In a food chain consisting of four trophic levels, if the energy present in the top level is 48 kcal/m2/yr, how much energy do you expect in herbivores? (Use an energy transfer rate of 10%.)

Question

A.  4.8 kcal/m2/yr
B.  48 kcal/m2/yr
C.  480 kcal/m2/yr
D.  4,800 kcal/m2/yr
E.  48,000 kcal/m2/yr

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
 
Gather Content
· What do you already know about energy flow?
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

C.  480 kcal/m2/yr


Clarify Question
· What is the key concept addressed by the question?
        o This question addresses energy flow.
· What type of thinking is required?
        o This question is asking you to analyze the information given, using logic, to dissect the problem and determine the answer.
 
Gather Content
· What do you already know about energy flow?
        o Energy flow between trophic levels is inefficient. Whenever organisms use chemical-bond or light energy, some of it is converted to heat. Consistent with the Second Law of Thermodynamics, a partial conversion to heat is inevitable. Put another way, animals and plants require chemical-bond energy and light to stay alive, but as they use these forms of energy, they convert them to heat, which they cannot use to stay alive and which they cannot cycle back into the original forms. Fortunately for organisms, the Earth functions as an open system for energy, because light arrives every day from the Sun.
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o The food chain has four trophic levels: primary producer, herbivore, primary carnivore, and secondary carnivore.
        o We are told that the top level (level 4, secondary carnivores) has 48 kcal/m2/yr.
        o If the energy transfer rate is 10%, then the primary carnivores level (level 3) will have 10x the energy of the next level up.The primary carnivore level (level 3) therefore, should have 480 kcal/m2/yr.
        o The herbivores level (level 2) will then have 10x that, or4,800 kcal/m2/yr.
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o The question required you to analyze the information given, using logic, to dissect the problem and determine the answer.
        o Did you recognize that energy is lost between each trophic level of a food chain?