Commensalism & Parasitism

What is commensalism in ecology?

Commensalism is a symbiotic relationship where one species benefits while the other species is unaffected (neither helped nor harmed).

Give a marine example of commensalism involving clownfish.

Clownfish (Amphiprioninae) live among the stinging tentacles of sea anemones:

• Clownfish benefit by gaining protection from predators (immunity to toxins) and eating leftover food.

• Sea anemones appear unaffected (no gain or loss).

What is parasitism?

Parasitism is a symbiotic interaction where one species (parasite) benefits at the expense of another (host). The host is harmed, often losing energy, health, or reproductive success.

How can parasitism be categorized based on parasite size?

• Microparasites: Microscopic parasites (e.g., Plasmodium protozoan, which causes malaria in humans).

• Macroparasites: Larger parasites visible to the naked eye (e.g., adult tapeworms inside intestines, lice on animal skin).

What is the difference between endoparasites and ectoparasites?

• Endoparasites live inside the host’s body (e.g., tapeworms in intestines).

• Ectoparasites live on the outside of the host (e.g., lice, ticks, fleas).

What is social parasitism?

Social parasitism occurs when a parasite exploits or manipulates the social behaviour of its host, instead of feeding directly on its body.

What is brood parasitism and give an example.

Brood parasitism is when one bird lays its eggs in another bird’s nest, tricking the host into raising its offspring.

• Example: The common cuckoo (Cuculus canorus) removes the host bird’s eggs, lays its own, and leaves. The host parents incubate and feed the cuckoo chicks, raising them as if they were their own.

Why is parasitism different from predation?

Predation kills the prey immediately, while parasitism usually keeps the host alive but harms it over time (draining energy, health, or reproductive ability). Parasites depend on host survival for their own survival.