Ecological Potency: Definition & Explanation

There is an innumerable number of different animal and plant species. All of these types can have different variations of abiotic and biotic environmental factors that they can tolerate. The ecological potency (or ecological tolerance) indicates within what range of values of the environmental factor a given species can exist.

Ecological Potency Definition

The ecological potency or ecological tolerance describes the breadth of the tolerance range of an organism within a community, taking into account both biotic and abiotic environmental factors that affect it.

Abiotic environmental factors are all chemical and physical environmental conditions that are exclusively related to the inanimate environment, such as temperature and light radiation.

Biotic environmental factors are all environmental influences of the living environment that affect living beings, such as competition between species.

If you would like to know more about abiotic and biotic environmental factors, please have a look at the appropriate explanations.

Thus, the ecological potency describes the tolerance range, in which a species is actually found in the environment. Therefore, the ecological potency for each kind is different, even if they occur in the same environment.

An organism has high ecological potency if it has a wide tolerance range, and low ecological potency if an organism has smaller tolerance ranges.

Ecological Potency Simply Explained

Not only do physiological tolerances of the organism play a role in ecological potency (i.e., the genetically determined tolerance to the most diverse environmental conditions), but also the biotic environmental factors. These include the competitor species. To describe how important a particular environmental factor is to an organism, the term ecological valence is important.

The ecological valence describes the value of one or different ecological factors compared to a certain living being. Under the physiological tolerance, one understands the genetically determined tolerance towards a certain abiotic environmental factor in a non-competitive environment. So, this is more of a theoretical value.

Ecological Potency Tolerance Curve

In the figure, you can see a typical tolerance curve determined by any abiotic environmental factor. The intensity of life processes is shown here in relation to the intensity of environmental factors. The tolerance range describes the range in which the survival of an organism is still possible. The limit points of this tolerance range are minimum and maximum.

The representation of the tolerance curve is a purely theoretical representation, determined by the genetic conditions of the organism.

Minimum and Maximum

That minimum and the maximum are the points at which the tolerance range ends and life of the organism is no longer possible. If these points are exceeded, the living being dies.


If the intensity of the environmental factor approaches the minimum or maximum, the organism can still survive for a limited time. Reproduction cannot take place in the area of pessimism since the focus here is purely on survival.

Preference (Range of Preference) and Optimum

That preferential or preference area describes the preferred area of a living being. It is the range most suitable for the organisms in question. Here, they are exposed to the least stress. Both reproduction and all other life processes can take place here without any problems. The point of the highest intensity of life processes is called optimum.

Minimum Law

In nature, there are always several environmental factors for a given species that can be described with ecological potency. Therefore, the occurrence and survival of a species is always limited by the environmental factor that is furthest from optimal.

Liebig’s law of the minimum states that the growth of organisms is always restricted by the scarcest resource.

Mainly, Liebig’s law of the minimum describes a phenomenon from the plant world because one can better document the growth and yield of plants than is the case with animals. The environmental factors that Liebig describes in his law are primarily abiotic factors such as temperature, light, pH, or nutrient concentration. Classically, the law of the minimum is represented by a barrel filled with water, from which water flows until the water has reached the height of the lowest plank.

Euryok and Stenok

With the terms of euryoecia and the stenocry, you can measure the width of the tolerance range to describe a kind. If you want to describe organisms in terms of a specific environmental factor, you can expand the term:

  • Environmental Factor: Suffix
  • Food: Euryphagous / Stenophagous
  • Salinity: Euryhaline / Stenohaline
  • Temperature: Eurytherm / Stenotherm
  • Moisture of the Soil: Euryhygr / Stenohygr
  • Oxygen Content: Euryoxygenic / Stenooxygenic
  • Water Depth: Eurybatic / Stenobatic
  • Geographical Location: Eurytopic / Stenotopic


As euryok refers to species that have a very wide tolerance range. Euryoke or eurypotent species are able to withstand large fluctuations in environmental factors.

Seagulls are a vivid example of a Euryokean animal species. On the one hand, most seagull species are omnivores, as you may have noticed on your last visit to the sea. Especially in habitats where seagulls live close to people, they like to eat everything you drop or they search through garbage cans for food. On the other hand, seagulls have a high salt tolerance, since they mainly cover their fluid requirements with salty seawater. They have special salt glands on their skulls to excrete excess salt.


As stenok refers to species that have a very narrow tolerance range. Stenoke or stenopotent species tolerate fluctuations in environmental factors only to a limited extent. If the organisms are highly dependent on an abiotic environmental factor, they can also be called Pointer Types (Indicator) because they indicate where to find the required intensity of a particular environmental factor.

At pointer types, these are mainly plants that can only be found in very specific areas of a habitat. An example of a species that indicates particularly acidic soil is the blueberry. Their ecological niche includes acidic and nutrient-poor soils. The soil is too acidic for other plant species, and it is therefore not possible to survive. However, if the pH of the soil changes, i.e., continues to rise or fall, the blueberry cannot adapt well and will die.

An ecological niche is the term given to the interrelationship of a species and the abiotic and biotic environmental factors that affect it. If that’s not enough of an explanation for you, then feel free to take a look at the appropriate explanation.

Ecological Potency Example

An example that shows the difference between the physiological and the ecological potency can be recognized in the Scots pine. Because of their physiological and genetic prerequisites, it could grow on almost any soil because it has a high moisture tolerance, i.e., a euryhygr physiological potency. However, under natural conditions, in which biotic environmental factors also play a major role, it occurs almost exclusively in very dry locations. Thus, its ecological potency is low in relation to the water content in the soil, so it is stenohygr.

Key Takeaways

  • Ecological potency (Ecological Tolerance) is the range of tolerance of an organism to all influencing factors abiotic and biotic environmental factors.
  • The physiological potency is the tolerance range determined by genetic conditions towards certain abiotic environmental factors.
  • The tolerance curve is divided into that pessimism, the preferential and the optimum as a point of highest intensity of life processes. Minimum and maximum mark the lower and upper borders of the tolerance range.
  • As euryok refers to species that have a very wide tolerance range.
  • As stenok refers to species that have a very narrow tolerance range.
  • Pointer types are stenöke species found only within a small range of intensity of an environmental factor.


  1. Jens Boenigk (2021). Boenigk Biology.
  2. Townsend et al. (2009). Ecology.

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