Ontario Operator-in-Training (OIT) Practice Exam

What protective strategy might some protozoa employ in harsh conditions?

1. Forming spores

2. Creating biofilms

3. Forming cysts or oocysts

4. Reproducing rapidly

The correct answer is: Forming cysts or oocysts

Protozoa often face challenging environmental conditions such as extreme temperatures, desiccation, or lack of nutrients. To survive these harsh circumstances, many protozoa can form cysts or oocysts. This protective strategy involves encasing themselves in a thick, resistant outer layer, which helps them to withstand extreme conditions. Cysts and oocysts are dormant forms of protozoa that are resistant to desiccation, heat, and other environmental stresses. When conditions improve, these dormant forms can reactivate, allowing the organism to return to its active state and resume normal functions, including reproduction. While forming spores is another way some microorganisms withstand harsh conditions, it is more commonly associated with fungi and certain bacteria rather than protozoa. Creating biofilms is more related to the collective behavior of microbial communities than individual survival, and reproducing rapidly does not provide a protective mechanism but rather a means of population expansion during favorable conditions. Therefore, the strategy of forming cysts or oocysts is a well-established method for protozoa to endure unfavorable environments until they are once again optimal for survival.