Biogeochemical Cycles Where do macromolecules come from & Where do they go?

Elements transferred between compartments (pools) Active: accessible to living things Storage: inaccessible

Biogeochemical Cycle Overview

What is a Biogeochemical Cycle? Reuse of materials in ecosystem by living organisms Biological components (biotic): – Producers – Consumers – Detritivores (scavengers & decomposers) Geological components (abiotic): – Atmosphere (gases & water vapor) – Solid crust of the earth (minerals & chemicals) – Earth’s water (oceans, lakes & rivers)

Biogeochemical Cycles Water – needed to make CARBOHYDRATES, LIPIDS, PROTEINS

THE WATER CYCLE

Other Biogeochemical Cycles Water cycle Carbon – needed to make CARBOHYDRATES, LIPIDS, PROTEINS, & NUCLEIC ACIDS

CARBON CYCLE atmosphere biosphere respiration photosynthesis

CARBON CYCLE

atmosphere biosphere respiration photosynthesis combustion

Other Biogeochemical Cycles Water cycle Carbon cycle Nitrogen – needed to make PROTEIN & NUCLEIC ACIDS

Nitrogen Cycle atmosphere biosphere loss fixation gain denitrification

Nitrogen Cycle Despite abundance in the atmosphere (77% of Earth’s atmosphere made of N 2 gas) nitrogen is actually a limiting factor to plant growth Most organisms cannot use elemental N 2 and must use nitrogen present in soil minerals N 2 gas is “fixed” into these nitrogen compounds mainly by bacterial processes

Stages of Nitrogen Cycle Ammonification – Most soil nitrogen is result of decomposition of nitrogenous compounds by bacteria (amino acids, proteins, etc.) – These bacteria release excess nitrogen in the form of ammonia (NH 3 ) or ammonium ions (NH 4 + )

Stages of Nitrogen Cycle Ammonification Nitrification (by nitrogen-fixing bacteria) –S–Several species of bacteria able to oxidize ammonia to get energy for metabolism: –A–Although nitrite (NO 2 - ) is toxic, it is quickly changed to nitrate (NO 3 - ) by another group of bacteria: –M–Most plants take up nitrogen in the form of nitrate 2NH 3 + 3O 2  2NO H + + 2H 2 O 2NO O 2  2NO 3 - NITRATE

Stages of Nitrogen Cycle Ammonification Nitrification Assimilation –R–Requires energy expenditure to attach ammonium ions to carbon-containing compounds –A–Amino acids produced: Amino acids form PROTEINS

Loss of Soil Nitrogen Nitrates steadily lost from cycle by: – Harvesting plants – Soil erosion – Fire – Leaching – Denitrifying bacteria – these break down nitrate into N 2 gas (in the absence of oxygen); usually takes place in poorly drained soil

NITROGEN CYCLE ANIMATION

Other Biogeochemical Cycles Water cycle Carbon cycle Nitrogen cycle Phosphorus – needed to make DNA & RNA (nucleic acids) as well as ATP (the energy currency of cells)

PHOSPHORUS CYCLE

Other Biogeochemical Cycles Water cycle Carbon cycle Phosphorus Sulfur – needed to make certain proteins

SULFUR CYCLE

Questions: What would happen if a biogeochemical cycle “slowed down” or “sped up?” What might cause such a thing to happen? Turn to your neighbor and explain. Then write a summary of what you both concluded.