biosphere constant input of energy energy flows through nutrients cycle ecosystems
TRANSCRIPT
biosphere
constant inputof energy
energy flowsthrough
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
abioticreservoir
nutrientsmade availableto producers
geologicprocesses
consumers
consumers
producers
decomposers
abioticenvironment
nutrientsENTER FOOD CHAIN
= made availableto producers
geologicprocesses
return toabiotic
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
Evaporation Precipitation PrecipitationTranspiration
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 (CO2) with the atmosphere
On land, plants take up CO2 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 CO2
The Carbon Cycle
In aquatic systems the exchange of carbon with the atmosphere is indirect
Dissolved CO2 from the air combines with water to produce bicarbonate ions (HCO3
-)
These ions are taken up by aquatic photosynthetic organisms
When aquatic organisms respire, they again give off bicarbonate ions, which are converted back to CO2
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
RespirationDiffusion
CALCIUM CARBONATE SHELLS
LIMESTONE
Disruption of the Carbon Cycle
The total amount of carbon dioxide in the atmosphere is increasing every year
More CO2 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 CO2 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
ROCKSEWAGE
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 (N2) can be converted into ammonium (NH4
+) 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
N2 can also be converted into nitrate (NO3
-) in a process called nitrification
Nitrification can occur in two ways:
N2 is converted into NO3- in the atmosphere
when cosmic radiation, meteor trails and lightning cause it to react with oxygen
NH4+ in the soil is converted first into NO2
- (nitrite) and then into NO3
- by nitrifying bacteria
The Nitrogen Cycle
Denitrification is the conversion of NO3-
back into N2 by denitrifying bacteria
Denitrification balances nitrogen fixation
LAND / WATER
ATMOSPHERE
AMMONIUM (NH4+)
ORGANIC WASTES
PLANTS / PHYTOPLANKTON
NITRATE (NO3-)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 (N2)
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 (N2O), which is a greenhouse gas and also contributes to ozone depletion
Disruption of the Nitrogen Cycle
Burning of fossil fuels releases nitrogen oxides (NOX) and sulfur dioxide (SO2) 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