4. Net primary productivity represents the biomass available to:
A.
Only decomposers
B.
Only producers
C.
Consumers and decomposers
D.
Only sunlight-dependent organisms
Correct Answer:
Consumers and decomposers
Explanation:
The organic matter remaining after producer respiration forms the food and energy source available to consumers and decomposers.
5. Compared with gross primary productivity, net primary productivity is usually:
A.
Greater
B.
Equal to twice the gross productivity
C.
Less
D.
Unrelated
Correct Answer:
Less
Explanation:
Net primary productivity is less than gross primary productivity because some energy is used by producers for respiration.
6. Which process reduces gross primary productivity to net primary productivity?
A.
Respiration by producers
B.
Pollination by insects
C.
Seed dispersal
D.
Water absorption by roots
Correct Answer:
Respiration by producers
Explanation:
Producer respiration consumes part of the organic matter formed during photosynthesis, leaving the net productivity.
7. If producers have a gross primary productivity of 80 grams per square metre per year and use 20 grams for respiration, their net primary productivity is:
A.
20 grams per square metre per year
B.
60 grams per square metre per year
C.
80 grams per square metre per year
D.
100 grams per square metre per year
Correct Answer:
60 grams per square metre per year
Explanation:
Net primary productivity equals gross primary productivity minus respiration: 80 - 20 = 60 grams per square metre per year.
8. Net productivity is commonly expressed as the rate of production of:
A.
Organic matter remaining after respiratory loss
B.
Oxygen used during respiration only
C.
Water lost through evaporation
D.
Minerals present in soil
Correct Answer:
Organic matter remaining after respiratory loss
Explanation:
Net productivity measures the rate at which organic matter accumulates after producer respiration has been deducted.
9. When respiratory loss increases but gross primary productivity remains constant, net productivity will:
A.
Increase
B.
Decrease
C.
Remain permanently zero
D.
Become equal to respiration
Correct Answer:
Decrease
Explanation:
Since net productivity is gross productivity minus respiration, an increase in respiratory loss causes net productivity to decrease.
10. A plant community has zero net productivity when: