Zoology - Organisms and Populations Question with Solution | TestHub

The (+,-) symbols can be applicable for both predation and parasitism. But according to the question, it is denoting parasitism. Parasites that feed on the external surface of the host organism are called ectoparasites. The most familiar examples of this group are lice on humans and ticks on dogs. Many marine fishes are infested with ectoparasitic copepods. Cuscuta, a parasitic plant that is commonly found growing on hedge plants, has lost its chlorophyll and leaves in the course of evolution. It derives its nutrition from the host plant which it parasitises.