1. Food webs and energy flow in ecosystems

2. Food Chain Food chains are different from food webs. In a food chain there is just one path for energy.

3. Food Chains Food chains have several ‘trophic” levels. Primary producers Primary consumer Secondary consumer And so on

4. Trophic Levels Primary producers are called autotrophs Primary consumers eat primary producers Secondary consumers eat primary consumers

5. PRODUCERS Plants are producers because they can produce their own energy from sunlight.

6. Primary Consumers Animals cannot produce their own food so they are called consumers. Cows are primary consumers because they eat the producers.

7. Secondary Consumers Secondary consumers eat the primary consumers.

8. Types of consumers Herbivores eat only plants. Carnivores eat other animals. Omnivores eat everything.

9. Decomposers Feed on decaying material.

10. Energy loss The further up the food chain the less food and therefore less energy.

11. Energy Flow in an Ecosystem Biomass Ecological efficiency Pyramid of energy flow

12. Fig. 3-18, p. 49 Secondary consumers (perch) 10 100 1,000 10,000 Usable energy available at each tropic level (in kilocalories) Heat Producers (phytoplankton) Tertiary consumers (human) Primary consumers (zooplankton) Pyramid of Energy Flow Decomposers

13. Biomass Productivity Gross primary productivity (GPP) Net primary productivity (NPP) NPP and populations

14. Fig. 3-19, p. 49 Energy lost and unavailable to consumers Respiration Growth and reproduction Sun Photosynthesis Gross primary production Net primary production (energy available to consumers) Differences between GPP and NPP

15. Primary productivity Primary productivity is the amount of carbon (organic matter) produced by organisms –Mostly through photosynthesis Energy source = solar radiation –Also includes chemosynthesis Energy source = chemical reactions

16. Fig. 3-20, p. 50 Swamps and marshes Tropical rain forest Temperate forest Northern coniferous forest (taiga) Savanna Agricultural land Woodland and shrubland Temperate grassland Tundra (arctic and alpine) Desert scrub Extreme desert Aquatic Ecosystems Estuaries Lakes and streams Continental shelf Open ocean Terrestrial Ecosystems 800 1,600 2,400 3,200 4,000 4,800 5,600 6,400 7,200 8,000 8,800 9,600 Average net primary productivity (kcal/m 2 /yr) Net Primary Productivity in Major Life Zones and Ecosystems

17. Net Productivity Some of GPP used to stay alive, grow and reproduce NPP is what’s left Most NPP –Estuaries, swamps, tropical rainforests Least NPP –Open ocean, tundra, desert Open ocean has low NPP but its large area gives it more NPP total than anywhere else