Any living organism chooses the conditions most favorable for its dwelling and providing it with the opportunity to fully eat. The fox chooses a place to live, where many hares live. The lion settles closer to the herds of antelopes. The sticking fish not only travels by attaching itself to the shark, but also has a meal with it.
Plants, although deprived of the opportunity to consciously choose a habitat, but mainly grow also in the most comfortable places for themselves. Nettle, often demanding nitrogen nutrition, often accompanies gray alder. The fact is that alder cohabits with bacteria that enrich the soil with nitrogen.
Food network - a kind of symbiosis
Here we are faced with a certain type of relationship. We are talking about the so-called symbiosis. This is a direct relationship in which both organisms benefit. They are also called food webs and chains. Both terms have a similar meaning.
What is the difference between the food chain and the food web? Separate groups of organisms (fungi, plants, bacteria, animals) constantly exchange among themselves certain substances and energy. This process is called the food chain. The exchange between groups is carried out while eating one by another. The process of interaction between such chains is called the food web.
How organisms are interconnected
It is known that leguminous plants (clover, mouse peas, caragans) coexist with nodule bacteria that convert nitrogen into forms that are absorbed by plants. In turn, bacteria get the organic substances they need from plants.
A similar relationship develops between flowering plants and mushrooms. It is no coincidence that many of them are called birch bark, boletus, oak. Sometimes mycorrhizal fungi are an indispensable factor for seed germination. This is especially important for the orchid family. In the tropics, a small heron feeds on parasites, pecking them from ungulates. Some hymenopteran insects obtain nectar from legume flowers, for which they are the only pollinators.
Food Network Examples
Many of the relationships described are specific. However, in each biocenosis there are relationships in which each population takes part. This is a food or trophic (trophos - food) relationship.
Examples of food webs and chains:
- Many animals eat plant foods. They are called herbivores, herbivores, and granivivores.
- There are animals that eat other animals. They are called carnivores, predators, insectivores.
- There are predatory bacteria and fungi.
- Many animals, bacteria, viruses, fungi, and sometimes plants not only feed on other organisms, but also live on them. These are parasites (parasitos - parasites).
- Finally, numerous bacteria and fungi feed on organic debris. These are saprotrophs (sapros - rotten).
In all cases, an organism that feeds on others benefits one-sidedly. Participating in the process of nutrition, all individuals of the population provide themselves with energy and various substances necessary for their vital functions. The population serving as an object of nutrition is negatively affected by predators eating it.
Autotrophs and heterotrophs
Recall that according to the methods of nutrition, organisms are divided into two groups.
Autotrophic (autos - itself) organisms live off an inorganic source of hydrocarbon. This group includes plants.
Heterotrophic (heteros - other) organisms live off an organic source of hydrocarbon. This group includes fungi, bacteria. If autotrophs are independent of other organisms in the source of carbon and energy, then heterotrophs in this respect are completely dependent on plants.
Competitive relationships between groups
Relationships leading to oppression of one of the partners are not necessarily related to nutritional relationships. Many weeds secrete metabolites that inhibit plant growth. Dandelion, wheat grass creeping, cornflower depressing effect on oats, rye and other cultivated cereals.
Populations of many species live in each biocenosis, and the relationships between them are diverse. We can say that the population is limited in its capabilities by these relations and must find its place inherent only.
The level of environmental habitat availability determines the existence of many niches. The number of species populations forming a biocenosis also depends on this. In a favorable climate of the steppes, biocenoses are formed, consisting of hundreds of species, and in the tropical climate of the forest, from thousands of species of organisms. Desert biocenoses in a hot climate have several dozen species.
The spatial distribution of populations is equally variable. Rainforests are multi-tiered, and living organisms fill the entire volume of space. In deserts, biocenoses are simple in structure, and populations are few in number. Thus, it can be seen that the joint life of organisms in biocenoses is unusually complex. Nevertheless, plants and animals, fungi and bacteria unite in biocenoses and exist only in their composition. What are the reasons for this?
The most important of them is the need for living organisms in nutrition, in trophic dependence on each other.