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  1. Problems
  2. /A chain of a pond has 8000 kJ of energy in each square metre in a year at the first trophic level…
EasyBiologyHigh School (11–12)Ecology and Environment › Ecosystems and Food ChainsNumericalAPA-LevelIB

A chain of a pond has 8000 kJ of energy in each square metre in a year at the first trophic level…

StemPy LabContributed by StemPy Lab

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

A chain of a pond has 8000 kJ8000\ \text{kJ}8000 kJ of energy in each square metre in a year at the first trophic level. Only 10%10\%10% of the energy passes to each next level.

  1. How much energy is there at T2?
  1. How much at T3?
  1. How much at T4?

Check your answer

Work it out on paper, then type your number. The answer itself stays hidden.

kJ
kJ
kJ
Need a reminder? The key ideaShowHide

The Sun is the only source of energy for ecosystems, except the deep sea hydrothermal ones. Less than 50%50\%50% of the sunlight is PAR, and plants capture 222 to 10%10\%10% of the PAR. The flow of energy is one way. Only about 10%10\%10% of the energy passes from one trophic level to the next.

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

Given. 8000 kJ8000\ \text{kJ}8000 kJ at T1. 10%10\%10% passes on.

Plan. Multiply by 0.100.100.10 for each step.

Step 1. (a) 8000×0.10=800 kJ8000 \times 0.10 = 800\ \text{kJ}8000×0.10=800 kJ.

Step 2. (b) 800×0.10=80 kJ800 \times 0.10 = 80\ \text{kJ}800×0.10=80 kJ.

Step 3. (c) 80×0.10=8 kJ80 \times 0.10 = 8\ \text{kJ}80×0.10=8 kJ.

Answer: 800 kJ800\ \text{kJ}800 kJ; 80 kJ80\ \text{kJ}80 kJ; 8 kJ8\ \text{kJ}8 kJ.

Check. Each level has one tenth of the level below.

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