Question

Annual NPP of land area on the earth is_____

• A. < 55 billion tons
• B. between 55 t0100 billion tons
• C. About 115 billion tons
• D. 225 billion tons
• A. Net primary productivity
• B. Gross primary productivity
• C. Primary productivity
• D. Secondary productivity
• A. Annual NPP of land area is higher than oceans.
• B. NPP is greater than GPP in terrestrial ecosystems.
• C. Secondary productivity is always higher than Primary productivity in Oceanic ecosystem.
• D. Primary productivity is unaffected by environmental factors.
• A. Photosynthesis
• B. Mineralization
• C. Purification
• D. Respiration
• A. $\text{g m}^2/\text{yr}$
• B. $\text{Kg/Km}^2/\text{yr}$
• C. $\text{g/yr}$
• D. $\text{g/m/yr}$

Answer 1

The Correct Option is C

The annual Net Primary Productivity (NPP) of the whole biosphere is approximately \(170\) billion tons.

The annual NPP of oceans is approximately \(55\) billion tons. 

Therefore, the annual NPP of land is: 
\[ \text{NPP}_{\text{land}} = \text{NPP}_{\text{total}} - \text{NPP}_{\text{oceans}} \] \[ \text{NPP}_{\text{land}} = 170 - 55 \] \[ \text{NPP}_{\text{land}} = 115 \text{ billion tons} \] Hence, the annual NPP of land area on the Earth is approximately \(115\) billion tons. 

Final Answer: \(\boxed{115\text{ billion tons}}\)

Answer 2

Photosynthetic plants are producers, and the productivity associated with producers is called primary productivity.

• Gross Primary Productivity (GPP) is the total amount of organic matter produced by plants through photosynthesis.
• A part of GPP is used by plants in respiration.
• The remaining biomass is called Net Primary Productivity (NPP).

\(NPP=GPP−R\text{NPP} = \text{GPP} - R\)

where RR is the respiratory loss.

Hence, GPP, NPP, and primary productivity are all associated with photosynthetic plants.

Secondary productivity, however, refers to the rate of formation of new organic matter by consumers or heterotrophs, not by photosynthetic plants.

Correct Answer: 4. Secondary productivity

Answer 3

Concept:
Evaluating ecosystem energetics requires analyzing how primary and secondary production rates vary between marine and terrestrial biomes under different environmental constraints.

Step 1: Evaluating Statement (A):
From the passage and global ecological data, annual terrestrial Net Primary Productivity is approximately $115\text{ billion tons}$, whereas oceanic NPP is approximately $55\text{ billion tons}$.
Consequently, the annual NPP of the land area is substantially higher than that of the oceans, making statement (A) factually and conceptually correct.

Step 2: Evaluating Alternative Statements:
- Statement (B): In terrestrial ecosystems, plants expend a significant fraction of fixed energy ($20-50\%$) on cellular respiration ($R$).
Because $\text{NPP} = \text{GPP} - R$, NPP is always less than GPP. Thus, statement (B) is incorrect.
- Statement (C): Under the Second Law of Thermodynamics and Lindeman's 10% efficiency rule, energy transfer between trophic levels involves metabolic losses, meaning secondary productivity is always lower than primary productivity. Thus, statement (C) is incorrect.
- Statement (D): Primary productivity varies strongly with solar irradiance, ambient temperature, water availability, and soil nutrient levels, as noted in the passage. Thus, statement (D) is incorrect.
Final Answer:
The correct statement is that the annual NPP of land area is higher than oceans, corresponding to option (A).

Answer 4

Concept:
Decomposition is an essential ecological process in which decomposers (bacteria and fungi) break down complex organic detritus into simpler inorganic substances.
The process comprises five distinct steps: fragmentation, leaching, catabolism, humification, and mineralization.

Step 1: The Stages of Decomposition:
1. Fragmentation: Detritivores (such as earthworms) break down dead plant and animal remains into smaller particles.
2. Leaching: Water-soluble inorganic nutrients percolate into soil horizons and precipitate as unavailable salts.
3. Catabolism: Fungal and bacterial extracellular enzymes degrade complex detritus into simpler organic molecules.
4. Humification: Decomposed matter is converted into humus, a dark, amorphous, colloidal substance that is highly resistant to microbial action and serves as a nutrient reservoir.
5. Mineralization: As stated directly in the passage, humus is further broken down over time by specialized soil microbes, releasing bound inorganic mineral nutrients ($\text{NH}_4^+$, $\text{NO}_3^-$, $\text{HPO}_4^{2-}$, $\text{K}^+$, $\text{Ca}^{2+}$, $\text{SO}_4^{2-}$) into the soil solution.

Step 2: Conclusion:
The specific process that converts organic matter to release bioavailable inorganic ions into the soil is called mineralization.
Final Answer:
The release of inorganic nutrients through organic matter decomposition is mineralization, corresponding to option (B).

Answer 5

Concept:
In ecological energetics, productivity is defined as the rate of biomass or energy accumulation per unit surface area per unit time.
Dimensional consistency requires expressing productivity as:
\[ \text{Productivity Dimensions} = \frac{[\text{Mass}]}{[\text{Area}] \times [\text{Time}]} \quad \text{or} \quad \frac{[\text{Energy}]}{[\text{Area}] \times [\text{Time}]} \]

Step 1: Dimensional Analysis of the Standard Unit:
As noted in the comprehension text, primary productivity is commonly reported in:
\[ \text{g}\cdot\text{m}^{-2}\cdot\text{yr}^{-1} = \frac{\text{g}}{\text{m}^2\cdot\text{yr}} \] In base SI dimensions, this represents:
\[ [\text{Mass}] \cdot [\text{Length}]^{-2} \cdot [\text{Time}]^{-1} \]

Step 2: Evaluating the Given Options:
- Option (A): $\text{g m}^2/\text{yr} = [\text{Mass}] \cdot [\text{Length}]^2 \cdot [\text{Time}]^{-1}$. This multiplies mass by area rather than dividing by it, which is dimensionally incorrect.
- Option (B): $\text{Kg/Km}^2/\text{yr} = \frac{\text{kg}}{\text{km}^2\cdot\text{yr}}$. This has the dimensions:
\[ \frac{[\text{Mass}]}{[\text{Area}] \times [\text{Time}]} = [\text{Mass}] \cdot [\text{Length}]^{-2} \cdot [\text{Time}]^{-1} \] Because kilograms ($\text{kg}$) represent mass, square kilometers ($\text{km}^2$) represent surface area, and years ($\text{yr}$) represent time, this formulation is dimensionally valid for landscape-scale productivity.
- Option (C): $\text{g/yr} = [\text{Mass}] \cdot [\text{Time}]^{-1}$, which omits the unit area requirement.
- Option (D): $\text{g/m/yr} = [\text{Mass}] \cdot [\text{Length}]^{-1} \cdot [\text{Time}]^{-1}$, which divides by linear distance rather than surface area.
Final Answer:
The dimensionally correct unit for primary productivity is $\text{Kg/Km}^2/\text{yr}$, corresponding to option (B).