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1. The total mass of living plants, animals, fungi, and bacteria in a given area.
2. The mass of a particular type of organic matter such as trees, plant crops, manures, and other organic materials that may be used to manufacture biofuels such a biogas.

Estimates of biomass are usually expressed in grams or kilograms per square metre.


Energy Flow

● The flow of energy from an ecosystem to an organism and from one organism to another
● Every organism plays two roles in energy flow:
1. Obtains food energy from ecosystem
2. Contributes energy to ecosystem



● Organisms that "produce" food in the form of carbohydrates during photosynthesis.
● Plants are an example of a producer.
● Carbohydrates stored in plants become an energy source for other life forms.



● Organisms that consume other things (ie. producers, or other consumers) for energy. They do not produce their own food.
● An insect (ie. bee) that feeds on a plant (ie. sunflower) is an example of a consumer.
● A consumer may become an energy source if consumed by another consumer.
● There are different levels of consumers (ie. primary, secondary, tertiary, etc.)



● The breaking down of organic wastes and dead organisms
● Through this process, organisms continue to contribute to the energy flow in an ecosystem, even after their death.



● The action of living organisms breaking down the organic wastes and dead organisms.
● Decomposition carried out by living organisms



● Organisms that change waste and dead organisms into usable nutrients. (ie. bacteria and fungi)
- These nutrients are then made available to other organisms in soil and water and link the biotic/abiotic components of an ecosystem.


List the different ways in which energy flow and feeding relationships are modelled.

1. Food chains
2. Food webs
3. Food pyramids


Food chain

● Show the flow of energy from plant to animal and from animal to animal.
● Follows a single path as energy flows from one trophic level to the next in an ecosystem.


Trophic level

● Each step in a food chain is called a trophic level
● Primary producers are one the first trophic level.
- Primary consumers (organisms that consume these producers) would be the second trophic level, and so on.
● Only~10% of energy is transferred to the next trophic level


Primary consumer

● Consumers that consume producers
- ie. grasshoppers, deer, any herbivore
● Second trophic level


Secondary consumer

● Consumers that consume primary consumers
- ie. frogs, crabs, etc.
● Third trophic level


Tertiary consumer

● Consumers that consume secondary consumers
- ie. wolves, lions, hawks, etc.



● Consumers that obtain their energy and nutrients by eating the bodies of small dead animals, dead plant matter, and animal wastes.
● Feed at every trophic level



● Primary consumers that eat plants
● Examples include: bighorn sheep, western tiger swallowtail butterflies (pg. 61)



● Secondary/tertiary consumers
- Carnivores that eat secondary consumers are often referred to as top carnivores, top consumers, or top predators
● Eat other consumers
● Examples of carnivores include grey wolves and hobo spiders (pg. 62)



● Consumers that eat both plants and animals
● They are found on more than one trophic level


Food web

● Formed by interconnected food chains
● Models of the feeding relationships within an ecosystem


Food pyramid

● Shows the loss of energy from one trophic level to another
● Often referred to as ecological pyramids


What are the different types of ecological pyramids?

1. Pyramid of biomass
2. Pyramid of numbers
3. Pyramid of energy


Pyramid of biomass (What is it? What are the limitations?)

● An ecological pyramid that shows the number of organisms at each trophic level multiplied by their mass, which compensates for differences in size among organisms
● Limitations:
- In some ecosystems, the biomass of lower trophic levels can be less than that of higher trophic levels.
(ie. in aquatic ecosystems, pyramids of biomass may be inverted because of the rapid reproduction rates of primary producers such as algae.)


Pyramid of numbers (What is it? What are the limitations?)

● An ecological pyramid that shows the number of organisms at each trophic level
● Limitations:
- The sizes of individual organisms vary greatly, and thus their energy needs vary greatly
- The range of numbers from the producers to the tertiary consumers may be so great that it is impossible to represent the scale of the pyramid accurately.


Pyramid of energy (What is it? What are the limitations?)

