biosphere constant input of energy energy flows through nutrients cycle Ecosystems

Chemical Cycling  Organisms require various organic and inorganic nutrients to survive, such as water, carbon dioxide, phosphorous and nitrogen  Chemicals cycle as organic nutrients  Nutrients pass one-way through the food chain from one trophic level to another  Once used, nutrients are returned back to the producers by excretion and death

consumers decomposers abiotic reservoir nutrients made available to producers geologic processes consumers producers decomposers abiotic environment nutrients ENTER FOOD CHAIN = made available to producers geologic processes return to abiotic environment

Global Biogeochemical Cycles  The pathways through which these chemicals circulate are known as biogeochemical cycles  They involve both living (biological) and non-living (geological) components

Global Biogeochemical Cycles  Chemical cycling involves: 1.A reservoir – Source normally unavailable to organisms, such as fossil fuels, minerals in rocks and ocean sediments 2.An exchange pool – Source from which organisms take chemicals, such as the atmosphere, soil and water 3.The biotic community – Chemicals cycle through food chains

Global Biogeochemical Cycles  Human activities may upset the natural balance of chemical cycles by removing chemicals from reservoirs and exchange pools

The Water Cycle  Water evaporates from:  Oceans  Bodies of fresh water, e.g. lakes  Soil  Plants (transpiration)  Water vapour forms clouds and condenses back into a liquid  Water returns to the Earth in the form of precipitation, i.e. rain, snow, hail, fog

The Water Cycle  Most precipitation falls directly into the oceans  Precipitation on land either:  Forms surface water (lakes, rivers)  Sinks into the ground (groundwater, aquifers)  Water eventually returns to the oceans

LANDOCEAN ATMOSPHERE FRESHWATER WATER IN ATMOSPHERE GROUNDWATER WATER IN OCEAN WATER IN ATMOSPHERE PLANTS EvaporationPrecipitation Transpiration Evaporation Runoff Wind

The Water Cycle and Humans  The human population depends on a constant supply of fresh water  In some areas, groundwater is being depleted faster that it is replenished  Water pollution also poses a threat to water supplies  Deforestation breaks the water cycle, resulting in desertification

The Carbon Cycle  Living organisms exchange carbon dioxide (CO 2 ) with the atmosphere  On land, plants take up CO 2 from the atmosphere during photosynthesis and convert it into organic carbon, which is a food source for other organisms  During cellular respiration, organisms release some of this carbon back into the atmosphere as CO 2

The Carbon Cycle  In aquatic systems the exchange of carbon with the atmosphere is indirect  Dissolved CO 2 from the air combines with water to produce bicarbonate ions (HCO 3 - )  These ions are taken up by aquatic photosynthetic organisms  When aquatic organisms respire, they again give off bicarbonate ions, which are converted back to CO 2

The Carbon Cycle  Photosynthesis and respiration cause carbon to cycle in the environment very quickly  However, some carbon remains in an organic form for a longer period and is only released back to the atmosphere when organisms die and decay  Sometimes organic carbon can be transformed into fossil fuels (coal, oil, natural gas), where it can remain for millions of years

CARBON DIOXIDE AQUATIC ORGANISMS BICARBONATE IONS ANIMALS DEAD ORGANISMS AND ANIMAL WASTE FOSSIL FUELS (COAL, OIL, NATURAL GAS) WATERLAND ATMOSPHERE Decay Photosynthesis Destruction of vegetation LAND PLANTS Combustion Respiration Diffusion CALCIUM CARBONATE SHELLS LIMESTONE

Disruption of the Carbon Cycle  The total amount of carbon dioxide in the atmosphere is increasing every year  More CO 2 is being deposited into the atmosphere than is being removed  This increase is due to fossil fuel combustion and destruction of forests by humans  An increase in CO 2 contributes to the greenhouse effect

Greenhouse Effect  Greenhouse gases:  Carbon dioxide, nitrous oxide, methane  Allow sunlight to pass through the atmosphere  Prevent the escape of infrared rays by reflecting them back to Earth  Results in heat being trapped in the atmosphere and global warming

