1. Ecosystems: What Are They and How Do They Work?
Chapter 3.4
Ecosystems: What Are They and How Do They Work?

2. 3-4 What Happens to Energy in an Ecosystem?
Concept 3-4A Energy flows through ecosystems in food chains and webs.
Concept 3-4B As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each succeeding feeding level decreases.

3. Primary Producers / Autotrophs

4. Primary Consumers / Herbivores

5. Secondary Consumers / Carnivores

6. Tertiary & Quaternary Consumers Predators

7. Omnivores

8. Decomposers and Detrivores
Decomposers: Recycle nutrients in ecosystems.
Detrivores: Insects or other scavengers that feed on wastes or dead bodies.
Figure 3-13

9. Decomposers

10. Aerobic and Anaerobic Respiration: Getting Energy for Survival
Organisms break down carbohydrates and other organic compounds in their cells to obtain the energy they need.
This is usually done through aerobic respiration.
The opposite of photosynthesis

11. Two Secrets of Survival: Energy Flow and Matter Recycle
An ecosystem survives by a combination of energy flow and matter recycling.
Figure 3-14

12. BIODIVERSITY
Figure 3-15

13. Biodiversity Loss and Species Extinction: Remember HIPPO
H for habitat destruction and degradation
I for invasive species
P for pollution
P for human population growth
O for overexploitation

14. ENERGY FLOW IN ECOSYSTEMS
Food chains and webs show how eaters, the eaten, and the decomposed are connected to one another in an ecosystem.
Figure 3-17

15. Food Webs
Trophic levels are interconnected within a more complicated food web.
Figure 3-18

16. Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs
In accordance with the 2nd law of thermodynamics, there is a decrease in the amount of energy available to each succeeding organism in a food chain or web.

17. Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs
Ecological efficiency: percentage of useable energy transferred as biomass from one trophic level to the next.
Figure 3-19

18. 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

19. 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

20. What are nature’s three most productive and three least productive systems?
Figure 3-22

21. Importance of Baseline Ecological Data
We need baseline data on the world’s ecosystems so we can see how they are changing and develop effective strategies for preventing or slowing their degradation.
Scientists have less than half of the basic ecological data needed to evaluate the status of ecosystems in the United Sates (Heinz Foundation 2002; Millennium Assessment 2005).