Assistant Laboratory Animal Technician (ALAT) Practice Exam

What is a parasite in biological terms?

1. An organism that lives independently

2. An organism that benefits its host

3. An organism that lives on or in a host for nourishment

4. An organism that is harmful to all living beings

The correct answer is: An organism that lives on or in a host for nourishment

In biological terms, a parasite is specifically defined as an organism that lives on or in a host and derives nourishment at the host's expense. This relationship is characterized by the fact that the parasite depends on the host for its survival and sustenance, often causing harm to the host in the process. The essence of parasitism lies in this dependence and detrimental impact on the host organism, which typically suffers from the presence of the parasite. The other options emphasize different interactions or characteristics that do not accurately capture the nature of parasitism. For instance, an organism that lives independently does not engage in a parasitic relationship, while the idea of benefiting its host implies a mutualistic association rather than a parasitic one. Lastly, describing a parasite as harmful to all living beings is overly broad and not entirely accurate, as the harm is specifically directed towards the host, and many organisms can coexist without being negatively impacted by parasites. This distinction is crucial in understanding the unique relationship parasites have with their hosts.