The Phosphorous Cycle

Section 4.5

The Phosphorous Cycle

• Uses of phosphorous by organisms:– Phosphorous, like nitrogen and carbon, is an

important element needed by organisms.

The Phosphorous Cycle

• Cell membranes:– They are made of a phospholipid bilayer in all

cells.

The Phosphorous Cycle

• Hard tissues:– Shells, bones and teeth all contain phosphorous.

The Phosphorous Cycle

• Nucleic acids:– The “side rails” of DNA and RNA contain

phosphorous.

The Phosphorous Cycle

• ATP – adenosine triphosphate:– A high energy molecule (produced during cellular

respiration).– It stores all energy for living things.

The Phosphorous Cycle

• The element phosphorous:

The Phosphorous Cycle• Where do we get phosphorous?– The Earth’s crust:• It’s stored in rocks,• It gets released when

rocks weather anderode.• Phosphate (PO4)

is released anddissolves inwater.

• Where do we get phosphorous?– Rivers and runoff• It gets carried from the surface of the

land by runoff into rivers and oceans. (runoff/leaching)

The Phosphorous Cycle

• Where do we get phosphorous?– Humans• It’s in artificial fertilizers (they contain N, P and K).• It’s in animal manure.• It’s in outflows from

sewage plants.• It’s in industrial

wastes.

The Phosphorous Cycle

The Phosphorous Cycle

• The short phosphorous cycle:– Organisms die and decompose.– Decomposers release phosphates into the soil.– Phosphates dissolve in water.– Producers (plants) take in dissolved phosphates

through their roots.

The Phosphorous Cycle

• The long phosphorous cycle:– Plants and animals die.– Phosphates in their bodies sink to the ocean floor.– The phosphates become covered in sediment

layers.– The layers turn into sedimentary rock.– Geological uplifting exposes the rock to

weathering that releases the phosphates into the soil.