We explain what a trophic or food web is, differences with a trophic chain and its characteristics in terrestrial or aquatic environments.
What is a trophic web?
The food web, food web, or food cycle is called the natural 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 some living beings to others within a specific habitat . In other words, the sum of all the trophic 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 organic matter from other living beings and what type of living beings they usually feed on.
That is to say that among the heterotrophs are:
- Herbivoresor primary consumers. They feed on plants and other autotrophs.
- Carnivoresor secondary consumers. They feed on herbivores.
- Tertiary predatorsor consumers. They feed on both primaries and secondaries.
- Decomposing organisms. They are also heterotrophs , but they feed on decomposing organic matter, that is, dead.
All this classification is contemplated in trophic networks, an ecological perspective that was inaugurated by the English zoologist Charles Elton with his text Animal Ecology (1927), the first attempt to organize living beings into functional groups according to their way of nourishing themselves.
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.
It can serve you: Food chain
aquatic food web
The aquatic food web includes animals that do not live in water but feed there.
In aquatic ecosystems , food webs are fully adapted to life in, under, and on the surface of the water . This applies to large bodies of water such as oceans , lakes, and other bodies of water .
Aquatic food chains usually start with algae and a certain type 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 , when not small fish, sponges or other simple life forms .
The next link involves larger fish, jellyfish, and other very early predators . The third consumer link already shows good-sized fish, and even some final predators.
These chains must include actors who feed on the sea , but do not live in it , such as seabirds (such as pelicans) capable of fishing from schools on the surface.
Marine mammals (seals, walruses, whales) also take part in trophic webs , which usually act as final predators (except in the case of the seal, 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 . Scavenger 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.
More in: Aquatic ecosystem
terrestrial food web
In terrestrial food webs, predators find a wide variety of prey.
In terrestrial ecosystems , trophic webs are even larger than marine ones, since a gigantic variety of autotrophic organisms (plants) intervene in them.
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 volumes, to symbiotic fungi and decomposers, leaf-eating insects and a huge etcetera.
Likewise, such a variety of herbivores supports an equally diversified number of secondary consumers , among which are especially small rodents, some primates and arthropods such as spiders.
They also depend on tertiary consumers, larger and with a carnivorous appetite, such as big 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, scavengers or larvae of various kinds.
Food web and food chain
The difference between food webs and food chains is subtle: the sum of the food chains in an ecosystem will result in a food web . Food chains are linear, generally involving a single species from each food rung.
The networks instead try to combine them all to establish a map of how matter flows within the set of trophic relationships of a given place. That is why networks are more complex, more abundant, and more difficult to graph and conceive of .
Trophic pyramids and their levels
The trophic pyramid indicates how the number of beings at each level decreases.
The functional groups listed up to here (producers, primary, secondary and tertiary consumers, decomposers) that make up all the trophic chains and webs, can be visually organized based on the abundance criteria of each group .
In other words, the further away one is from the producing organisms , the less abundant life tends to be, given that the energy and nutritional requirements tend to be higher, due to having larger species. In this way, food chains and webs 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 the decomposers at the base , 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 to those above.
On the producers will be the primary or herbivorous consumers, and on 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, which is 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 have nothing on top, but will be nutritionally dependent on all levels below. However, it is important to remember that they also serve as food for decomposers.
desert food web
In the desert, plants are much less abundant than in other ecosystems.
The desert is an intense ecosystem, of 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 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, including xerophytic plants, such as cacti, never too numerous, unlike other ecosystems.
Instead, the decomposers are much more abundant compared to the other levels : insects, scavengers and microorganisms, since in the desert the intense conditions mean that nothing goes to waste.
Based on these decomposers, rather than on plants, the rest of the trophic web is sustained . In it are small primary consumers, mostly insects and some small rodents.
They are fed by hunting arthropods (such as scorpions), poisonous snakes or some small birds. And finally there is a third consumer link made up of birds of prey , snakes of a good size or some canids such as the coyote, depending on the location and the type of desert.