Which statement best defines a limiting factor in biology?

• A. A resource that restricts the rate of a process.
• B. A resource that increases population growth.
• C. An inherited trait.
• D. A random mutation.

Answer: (A)

A limiting factor is something in the environment that prevents a process from happening faster or a population from growing larger. In biology, this means a resource or condition that restricts rate—like not enough food, space, or water, or harsh temperatures that slow metabolism. The best statement captures this idea: a resource that restricts the rate of a process. The other options describe things that don’t directly limit growth or rate—an inherited trait, a random mutation, or a resource that promotes growth. For example, when food is scarce, the rate of photosynthesis or reproduction slows down, illustrating how a limiting factor controls the outcome.