● An ecological pyramid that shows the amount of energy that is available at each trophic level
● Limitations:
- It is difficult to obtain exact values of available energy in an ecosystem


How much energy is transferred between trophic levels?

Only ~10% of the energy is actually converted into animal biomass/stored.


What happens to the energy that is not transferred to the next trophic level?

● Used to obtain/digest food, repair damaged tissues, other life functions, etc.
● 80-90% of the food energy is used for chemical reactions in the body and eventually is lost to the ecosystem in the form of heat.



● Chemicals that are required for plant and animal growth and other life processes.
● They are accumulated for short and long periods of time in Earth's atmosphere, oceans, and land masses



● Accumulations of nutrients for short or long periods of time in Earth's atmosphere, oceans, and land masses.


Nutrient cycles

● The continuous flow of nutrients in and out of stores
● Nutrient cycles are nearly in balance because, without human interference, the amounts of nutrients flowing into the stores are nearly the same as the amounts flowing out of the stores


How does human activity affect nutrient cycles in general?

● Activities such as land clearing, agriculture, urban expansion, mining, industry, and motorized transportation can affect a nutrient cycle by increasing the amounts of nutrients in the cycle faster than natural biotic/abiotic processes can move them back to the stores.
● Over time, increase amounts of nutrients in the atmosphere/oceans/land can have significant effects on the environment


What are the three important nutrient cycles covered in section 2.2?

1. Carbon cycle
2. Nitrogen cycle
3. Phosphorus cycle


Where are short-term stores of carbon found?

● Vegetation on land/oceans
● Animals
● Decaying organic matter in soil
● Atmosphere (CO2)
● Top layer of the ocean


Where are long-term stores of carbon found?

● Intermediate/deep ocean waters
● Coal/oil/gas deposits
● Marine sediments/sedimentary rock



● The process that contributes to the formation of sedimentary rock
● During sedimentation, soil particles and decaying/dead organic matter accumulate in layers on the ground or at the bottom of oceans and other large bodies of water.
- These layers are turned into rock by slow geological processes that take place over long periods of time
- Some marine sediments and sedimentary rock form from the shells of marine organisms such as coral and clams, which contain calcium carbonate.


What is carbonate? How does it relate to sedimentation?

● A combination of carbon and oxygen that is dissolved in ocean water.
● Found in the shells of some marine organisms
- When these marine organisms die, their shells accumulate on the ocean floor, forming carbonate-rich deposits. The carbonate eventually becomes sedimentary rock (limestone) over time.


What are some of the major stores of carbon on Earth?

In order from the most carbon to least:

1. Marine sediments/Sedimentary rock
2. Oceans (intermediate and deep water)
3. Coal deposits
4. Soil and organic matter
5. Atmosphere
6. Terrestrial vegetation
7. Oil and gas deposits

(Refer to table on pg. 73)


List some natural processes that cycle carbon through ecosystems.

1. Photosynthesis
2. Cellular respiration
3. Decomposition
4. Ocean processes
5. Natural events (ie. volcanic eruptions, forest fires, etc.)


What is photosynthesis?
What equation can it be represented by?

● A chemical reaction in plants and some micro-organisms that converts solar energy into chemical energy- it is an important process in which carbon and oxygen are cycled through ecosystems
● During photosynthesis, carbon (in the form of carbon dioxide) enters through the leaves of plants and reacts with water in the presence of sunlight to produce oxygen and energy-rich sugars (carbohydrates)- a usable form of energy for produces.
- By eating plants, consumers obtain some of this energy and also take carbon into their cells.
● Equation: energy (sunlight) + 6CO2 + 6H2O -> C6H12O6 + 6O2
(lower subscript does not work on Brainscape, but you can figure it out.)


What is cellular respiration?
What equation can it be represented by?

