Question

use the energy pyramid below to answer this question. using the 10% rule, if the grass takes in 2500 units of energy from the sun, how much energy is available to the frog ecological pyramid a. 25 units b. 2500 units c. 250 units

Explanation:

Step1: Identify the trophic levels

Grass is a producer (first trophic level). Let's assume the food chain is Grass → Insect → Frog (so frog is at the third trophic level from grass). Wait, actually, in an energy pyramid, each level above gets 10% of the previous. Let's see: Grass (level 1) → next level (herbivore, level 2) → then frog (level 3, if frog is a secondary consumer). Wait, maybe the grass is level 1, then the next level (say, insect) is level 2, then frog is level 3. Wait, no, maybe the grass is level 1, then the primary consumer (level 2) gets 10% of grass's energy, then the secondary consumer (frog) gets 10% of level 2's energy. Wait, but maybe the frog is two levels above grass? Wait, let's re - examine. The 10% rule: energy transferred from one trophic level to the next is about 10%. So grass (producer, level 1) has 2500 units. Then the next level (primary consumer, level 2) gets 10% of 2500, which is \(2500\times0.1 = 250\) units. Then the next level (secondary consumer, frog) gets 10% of 250, which is \(250\times0.1=25\) units? Wait, no, maybe the frog is at the second level above grass? Wait, maybe the energy pyramid has grass at the bottom (level 1), then the next level (level 2) is the herbivore, then level 3 is the frog. Wait, but let's check the options. Option A is 25, B is 2500, C is 250. Wait, maybe I made a mistake in the trophic levels. Wait, maybe the frog is at the second trophic level from grass? No, grass is producer (level 1), then primary consumer (level 2) eats grass, then secondary consumer (frog) eats primary consumer. So level 1: 2500, level 2: \(2500\times0.1 = 250\), level 3: \(250\times0.1=25\). But wait, maybe the frog is at level 2? No, grass is level 1 (producer), then the next level is primary consumer (herbivore), then frog is secondary consumer (level 3). So the energy available to frog is 25 units? But wait, maybe the diagram shows grass at the bottom, then the next level (say, insect) is level 2, then frog is level 3. Wait, let's calculate again.

Wait, the 10% rule: each trophic level gets 10% of the energy from the level below. So if grass is level 1 (2500 units), level 2 (primary consumer) gets \(2500\times\frac{10}{100}=250\) units. Then level 3 (secondary consumer, frog) gets \(250\times\frac{10}{100} = 25\) units. So the energy available to frog is 25 units.

Step2: Calculate energy for each level

• Level 1 (Grass): 2500 units.
• Level 2 (Primary consumer, e.g., insect): \(2500\times0.1=250\) units.
• Level 3 (Secondary consumer, Frog): \(250\times0.1 = 25\) units.

Answer:

A. 25 units