Types of Biotic Interactions
In a biological community, species interact with one another in various ways. These interactions can be classified based on whether they are harmful, beneficial, or neutral to the species involved. Interactions where at least one species is harmed are called negative interactions, those where both species benefit are positive interactions, and those where neither species is affected are called neutral interactions.
The major types of interspecific interactions include:
1. Amensalism
Amensalism is a negative association in which one species inhibits or harms another species without itself being affected.
- Example: The bread mould fungus Penicillium produces the antibiotic penicillin, which inhibits the growth of certain bacteria. This benefits Penicillium by reducing competition for resources while the bacteria are harmed.
2. Predation
In predation, one species, the predator, captures, kills, and eats another species, the prey.
- This interaction benefits the predator while harming the prey.
- Example: Leopards, tigers, and cheetahs use speed, claws, and teeth to hunt and kill their prey.
3. Parasitism
In parasitism, one species, the parasite, lives in or on another species, the host, and derives nourishment and often shelter at the host’s expense.
- The parasite benefits while the host is harmed.
- Examples: Cuscuta (dodder) and Loranthus (mistletoe) parasitize flowering plants. In animals, tapeworms, roundworms, malarial parasites, bacteria, fungi, and viruses are common parasites.
4. Competition
Competition is an interaction where both species are harmed as they vie for the same limited resources such as food, water, shelter, nesting sites, mates, or space.
- Competition can be:
- Intraspecific: between individuals of the same species; very intense.
- Interspecific: between individuals of different species.
- Example: Different predators competing for the same prey.
5. Commensalism
In commensalism, one species (the commensal) benefits while the other (the host) is neither harmed nor benefited.
- Examples:
- The remora (suckerfish) attaches to a shark to gain protection, transport, and leftover food, while the shark remains unaffected.
- Epiphytes (mosses, ferns, orchids) grow on trees for support, sunlight, and moisture without harming the tree.
6. Mutualism
Mutualism is a positive association where both species benefit.
- Examples:
- The sea anemone lives on the shell of a hermit crab, providing protection with its stinging cells, while benefiting from food scraps and transport.
- Termites and intestinal flagellates: Termites eat wood but cannot digest cellulose. Flagellates in their gut break down cellulose into sugars, which benefit both partners.
- Pollination: Bees get nectar from flowers while helping plants in cross-pollination.
When the mutualistic relationship is so close that neither species can survive without the other, it is called symbiosis.
7. Neutralism
Neutralism refers to an interaction between two species that does not significantly affect either species.
- In reality, true neutralism is rare because most interactions in an ecosystem have some level of impact, however small.
- Neutralism is often used to describe interactions that are negligible or insignificant.