What is Amensalism? Definition, Types, Examples

In an ecosystem, different types of biological interaction occurred for the proper functioning of an ecosystem. Amensalism is a type of interspecific interaction. Biological interaction is of two type-interspecific and intraspecific, they play a major role in maintaining the food webs.

The interaction of populations of two different species leads to interspecific interactions. These interspecific interactions could be either beneficial,  neutral, detrimental to one of the species, or both. A ‘+’ sign for beneficial interaction is represented by a + sign, neutral interaction is assigned as 0 and detrimental interaction is represented as minus (-).

Population Interactions

Interaction	Species A	Species B
Mutualism	+	+
Competition	–	–
Predation	–	+
Parasitism	–	+
Commensalism	0	+
Amensalism	0	–

Amensalism 

This single-sided interaction between species. Here there is a negative or harmful effect on one species but a neutral or neither beneficial nor harmful effect on another species.  Simply, amensalism is a form of single-sided competition.

Examples of Amensalism

• Adenostoma Fasciculatum– commonly called chamise produces a chemical that is water-soluble. This chemical gets aggregated over the surface of chamise leaves during dry periods. At the time of rainfall, this accumulated chemical substance gets washed off due to water solubility nature and spreads into the soil where it hinders the germination process and growth of many plants.
• Juglans nigra commonly called the black walnut tree secretes a chemical Juglone from its roots. This chemical kills the plants that are around the black walnut tree.
• Another example of amensalism is small plants that grow under big trees. These big trees hinder the amount of available sunlight and obstruct the required sunlight to the small plants under them.
• Penicillin commonly called bread mold produces a chemical substance called penicillin. This penicillin is an antibiotic, i.e. kills bacteria.
• Algal Bloom causes the death of many fishes present in the water bodies.

Importance of Amensalism

Such biological interaction is used to control the growth of harmful bacteria. For example, Penicillin is used widely as an antibiotic to restrict the growth of many bacteria. Here penicillin inhibits and shows (0), and the growth of bacteria is negatively affected (-).

Modes of Amensalism

Amensalism is of 2 types Competetion and Antibiosis

Competition

Stronger organism dominates over the lower organism for food and shelter, such physical interaction of organisms is known as competition. Competition between the species occurs because the ecosystem is not the ideal environment. So the shortage of food and shelter leads to competition. The result of the competition depends on the species. 

Between Inferior and Superior

Bettles and goats both feed on the shrub. but during feeding beetles get harmed and goats persist in any damage. Goats during feeding harmed the beetles as they are the dominating (superior) ones over the beetles (inferior).

Between two similar species

Competition between the species occurred for food, mate, and shelter. They are more dangerous interactions. For example, male lions are fighting for their mate both lions get injured or either of them will be dead. 

Antibiosis

Certain species of plants or organisms produce harmful chemical substances that are dreadful to animals. Vuillemin gave the term antibiosis. The most acceptable example of the antibiosis is penicillin antibiotic.

Examples of Antibiosis

• Roots of Tagetes species commonly called marigolds produce terthienyls. These terthienlys inhibit the growth of nematodes and fungi.
• Green, red, and blue algae form algal blooms and produce toxic chemicals that are harmful to fish. This process is termed antibiosis.
• Antibiotics that restrict bacterial growth, penicillin produced by Penicillium notatum fungus, restricts bacterial growth. 

Amensalism Vs. Commensalism

These are both biological interactions. But amensalism and commensalism are totally opposite. Commensalism is the interaction in which one species benefits and the other species get harmed (+,-), and in amensalism, one species gets harmed and one neither gets harmed nor benefits.

Example of Commensalism

• Whales and Barnacles
• Tree frogs on plants

FAQs on Amensalism

Question 1: What is Amensalism?

Answer: 

It is a biological interaction between two species in which one gets harmed and one species is neutral (0).

Question 2: What is Antibiosis?

Answer:

Some organisms secrete poisonous substances that are harmful to other animals this process is called Antibiosis.

Question 3: Explain one example of amensalism.

Answer: 

Amensalism is a 0/- relationship between species in contact. A widely accepted example of amensalism is penicillin antibiotics which inhibit the growth of other bacteria.

Question 4: What are the various interspecific competitions that exist in nature?

Answer:

• Mutualism: Here both species benefit from each other 
• Competition:  In this interaction, both species will lose to each other. 
• Predation and Parasitism: Here only one species is benefitted (i.e predator and parasite) and the interaction is destructive to the other species (i.e host and prey). 
• Commensalism: This is +/0 interaction. Here one species is benefitted and another is neither benefitted nor harmed. 
• Amensalism: If one species is harmed and the other is neither harmed nor benefitted from the interaction is termed Ammensalism.

Question 5: What are interspecific interactions?

Answer:

The interaction of populations of two different species leads to interspecific interactions. These interspecific interactions could be either beneficial,  neutral, or destructive to other species.