Question

Which one of the following is categorized as a parasite, in the true sense?

• A. The duck lays its egg in another duck's nest
• B. Orchid growing on a tree
• C. Fleas living on a dog
• D. Fungus that infects an ant and eventually grow out of its exoskeleton

Answer 1

The correct option is C Fleas living on a dog

A parasite is an organism which lives in or on another organism (its host) and benefits by deriving nutrients at the other's expense and does not kill the host. A parasite in the true sense, is usually much smaller than its host, lives a shorter period of time, often reproduces within (or on) its host, and often does not kill its host. Such an example here is the flea living on the dog. The duck laying egg inside another duck's nest is a form of parasitism called brood parasitism, and the fungus that infects the ant is a parasitoid. Parasitoids are much closer in size to their hosts, they live about the same length of time, most are incapable of reproducing in or on their hosts (they require a free-living period), and they usually kill their hosts. The orchid growing on the tree, although it derives its nourishment from the tree, it does not harm the tree, therefore the relationship is truly commensalism.