Biology STAAR (State of Texas Assessments of Academic Readiness) Practice Test

In which type of symbiotic relationship does one organism benefit while the other is unharmed?

1. Mutualism

2. Parasitism

3. Commensalism

4. Competition

The correct answer is: Commensalism

In a symbiotic relationship characterized as commensalism, one organism benefits while the other remains unaffected. This interaction involves two different species where one species gains advantages, such as food or shelter, without causing any harm or benefit to the other species involved. This scenario is a key aspect of ecological relationships, highlighting the myriad ways organisms can interact within their environments. Mutualism, in contrast, involves both organisms benefitting from the relationship. Parasitism is where one organism benefits at the expense of the other, often causing harm. Competition refers to the struggle between organisms for the same resources, resulting in a detrimental effect for both participants. Commensalism can be observed in many natural settings, such as barnacles adhering to whales, where the barnacles receive mobility and access to feeding opportunities while the whales are largely unaffected.