Which one of the following options represents correct values for Pn, NA, R and l in kcal
respectively, if Pn-1 = 1000 kcal, 1/ Pn-1 = 20%, A/1 = 35% and Pn/A= 20%?
(1) 56 14 130              200
(2) 14           130              56                200
(3) 200                   130              56                14
(4) 56           130              200              14

Introduction

Understanding energy flow within and between trophic levels is essential for ecology. This article demonstrates how to use given percentages to calculate the values for biomass production (Pn), not assimilated (NA), respiration (R), and ingested (I) energy at a single trophic level.

Step-by-Step Calculation

1. Given Parameters and Symbols

• Pn-1 = 1000 kcal (biomass production at previous trophic level)

• I / Pn-1 = 20% (amount ingested as a fraction of previous trophic level production)

• A / I = 35% (amount assimilated as a fraction of ingested)

• Pn / A = 20% (biomass production as a fraction of assimilated)

Symbols:

• I = amount ingested

• NA = amount not assimilated

• R = respiration

• Pn = biomass production at this trophic level

• A = amount assimilated

2. Calculate Ingested Energy (I)

$$I=0.20\times Pn-1=0.20\times 1000=200\text{ kcal}$$

3. Calculate Assimilated Energy (A)

$$A=0.35\times I=0.35\times 200=70\text{ kcal}$$

4. Calculate Biomass Production (Pn)

$$Pn=0.20\times A=0.20\times 70=14\text{ kcal}$$

5. Calculate Not Assimilated Energy (NA)

$$NA=I-A=200-70=130\text{ kcal}$$

6. Calculate Respiration (R)

$$R=A-Pn=70-14=56\text{ kcal}$$

Summary Table

Matching the Options

The question asks for Pn, NA, R, I in that order.

• Option (2): 14, 130, 56, 200

This matches the calculated values.

Conclusion

The correct values for Pn, NA, R, and I are 14, 130, 56, and 200 kcal respectively.

Correct answer:
(2) 14 130 56 200