Question
What is the principal source of energy input into an ecosystem?
A) decomposers
B) herbivores
C) producers
D) the Sun
▶️ Answer/Explanation
Solution
Ans: D
The Sun (D) is the ultimate source of energy for nearly all ecosystems. Here’s why:
- Producers (plants/algae) convert solar energy into chemical energy via photosynthesis.
- Herbivores (B) and decomposers (A) rely on this energy indirectly.
- While producers (C) are essential for energy transfer, they depend on the Sun’s energy.
Thus, the Sun is the primary energy input, making D the correct answer.
Question
The diagram shows the amount of energy in kJ m-2 yr-1 at each trophic level of a food chain.
Approximately how much energy is lost between the producers and the secondary consumers?
A) 0.2%
B) 2.0%
C) 84%
D) 98%
▶️ Answer/Explanation
Solution
Ans: D
Energy loss is calculated as: (88,000-2,000)/88,000 × 100 = 97.7% ≈ 98%. This massive loss occurs because energy is wasted as heat (respiration), undigested materials, and movement at each trophic level, following the 10% rule in ecosystems.