Chapter 3: The Biosphere Section 4: Cycles of Matter

Recycling in the Biosphere Unlike the one-way flow of energy, matter is recycled within and between the ecosystem Biogeochemical Cycles: elements pass from one organism to another and among parts of the biosphere through closed loops that are powered by the flow of energy Consists of biological processes, geological processes, and chemical processes. Human activity also plays a large roll.

Biological Processes: includes any and all activities performed by living organisms Ex: breathing, “burning” food energy, & eliminating water products Geological Processes: include volcanic eruptions, the formation and breakdown of rock, & major movements of matter within and below the surface of the earth Chemical & Physical Processes: includes the formation of clouds and precipitation, the flow of running water, & the action of lightning Human Activity: include the mining and burning of fossil fuels, the clearing of land for building and farming, the burning of forests, & the manufacture and use of fertilizers

Water Cycle Water cycle continuously moves water between the atmosphere, the land, & the oceans Water vapor condenses & falls to earth’s surface: precipitation Some water percolates into the soil & becomes groundwater Water is heated by the sun & reenters the atmosphere by evaporation Water also evaporates from trees & plants by transpiration Transpiration is the process where water travels through a plant and evaporates from the leaves as water vapor

Nutrient Cycles Every organism needs nutrients to build tissues and carry out life functions. Like water, nutrients pass through organisms and the environment through biogeochemical cycles. The three pathways, or cycles that move carbon, nitrogen, and phosphorus through the biosphere are especially critical for life.

Carbon & Oxygen Cycles All organisms are made of carbon(organic matter) Animals, plants, & other photosynthesizing organisms play an important role in cycling carbon & oxygen through an ecosystem Plants use CO2 in air to build organic molecules during photosynthesis Also in photosynthesis O2 is released Many animals use O2 to help break down organic molecules which releases energy & CO2 Plants again take in the CO2 Respiration: The process of exchanging of O2 & CO2 between organisms & their surroundings

Carbon & Oxygen Cycles Combustion: burning of substance; releases carbon into the atmosphere All living things have carbon in them; burning living things release CO2 Decomposing of living things also releases CO2 Fossil fuels(oil & coal) are made of remains of dead animals & plants; therefore the burning of fossil fuels releases CO2

Nitrogen Cycle Nitrogen gas (N2) makes up 78% of the atmosphere. Bacteria in the soil convert N2 into ammonia through the process of nitrogen fixation. Plants use the ammonia to make proteins and DNA/RNA. Animals eat the plants and digest the proteins and DNA/RNA. Animals return the nitrogen to the soil through urine and feces. Bacteria obtain energy by converting nitrates into nitrogen gas, which is released into the atmosphere in a process called denitrification.

Phosphorus Cycle Phosphorus forms the molecules in DNA & RNA Phosphorus is found in inorganic remains, phosphate rock and soil minerals, & in dissolved phosphate and phosphate sediments in the ocean Phosphate cycles between organisms and the soil on land Organic phosphate cycles through the food web from producers to consumers and to the rest of the ecosystem Some phosphate is washed into the water and eventually makes it to the ocean where marine organisms process and incorporate it into biological compounds

Nutrient Limitation If ample sunlight and water are available, the primary productivity of an ecosystem may be limited by the availability of nutrients Limiting Nutrient: the nutrient whose supply limits the productivity of an ecosystem We supplement the nutrient limitation in soil by using products like fertilizers to supplement nutrients that would limit productivity In the oceans when there are large amounts of run off that come from land after a heavy rain or storm there is suddenly an increase in nutrients which can spike growth & productivity