# Ecological Efficiency Question

#### DMD-2-B

##### Senior Member
10+ Year Member
7+ Year Member
I ran across this question and was wondering what you guys thought the answer was. I thought it was pretty simple till I saw I got it wrong, so I'd like to hear your strategies for attacking this one if you don't mind!

The ecological efficiency is only 5% from one trophic level to the next. For every 250 J of energy required by the secondary consumers, what is the minimum amount of energy the primary producers will have to generate?

#### wlee009

##### Member
10+ Year Member
5+ Year Member
250J*20= 5000J required for primary consumers
5000J*20= 100000J produced by producers

Did I do it right?

#### Notoriousjae

##### DAT Rockstar
10+ Year Member
wlee009 said:
250J*20= 5000J required for primary consumers
5000J*20= 100000J produced by producers

Did I do it right?

why did you multiply 250J by 20?

#### keibee82

##### Blue_tooth...
10+ Year Member
DMD-2-B said:
I ran across this question and was wondering what you guys thought the answer was. I thought it was pretty simple till I saw I got it wrong, so I'd like to hear your strategies for attacking this one if you don't mind!

The ecological efficiency is only 5% from one trophic level to the next. For every 250 J of energy required by the secondary consumers, what is the minimum amount of energy the primary producers will have to generate?
250 / 0.05 = 5000
5000 / 0.05 = 100000

#### Notoriousjae

##### DAT Rockstar
10+ Year Member
keibee82 said:
250 / 0.05 = 5000
5000 / 0.05 = 100000

oh ok that makes more sense cuz i was wondering where he got that 20 from

OP
D

#### DMD-2-B

##### Senior Member
10+ Year Member
7+ Year Member
keibee82 said:
250 / 0.05 = 5000
5000 / 0.05 = 100000
Yes, you did it right. I still don't really understand though. My point of confusion is why divide by .05 twice? I divided only once, thinking that 250 is the five percent that was passed down from the original 5000.

Clearly I am overlooking something. Would you mind explaining the reasoning?

Thanks!

#### Resonance

##### Member
10+ Year Member
7+ Year Member
DMD-2-B said:
Yes, you did it right. I still don't really understand though. My point of confusion is why divide by .05 twice? I divided only once, thinking that 250 is the five percent that was passed down from the original 5000.

Clearly I am overlooking something. Would you mind explaining the reasoning?

Thanks!
dividing it once only give the minimum for the primary consumer, the question wants the minimum for the primary producer.

OP
D

#### DMD-2-B

##### Senior Member
10+ Year Member
7+ Year Member
Resonance said:
dividing it once only give the minimum for the primary consumer, the question wants the minimum for the primary producer.
thank you!