A complete overview of Amensalism
Many different relationships exist between various species of earth. However, not all of them are positive. Amensalism is one such example of a negative correlation between two species. Let us understand what is amensalism? Amensalism refers to an ecological interaction between two species, but in this association among organisms of two different species, one is destroyed or inhibited, and the other remains unaffected. Moreover, amensalism is frequently used to refer to asymmetrical competitive interaction.
Examples of Amensalism
Some of the notable amensalism examples are mentioned below.
Penicillium secretes penicillin, which kills various bacteria
Roots of black walnut release juglone, which is a toxic material that destroys other herbaceous plants within its range
Streptomyces is an actinomycete that inhibits the growth of bacteria. It is mostly used as antibiotics
Convolvulus arvensis hinders the development of wheat.
Types of Amensalism
As mentioned earlier, amensalism meaning is a reaction in which one organism is harmed and the other stays unaffected. Now this interaction between two species can be divided into two categories, antibiosis and competition.
Antibiosis Definition
The word antibiosis comes from the French word ‘antibiosis’. It was coined by Vuillemin in 1889-1890 to define an antagonistic relationship between various organisms within an ecosystem. Additionally, this biological interaction between two organisms is detrimental to at least one of them. A classic antibiosis example is a penicillium. Penicillin secreted by bread mould penicillium has a devastating effect on bacteria. Thus, it has become a potent medicine to combat bacterial infections.
Another typical example of this phenomenon is juglone secreted by black walnut trees. This toxic element can destroy other plants residing within its root zone.
Other examples of antibiosis comprise the relationship between antibiotics and bacteria. Moreover, the study of antibiosis and its importance in antibiotics has led to new discoveries in microbiology. Molecular processes like cell wall synthesis and recycling have enabled researchers to get a better understanding of antibiotics. Furthermore, scientists can now better understand how antibiotics affect beta-lactam development via antibiosis. Additionally, they can now establish the relationship and interactions of particular drugs where bacteria are subjected to the compound.
Competition Definition
Competition in biology refers to an amensalism relationship between two species competing for survival. This competition stems from the fact that resources on earth are limited, and there is not enough for everyone. The consequences of competition vary based on the species competing for a particular resource. Furthermore, this competition can be classified into four different categories.
Between Inferior and Superior:
In case the competition is between an inferior and a superior species such as a goat and a beetle, one is bound to be eliminated. Beetles and goats depend on shrubs for their food. However, while consuming it, goats remained unharmed, but a beetle might get hurt. Beetles not only lose a substantial quantity of their food but stand the chance of getting eaten by a goat.
Between Two Similar Species:
On the other hand, a competition between two related species is a more balanced affair. For instance, if a lion and a tiger fight over a deer, probably either of them will be dead or both of them will be injured.
Between Two Organisms of Similar Species: In this scenario, the competition is between two organisms of the same species. For example, when two tigers fight each other for a single pray. They may have killed it together, but now they are competing for the largest share.
Between Two Organisms From Different Species:
This scenario occurs when two organisms of different species compete for a single resource. The previous example of a lion and a tiger fighting for one deer is a fitting example here.
Amensalism is necessary to retain the balance in the ecosystem. You can visit the official app of Vedantu to access other topics of biology apart from amensalism meaning. You can also install the Vedantu app to take your notes
FAQs on Amensalism
1. What is amensalism in ecology?
Amensalism is a type of negative ecological interaction between two different species in which one species is harmed or inhibited, while the other species remains completely unaffected. This relationship is symbolised as a (-/0) interaction, where '-' denotes a harmful effect and '0' denotes a neutral or no effect.
2. What are some classic examples of amensalism as per the CBSE syllabus?
According to the CBSE Biology curriculum for the 2025-26 session, some key examples of amensalism include:
- The bread mould Penicillium secretes penicillin, a chemical that kills various species of bacteria. The mould is unaffected, but the bacteria are harmed.
- The black walnut tree (Juglans nigra) releases a chemical called juglone from its roots, which is toxic and prevents the growth of other plants within its root zone.
- The plant Convolvulus arvensis is known to hinder the growth of wheat plants when they grow nearby, demonstrating a form of chemical interference.
3. How is amensalism classified as a negative interaction?
Amensalism is classified as a negative interaction because at least one of the participating organisms experiences a detrimental effect. Even though the other organism is unaffected, the presence of harm, inhibition of growth, or destruction of one party is sufficient to categorise the entire relationship as negative from an ecological perspective.
4. What is the key difference between amensalism and commensalism?
The key difference lies in the effect on the first organism. In amensalism (-/0), one organism is harmed while the other is unaffected. In commensalism (+/0), one organism benefits while the other is unaffected. For example, penicillin killing bacteria is amensalism, whereas an orchid growing on a tree for support (without harming it) is commensalism.
5. How can one distinguish between amensalism and competition?
While related, they are distinct interactions. Competition (-/-) is an interaction where both species are negatively impacted because they rely on the same limited resources. In contrast, amensalism (-/0) involves one species being harmed while the other shows no discernible effect. Amensalism is often viewed as a form of asymmetrical competition, where one organism is so much stronger or more efficient that it harms its competitor without being affected itself.
6. Why is the interaction between Penicillium mould and bacteria a prime example of antibiosis, a form of amensalism?
This is a classic example of antibiosis because one organism (the mould) produces a specific biochemical substance (penicillin) that is detrimental to another (the bacteria). This fits the definition of amensalism perfectly because:
- The bacteria are harmed (their growth is inhibited or they are killed).
- The Penicillium mould is unaffected by the bacteria in this context; it does not gain or lose anything from killing them.
7. In amensalism, one organism is harmed while the other is unaffected. How does this differ from parasitism?
This is a common point of confusion. The critical difference is the outcome for the second organism. In amensalism (-/0), the organism causing the harm is unaffected and does not derive any benefit from the interaction. In parasitism (+/-), the parasite actively benefits (+) by living on or in the host, from which it derives nourishment or shelter, thereby harming the host (-). The key distinction is the absence of benefit for the harming organism in amensalism.
8. What is the ecological importance of amensalism in an ecosystem?
Amensalism plays a significant role in structuring biological communities and maintaining ecosystem balance. For instance, allelopathy (chemical inhibition by plants like the black walnut) can regulate plant distribution and diversity by preventing other species from growing nearby. This reduces competition for resources for the dominant species. Similarly, antibiosis can control microbial populations, influencing soil health and decomposition cycles. It is a natural mechanism for population control and shaping the composition of an ecosystem.
