bio Q....need help understanding

[illbirz]

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Hows the answer D? if its 5%, doesnt it mean that the next level will need however much the previous level needed plus 5%? ...if thats da case then it cant be 100000. Very lost, can some1 help? thanks.


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?
A. 500 J B. 5,000 J C. 10,000 J D. 100,000 J E. 200,000 J

 

[klutzy1987]

Hows the answer D? if its 5%, doesnt it mean that the next level will need however much the previous level needed plus 5%? ...if thats da case then it cant be 100000. Very lost, can some1 help? thanks.


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?
A. 500 J B. 5,000 J C. 10,000 J D. 100,000 J E. 200,000 J

I think the answer is B but you r saying its d is that the answer in an answer key or something??. I would think that 5% of the previous level of energy is 250 j therefore the previous level is that times 20 which is 5000. But i guess im wrong

 

[scuzfly]

I'm still working on how to solve this one myself but what you're thinking is wrong.
5% efficency means that 95% of what the primary producer makes is useless to the next level.

Doing 250/.05 = x
x is the number of Joules of energy passed onto the next generation. calculating 250/.05 gives you the number of Joules the primary producers need to make for the secondary producers to get enough energy.
95% of energy from primary producers is wasted since we only have 5% efficency.
5000 is 5% of 100,000 and 95% of 100,000 is 95,000 which means you have correct math.

You could probably eliminate A and B right off the bat. It just doesn't seem to be enough if you think of what 5% of those numbers is.

 

[raiden117]

Think of it this way guys. 250J is 5% of the energy created from the primary consumers. So .05x = 250 where x is the total energy of the primary consumers. This gives you 5000J for the total energy in primary consumers. Now, if you apply the same concept towards primary producers where 5000J is 5% of the total energy produced in in the primary producer level, you get 100,000J, or Answer choice D

 

[gomawum]

simple way to calculate

x is the energy produced by primary producer
(.05)x = energy in primary consumer
(.05^2x = energy in 2ndary consumer = 250J in this case

 

[bigstix808]

Hows the answer D? if its 5%, doesnt it mean that the next level will need however much the previous level needed plus 5%? ...if thats da case then it cant be 100000. Very lost, can some1 help? thanks.


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?
A. 500 J B. 5,000 J C. 10,000 J D. 100,000 J E. 200,000 J

primary PRODUCERS make 100,000 Joules (E1)
primary CONSUMERS use 5% = 5000 Joules (E2)
secondary CONSUMERS use 5% = 250 Joules (E3)

or to look at it another way...

secondary CONSUMERS use 250 Joules which is 5% of what the primary CONSUMERS are comprised of (E2 = 250 J / 0.05 = 5000J). Now that 5000 J is only 5% of what the primary PRODUCERS actually made which is (E1 = 5000 J / 0.05 = 100,000J).

concluding that you can just use the formula:
E / e^n -- E = energy at highest trophic level; e = efficiency from one trophic level to the next (in decimal form); n = number trophic intervals down to primary producers --> 250J / (0.05^2) = 100,000 J

hope that clears up ANY confusion 😎

 

[illbirz]

WOW....i c others were confused as well. GOod thing i asked that Q. THANK YOU ALL for your inputs. I have E/e^n tatooed in to my brain. 😀👍 ~suppose to be his hand, lol~