Which is an example of a limiting resource in an ecosystem?

• A. Temperature.
• B. Predators.
• C. Sunlight.
• D. Nutrient availability such as phosphorus.

Answer: (D)

Limiting resources are the essential needs that constrain how much life can grow when they are in short supply. Phosphorus availability fits this idea well because phosphorus is crucial for making DNA, RNA, ATP, and cell membranes, yet it often exists in low concentrations in soils and water. When phosphorus is scarce, organisms can’t synthesize the molecules they need to grow and reproduce, so population growth slows even if other things like light or temperature are adequate. This is why phosphorus availability is a classic limiting resource in many ecosystems.

Temperature is an environmental condition that affects how fast processes run, but it’s not a resource that organisms consume or compete for. Sunlight is a source of energy for photosynthesis and can be limiting in some situations (like deep water or dense shade), but in many ecosystems it’s readily available, so it’s not the typical limiting nutrient lot of questions focus on. Predators influence population size through predation rather than serving as a scarce resource that organisms must compete to obtain.