Amensalism-Defination & Examples

Amensalism is the interaction between organisms wherein one is inhibited or killed while it does not affect the other. This topic is an important part of the Class 12 chapter Organism and Population. Amensalism involves the release of chemical substances or other forms of inhibition of one from the other affecting ecosystems and population dynamics. Amensalism meaning, amensalism examples, and comparison with commensalism are discussed in this article. This topic is important for the students preparing for CBSE or entrance exams with biology as a major subject like NEET, and AIIMS.

What is Amensalism?

Amensalism is the affiliation of organisms from two distinct species, in which one is prevented from thriving or is wiped out while the other is untouched. Different animals on Earth have a wide variety of interactions. Not all of them, though, are good. One such instance of a bad association between two species is amensalism.

Amensalism is the term used to describe an ecological relationship between two species, although, in this association, one species' creatures are killed out or hindered while the other is untouched. Asymmetrical competitive engagement is also frequently referred to as amensalism.

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Amensalism Meaning and Definition

Amensalism Definition in Biology: Amensalism is the phenomenon where one species is adversely affected while the other remains unaffected in the interaction between two species. This relation is mainly negative for one species but neutral for the other.

Amensalism Meaning: It is a type of relationship in which one organism is inhibited or destroyed by the action of another organism that is left uninhabited.

Modes of Amensalism

There are two main modes of Amensalism, which are divided into Antibiosis and Competition. In both types of amensalism, one organism is harmed, while the other one is unharmed.

Antibiosis

Definition: Antibiosis, from the French term "antibiosis," refers to an antagonistic relationship that involves harming one organism by chemicals or actions from another organism. The term was first introduced by Vuillemin in 1889–1890.

Mechanism: It works by releasing chemicals or toxins that inhibit or kill other organisms.

Examples of Antibiosis

Penicillium mould and bacteria: Penicillin is bactericidal, produced by the mould Penicillium. It is due to this discovery that penicillin was developed as an antibiotic against bacterial infections.

Black walnut trees and other plants: Juglone is the toxin found in the black walnut tree that stops the growth and kills the plants within the root zone of the tree. This reduces competition.

Interaction of microbes and antibiotics: The mechanism through which specific antibiotics act on bacterial cells thus involves interference with the synthesis process of their cell walls, which also occurs in antimicrobial relationships.

Competition

Definition: In amensalism competition, two species compete with scarce resources. For one organism, the other one will cause damage as it is not affected.

Mechanism: It occurs due to organisms competing over limiting resources, like food, space, or light, which may not be available to all the competitors.

Types of Competition

Intraspecific Competition: Individuals belonging to the same species in competition for resources. This includes competition amongst the plants of the same species for sunlight.

Interspecific Competition: competition of different species for the same resource, such as plants from different species competing for water.

Interference Competition: where direct interference to another species accessing resources is experienced (for example one plant releasing chemicals to prevent another close plant from growing).

Exploitation Competition: indirect competition of species by depleting the pool of shared resources (for example, animals consuming the same food source and reducing its availability for others).

Amensalism Examples class 12

Here are some examples of amensalism:

• Penicillin, produced by penicillium, kills a variety of microorganisms.

• Black walnut roots exude juglone, a poisonous substance that kills other herbaceous plants in their vicinity.

• The actinomycete streptomyces prevents bacterial development. Most commonly, antibiotics are used.

• Convolvulus arvensis prevents wheat from growing.

Difference between Commensalism and Amensalism

The major difference between commensalism and amensalism is described below:

Tips, Tricks and Strategies to Prepare Amensalism for Exams

Here are some tips and tricks to prepare amensalism for different exams:

• Diagrams and Tables: Include diagrams of amensalism, as exemplified by the suppression by Penicillium of the growth of bacteria. Complete comparison tables on amensalism compared to commensalism.
• Mnemonics: Use simple phrases like "A-N: Affect None" to remind you that amensalism only affects one organism.
• Flashcards: This uses words such as Amensalism, Chemical Inhibition, and Juglone Release to learn those important terms.
• Visualization Tools: Observe animations to see how chemical from plants or fungi inhibits other organisms, with this providing a better understanding of amensalism.
• Real-Life Applications: Relate how the above issues apply to real-life situations, such as how certain trees inhibit the growth of other plants or how these can limit practices such as gardening and forestry.

Types of Questions and Weightage of Amensalism in Exams

The table below indicates the weightage and types of questions asked from amensalism in different exams:

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