Question

The table below shows the production in two ecosystems in the temperate zone: A rainforest and a field with an annual crop. All results are stated in ${\text{MJ/m}}^2/\mathrm{year}$(1 MJ = 106 J).

$\begin{array}{ccc}& \text{[I] Rainforest}& \text{[II] Field with an annual crop}\\ \text{Gross Primary Production (GPP)}& 188& 102\\ \text{Respiration (autotrophs)}& 134& 38\\ \text{Respiration (heterotrophs)}& 53& 3\end{array}$

(1) Of these two ecosystems, which has a higher ratio of respiration by heterotrophic organisms to net primary production (NPP)?
(a) I
(b) II
(c) They are the same

(2) What is the reason?
(a) The rainforest has larger GPP and more consumers than the crop field.
(b) The rainforest has larger NPP and more consumers than the crop field.
(c) The rainforest has smaller GPP and more consumers than the crop field.
(d) The rainforest has smaller NPP and more consumers than the crop field.
(e) The rainforest has smaller NPP and less consumers than the crop field.

• A. $\begin{array}{cc}\text{(I)}& \text{(II)}\\ \text{a}& \text{d}\end{array}$
• B. $$\begin{array}{cc}\text{(I)}& \text{(II)}\\ \text{d}& \text{a}\end{array}$$
• C. $$\begin{array}{cc}\text{(I)}& \text{(II)}\\ \text{b}& \text{a}\end{array}$$
• D. $$\begin{array}{cc}\text{(I)}& \text{(II)}\\ \text{a}& \text{c}\end{array}$$

Answer 1

The correct option is A $\begin{array}{cc}\text{(I)}& \text{(II)}\\ \text{a}& \text{d}\end{array}$

For 1:
NPP = GPP - respiration [by plants]
The ratio of respiration by heterotrophic organisms to net primary production (NPP) in case of (I) rainforest is = 53:54
The ratio of respiration by heterotrophic organisms to net primary production (NPP) in case of (II) field with annual crop is = 3:64
I has higher ratio than II hence, option a is correct.

For 2:
The rainforest has smaller NPP (54) and more consumers (represented by respiration 53) than the crop field (NPP= 64; consumer (respiration) =3); that makes option d the correct. answer.