IB Environmental systems and societies Topic 2.2I Productivity and Ecological Efficiency Revision Notes (HL)

IB Environmental systems and societies Topic 2.2I Productivity and Ecological Efficiency Revision Notes (HL) | RevisionDojo

Written by official IB examiners

Productivity: energy fixed by producers sets the ceiling for every trophic level above

Primary productivity is the rate at which producers fix energy into biomass using an external energy source and inorganic carbon and nutrients.
1. It is measured in kg C m⁻² yr⁻¹, meaning kilograms of carbon fixed per square metre per year.
2. It sets the energy foundation on which all consumers depend.

Definition

Primary productivity

Primary productivity is the rate of production of biomass using an external energy source and inorganic sources of carbon and other elements.

GPP and NPP: net productivity is what is left after producers respire

Gross primary productivity (GPP) is the total energy fixed by producers before any is used.
Net primary productivity (NPP) equals GPP minus the energy lost to producer respiration.
1. NPP is the biomass actually available to primary consumers and to human harvest.
2. NPP therefore sets the carrying capacity of an ecosystem.

GPP and NPP are developed further in 2.2E, so here focus on how they set the harvestable ceiling.

Definition

Net primary productivity

Net Primary Productivity (NPP) refers to the amount of carbon that is captured by plants through photosynthesis and is available for growth and reproduction after subtracting the energy used by the plants for cellular respiration.

What limits primary productivity

Light availability: more sunlight raises the rate of photosynthesis.
Temperature: warmth speeds up the enzymes that drive photosynthesis.
Water availability: reliable rainfall supports continuous growth.
Nutrient supply: nitrogen and phosphorus often cap how fast producers can grow.
Ecosystem type: terrestrial systems are limited mainly by temperature and rainfall while aquatic systems are limited mainly by nutrients.

Example

Tropical rainforests have high productivity because sunlight, warmth and rainfall are all abundant.
Deserts have low productivity because water is scarce.
Estuaries have high productivity because shallow, sunlit water sits over nutrient-rich sediments.

How primary productivity is measured

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Tip

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Productivity: energy fixed by producers sets the ceiling for every trophic level above

Primary productivity is the rate at which producers fix energy into biomass using an external energy source and inorganic carbon and nutrients.
1. It is measured in kg C m⁻² yr⁻¹, meaning kilograms of carbon fixed per square metre per year.
2. It sets the energy foundation on which all consumers depend.

Definition

Primary productivity

Primary productivity is the rate of production of biomass using an external energy source and inorganic sources of carbon and other elements.

GPP and NPP: net productivity is what is left after producers respire

Gross primary productivity (GPP) is the total energy fixed by producers before any is used.
Net primary productivity (NPP) equals GPP minus the energy lost to producer respiration.
1. NPP is the biomass actually available to primary consumers and to human harvest.
2. NPP therefore sets the carrying capacity of an ecosystem.

GPP and NPP are developed further in 2.2E, so here focus on how they set the harvestable ceiling.

Definition

Net primary productivity

What limits primary productivity

Light availability: more sunlight raises the rate of photosynthesis.
Temperature: warmth speeds up the enzymes that drive photosynthesis.
Water availability: reliable rainfall supports continuous growth.
Nutrient supply: nitrogen and phosphorus often cap how fast producers can grow.
Ecosystem type: terrestrial systems are limited mainly by temperature and rainfall while aquatic systems are limited mainly by nutrients.

Example

Tropical rainforests have high productivity because sunlight, warmth and rainfall are all abundant.
Deserts have low productivity because water is scarce.
Estuaries have high productivity because shallow, sunlit water sits over nutrient-rich sediments.

How primary productivity is measured

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

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Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

Topic 1: Foundation 3 subtopics

Topic 2: Ecology5 subtopics

Topic 3: Conservation and biodiversity3 subtopics

Topic 4: Water4 subtopics

Topic 5: Land2 subtopics

Topic 6: Atmosphere and climate change4 subtopics

Topic 7: Natural resources3 subtopics

Topic 8: Human populations and urban systems3 subtopics

HL lenses 3 subtopics

IB Environmental systems and societies 2.2I Productivity and Ecological Efficiency Notes

Topic 1: Foundation 3 subtopics

Topic 2: Ecology5 subtopics

Topic 3: Conservation and biodiversity3 subtopics

Topic 4: Water4 subtopics

Topic 5: Land2 subtopics

Topic 6: Atmosphere and climate change4 subtopics

Topic 7: Natural resources3 subtopics

Topic 8: Human populations and urban systems3 subtopics

HL lenses 3 subtopics

Productivity: energy fixed by producers sets the ceiling for every trophic level above

GPP and NPP: net productivity is what is left after producers respire

What limits primary productivity

How primary productivity is measured

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

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Productivity: energy fixed by producers sets the ceiling for every trophic level above

GPP and NPP: net productivity is what is left after producers respire

What limits primary productivity

How primary productivity is measured

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account