1. Commensalism is a biotic interaction that is beneficial to one organism, the commensal, while the other is unaffected.

2. Feeding relationships are the most common examples of commensal interactions. Probably the most well-known examples are those of birds with grazing animals and clownfish with sea anemones. Birds such as egrets often cling to grazing animals, such as cattle or wildebeast, and feed on the parasites on their backs.

3. The tentacles of anemones contain stinging cells that paralyse most fish but the clownfish are unaffected by them. Clownfish live happily in amongst the tentacles, feeding on scraps of food from the prey of the anemone and even laying their eggs between the tentacles. The clownfish coats itself in the mucus secreted by the anemone, this enables it to live in close proximity as it is not seen as a foreign species so is not attacked. The anemone does not benefit from the relationship, but is not harmed by it either.

4. Although one organism gains from the interaction the other is not always completely unharmed. The organism may not be harmed significantly but it may have slight energy losses due to carrying or feeding another organism. Why Is It So Difficult To Achieve True Commensalism? Answer