Q55.3-1CC - Campbell Biology

Question

If an insect that eats plant seeds containing 100 J of energy uses 30 J of that energy for respiration and excretes 50 J in its feces, what is the insect’s net secondary production? What is its production efficiency?

Step-by-Step Solution

Answer

The net secondary production by the plant’s seed-eating insect will be equal to 20 J, and the production efficiency of this organism will be equal to around 40%.

Step 1: Net secondary production

The net secondary production can be explained as the amount of energy that is left within a consumer organism after it has spent some of its gross energy on life processes. The loss of energy can be due to mechanisms such as respiration and also due to the process of excretion.

Step 2: Production efficiency

In the context of ecological science, production efficiency can be described as the value obtained by dividing net secondary production by total assimilated primary production and then multiplying the result with 100. The assimilated primary production does not include energy loss due to excretion.

Step 3: Net secondary production and production efficiency of the insect

The insect feeds on seeds of various plants and comprises 100 J of energy; from this, 50 J is lost in excretion, and 30 J is lost due to respiration. Thus, the net secondary production of this insect is $100J-(30+50)J=20J$

The assimilation of primary production for the insect will be $100J-50J=50J$ (energy lost in excretion). The production efficiency of this insect can be calculated as $\frac{20}{50}\times 100=40\%$