Nutrient Cycles & Thermodynamics

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

Biogeochemical Nutrient Cycles

Biogeochemical Nutrient Cycles Hydrologic Carbon-Oxygen Nitrogen Phosphorus Sulfur Rock

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

Hydrologic Cycle

The hydrologic cycle

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

Reserviors

Residence Times

The carbon-oxygen cycle

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

The nitrogen cycle

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

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.

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.

The phosphorus cycle

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

The sulfur cycle

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

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 25

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?

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

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

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

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 30

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 31

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 32

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

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 34

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 35

Pyramids of energy, biomass, and numbers

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 37

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

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