chemicals moving through ecosystems 

biotic and abiotic processes

cross the boundaries of ecosystems

-one ecosystem may import or export carbon to others

-only cycle that is not of an element

-60% of human body is water

-amount available determines the nature and abundance of organisms present

-can be synthesized (during cellular respiration)and broken down(during photosynthesis)

-liquid water from Earth's surface evaporates into the atmosphere

-evaporation occurs from surfaces of oceans, lakes, and rivers

- 90% of evaporation in terrestrial ecosystems is through plants

-evaporated water exists in the atmosphere as a gas

-cools and falls to the surface as precipitation

-underground water

-occurs in aquifers

-most important reservoir of water on land: 95% of fresh water used in U.S

-Two Subparts:

-upper layer constitutes water table(flows into streams and is partly accessible to roots of plants

-lower layer can be tapped by wells(out of plants reach)

-permeable underground layers of rock, sand, and gravel that is saturated with water

-flows much slower than surface water, few millimeters to a meter a day

-used for agricultures and domestic needs

-changes in water supply of ecosystem can radically alter the nature of the ecosystem

-Deforestation disrupts the local water cycle (human activities alter water cycle)

-water that falls as rain drains away into rivers rather than forming clouds and falling again

-tropical rain forest to semiarid deserts deprive native species of their natural habitat

-20% of human body weight

-carbon fixation

-aerobic cellular respiration releases CO2

-methanogens

-decaying organisms produce CO2

microbes that produce methane CH4 by anaerobic cellular respiration

they live in oxygen free sediments

-can cause large consequences if continued for many years

-earths present reserves of coal and other fossil fuels were built up over geological time

-human burning of fossil fuels is creating large imbalances in Carbon Cycle

-[ ] of CO2 in the atmosphere is growing up yr by yr

-component of all proteins and nucleic acids

-elements usually are shortest supply

-atmosphere is 78% nitrogen

-availability:

-most plants and animals cannot use N2 (gas)

-use NH3 (ammonia) and NO3- (nitrate ions) instead that are synthesized by plants and algae

(N)- after NH3 is synthesized other prokaryotic microbes oxidize part of it to form NO3-

N2-->NH3-->NO3-

(D)-prokaryotic microbes (archaea and bacteria) are able to convert NO3- ---> N2

-nitrogenous wastes and fertilizer use radically alter the global nitrogen cycle

-humans have doubles the rate of transfer of N2 in useable forms into soils and water

-is required by all organisms

-occurs in nucleic acids, membrane phospholipids, and ATP

-has no significant gas form and doesn't cycle through atmosphere

-exist in ecosystems in only 1 oxidation state, phosphate PO_4_^3-

-plants and algae use free inorganic phosphorus, animals eat plants to obtain their phosphorus

-weak link in an ecosystem; shortest supply relative to the needs of organisms

-nitrogen and phosphorus can also be limiting nutrients for terrestrial and aquatic ecosystems

-iron is the limiting nutrient for algal populations (phytoplakton) in about 1/3 of world's oceans