[Biology Class Notes] on Amensalism Pdf

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 to access other topics of biology apart from amensalism meaning. You can also install the app to take your notes