● The process in which both plants and animals release carbon dioxide back into the atmosphere by converting carbohydrates and oxygen into carbon dioxide and water
● During cellular respiration, energy is released within the cells of organisms and made available for growth, repair, and reproduction.
● Carbon dioxide is released as a waste product.
● Equation: C6H12O6 + 6O2 -> 6CO2 +6H2O + energy
(again, lower subscript is not supported- use your IB knowledge to work this out.)


How is decomposition related to the carbon cycle?

● Decomposers convert organic molecules such as cellulose (a type of carbohydrate found in plants) back into carbon dioxide, which is released into the atmosphere.


How does ocean mixing work?
How does it affect the carbon cycle?

● Ocean mixing moves carbon throughout the world's oceans and pumps more carbon into the oceans than is released back into the atmosphere.
● Process (pg. 75):
- Carbon dioxide dissolves in the cold ocean waters found at high latitudes.
- This cold water sinks and moves in deep ocean currents towards the tropics.
-As the water warms up in the tropics, it rises, mixing with water at intermediate levels and at the surface.
- Some carbon dioxide is released to the tropical atmosphere as ocean currents carry the warmed water back toward polar areas.


What role do volcanoes and forests play in the carbon cycle?

● Some carbon is released from volcanoes following the subduction and melting of sedimentary rock in tectonic plates.
● Some carbon dioxide is released from decomposing trees
● During forest fires, carbon dioxide is rapidly released


What kind of human activities have affected the natural carbon cycles?

● Industry
● Motorized transportation
● Land clearing
● Agriculture
● Urban expansion


How does human activity affect the natural carbon cycle?

● Since the industrial revolution, the amount of carbon dioxide gas in the atmosphere has increased over 30%.
● Human activities that involve burning fossil fuels have reintroduced carbon into the cycle that was removed from it long ago and stored deep within the Earth.
- So much carbon is released so quickly into the atmosphere that the natural carbon cycle cannot move it all into other stores.
● Clearing land for agriculture and the expansion of cities reduces the total amount of carbon taken from the atmosphere by plants during photosynthesis
- Farmed plants usually remove less carbon than natural vegetation


Where is nitrogen stored?

● The largest store of nitrogen is the atmosphere where it is found in the form of nitrogen gas (N2).
- 78% of the Earth's atmosphere is nitrogen gas.
● Other major stores include oceans and organic matter in soil.
● In terrestrial ecosystems, living organisms, lakes, and marshes also store nitrogen, but in much smaller amounts.


Through what processes is nitrogen made available to plants and animals? Why is this necessary?

● Much of the nitrogen cycle involves processes that convert nitrogen into forms usable by plants/animals because most organisms cannot use nitrogen in the form of nitrogen gas, which is the most abundant form of nitrogen.
- These processes include:
1. Nitrogen fixation
2. Nitrification
3. Uptake
- Plants can use nitrogen in the form of ammonium (NH4 +) and nitrate (NO3 -)


What is nitrogen fixation?

● The process in which nitrogen gas is converted into compounds that contain nitrate or ammonium


Where does nitrogen fixation occur?

● Atmosphere
● Soil
● Water bodies


When does atmospheric nitrogen fixation occur?

● It occurs when nitrogen gas (N2) is converted into nitrate (NO3 -) and other nitrogen-containing compounds by lightning.
- Lightning is an electrical discharge of static electricity in the atmosphere that provides the energy that is necessary for nitrogen to react with oxygen to form these compounds
- The nitrate/other nitrogen-containing compounds enter terrestrial and aquatic ecosystems in rain. Only a small amount of nitrogen-containing compounds are fixed in the atmosphere as a result of this process.


When does nitrogen fixation occur in the soil?

● It occurs when nitrogen gas (N2) is converted into ammonium (NH4 +) by bacteria during the decomposition process.
● Nitrogen-fixing bacteria play a significant role in nitrogen-fixation


Nitrogen-fixing bacteria

● Certain species of bacteria that play a significant role in nitrogen fixation.
● Convert nitrogen gas (N2) into ammonium (NH4 +)


When does nitrogen fixation occur in aquatic ecosystems?

