Which of the following best explains how a nutrient can act as a limiting factor in an ecosystem?

• A. A nutrient limits population growth when it is in short supply, restricting the productivity of organisms that depend on it.
• B. A nutrient has no effect on the productivity of organisms in an ecosystem.
• C. A nutrient always increases population growth regardless of its concentration.
• D. A nutrient only affects the ecosystem if it is completely absent.

Answer: (A)

Verified step by step guidance

1. Understand the concept of a limiting factor: A limiting factor is any resource or condition that restricts the growth, abundance, or distribution of organisms in an ecosystem. In this case, the nutrient is the resource being discussed.
2. Recognize the role of nutrients in ecosystems: Nutrients are essential for the growth and survival of organisms. For example, nitrogen and phosphorus are critical for plant growth, and their availability can directly influence the productivity of an ecosystem.
3. Analyze the relationship between nutrient availability and population growth: When a nutrient is in short supply, it can limit the growth of organisms that depend on it. This is because organisms cannot grow or reproduce effectively without sufficient access to essential nutrients.
4. Evaluate the incorrect options: A nutrient does not always increase population growth regardless of its concentration, as excessive nutrients can lead to negative effects like eutrophication. Similarly, a nutrient does not need to be completely absent to affect an ecosystem; even a shortage can have significant impacts. Lastly, a nutrient does have an effect on productivity, contrary to the statement that it has no effect.
5. Conclude that the correct explanation is: A nutrient limits population growth when it is in short supply, restricting the productivity of organisms that depend on it. This aligns with the concept of a limiting factor in ecology.