We explain what a food or food web is, differences with a food chain and its characteristics in terrestrial or aquatic environments.
What is a food web?
The natural food cycle is called the food web, food web, or food cycle. interconnection of all food chains belonging to an ecological community. It is generally represented visually, in the form of a network or also a pyramid.
Let us remember that these food chains linearly describe the way in which matter and energy pass from one living being to another within a specific habitat. In other words, the sum of all the food chains of an ecosystem will result in its food web.
The trophic relationships between various forms of life are understood based on a primary and fundamental distinction between organisms:
- Autotrophic organisms They are capable of synthesizing their nutrients from inorganic matter.
- Heterotrophic organisms They are incapable of said synthesis and therefore are forced to consume the organic matter of other living beings, whether they are autotrophs or heterotrophs in turn.
Each of these categories makes up a trophic level, in which all living beings can be classified. However, heterotrophic or consumer organisms are subdivided into different groups, depending on what strategies they implement to consume the organic matter of other living beings and what type of living beings they usually feed on.
That is to say that among the heterotrophs there are:
- Herbivores or primary consumers They feed on plants and other autotrophic beings.
- Carnivores or secondary consumers They feed on herbivores.
- Predators or tertiary consumers They feed on both primaries and secondary ones.
- Decomposer organisms. They are also heterotrophic, but they feed on decomposing, that is, dead, organic matter.
All this classification is contemplated in food networks, an ecological perspective that the English zoologist Charles Elton inaugurated with his text animal ecology (1927), first attempt to organize living beings into functional groups according to their way of nutrition.
Then the contributions on the subject of Raymond Lindeman (1942) were added, insisting on the vital role of decomposers in the ecological circuit. All of this is vital for the understanding that we currently have of the way in which matter and energy are transmitted throughout the food webs of an ecosystem.
Aquatic food web
In aquatic ecosystems, food webs are completely adapted to life in, under and on the surface of water. This applies to large bodies of water such as oceans, lakes and other water reservoirs.
Aquatic food chains usually start in algae and certain types of photosynthetic microorganisms that float on the surface, called phytoplankton, and that play the role of autotrophic producers.
The primary consumers feed on them, generally other microorganisms (zooplankton) or tiny crustaceans, if not small fish, sponges or other simple life forms.
The next link involves larger fish, jellyfish and other top predators. The third link of consumers already shows good-sized fish, and even some final predators.
Actors who feed on the sea, but do not live in it, must be incorporated into these chains such as seabirds (such as pelicans) capable of fishing from schools on the surface.
Marine mammals (seals, walruses, whales) also intervene in food networks, which usually act as final predators (except in the case of the seal, the favorite prey of the orca whale and certain sharks). In lakes, rivers or certain islands, amphibians and reptiles also participate as active predators depending on their size (such as crocodiles).
Likewise, the decomposers of the sea are legion. Scavenging crustaceans, tiny fish and various types of microorganisms take care of the organic matter left over from hunting, which in turn constitutes a rain of food for the deepest and darkest regions of the sea.
Terrestrial food web
In terrestrial ecosystems, food webs are even vaster than marine ones, since in them a gigantic variety of autotrophic organisms are involved (floors).
As a consequence, There is a wide diversity of primary consumers: from insects that feed on sap or nectar, through fruit-eating birds and ruminant herbivores of various sizes, to symbiotic and decomposer fungi, leaf-eating insects and a huge etcetera.
In addition, such a variety of herbivores supports an equally diversified number of secondary consumers which especially include small rodents, some primates and arthropods such as spiders.
Tertiary consumers, of larger size and carnivorous appetite, also depend on them, such as large hunting cats, bears, lizards, birds of prey, higher primates and, of course, humans.
The most common decomposers are bacteria and other microorganisms, as well as fungi, scavenging insects or larvae of various types.
Food web and food chain
The difference between food webs and food chains is subtle: The sum of the food chains of an ecosystem will result in a food web. Food chains are linear, generally involving a single species from each food step.
Networks, on the other hand, try to combine them all to establish a map of how matter flows within the set of trophic relationships of a given place. That's why networks are more complex, more abundant and more difficult to graph and conceive.
Trophic pyramids and their levels
The functional groups listed so far (producers, primary, secondary and tertiary consumers, decomposers) that make up all food chains and networks, can be visually organized based on the abundance criterion of each group.
That is to say, the further away you are from the producing organisms, the less abundant life tends to be, given that the energy and nutritional requirements tend to be higher, as there are larger species. In this way, food chains and networks can be illustrated in the form of a pyramid: the trophic pyramid.
The pyramid will be sectioned into levels, each one corresponding to a trophic link having at the base the decomposers, and next to them the producers, forming the base of the pyramid: abundant and primary, they do not depend on any link, but they support those above.
Above the producers there will be the primary consumers or herbivores, and above them the secondary and tertiary consumers, with as many levels as necessary, as we tend towards larger species, greater appetite, but at the same time less abundance, something represented in the narrowing of the pyramid towards its tip.
Thus, for example, the final predators, located at the very tip of the pyramid, will not have anything above them, but will depend nutritionally on all the lower levels. However, it is important to remember that they also serve as food for decomposers.
Desert food web
The desert is an intense ecosystem, with life adapted to resist the brutal daily temperatures and the terrible drought, which is quite a challenge given that there is scarce vegetation in these places, designed to resist for a long time without water or to capture it from the air, and therefore a very low rate of biodiversity.
However, In the desert it is possible to find all the trophic levels of a pyramid: the producers, among which will be xerophytic plants, such as cacti, never too numerous, unlike other ecosystems.
Instead, decomposers are much more abundant compared to the other levels: insects, scavengers and microorganisms, since in the desert the intense conditions mean that nothing is wasted.
Based on these decomposers, more than plants, the rest of the food web is sustained. It contains small primary consumers, mostly insects and some small rodents.
Hunting arthropods (such as scorpions), poisonous snakes or some small birds feed on them. And finally there is a third link of consumers made up of birds of prey, large snakes or some canids such as coyote, depending on the location and type of desert.
Continue with: Desert animals
References
- “Food web” on Wikipedia.
- “Food network. The sea in depth” (video) in eduCaixa.
- “Food chain and food web” in Ovacen.
- “Food Web: Knowledge and Applications” in Nature.
- “Food chains and food webs” on BBC Bitesize.
