Which of the following associations is an example of epiphytism?

Analyze the question: It asks which association is an example of epiphytism.

Explain the concept: An epiphyte is a plant that grows on the surface of another plant (usually a tree) for physical support only. It does not take water or nutrients from its host, so the host is not harmed. Epiphytes make their own food by photosynthesis and absorb moisture from the air and rain. Examples are ferns, orchids and mosses growing on tree trunks or branches.

Check each option:

• A. Lice in human hair: Lice are animals that feed on the host's blood or skin. This is parasitism, not epiphytism.
• B. Mistletoe on citrus fruit tree: Mistletoe is a plant that grows on another plant, but it sends haustoria into the host to absorb water and minerals. This is parasitism (a partial parasite or hemiparasite), not true epiphytism. (Note also that mistletoe grows on the citrus tree, not on the fruit.)
• C. Egret on cow: The egret eats ticks and insects from the cow, and the cow is rid of pests. This is mutualism (or commensalism, depending on how it is viewed).
• D. Fern on palm tree: The fern grows on the palm trunk only for support and makes its own food. This is epiphytism.

Tip: Think of epi = "upon" and phyte = "plant". An epiphyte is a plant that sits on another plant for support and takes nothing from it. If the plant takes nutrients from its host (like mistletoe), it is a parasite instead.