1. Nutrient Cycles & Thermodynamics

2. DO NOW
Draw the hydrologic cycle
Label all parts of your diagram

3. Biogeochemical Nutrient Cycles

4. Biogeochemical Nutrient Cycles
Hydrologic
Carbon-Oxygen
Nitrogen
Phosphorus
Sulfur
Rock

5. Biogeochemical Cycles
describe the flow of essential elements from the environment, through living organisms, and back into the environment

6. Nutrients circulate through ecosystems
Physical matter is circulated continually in an ecosystem
Nutrient (biogeochemical) cycle = the movement of nutrients through ecosystems
Atmosphere, hydrosphere, lithosphere, and biosphere
Pools (reservoirs) = where nutrients reside for varying amounts of time
Flux = movement of nutrients among pools, which change over time and are influenced by human activities
Sources = pools that release more nutrients than they accept
Sinks = accept more nutrients than they release 6

7. Hydrologic Cycle

8. The hydrologic cycle

9. Hydrologic Cycle (water cycle)
1. Reservoir – oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land
2. Assimilation – plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water
3. Release – plants transpire, animals breathe and expel liquid wastes

10. Reserviors

11. Residence Times

12. The carbon-oxygen cycle

13. Carbon-Oxygen Cycle (carbon is required for building organic compounds)
1. Reservoir – atmosphere (as CO2), fossil fuels (gas, oil, coal), durable organic materials (for example: cellulose).
2. Assimilation – plants use CO2 in photosynthesis; animals consume plants
3. Release – plants and animals release CO2 through respiration and decomposition; CO2 is released as wood and fossil fuels are burned

14. The carbon cycle
Carbon is found in carbohydrates, fats, proteins, bones
Carbon cycle = describes the routes that carbon atoms take through the environment
Photosynthesis moves carbon from the air to organisms
Respiration returns carbon to the air and oceans
Decomposition returns carbon to the sediment, the largest reservoir of carbon
Ultimately, it may be converted into fossil fuels
The world’s oceans are the second largest reservoir of carbon 14

15. Humans affect the carbon cycle
Burning fossil fuels moves carbon from the ground to the air
Cutting forests and burning fields moves carbon from organisms to the air
Today’s atmospheric carbon dioxide reservoir is the largest in the past 650,000 years
The driving force behind climate change
The missing carbon sink: 1-2 billion metric tons of carbon are unaccounted for
It may be the plants or soils of northern temperate and boreal forests

17. The nitrogen cycle

18. Nitrogen Cycle (Nitrogen is required for the manufacture of amino acids and nucleic acids)
1. Reservoir – atmosphere (as N2); soil (as NH4+ or ammonium, NH3 or ammonia, N02- or nitrite, N03- or nitrate

19. Nitrogen Cycle
2. Assimilation – plants absorb nitrogen as either NH4+ or as N03-, animals obtain nitrogen by eating plants and other animals. The stages in the assimilation of nitrogen are as follows:
Nitrogen Fixation: N2 to NH4+ by nitrogen-fixing bacteria (prokaryotes in the soil and root nodules), N2 to N03- by lightning and UV radiation.
Nitrification: NH4+ to N02- and N02- to N03- by various nitrifying bacteria.

20. Nitrogen Cycle
3. Release – Denitrifying bacteria convert N03- back to N2 (denitrification); detrivorous bacteria convert organic compounds back to NH4+ (ammonification); animals excrete NH4+ (or NH3) urea, or uric acid.

21. The nitrogen cycle
Nitrogen comprises 78% of our atmosphere, and is contained in proteins, DNA and RNA
Nitrogen cycle = describes the routes that nitrogen atoms take through the environment
Nitrogen gas is inert and cannot be used by organisms
Nitrogen fixation = Nitrogen gas is combined (fixed) with hydrogen by nitrogen-fixing bacteria to become ammonium
Which can be used by plants

22. Nitrification and denitrification
Nitrification = bacteria that convert ammonium ions first into nitrite ions then into nitrate ions
Plants can take up these ions
Animals obtain nitrogen by eating plants or other animals
Denitrifying bacteria = convert nitrates in soil or water to gaseous nitrogen, releasing it back into the atmosphere

23. Humans affect the nitrogen cycle
Haber-Bosch process = synthetic production of fertilizers by combining nitrogen and hydrogen to synthesize ammonia
Dramatically changed the nitrogen cycle
Humans are fixing as much nitrogen as nature does
Increased emissions of nitrogen-containing greenhouse gases
Calcium and potassium in soil washed out by fertilizers
Acidified water and soils
Moved more nitrogen into plants and terrestrial systems
Reduced biodiversity of plants adapted to low-nitrogen soils
Changed estuaries and coastal ecosystems and fisheries

24. Human inputs of nitrogen into the environment
Fully half of nitrogen entering the environment is of human origin

26. The phosphorus cycle
Phosphorus is a key component of cell membranes, DNA, RNA, ATP and ADP
Phosphorus cycle = describes the routes that phosphorus atoms take through the environment
No significant atmospheric component
Most phosphorus is within rocks and is released by weathering
With naturally low environmental concentrations, phosphorus is a limiting factor for plant growth

