1. Cycles of the Earth & Biogeochemical Cycles Phosphorus Cycle
Slides

2. The phosphorus cycle
Phosphorus (P) is a key component of cell membranes, DNA, RNA, ATP and ADP
Phosphorus cycle = describes the routes that phosphorus atoms take through the environment

3. mining Fertilizer excretion Guano agriculture weathering uptake by
autotrophs
uptake by
autotrophs
leaching, runoff
Marine
Food
Webs
Dissolved
in Ocean
Water
Dissolved
in Soil Water,
Lakes, Rivers
Land
Food
Webs
death,
decomposition
death,
decomposition
Figure 3.31
Natural capital: simplified model of the phosphorus cycle. Phosphorus reservoirs are shown as boxes; processes that change one form of phosphorus to another are shown in unboxed print. QUESTION: What are three ways in which your lifestyle directly or indirectly affects the phosphorus cycle? (From Cecie Starr and Ralph Taggart, Biology: The Unity and Diversity of Life, 9th ed., Belmont, Calif.: Wadsworth © 2001)
weathering
sedimentation
settling out
uplifting over
geologic time
Marine Sediments
Rocks
Fig. 3-31, p. 77

4. The phosphorus cycle
Most phosphorus is within rocks. It is released by weathering
There is no significant atmospheric component
With naturally low environmental concentrations
Phosphorus is a limiting factor for plant growth

5. Phosphorus Cycle

6. Phosphorus (P) Cycle Problem: No phosphorus in atmosphere
Phosphorus needed to make ATP, DNA, lipids
Step 1: Phosphorus released by weathering of rocks P P

7. Phosphorus (P) Cycle
Step 2: Producers absorb P into their roots P P P

8. Phosphorus (P) Cycle Step 2: Producers absorb P into their roots
Step 3: Consumers ingest P when plants eaten P P P P P

9. Phosphorus (P) Cycle Step 2: Producers absorb P into their roots
Step 3: Consumers ingest P when plants eaten
Step 4: Decomposer s breakdown dead matter and release P into soil
Cycle repeats P P P P P P

10. Phosphorus (P) Cycle Human Contribution P P P P
Adding excess P from fertilizers
P washes into lakes, etc…
Excess P causes extreme algae growth P P

11. 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

12. Phosphorus Cycle
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
Assimilation – plants absorb inorganic PO43- (phosphate) from soils; animals obtain organic phosphorus when they plants and other animals
Release – plants and animals release phosphorus when they decompose; animals excrete phosphorus in their waste products

13. Effects of Human Activities on the Phosphorous Cycle
We remove large amounts of phosphate from the earth to make fertilizer.
We reduce phosphorous in tropical soils by clearing forests.
We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers.

14. Phosphorus Cycle