1. Chapter 55: Ecosystems

2. Ch. 55 Warm-Up
Ch. 55 Terms:
Autotroph
Heterotroph
Detritivore
Gross primary production (GPP)
Net primary production (NPP)
Biogeochemical cycle
Nitrogen fixation
Draw an energy pyramid and label the following trophic levels:
Primary producer
Primary consumer
Secondary consumer
Tertiary consumer
What is an example of an organism at each level of the pyramid in #1?
If 5000 J of energy is available in producers, how much of that energy would be available to tertiary consumers?

3. Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis
E.U.2A: Growth, reproduction, and maintenance of the organization of living systems require free energy and matter.
E.K.2A1: All living systems require constant input of free energy
Life requires a highly ordered system

4. Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis
EU 2.D: Growth and dynamic homeostasis of a biological system are influenced by changes in the system’s environment.
EK 2.D.1: All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy.

5. Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties.
EU 4.A: Interactions within biological systems lead to complex properties.
EK 4.A.6: Interactions among living systems and with their environment result in the movement of matter and energy.

6. You Must Know:
How energy flows through the ecosystem (food chains and food webs)
The difference between gross primary productivity and net primary productivity.
The carbon and nitrogen biogeochemical cycles.
Biogeochemical cycles such as the carbon and nitrogen cycle and how they may impact individual organisms and/or populations and ecosystems

7. Unit 1 Ecology: Chapter 55 Ecosystems
Ecosystem = all the organisms living in a community, as well as the abiotic factors with which they interact
Involves two unique processes:
Energy “flow”
Chemical “cycling”
Energy flows through ecosystems while matter cycles within them
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8. 55.1 Physical laws govern energy flow and chemical cycling in ecosystems
Conservation of Energy
The first law of thermodynamics: energy cannot be created or destroyed, only transformed
Energy enters an ecosystem as solar radiation, is conserved, and flows from organisms as heat
The second law of thermodynamics: every exchange of energy increases the entropy of the universe
In an ecosystem, energy conversions are not completely efficient, some energy is lost as heat

9. The arrows show how chemical energy in food flows through various trophic levels or energy transfers, most of the energy is degraded to heat in accordance with the second law of energy.

10. Physical laws govern energy flow and chemical cycling in ecosystems
Conservation of mass
Matter, like energy cannot be created or destroyed
Chemical elements, or matter, is continually cycled within ecosystems
Elements move between ecosystems as inputs/outputs
Ecosystems are open systems, absorbing energy and mass and releasing heat and waste products

11. Overview of energy & nutrient dynamics

12. 55.2 Energy Flow in an Ecosystem
Energy flow can be traced through the feeding or trophic levels in a food chain or web.
Energy cannot be recycled  must be constantly supplied to an ecosystem (mostly by SUN)
The autotrophs (“self feeders”) are the primary producers, and are usually photosynthetic (plants or algae).
They use light energy to synthesize sugars and other organic compounds.
Heterotrophs (“other feeders”) – can’t make own food – must eat autotrophs or other heterotrophs

13. Heterotrophs are at trophic levels above the primary producers and depend on their photosynthetic output.

14. Herbivores that eat primary producers are called primary consumers.
Carnivores that eat herbivores are called secondary consumers.
Carnivores that eat secondary consumers are called tertiary consumers.
Another important group of heterotrophs is the detritivores, or decomposers.
They get energy from detritus, nonliving organic material, and play an important role in material cycling.
Main decomposers: Bacteria (prokaryotes) and fungi

15. Primary Production
Primary production = amt. of light energy that is converted to chemical energy
Gross primary production (GPP): total primary production in an ecosystem
Net primary production (NPP) = gross primary production minus the energy used by the primary producers for respiration (R):
NPP = GPP – R
NPP = storage of chemical energy available to consumers in an ecosystem

16. Gross/Net Primary Production
Only a small fraction of solar energy actually strikes photosynthetic organisms, and even less is of a usable wavelength

17. Figure 55.6 Global net primary production in 2002
Tropical rain forests and coral reefs are among the most productive ecosystems per unit area
Marine ecosystems are relatively unproductive per unit area, but contribute much to global net primary production because of their volume 17

18. Aquatic system: primary production affected by:
Light availability (↑ depth, ↓ photosynthesis)
Nutrient availability (N, P in marine env.)
A nutrient-rich lake that supports algae growth is eutrophic.
Terrestrial ecosystems primary production is affected by
Temperature
Moisture
Evapotranspiration – combines both factors

19. Unit 1 Ecology: Chapter 55 Ecosystems
55.3 Energy transfer between trophic levels is typically only 10% efficient
Production efficiency: only fraction of E stored in food
Each level, energy is lost:
heat, movement, reproduction, other life processes
Energy used in respiration is lost as heat
Energy flows (not cycle!) within ecosystems
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20. Because of this loss, food chains are short
If only 10% is pass on from primary producer to primary consumers then only 1% of net primary production (10% of 10%) is available to the secondary consumer
Because of this loss, food chains are short
Ecological pyramids – diagrams that give insight into food chains
Biomass
Energy
Pyramid of Numbers

