Biology Regents Practice Exam

Which example represents maintaining dynamic equilibrium?

1. A plant wilting due to water loss

2. A plant turning yellow in low light

3. Insulin release when glucose levels are high

4. A person sweating in low temperature

The correct answer is: Insulin release when glucose levels are high

Maintaining dynamic equilibrium refers to the ability of an organism to regulate its internal environment despite external changes. The correct example of this concept is the release of insulin when glucose levels are high. This process is part of the body's homeostatic mechanisms, which work to keep blood sugar levels within a normal range. When glucose levels rise after eating, the pancreas senses this increase and releases insulin, a hormone that allows cells to take in glucose for energy or store it for later use. This response helps to lower the blood glucose levels back to a stable point, demonstrating a key aspect of dynamic equilibrium—where the internal conditions are actively maintained despite fluctuations in external factors (like food intake). In contrast, the other examples do not reflect this active maintenance of internal stability. A plant wilting due to water loss indicates a failure to maintain turgor pressure and overall health, which is an example of disorder rather than equilibrium. A plant turning yellow in low light also shows a lack of necessary conditions for photosynthesis, leading to stress rather than equilibrium. Lastly, a person sweating in low temperatures is an inappropriate response to maintain temperature balance, as sweating is typically a mechanism to cool down the body rather than regulate it in a colder environment. Hence, they do not