Cycles of the Earth & Biogeochemical Cycles Phosphorus Cycle Slides 93-105

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

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

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

Phosphorus Cycle

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

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

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

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

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

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

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

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.

Phosphorus Cycle https://www.youtube.com/watch?v=uLeRXLg5R4k