21. Pyramid of net production
10% transfer of energy from one level to next

22. Ecological pyramids give insight to food chains
Loss of energy limits # of top-level carnivores
Most food webs only have 4 or 5 trophic levels
Pyramid of Numbers
Pyramid of Biomass

23. 55.4 Matter Cycles in Ecosystem
Biogeochemical cycles: nutrient cycles that contain both biotic and abiotic components
Contain organic  inorganic parts of an ecosystem
Nutrient Cycles:
Water
Carbon
Nitrogen
Phosphorus

24. Figure 55.13 A general model of nutrient cycling

25. Unit 1 Ecology: Chapter 55 Ecosystems
The Water Cycle
Water is essential to all organisms
Liquid water is the primary physical phase in which water is used
The oceans contain 97% of the biosphere’s water; 2% is in glaciers and polar ice caps, and 1% is in lakes, rivers, and groundwater
Water moves by the processes of evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater
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26. Water Cycle
Water is essential to ALL life, and it’s availability influences the rates of primary productivity and decomposition

27. Unit 1 Ecology: Chapter 55 Ecosystems
The Carbon Cycle
Carbon-based organic molecules are essential to all organisms
Photosynthetic organisms convert CO2 to organic molecules that are used by heterotrophs
Carbon reservoirs include fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, the atmosphere, and sedimentary rocks
CO2 is taken up and released through photosynthesis and respiration; additionally, volcanoes and the burning of fossil fuels contribute CO2 to the atmosphere
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28. Carbon Cycle
CO2 is removed from the atmosphere by photosynthesis, added back to the atmosphere by burning fossil fuels

29. Unit 1 Ecology: Chapter 55 Ecosystems
The Nitrogen Cycle
Nitrogen is a component of amino acids, proteins, and nucleic acids
The main reservoir of nitrogen is the atmosphere (N2), though this nitrogen must be converted to NH4+ or NO3– for uptake by plants, via nitrogen fixation by bacteria
Organic nitrogen is decomposed to NH4+ by ammonification, and NH4+ is decomposed to NO3– by nitrification (by bacteria)
Denitrification converts NO3– back to N2 (by bacteria)
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30. Nitrogen Cycle Nitrogen fixation: N2  plants by bacteria
Nitrification:
ammonium  nitrite  nitrate
Absorbed by plants
Denitrification:
Release N to atmosphere
Nitrogen Cycle

31. Unit 1 Ecology: Chapter 55 Ecosystems
The Phosphorus Cycle
Phosphorus is a major constituent of nucleic acids, phospholipids, and ATP
Phosphate (PO43–) is the most important inorganic form of phosphorus
The largest accumulations of phosphorus are in sedimentary rocks of marine origin, the oceans, and organisms
Phosphate binds with soil particles, and movement is often localized
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32. Phosphorus Cycle
Weathering of rocks adds phosphorus to the soil, where it is taken up by producers, then the producers are eaten by consumers. It is then returned to the soil by excretion or decomposition.

33. 55.5 Human activities now dominate most chemical cycles on Earth
As the human population has grown rapidly in size, our activities and technological capabilities have disrupted the tropic structure, energy flow, and chemical cycling of ecosystems.
Humans have altered nutrient cycles so much that we can no longer understand any cycle without taking these affects into account

34. Mississippi basin dead zone (red)
Eutrophication
Excess nitrogen from agriculture enters aquatic ecosystems
Algae and bacteria bloom/die  reduce oxygen  fish and invertebrates die
Mississippi basin dead zone (red)

35. Acid Precipitation
Rain, snow, or fog with a pH less than 5.6
Caused by burning of wood & fossil fuels  release sulfur oxides and nitrogen oxides
React with water in the atmosphere to produce sulfuric and nitric acids

36. Biological Magnification
Toxins become more concentrated in successive trophic levels of a food web
Toxins can’t be broken down & magnify in concentration up the food chain
Problem: mercury in fish

37. Greenhouse Effect
Greenhouse Effect: absorption of heat the Earth experiences due to certain greenhouse gases
CO2 and water vapor absorb infrared radiation and re- reflect back toward Earth
The Earth needs this heat, but too much could be disastrous.

38. Rising atmospheric CO2
Since the Industrial Revolution, the concentration of CO2 in the atmosphere has increased greatly as a result of burning fossil fuels.

39. Global Warming
Studies predict a doubling of CO2 in the atmosphere will cause a 3ºC increase in the average temperature of Earth.
Rising temperatures could cause polar ice cap melting, which could flood coastal areas.
Approach: stabilize use of fossil fuels and reduce deforestation

40. Human activities are depleting the atmospheric ozone
Unit 1 Ecology: Chapter Ecosystems
Human activities are depleting the atmospheric ozone
Life on earth is protected from the damaging affects of ultraviolet radiation (UV) by a layer of O3, or ozone.
Chlorine-containing compounds erode the ozone layer
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