Earth’s Radiation Balances

Greenhouse Effect  If Earth’s temperature rises:  Glaciers will melt  Sea levels will rise  More water will evaporate  More rain will occur along the coast, but it will be drier inland, leading to droughts  Species will become extinct as habitats and ecosystems change

The Phosphorous Cycle  The phosphorus is a sedimentary cycle because phosphorous never enters the atmosphere  Phosphorous cycles between rocks on land and ocean sediments  Slow weathering of rocks releases phosphate ions into the soil

The Phosphorous Cycle  Phosphate taken up by plants and incorporated into organic molecules, (ATP, nucleotides, phospholipids)  Consumers get their phosphate from the producers  Decomposition makes some phosphorous available in the soil to producers again

The Phosphorous Cycle  Some phosphate washes into aquatic systems, where it is used by aquatic organisms  Phosphate that settles in ocean sediments returns to land again via geological processes

PHOSPHATE IN SOLUTION ORGANISMS SEDIMENT DETRITUS WATERLAND DECOMPOSERS PLANTS ANIMALS ROCK SEWAGE TREATMENT PLANTS FERTILIZER Plant and animal wastes Weathering Phosphate mining Geologic uplift PHOSPHATE IN SOIL Runoff

Disruption of the Phosphorous Cycle  Humans mine phosphate ore for production of fertilizers and detergents  Runoff of extra phosphate from these activities can lead to eutrophication (over-enrichment) of waterways  This can lead to algal blooms  Algal blooms are followed by shortage of oxygen as decomposers use up all the oxygen to break down decaying algae  Followed by huge losses of fish

The Nitrogen Cycle  Nitrogen makes up 78% of atmosphere  Nitrogen is essential to living organisms for the formation of amino acids and nucleic acids  Plants cannot absorb nitrogen gas, and depend on bacteria and physical processes to convert nitrogen into a useable form (ammonium or nitrate)

The Nitrogen Cycle  Atmospheric nitrogen (N 2 ) can be converted into ammonium (NH 4 + ) by:  Free-living bacteria in the soil  Nitrogen-fixing bacteria living in the nodules on the roots of legumes  Some cyanobacteria in aquatic systems

The Nitrogen Cycle  N 2 can also be converted into nitrate (NO 3 - ) in a process called nitrification  Nitrification can occur in two ways:  N 2 is converted into NO 3 - in the atmosphere when cosmic radiation, meteor trails and lightning cause it to react with oxygen  NH 4 + in the soil is converted first into NO 2 - (nitrite) and then into NO 3 - by nitrifying bacteria

The Nitrogen Cycle  Denitrification is the conversion of NO 3 - back into N 2 by denitrifying bacteria  Denitrification balances nitrogen fixation

LAND / WATER ATMOSPHERE AMMONIUM (NH 4 +) ORGANIC WASTES PLANTS / PHYTOPLANKTON NITRATE (NO 3 -) Nitrification (nitrifying bacteria) Nitrogen fixation (nitrogen-fixing bacteria in soil and on nodules; cyanobacteria) Nitrification (lightning, cosmic radiation, meteor trails) Denitrification (denitrifying bacteria) Human activities FERTILIZERS ACID RAIN NITROGEN GAS (N 2 )

Disruption of the Nitrogen Cycle  Production of fertilizers from nitrogen gas nearly doubles the natural fixation rate  Fertilizer runoff results in eutrophication of water bodies  Use of fertilizers results in release of nitrous oxide (N 2 O), which is a greenhouse gas and also contributes to ozone depletion

Disruption of the Nitrogen Cycle  Burning of fossil fuels releases nitrogen oxides (NO X ) and sulfur dioxide (SO 2 ) into the atmosphere  These combine with water vapour to form acids  Acids return to earth as acid rain

Acid Rain  Acid rain dramatically reduces pH of surface waters in some areas  Causes heavy metals to leach out rocks, poisoning aquatic organisms  Fish are unfit for human consumption  Corrodes metals, marble and stonework in cities

Acid Rain  Plants die due to increased soil acidity