Principles of Biology - Biology 102
Spring Quarter
Lake Tahoe Community College
Instructor: Sue Kloss
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Ch. 55 - Ecosystems
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I. Ecosystem Structure and Dynamics
A. Ecosystems and physical laws
1. Laws of thermodynamics
B. Ecosystem – biotic community and abiotic environment
1. Energy flow is linear
2. Chemical cycling is circular
C. Trophic structure is key factor in ecosystem dynamics
1. trophic structure
2. food web
II Physical and chemical factors limit primary production
A. Ecosystem energy budgets
1. visible light
2. Gross primary production (GPP)
3. Limiting factors
III. Energy transfers
A. Energy Supply
1. earth solar energy
2. only 1% converted to chemical energy
3. different ecosystems produce wildly varying amts of biomass
B. meat is a luxury for humans
C. Pyramid of numbers
1. with so many consumers, how can many terrestrial ecosystems support large, standing crops?
2. green world hypothesis
3. factors that keep herbivores in check
IV. Biological and geochemical processes
A. Chemicals are recycled
1. no extraterrestrial sources of food or water
2. water, carbon, nitrogen and phosphorous
B. Water moves thru biosphere in global cycle
C. Carbon Cycle depends on Ps and Respiration
D. Nitrogen cycle relies on bacteria
G. Ecosystem alteration can upset chemical cycling
V. Human Population is disrupting chemical cycles
A. Nutrient enrichment
1. different types of systems hold nutrients for different lengths of time
2. Contamination of aquatic ecosystems
B. Acid Precipitation
1. Acid precip has pH < 5.6
C. toxins in the Environment
1. Biological magnification
D. Carbon Dioxide in atmosphere
1. global warming and greenhouse effect
2. migration of plants and animals
E. depletion of Ozone
Ch. 55 Objectives
Wk. 10 meeting 2
1. Describe the fundamental relationship between autotrophs and heterotrophs in an ecosystem.
2. Explain how the first and second laws of thermodynamics apply to ecosystems.
3. Explain how decomposition connects all trophic levels in an ecosystem.
4. Explain why the amount of energy used in photosynthesis is so much less than the amount of solar energy
that reaches Earth.
5. Define and compare gross primary production and net primary production.
6. Compare primary productivity in specific marine, freshwater, and terrestrial ecosystems.
7. Explain why energy is said to flow rather than cycle within ecosystems.
8. Explain what factors may limit production in aquatic ecosystems.
9. Explain why areas of upwelling in the ocean have exceptionally high levels of primary production.
Wk 11 meeting 1
10. Distinguish among pyramids of net production, pyramids of biomass, and pyramids of numbers.
11. Explain why worldwide agriculture could feed more people if all humans consumed only plant material.
12. Explain the green-world hypothesis. Describe five factors that may act to keep herbivores in check
13. Describe the four nutrient reservoirs and the processes that transfer the elements between reservoirs.
14. Name the main processes driving the water cycle.
15. Name the major reservoirs of carbon.
16. Describe the nitrogen cycle and explain the importance of nitrogen fixation to all living organisms. Name
three other key bacterial processes in the nitrogen cycle.
17. Describe the phosphorus cycle and explain how phosphorus is recycled locally in most ecosystems.
18. Explain how decomposition affects the rate of nutrient cycling in ecosystems.
19. Describe how net primary production and the rate of decomposition vary with actual evapotranspiration.
19. Describe the experiments at Hubbard Brook that revealed the key role that plants play in regulating nutrient
cycles.
20. Describe how agricultural practices can interfere with nitrogen cycling.