Which best defines homeostasis? modifying the external environment maintaining a stable internal environment controlling what enters and exits the cell movement of materials into the cell
The Correct Answer and Explanation is:
The correct answer is maintaining a stable internal environment.
Homeostasis is a fundamental concept in biology that describes the ability of an organism or a cell to maintain a constant and balanced internal state, despite changes in external conditions. This process is essential for survival, as the biochemical reactions that sustain life, primarily those involving enzymes, can only occur within a very narrow range of conditions like temperature, pH, and chemical concentrations.
The phrase “maintaining a stable internal environment” accurately captures this core principle. For example, humans must maintain a core body temperature around 37°C (98.6°F). If the external temperature drops, the body initiates mechanisms like shivering to generate heat. If it gets too hot, the body sweats to cool down. Similarly, blood glucose levels are tightly regulated by hormones like insulin and glucagon to ensure cells have a consistent energy supply without being damaged by excess sugar. This constant adjustment and regulation is the essence of homeostasis.
Let’s consider why the other options are not the best definition. “Controlling what enters and exits the cell” describes the function of the cell membrane, which is a critical mechanism for achieving homeostasis at the cellular level, but it is not the definition of homeostasis itself. Homeostasis is the broader outcome of many such regulatory mechanisms working together throughout an entire organism. “Movement of materials into the cell” is even more specific and incomplete, as it only describes one aspect of cellular transport. Finally, “modifying the external environment,” such as a beaver building a dam, is a behavioral adaptation, not the internal physiological regulation that defines homeostasis. Therefore, maintaining a stable internal environment is the most comprehensive and accurate definition of the term.
