Ecological efficiency question

[lakers2009]

If ecological efficiency is only 5% from level to the next. For every 250J required by sec consumer, what is the min amt of energy the primary producers must generate? A: 100,000 J. Explanation is 250/[(.05)^2]. Why divide by .05^2? Should this be 5000 J rather? I was thinking, if 250J is 5%, then 500J is 10%, thus 5000J would be from 100%. Right?

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[UCB05]

If ecological efficiency is only 5% from level to the next. For every 250J required by sec consumer, what is the min amt of energy the primary producers must generate? A: 100,000 J. Explanation is 250/[(.05)^2]. Why divide by .05^2? Should this be 5000 J rather? I was thinking, if 250J is 5%, then 500J is 10%, thus 5000J would be from 100%. Right?

secondary consumer < primary consumer < primary producer
There's 2 trophic levels difference. Therefore the primary producers need to produce 250J -> 5000J -> 100,000J to feed secondary consumers. 250 is 5% of x is 5% of y.

 

[lakers2009]

secondary consumer < primary consumer < primary producer
There's 2 trophic levels difference. Therefore the primary producers need to produce 250J -> 5000J -> 100,000J to feed secondary consumers. 250 is 5% of x is 5% of y.

Doh! I forgot that sec is 2 away, not 1. Thanks for the reminder.