● It occurs when nitrogen gas (N2) is converted into ammonium (NH4 +) by certain species of cyanobacteria
- Cyanobacteria are blue-green bacteria that manufacture their own food during photosynthesis
- Nitrogen-fixing cyanobacteria make these nitrogen compounds available to plants in the surface waters of oceans, wetlands, and lakes


What is nitrification? Why is it important?

● A process in which ammonium (NH4 +) is converted into nitrate (NO3 -) by nitrifying bacteria
● Takes place in two stages
1. Certain species of nitrifying bacteria convert ammonium (NH4 +) into nitrite (NO2 -).
2. Different species of nitrifying bacteria converts the nitrite (NO2 -) into nitrate (NO3 -)
● Once nitrates are made available through nitrification, the nitrates can enter plant roots and eventually be incorporated into plant proteins.
- The uptake of nitrates is important for both plants and for other organisms, because consumers incorporate nitrogen into the proteins in their own tissues when consuming other organisms.


What role do decomposers play in the nitrogen cycle?

● Some types of decomposer bacteria/fungi are able to take the nitrogen trapped in the proteins and DNA of dead organisms and convert it back to ammonium (NH4 +).
● Some bacteria species decompose urea (a waste product) that is excreted by animals and then convert it into ammonium (NH4 +)


How is nitrogen returned to the atmosphere?

● Denitrification (nitrate -> nitrogen gas)
● Nitrogen is also returned to the atmosphere as ammonia (NH3) in volcanic ash and nitrogen oxide gases such as nitrogen oxide and nitrogen dioxide.



● A process in which nitrogen is returned to the atmosphere
- In terrestrial and aquatic ecosystems, this process is done by denitrifying bacteria
● Nitrate (NO3 -) is converted back into nitrogen gas (N2).


Denitrifying bacteria

● Bacteria that convert nitrate (NO3 -) back into nitrogen gas (N2) through a series of chemical reactions.
- This conversion process is referred to as denitrification


How is nitrogen removed from ecosystems?

● Nitrogen is removed from ecosystems when excess nitrate/ammonium is washed from soil into groundwater and streams, where it eventually settles at the bottom of oceans/lakes/rivers in sediments.
- These sediments eventually form rock, making the nitrogen unavailable until weathering releases it back into the water again.


How have human activities affected the nitrogen cycle over the years?
How much nitrogen is added to the atmosphere annually?

● Human activities have doubled the available nitrogen in the biosphere in the past 50 years
● Millions of tonnes of nitrogen are added to the atmosphere annually in the form of nitrogen oxide (NO) and nitrogen dioxide (NO2)


What kind of human activities affect the nitrogen cycle and how do they affect it?

● Fossil fuel combustion in power plants and processes such as sewage treatment
● Burning of fossil fuels in cars, trucks, and other motorized forms of transportation
● Clearing of forests and grasslands releases trapped nitrogen into the atmosphere
- These compounds are eventually returned to terrestrial and aquatic ecosystems as acid precipitation.
● The use of chemical fertilizers containing nitrogen compounds leads to excess nitrogen escaping back into the atmosphere or being leached from the soil by rain/irrigation water.
- The nitrogen that is leached gets into lakes/streams, causing eutrophication in aquatic systems.
● Using large areas of land to plant single crops of soybeans/peas/alfalfa/rice
- These crops fix atmospheric nitrogen, greatly increasing the rate of nitrogen fixation in the area


Acid precipitation

● Forms from dissolved nitrogen compounds in the moisture in clouds and falls back to Earth as nitric acid (HNO3).
● Contributes to eutrophication



● Removal of substances that have dissolved in moist soil by water (ie. rain, irrigation water, etc.)
● Contributes to eutrophication



● The process by which excess nutrients result in increased plant production and decay.


What negative impact does eutrophication have on aquatic ecosystems?

