NAVTA Practice Test

Lice.

1. Identify this worm.

2. Identify this parasite.

3. Identify this bacterium.

4. Identify this virus.

The correct answer is: Identify this parasite.

Identifying lice as a parasite is correct because lice are ectoparasites that infest the skin and hair of their hosts, feeding on blood or skin debris. They are part of the class Insecta and are specifically categorized under the order Phthiraptera. Lice depend on their host for survival and reproduction, which is a defining characteristic of parasites. Being an external organism that lives on a host and derives nutrients at the host's expense aligns with the definition of a parasite. The other options refer to entities that are categorized differently; worms are a different subgroup of organisms, primarily helminths, which are more complex in structure, and not applicable to lice. Bacteria and viruses are entirely different classes of microorganisms, with bacteria being single-celled prokaryotes and viruses being acellular entities that require a host cell to replicate. Lice do not fit into these categories, solidifying the appropriateness of identifying them as a parasite.