Question

(a) an energy pyramid for an ecosystem is shown.

producers (20,000 kcal)

part a
based on the energy pyramid, how much energy would be stored in the tertiary consumers in this ecosystem?
a 200 kcal
b 2 kcal
c 20 kcal
d 2,000 kcal

Explanation:

Step1: Recall energy pyramid rule

In an energy pyramid, only about 10% of energy is transferred to the next trophic level. Producers are at the base. Then primary consumers (10% of producers), secondary consumers (10% of primary), tertiary consumers (10% of secondary).

Step2: Calculate energy for primary consumers

Producers: 20,000 kcal. Primary consumers: \( 20,000 \times 0.1 = 2,000 \) kcal.

Step3: Calculate energy for secondary consumers

Secondary consumers: \( 2,000 \times 0.1 = 200 \) kcal.

Step4: Calculate energy for tertiary consumers

Tertiary consumers: \( 200 \times 0.1 = 20 \) kcal? Wait, wait, no—wait, the pyramid levels: producers (level 1), primary (level 2), secondary (level 3), tertiary (level 4). Wait, the pyramid in the image has producers at the bottom, then three levels above? Wait, maybe the levels: producers (20,000), then primary (10%: 2000), secondary (10%: 200), tertiary (10%: 20)? But wait, the options have 20 kcal as option C? Wait, no, wait—maybe I miscounted the levels. Wait, the pyramid shown: producers (bottom), then three layers above? Wait, the energy pyramid typically has producers (level 1), primary consumers (level 2), secondary (level 3), tertiary (level 4). So from producers (20,000) to primary: 20,000 0.1 = 2,000 (level 2). Level 3 (secondary): 2,000 0.1 = 200. Level 4 (tertiary): 200 * 0.1 = 20. Wait, but option C is 20 kcal. Wait, but let me check again. Wait, maybe the pyramid has producers, then primary, secondary, tertiary—so four levels? Wait, the diagram: producers (bottom), then three horizontal lines, making four levels? Wait, the producers are the bottom, then three layers above. So producers (level 1: 20,000), level 2 (primary: 2000), level 3 (secondary: 200), level 4 (tertiary: 20). So the answer should be 20 kcal, which is option C. Wait, but wait, maybe I made a mistake. Wait, the options: A.200, B.2, C.20, D.2000. Wait, let's recalculate:

Producers: 20,000 kcal (trophic level 1)

Primary consumers (trophic level 2): 10% of 20,000 = 2,000 kcal

Secondary consumers (trophic level 3): 10% of 2,000 = 200 kcal

Tertiary consumers (trophic level 4): 10% of 200 = 20 kcal

Yes, so tertiary consumers have 20 kcal. So option C.

Answer:

C. 20 kcal