● In a nitrogen-rich (eutrophic) environment, algae grows very quickly.
- This is called an algae bloom
● The excessive algae growth deprives other aquatic organisms of oxygen and sunlight.
● Could lead to the death of all fish in a lake
- Dead zone
● Some algae blooms produce neurotoxins that are transferred through the food web to shellfish, seabirds, marine mammals, and humans


What is phosphorus used for?

● It is essential for a variety of life processes in plants and animals
● Essential element in the molecule that carries energy from plant cells to animal cells
● Contributes to root development, stem strength, and seed production in plants
● Works with calcium in the development of strong bone tissues


How is phosphorus stored?

● Not stored in the atmosphere as a gas like carbon/oxygen/nitrogen!
● Trapped in phosphate (PO4 3-, HPO4 2-, H2PO4 -) that makes up phosphate rock and sediments of ocean floors.


How is phosphorus cycled through ecosystems?

● Weathering releases phosphate into the soil
● On land, plants quickly take up phosphate through their roots and animals obtain phosphate by eating the plants
● Decomposers break down animal waste/dead organisms to return phosphorus to the soil for producers to use again
● Phosphate enters aquatic ecosystems as a result of erosion, leaching, and run-off
● Water plants take up some dissolved phosphate and pass it through the aquatic food chain, but most of the phosphate in run-off settles on lakes and ocean bottoms, and will not enter the biotic community unless the sediment disturbed.
● The undisturbed sediment will eventually form sedimentary rock, and the phosphorus will be trapped for millions of years.
● When the process of geological uplift exposes the rock layers, the phosphorus will be made available and then cycle of weathering can begin again.


What is weathering?
What are the types of weathering that are involved in the phosphorus cycle?

● The process of breaking down rock into smaller fragments
● Chemical weather and physical weather are two types of weathering involved in the phosphorus cycle.


Chemical weathering

● A chemical reaction causes phosphate rocks to break down and release phosphate into soil


Physical weathering

● Processes such as wind, rain, and freezing release particles of rock and phosphate into soil


Geologic uplift

● Refers to the process of mountain building in which Earth's crust folds and deeply buried rock layers rise and are exposed


How do humans obtain phosphorus? What do they use the phosphorus for?

● In North America, phosphate rock is mined to make commercial fertilizers and detergents (ie. dishwasher detergent)
● On some islands in the South Pacific, guano (bird droppings) is mined as a natural fertilizer.
- Guano is rich in phosphate, nitrogen and potassium


How does human activity negatively impact the phosphorus cycle?

● The usage of commercial fertilizers/detergents containing phosphate, animal wastes from large-scale livestock farming, some industrial waste, and untreated human sewage enter waterways through run-off and leaching
- This increase in phosphate could lead to the death of fish and negatively affect other species that are sensitive to an overload of phosphorus
● The clearing of forests by the slash-and-burn method releases the phosphates contained in trees in the form of ash, which accumulates in soil
- Phosphate leeches from the ash and runs off into the water supply to settle on the bottom of water bodies such as lakes/oceans, where it becomes unavailable to organisms



● Chemicals used to eliminate pests, such as insecticides that kill insects and herbicides that kill weeds.



● In living organisms, the gradual build-up of synthetic and organic chemicals that cannot be broken down through the biodegradation process by decomposers
● General features of chemicals that accumulate are:
- not biodegradable
- fat soluable


When/how do chemicals accumulate in bioaccumulation?

● A chemical will accumulate if it is taken up and stored faster than it is broken down and excreted
● Chemicals bioaccumulate when pollutants are stored in plant tissue and in the fat tissue of animals
● Chemicals enter organisms through food intake, skin contact, or respiration


How does bioaccumulation of synthetic and organic chemicals negatively impact organisms?

