biology : class12 Productivity Measurement Units : Primary Productivity, Secondary Productivity, Gross Productivity, Net Productivity : Productivity MCQ Questions and Answers
Practice important
Productivity Measurement Units
MCQ questions and answers.
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MCQ Questions
1. A grassland has a primary productivity of 2.40 kg m−2 yr−1. What is its approximate productivity in g m−2 day−1, assuming a 365-day year?
A.
0.658 g m−2 day−1
B.
6.58 g m−2 day−1
C.
65.8 g m−2 day−1
D.
658 g m−2 day−1
Correct Answer:
6.58 g m−2 day−1
Explanation:
2.40 kg m−2 yr−1 equals 2400 g m−2 yr−1. Dividing by 365 gives approximately 6.58 g m−2 day−1.
2. An ecosystem records a net primary productivity of 18 g C m−2 day−1. What is the equivalent annual productivity per hectare?
A.
657 kg C ha−1 yr−1
B.
6,570 kg C ha−1 yr−1
C.
65,700 kg C ha−1 yr−1
D.
657,000 kg C ha−1 yr−1
Correct Answer:
65,700 kg C ha−1 yr−1
Explanation:
Annual productivity is 18 × 365 = 6570 g C m−2 yr−1. Since 1 hectare equals 10,000 m2, this is 65,700 kg C ha−1 yr−1.
3. A phytoplankton community has a productivity of 0.75 kJ m−2 h−1. What is the corresponding value in MJ ha−1 yr−1, assuming 365 days per year?
A.
6.57 MJ ha−1 yr−1
B.
65.7 MJ ha−1 yr−1
C.
657 MJ ha−1 yr−1
D.
6,570 MJ ha−1 yr−1
Correct Answer:
65.7 MJ ha−1 yr−1
Explanation:
The annual value is 0.75 × 24 × 365 = 6570 kJ m−2 yr−1, or 6.57 MJ m−2 yr−1. Multiplying by 10 converts it to 65.7 MJ ha−1 yr−1.
4. A forest ecosystem has a primary productivity of 450 g m−2 month−1. Assuming the same rate throughout the year, what is its annual productivity?
A.
540 g m−2 yr−1
B.
3,600 g m−2 yr−1
C.
5,400 g m−2 yr−1
D.
16,200 g m−2 yr−1
Correct Answer:
5,400 g m−2 yr−1
Explanation:
The annual productivity is obtained by multiplying the monthly productivity by 12: 450 × 12 = 5,400 g m−2 yr−1.
5. The gross primary productivity of an ecosystem is 24 MJ m−2 yr−1, while respiratory consumption is 9 MJ m−2 yr−1. What is the net primary productivity in J cm−2 day−1?
A.
0.411 J cm−2 day−1
B.
4.11 J cm−2 day−1
C.
41.1 J cm−2 day−1
D.
411 J cm−2 day−1
Correct Answer:
4.11 J cm−2 day−1
Explanation:
NPP = 24 − 9 = 15 MJ m−2 yr−1. This equals 15,000,000 J m−2 yr−1. Dividing by 10,000 cm2 per m2 and 365 days gives approximately 4.11 J cm−2 day−1.
6. Secondary productivity in a 250-hectare grassland is 3.6 g m−2 day−1. What total biomass production does this represent in one year?
A.
3,285 kg yr−1
B.
32,850 kg yr−1
C.
328,500 kg yr−1
D.
3,285,000 kg yr−1
Correct Answer:
3,285,000 kg yr−1
Explanation:
Annual productivity is 3.6 × 365 = 1314 g m−2 yr−1. A 250-hectare area contains 2,500,000 m2, giving 3.285 × 109 g, or 3,285,000 kg yr−1.
7. A productivity of 1 W m−2 is equivalent to approximately which annual energy productivity?
A.
0.0315 MJ m−2 yr−1
B.
0.876 MJ m−2 yr−1
C.
31.5 MJ m−2 yr−1
D.
315.4 MJ m−2 yr−1
Correct Answer:
31.5 MJ m−2 yr−1
Explanation:
One watt equals one joule per second. Over a year, 1 W m−2 gives 31,536,000 J m−2, or approximately 31.5 MJ m−2 yr−1.
8. A lake has a gross primary productivity of 1,200 kcal m−2 yr−1. Using 1 kcal = 4.184 kJ, what is this productivity in kJ ha−1 day−1?
A.
13.76 kJ ha−1 day−1
B.
137.6 kJ ha−1 day−1
C.
1,376 kJ ha−1 day−1
D.
13,760 kJ ha−1 day−1
Correct Answer:
137.6 kJ ha−1 day−1
Explanation:
The annual energy is 1200 × 4.184 = 5020.8 kJ m−2 yr−1. Conversion to hectares gives 50,208 kJ ha−1 yr−1; dividing by 365 gives approximately 137.6 kJ ha−1 day−1.
9. A producer shows a productivity of 0.42 mg m−2 cm−2 h−1. Interpreting the unit correctly as 0.42 mg cm−2 h−1, what is the equivalent productivity in g m−2 day−1?
A.
10.08 g m−2 day−1
B.
24.0 g m−2 day−1
C.
100.8 g m−2 day−1
D.
1,008 g m−2 day−1
Correct Answer:
100.8 g m−2 day−1
Explanation:
Because 1 cm2 equals 0.0001 m2, 1 mg cm−2 equals 10 g m−2. Thus, 0.42 mg cm−2 h−1 equals 4.2 g m−2 h−1, or 100.8 g m−2 day−1.
10. Which expression represents the same productivity as 5 g C m−2 day−1?
A.
0.05 kg C ha−1 day−1
B.
0.5 kg C ha−1 day−1
C.
50 kg C ha−1 day−1
D.
500 kg C ha−1 day−1
Correct Answer:
50 kg C ha−1 day−1
Explanation:
Since 1 g m−2 equals 10 kg ha−1, 5 g C m−2 day−1 is equivalent to 50 kg C ha−1 day−1.
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