27. Phosphorus Cycle (Phosphorus is required for the manufacture of ATP and all nucleic acids)
1. Reservoir – erosion transfers phosphorus to water and soil; sediments and rocks that accumulate on ocean floors return to the surface as a result of uplifting by geological processes
2. Assimilation – plants absorb inorganic PO43- (phosphate) from soils; animals obtain organic phosphorus when they plants and other animals
3. Release – plants and animals release phosphorus when they decompose; animals excrete phosphorus in their waste products

28. The phosphorus cycle

30. Humans affect the phosphorus cycle
Mining rocks for fertilizer moves phosphorus from the soil to water systems
Wastewater discharge also releases phosphorus
Runoff containing phosphorus causes eutrophication of aquatic systems

31. The sulfur cycle

32. Sulfur Cycle (Sulfur is required for the manufacture of proteins)
1. Reservoir – Earth’s crust as gypsum (CaSO4) and pyrite (FeS2), oceans as sulfate anions, atmosphere as sulfur dioxide (SO2)
2. Assimilation – sulfate (SO4 2–) is reduced by plants, fungi and prokaryotes
3. Release – plants and animals release sulfur when they decompose

34. The rock cycle
Rock cycle = The heating, melting, cooling, breaking and reassembling of rocks and minerals
Rocks help determine soil chemistry, which influences ecosystems
Helps us appreciate the formation and conservation of soils, mineral resources, fossil fuels, and other natural resources 34

35. The Nitrogen Cycle Game Questions
In the course of the Nitrogen Cycle, are nitrogen atoms themselves ever created? Ever destroyed? Ever changed into other compounds? Explain why or why not.
Discuss what moves on the game board represented the following processes of the Nitrogen Cycle:
Nitrogen Fixation
Nitrification
Ammonification
Assimilation
Denitrification

36. The Nitrogen Cycle Game Questions
Identify what other gases, besides, N2, can be produced during denitrification. For each gas you identify, describe what human activities facilitate the production of these gases.
Discuss why a natural ecosystem (assuming no anthropogenic interaction ) is not polluted by nitrogenous wastes from various organisms.

37. Hypoxia and the Gulf of Mexico’s Dead Zone
Observations: low oxygen levels - hypoxia
Hypothesis: caused by nutrients (fertilizers) that ran into the Gulf from rivers
Experiments: monitoring oxygen (long term), water sampling (N, NaCl. Bacteria, phytoplankton); observed life; analyzed historical data
Results: phytoplankton receiving too much phosphorus from farming & sewage treatment plants
As the phytoplankton die the decomposers use up available oxygen
Solution: reduce amount of phosphorus entering the Gulf – but How?

38. Newton’s Laws
Conservation of Mass – mass cannot be created or destroyed, but can be changed to energy

39. Newton’s Laws - First
Thermodynamics – inertia – an object in motion stays in motion unless acted upon by an outside force

40. Thermodynamics – entropy– disorder increases
Newton’s Laws - Second
Thermodynamics – entropy– disorder increases
Think of entropy as heat loss
We must add more energy to compensate for the heat loss

41. Energy passes through trophic levels
One of the most important species interactions is who eats whom
Matter and energy move through the community
Trophic levels = rank in the feeding hierarchy
Producers
Consumers
Detritivores and Decomposers 41

42. Producers: the first trophic level
Autotrophs (“self-feeders”) = organisms that capture solar energy for photosynthesis to produce sugars
Green Plants
Cyanobacteria
Algae
Chemosynthetic bacteria use the geothermal energy in hot springs or deep-sea vents to produce their food 42

43. Consumers: organisms that consume producers
Primary consumers = second trophic level
Organisms that consume producers
Herbivores consume plants
Deer, grasshoppers
Secondary consumers = third trophic level
Organisms that prey on primary consumers
Carnivores consume meat
Wolves, rodents, birds 43

44. Consumers occur at even higher trophic levels
Tertiary Consumers = fourth trophic level
Predators at the highest trophic level
Consume secondary consumers
Are also carnivores
Hawks, owls
Omnivores = consumers that eat both plants and animals

45. Detritivores and decomposers
Organisms that consume nonliving organic matter
Enrich soils and/or recycle nutrients found in dead organisms
Detritivores = scavenge waste products or dead bodies
Millipedes
Decomposers = break down leaf litter and other non-living material
Fungi, bacteria
Enhance topsoil and recycle nutrients 45

46. Energy, biomass, and numbers decrease
Most energy organisms use is lost as waste heat through respiration
Less and less energy is available in each successive trophic level
Each level contains only 10% of the energy of the trophic level below it
There are far fewer organisms at the highest trophic levels, with less energy available
A human vegetarian’s ecological footprint is smaller than a meat-eater’s footprint 46

47. Pyramids of energy, biomass, and numbers

48. Food webs show relationships and energy flow
Food chain = the relationship of how energy is transferred up the trophic levels
Food web = a visual map of feeding relationships and energy flow
Includes many different organisms at all the various levels
Greatly simplified; leaves out the majority of species 48

49. Some organisms play big roles
Keystone Species = has a strong or wide-reaching impact far out of proportion to its abundance
Removal of a keystone species has substantial ripple effects
Alters the food chain

50. Species can change communities
Trophic Cascade = predators at high trophic levels can indirectly affect populations of organisms at low trophic levels by keeping species at intermediate trophic levels in check
Extermination of wolves led to increased deer populations, which led to overgrazed vegetation and changed forest structure
Ecosystem engineers = physically modify the environment
Beaver dams, prairie dogs, fungi, insects, phytoplankton