● If accumulation of a substance is too high, it can be harmful
● Some chemicals are temporarily stored in fat tissue but are released from storage when fat is burned for energy
- These chemicals can be harmful to the animal if they are not metabolized (chemically changed) or are not excreted in the feces or urine.
● Synthetic/organic chemicals can affect the nervous, immune, and reproductive systems of animals. Bioaccumulation of these chemicals can cause birth defects in offspring or a complete failure to reproduce.
● The damage is not limited to only individual organisms. Entire ecosystems can be impacted when keystone species are affected.
- ie. if salmon are affected, all the other organisms that consume salmon will also be affected


Keystone species

● Species that can greatly affect population numbers and the health of an ecosystem.
● ie. Salmon are a keystone species in many British Columbia forest ecosystems.
- In autumn, they are an important food source for bears, wolves, eagles, and otters
- When they die, their decaying bodies become a rich source of nutrients (ie. nitrogen) for trees.
- Able to retain harmful chemicals in their body fat and transfer these chemicals to other organisms



● The process in which chemicals not only accumulate but become more concentrated at each trophic level.
- This happens because consumers must eat many times their body weight of prey during their lifetimes. Even a small concentration of chemicals in producers and primary and secondary consumers can build up to cause problems at higher trophic levels.
● Chemicals bioaccumulate and become biomagnified when pollutants are stored in plant tissue and in the fat tissue of animals
- Chemicals remained trapped until they are eaten and the tissues/fats are broken down for energy.



● Polychlorinated biphenyls
● Synthetic chemicals that were widely used from the 1930s-1970s in industrial products such as heat exchange, fluids, paints, plastics, and lubricants for electrical transformers.
● Banned in 1977 in North America due to growing concerns about their impact on the environment and human health.
● Has a long half-life
● Stay in organisms and the environment for a very long time, suppress the immune system, and probably cause cancer in humans
● Orcas are still greatly impacted by PCBs, retaining high levels of PCBs, and it is estimated that their reproductive success will affected until at least 2030, despite the PCBs being banned for decades.



● The time it takes for the amount of a substance to decrease by half


Explain how biomagnification occurs in an orca with PCBs.

● Orcas are high up on the food chain, and thus, even if the PCBs enter the food chain at a low level, by the time it gets to the orca, they are highly concentrated in the blubber
● When salmon stocks are low, magnification is increased because the blubber is burned for energy
● The PCBs are released into the orca's bloodstream where they interfere with immune functions, making the orca more susceptible to disease



● Persistent organic pollutants
● A class of compounds referring to carbon-containing compounds that remain in water and soil for many years
- PCBs belong to this class of compounds
● Many enter ecosystems in the form of insecticide sprays
- ie. DDT



● Dichlorodiphenyl trichloroethane
● An insecticide introduced in 1941 to control disease-carrying mosquitoes
● Despite now being banned in many countries because it biomagnifies, it continues to persist in the environment due to its long half-life
● Binds strongly to soil particles and persists for as long as 15 years
- Because it is bound in soil, it begins to accumulate in plants and then in the fatty tissue of fish/birds/animals that eat the plants
● When washed into streams and lakes, it affects aquatic food chains by first accumulating in plankton
● Considered toxic at levels of 5 ppm
● In animals, DDT is changed into a chemical form that bioaccumulates in fat tissue and can cause nervous system, immune system, and reproductive disorders



● Parts per million
● One ppm means one particle of a given substance mixed with 999.999 other particles
- This is equivalent to 1 drop of dye mixed with 150 L of water


Heavy metals

● Metallic elements with a high density that are toxic to organisms at low concentrations
● Within the biosphere, they do not degrade and cannot be destroyed
● Some are essential to human health in very small quantities (ie. copper, selenium, zinc.)
● Can be found in water and air, and are taken in through the food chain
● Can bioaccumulate within organisms and biomagnify, moving up the food chain like POPs.
● The three most polluting heavy metals are lead (Pb), cadmium (Cd), and mercury (Hg)



