Ecological Efficiency

If ecological efficiency is 10%, and the green plants capture 100 units of energy, about ____units of energy will be available to support herbivores and about ___units of energy will be available to support carnivores.

Productivity of Producers: The Rate Is Crucial

• Gross primary production (GPP) – Rate at which an

ecosystem’s producers convert solar energy into chemical energy as biomass.

Figure 3-20

Total amount of solar energy captured by producers via photosynthesis

Fig. 3-20, p. 66

Gross primary productivity(grams of carbon per square meter)

Net Primary Production (NPP)• NPP = GPP – R

– Rate at which producers use photosynthesis to store energy minus the rate at which they use some of this energy through respiration (R).

Figure 3-21

Energy captured minus energy lost

Fig. 3-21, p. 66Photosynthesis

Sun

Net primary production (energy available to consumers)

Growth and reproduction

RespirationEnergy lost and unavailable to consumers

Gross primary production

GPP: 3.8 kg C/M2/yearRate of cellular respiration is 2.4 kg C/M2/year….what is NPP?

• What are nature’s three most productive and three least productive systems?

• How productive are TRF as compared to lakes and streams?Figure 3-22

Fig. 3-22, p. 67

Average net primary productivity (kcal/m2 /yr)

Open ocean

Continental shelfLakes and streams

EstuariesAquatic Ecosystems

Extreme desertDesert scrub

Tundra (arctic and alpine)Temperate grassland

Woodland and shrublandAgricultural land

Savanna

North. coniferous forestTemperate forest

Terrestrial Ecosystems

Tropical rain forest

Swamps and marshes