development and evolution of nature.
Learning point
Ecological restoration
Ecological restoration refers to stopping human interference with the ecosystem to reduce the load pressure, relying on the self-regulation and self-organization ability of the ecosystem to make it evolve in an orderly direction, or using this self-recovery ability of the ecosystem, supplemented by artificial measures, to gradually restore the damaged ecosystem or make the ecosystem develop in a virtuous circle; Mainly refers to the restoration and reconstruction of the destroyed natural ecosystem under the influence of natural mutation and human activities.