● A extremely toxic heavy metal
- Has an accepted toxic level of 0.0012 ppm, although it not considered safe at any level.
- Harmful effects in humans may include anemia (blood condition), nervous system damage, sterility in men, low fertility rates in women, impaired mental development, and kidney failure. Similar effects are seen in fish/birds.
● Naturally present in all soils, generally in the range of 15 ppm to 40 ppm, but these levels have increased due to human activities
● In the past, lead was used in insecticides, in paints, and as an antiknock ingredient in gasoline.
- If you're curious about this antiknock thing:
● Today, most products and manufacturing processes have been changed to reduce the amount of lead entering the environment and nearly all lead-acid batteries are recycled
● Other uses (ie. electronics) still contribute to lead levels in the environment
- Much smaller percentages of electronics are recycled and consumer electronics make up 40% of the lead found in landfills



● A toxic heavy metal
- Highly toxic at very low levels to earthworms and other soil organisms
- Associated with higher death rates and lower reproduction/growth rates in fish
- Associated with lung diseases/cancer in smokers (tobacco plants easily absorb the metal), infertility and damage to the central nervous system, immune system, and DNA.
● Found in Earth's crust and is released into the environment through rock weathering, volcanoes, and forest fires
- Cadmium is stored in trees and is released into the air when trees burn
● Released in the manufacture of plastics and nickel-cadmium rechargeable batteries
● Enters soil/water through zinc production and phosphate ore mining
● Strongly chemically attracted to organic matter in soil
- When present in soil, it can be extremely dangerous, as plants take up the cadmium in their roots and animals eat the plants
● Half-life of cadmium in the kidneys and in bone tissue is 30 years.
- Ends up in the kidneys when ingested-- it travels from the digestive system to the liver to the kidneys.



● A heavy metal
● Organisms circulate mercury through the food chain
● Some bacteria in soils change compounds such as mercury sulfide into methylmercury
● Every year, up to 6000 tonnes of mercury are released through natural sources such as volcanoes, geothermal springs, and rock weathering.
● In the last 150 years, this annual amount has doubled through the burning of fossil fuels, waste incineration, mining, and industrial uses such at the manufacture of batteries (incl. ones that get thrown out & replaced on a weekly basis.)
● Coal burning accounts for more than 40% of mercury released into the atmosphere
● Mercury returns to the Earth in rainfall and dust and binds to soil particles to form compounds that are then transported by air and water



● Some bacteria in soils change compounds containing mercury into methylmercury
● A highly toxic compound that bioaccumulates in the brain, heart, and kidneys of vertebrates
● In humans, it is absorbed during digestion, then enters the blood and is stored in the brain. It affects nerve cells, the heart, kidneys, lungs, and suppresses the immune system.
● In fish, the levels of methylmercury depend on what they eat, how long they live, and how high they are in the food chain


List two methods to reduce the effects of chemical pollution

● Trap the contaminant in the soil
● Bioremediation


Explain the method of trapping contaminants in the soil as a means of reducing the effects of chemical pollution.

● One example is adding phosphate fertilizer to lead-contaminated soil.
- This causes a chemical reaction between the phosphate and the lead, which produces lead pyromorphite- a highly insoluble mineral
- Since pyromorphite is highly insoluble, it cannot be easily spread by water and is less likely to enter the food chain. Thus, the contaminant remains in the soil, but in a much less harmful form.



● The use of living organisms (usually micro-organisms/plants) to do the clean-up naturally, only faster through biodegradation
● Often used in resource industries such as forestry, mining, and energy production
- ie. Oil industries often use bacteria to clean up pollution created by spills and underground leaks
● Micro-organisms that naturally feed on chemicals and reduce them to non-toxic compounds can be added to contaminated soil
● Working at the molecular level, scientists have extracted enzymes from chemical-eating bacteria or pesticide-resistant insects and used these to create new environmental clean-up technologies
● Some plants (ie. fescue, alfalfa, juniper, and poplar trees) act as natural traps to biodegrade hazardous wastes in soil, taking in and concentrating heavy metals in their tissues
- In wetland ecosystems, water hyacinth and bulrushes may be used
● Plants can also act as stabilizers, reducing wind and water erosion that could spread the contaminants.