Biocenosis: what is it, its components and characteristics?
Let's see what biocenosis is and what are its different layers in nature.
An ecosystem is a Biological system made up of living and inert elements that interrelate in a series of complex chains and interactions. Thus, a specific ecosystem encompasses the biodiversity that inhabits and interacts in a physical space, with characteristic chemical and environmental properties. In the world, there are a total of 8 different types of ecosystems.
Despite this general definition, conceiving of an ecosystem as an enclosed and delimited space is a mistake.. Each ecosystem is made up of practically infinite microecosystems, with specialized characteristics and environments. Without going any further, the bark of a tree could be considered a microecosystem, since the conditions of light, humidity and availability of resources in this small space have nothing to do with the surface of the trunk or branches, for example.
Something as simple as the footprint of a large mammal can form a microecosystem for bacteria and small arthropods. Thus, the word "ecosystem" serves to roughly compartmentalize the variety of environments in the world, but not the actual biological needs of the different species of living beings. To delve more deeply into this term and its implications, today we tell you all about biocenosis, or what is the same, the living part of the ecosystem..
What is biocenosis?
A biocenosis (or biological community) is known as a the set of living beings that coexist, develop and interact in the same place.. In other words, this term encompasses all biological populations that coexist in space and time. This slightly abstract concept is essential to understand the general functioning of the ecosystem, because you must take into account the following:
Biotope (geographic space) + biocenosis (living things)= ecosystem.
Thus, the biotope refers to a physical space with specific physicochemical characteristics (temperature, light, humidity, pH and others) and the biocenosis, to the living beings that inhabit it.
Generally, when talking about a biological community, the first thing that comes to mind is large mammals and birds, striking for their size and ease of observation. Nothing could be further from the truth. we can distinguish the biocenosis in 3 main categories:
- Zoocenosis: refers to all animals in the ecosystem, from the most basic invertebrate to the largest superpredator.
- Phytocenosis: the variety of plants.
- Microbiocenosis: referring to microorganisms, i.e. protozoa, bacteria, microscopic fungi and other living things that are not directly observable.
Here are some interesting facts from a zoological point of view about the different strata that make up the biocenosis. Let's get to it.
You may have heard that at this level there is a concrete and easily explorable relationship: the trophic pyramid. Living beings base their existence on 3 events: survive, eat and reproduce..
To carry out the second task, animals "organize" (the quotation marks are necessary, as this is not a conscious behavior) when it comes to eating and preying, with the result that the biocenosis (and therefore the ecosystem) remains stable over time, at least ideally.
The trophic pyramid is conceived of as a series of linkswhere the base is represented by plants (producers) and the following spaces by herbivores, carnivores and superpredators (the "beak"), which feed on other hunting animals. This compartmentalization is rather basic and general, as many important feeding strategies, such as detritivores, parasites, hematophagous, necrophagous and many more, are left undescribed.
Thus, animals continuously interact with each other to eat, avoid being eaten, compete for resources and, exceptionally, to help each other.. The ecological niche represents this continuous "tug of war" between animals, because when two species overlap in terms of habits, resource exploitation and spatial occupation, one of the two is doomed to extinction or expulsion from the niche.
If we talk about phytocoenosis, we cannot leave out the term biomass. Biomass is defined as the weight of living material found in a given area at a given time.. This parameter can be expressed in normal or dry weight, generally with measures such as g/m2 and kg/m2. Although the strict concept must include animals and microorganisms, one of the most important indicators of the productivity of an ecosystem is the biomass represented by the phytocenosis, i.e., living plant beings.
To understand biomass, it is necessary to have a general understanding of net primary production, the rate at which new biomass is generated in an ecosystem, generally in the form of photosynthesis. For example, a swamp has a productive capacity of 2,500 gC/m2/year, while the value in a desert is tiny, at 3 gC/m2/year.
This is largely related to the trophic chain concept previously described, since it is estimated that from one level to the next there is a loss of 90% of the energy provided by the biomass consumed.. Thus, from a primary producer (plant) to a superpredator, which is 4 levels "up", a total change of 1,000 g/m2 to 1 g/m2 of transferable biomass can occur.
Let us not forget microbiocenosis, those living beings that cannot be perceived at first sight, but are nonetheless of great importance for ecosystems.. Without going any further, there are approximately 50 million bacterial cells in one gram of soil and one million bacterial cells in one milliliter of fresh water. With these data, it can be calculated that 15% of the total biomass of the planet corresponds to microscopic beings, or in other words, about 70 gigatons in weight.
We can say little more about microbiocenosis without entering into complex terms, beyond the fact that we also present it, as strange as it may sound. The microbiome that settles in our mucous membranes and intestines, for example, is a kind of microbiocenosis composed of bacteria that are generally symbionts and commensals.
Biocenosis is not watertight
The fact that a set of biological communities exist in the same space and time in a community does not mean that they will do so in the future. The biotope changes and, therefore, living beings must become accustomed to new challenges resulting from environmental variations (physical or chemical). (physical or chemical).
Communities can undergo variations over time, which is known as succession. These usually occur at very slow scales, and thanks to them, changes in populations occur, i.e., modifications in the biocenosis of the ecosystem itself.
In addition to all this, there are external factors that limit the biological distribution of a species, i.e., that it is part of a biocenosis and not of all the biocenoses of the planet at the same time. This concept is closely interrelated with that of the ecological niche, which we have touched on briefly above.. Some of these barriers are the following:
- Physical barriers: land, rivers, geographical features, cliffs and many other landscape formations.
- Climatic barriers: Living things develop and adapt to specific climatic conditions. Therefore, they cannot extend beyond a specific range without dying.
- Biological barriers: for example, the absence of food. A cow may be able to withstand the desert climate, but without grass, it would not last in the dunes for long.
These barriers between communities or biocenoses create complex but extremely interesting places from a biological point of view: ecotones. This is a transition zone, where all biological components are in tension. This is where the highest rates of energy exchange occur and, therefore, are often the places with the highest biodiversity richness.
As you may have noticed, every zoological term entails a series of widely interconnected previously settled concepts. We cannot understand a biocenosis, for example, without taking into account the ecological niche of species, trophic pyramids, barriers, biomass and productive capacity of an ecosystem, for example.
After all, all these terms condition the variety of populations of living beings that settle in a physical space.. Biotope and biocenosis create an ecosystem, but do not forget that neither of these two terms is immovable and infinite: ecosystems change continuously on a small or large scale, which is why biocenosis can undergo many variations along its evolutionary path.
- Biomass, mendoza.org. Retrieved January 31 from https://www.mendoza.conicet.gov.ar/portal/enciclopedia/terminos/Biomasa.htm#:~:text=The%20chain%20of%20biomass%20represents,energ%C3%ADa%20estimated%20at%20a%2090%25.
- Biological community, aitanatp.com. Retrieved January 31, from http://www.aitanatp.com/nivel6/ecosist/comunidad.htm.
- Gosset, A., Ferro, Y., & Durrieu, C. (2016). Methods for evaluating the pollution impact of urban wet weather discharges on biocenosis: a review. Water research, 89, 330-354.
- The biosphere, UM.es. Retrieved January 31 from https://www.um.es/sabio/docs-cmsweb/materias-may25-45/tema_5.pdf.
- Topic 2: Ecology, environmental factors and relationships in ecosystems, apuntesmareaverde.org.
(Updated at Mar 28 / 2023)