Ecosystems: Trophic Relationships

1. Ecosystems: Trophic Relationships

2. Metabolism • Photosynthesis fixes carbon into sugars • Respiration breaks down sugars and releases energy • Aerobic respiration occurs in the presence of oxygen • Anaerobic respiration or fermentation occurs in the absence of oxygen

3. Producers • Autotrophs synthesize sugars using energy from the sun or chemicals • Plants, algae, and bacteria on land • Lichen in early succession and tundra • Phytoplankton in the oceans

4. Primary Consumers • Herbivores • Zooplankton

5. Secondary Consumers • Carnivores

6. Tertiary Consumers • Top Carnivore

7. Omnivores • Most humans • Bears

8. Decomposers • Bacteria • Fungi • Break down decaying material

9. Detrivores • Feed on waste or dead bodies • Insects and scavengers

10. Energy Flow • Ecosystems recycle matter but energy flows one way • Decomposers break down nutrients so that they may be used by producers

11. Food Chain • Shows the path of energy from producer to consumer • Arrows show direction of energy flow

12. Trophic Levels

13. Other Pyramids

14. Ecological Efficiency • Ranges from 2-40% • Typically estimated at 10% • Ninety percent loss due to entropy (mostly heat)

15. Primary Productivity • Gross Primary Productivity (GPP) is the rate at which solar energy is converted to biomass • Net Primary Productivity (NPP) is the energy stored minus the energy used for metabolism • Measured in kcal/m2/yr

16. NPP by Ecosystem Type

17. Total NPP by Ecosystem Type

18. Food Web

19. Trophic Level Question • Each week, an owl must eat an average of five mice weighing 10 grams each in order to survive. How much plant material would each mouse have consumed? • Solve this problem, and include set up and units. • Explain how this scenario relates to trophic levels. • Assume that energy and mass are proportional with the same constant of proportionality for each of these organisms.

20. The Answer… • It is estimated that only 10 percent of the energy at each trophic level is available to organisms at the next higher level • One owl must consume five mice per week in order to survive.

21. More Answer… • Entropy occurs and not all of the grass is converted to biomass. • A 10-gram mouse would convert 10 percent of the plant material, so each mouse would have to consume 100 grams in order to survive.

22. More Answer… • The mouse utilizes some of this grass for normal living functions, plus releases some as waste material. • Grass is at the producer level. It makes up the greatest biomass, it is the most numerous, and it has the greatest combined energy of the system.

23. More Answer. • As herbivores, mice would make up the next trophic level, and have less biomass, fewer individuals, and less stored energy than the trophic level below it.