What is a parasite?

• A. An organism that protects another
• B. An independent species
• C. An organism that lives in or on another organism
• D. A type of bacteria

Answer: (C)

A parasite is defined as an organism that lives in or on another organism, known as the host, and derives nutrients at the host's expense. This relationship often harms the host, as the parasite can take resources or cause disease without providing any benefit in return. This symbiotic relationship is critical to understand because it highlights the potential risks associated with parasites, including their ability to spread diseases and impact both human health and agriculture.

In contrast, an organism that protects another does not fit the definition, as it describes a mutualistic relationship rather than parasitism. An independent species refers to organisms that can survive and thrive on their own without relying on a host, which is not the case for parasites. Lastly, while some parasites may be microorganisms, not all parasites are types of bacteria, as they can also include protozoa, worms, and other organisms. The essence of parasitism lies in the dependence on a host for survival and reproduction, making option C the most accurate definition.