Which of the following best distinguishes primary consumers from secondary consumers in an ecosystem?

• A. Primary consumers are always carnivores, while secondary consumers are always herbivores.
• B. Primary consumers obtain energy from sunlight, while secondary consumers obtain energy from chemical compounds.
• C. Primary consumers decompose organic matter, while secondary consumers produce their own food.
• D. Primary consumers feed directly on producers, while secondary consumers feed on primary consumers.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the roles of primary and secondary consumers in an ecosystem. Primary consumers are organisms that feed directly on producers (plants, algae, or other autotrophs), while secondary consumers feed on primary consumers.
2. Step 2: Eliminate incorrect options by analyzing their definitions. For example, primary consumers are not always carnivores; they are typically herbivores that consume producers. Secondary consumers, on the other hand, are often carnivores or omnivores that consume primary consumers.
3. Step 3: Recognize that primary consumers do not obtain energy directly from sunlight. Producers (like plants) are the ones that convert sunlight into chemical energy through photosynthesis. Primary consumers obtain energy by consuming these producers.
4. Step 4: Clarify that primary consumers do not decompose organic matter. Decomposers, such as fungi and bacteria, perform this role. Similarly, secondary consumers do not produce their own food; only producers (autotrophs) do this through photosynthesis or chemosynthesis.
5. Step 5: Conclude that the correct distinction is that primary consumers feed directly on producers, while secondary consumers feed on primary consumers. This aligns with the trophic levels in an ecosystem.