2.1 Energy Flow in Ecosystems

1
2.1 Energy Flow in Ecosystems

• Biomass is the total mass of all living things in
  a given area.
• Biomass is also sometimes used to the mass of
  organic materials used to produce biofuels such
  as biogas.
• Biomass is generally measured in g/m2 or kg/m2
• Within an organisms niche, the organism
  interacts with the ecosystem by
• Obtaining food from the ecosystem
• Contributing energy to the ecosystem
• Plants are called producers because they
  produce
• carbohydrates from carbon dioxide, water and the
  suns energy.
• Consumers get their energy by feeding on
  producers or other consumers.
• Decomposition is the break-down of wastes and
  dead organisms, by organisms called
  decomposers, through the process of
  biodegradation.

See pages 56 - 59
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Energy Flow and Energy Loss in EcosystemsFood
Chains

• Scientists use different methods to represent
  energy moving through ecosystems.
• Food chains
• Food webs
• Food pyramids
• Food chains show the flow of
• energy in an ecosystem
• Each step is a trophic level
• Feeding niche relationship
• Producers 1st trophic level
• Primary consumers 2nd trophic level
• Secondary consumers 3rd trophic level
• Tertiary consumers 4th trophic level

See pages 59 - 60
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Energy Flow and Energy Loss in EcosystemsFood
Chains (continued)

• Consumers in a food chain can be classified as
• Detrivores - consumers that obtain energy and
  nutrients from dead organisms and waste matter
• Includes small insects, earthworms, bacteria and
  fungi
• Detrivores feed at every trophic level
• Detrivores have their own, separate food chains,
• and are very numerous
• Herbivores - primary consumers
• herbivores eat plants (producers) only
• Carnivores - secondary or tertiary consumers
• Secondary consumers eat non-producers, such as
  herbivores
• Tertiary consumers eat secondary consumers
• Aka top consumers, top carnivores or top
  consumers
• Omnivores - consumers that eat both plants and
  animals
• Examples include humans and bears

This dung beetle is a detrivore.
See page 61
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Energy Flow and Energy Loss in EcosystemsFood
Webs

• Most organisms are part of many food chains.
• To represent interconnected food chains,
  scientists create a food web.
• Food webs are models of the feeding relationship
  in an ecosystem.
• Arrows in a food web represent the flow of energy
  and nutrients.
• Following the arrows leads to the top
  carnivore(s).

This food web represents a terrestrial ecosystem
that could be found in British Columbia.
See page 62
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Energy Flow and Energy Loss in EcosystemsFood
Pyramids

• Food pyramids show the changes in available
  energy from one trophic level to another in a
  food chain.
• Aka ecological pyramids
• Energy enters at the first tropic level
  (producers), where there is a large amount of
  biomass, and therefore much energy
• It takes large quantities of organisms in one
  tropic level to meet the energy needs of the next
  trophic level.
• Each level loses large amounts of the energy
• it gathers through basic processes of living.
• 80 - 90 of energy taken in by consumers
• is used in chemical reactions in the body,
• and is lost as heat energy.
• There is very little energy if left over for
• growth or increase in biomass.

See page 63
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Energy Flow and Energy Loss in EcosystemsFood
Pyramids (continued)

• Food pyramids are also known as ecological
  pyramids.
• Ecological pyramids may show biomass, population
  or energy numbers.
• The amount of life an ecosystem can contain is
  based on the bottom level of the ecological
  pyramid, where producers capture energy from the
  sun.
• Each level in the energy pyramid a loss of 90
  of total energy available
• Lower trophic levels have much
• larger populations than upper levels.
• This shows the importance of
• maintaining large, biodiverse
• populations at the lowest levels
• of the food pyramid.

See pages 63 - 64
Take the Section 2.1 Quiz
7
2.2 Nutrient Cycles in Ecosystems

• Nutrients are chemicals required for growth and
  other life processes.
• Nutrients move through the biosphere in nutrient
  cycles, or exchanges.
• Nutrients often accumulate in areas called
  stores.
• Without interference, generally the amount of
  nutrients flowing into a store equals the amount
  of nutrients flowing out.
• Human activities can upset the natural balance of
  nutrient cycles.
• Land clearing, agriculture, urban expansion,
  mining, industry and motorized transportation can
  all increase the levels of nutrients more quickly
  than the stores can absorb them.
• Excess nutrients in the biosphere can have
  unexpected consequences.
• There are five chemical elements required for
  life.
• Carbon, hydrogen, oxygen and nitrogen cycle
  between living things and the atmosphere.
• Phosphorous cycles in from sedimentary rock.

See pages 68 - 70
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Nutrient CyclesThe Carbon Cycle

• Carbon atoms are a fundamental unit in cells of
  all living things.
• Carbon is also an essential part of chemical
  processes that sustain life.
• Carbon can be stored in many different locations.
• Short-term shortage is found in aquatic and
  terrestrial organisms,
• and in CO2 in the atmosphere and top layers of
  the ocean.
• Longer-term storage is found in middle and lower
  ocean layers as dissolved CO2, and in coal, oil
  and gas deposits in land and ocean sediments.
• Sedimentation traps many long-term stores of
  carbon
• Layers of soil and decomposing organic matter
  become buried
• on land and under the oceans.
• Slowly, under great pressure over many years,
  coal, oil and gas form.
• Layers of shells also are deposited in sediments
  on the ocean floor, forming carbonate rocks like
  limestone over long periods of time.
• Carbon stores are also known as carbon sinks

See pages 71 - 72
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Nutrient CyclesThe Carbon Cycle (continued)

• Carbon is cycled through ecosystems in a variety
  of ways.
• Photosynthesis energy from the sun allows CO2
  and H2O to react
• CO2 H2O sunlight ? C6H12O6 O2
• Carbon in the atmosphere is transformed by plants
  into carbohydrates.
• Photosynthesis also occurs in cyanobacteria and
  algae in oceans.
• Cellular respiration carbohydrates release
  energy in consumers
• C6H12O6 O2 ? CO2 H2O energy
• The energy released is used for growth, repair
  and other life processes.
• Decomposition decomposers break down large
  quantities of cellulose
• Cellulose is a carbohydrate most other organisms
  cannot break down
• Ocean Processes CO2 dissolves in cold, northern
  waters and sinks
• Ocean currents flow to the tropics, the water
  rises and releases CO2
• This process is called ocean mixing.
• Eruptions and fires - volcanic eruptions can
  release CO2
• Forest fires also release CO2

See pages 73 - 76
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Nutrient CyclesThe Carbon Cycle (continued)
See page 76
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Nutrient CyclesThe Carbon Cycle (continued)

• Many human activities can influence the carbon
  cycle
• Since the start of the Industrial Revolution (160
  years ago), CO2 levels have increased by 30 from
  the increased burning of fossil fuels.
• The increase in CO2 levels in the previous 160
  000 years was 1 - 3
• Carbon is being removed from long-term storage
  more quickly than it naturally would as we mine
  coal and drill for oil and gas.
• CO2 is also a greenhouse gas, which traps heat in
  the atmosphere.
• Clearing land for agriculture and urban
  development reduces plants that can absorb and
  convert CO2.
• Farmed land does not remove as much CO2 as
  natural vegetation does.

See page 77
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Nutrient CyclesThe Nitrogen Cycle

• Nitrogen is very important in the structure of
  DNA and proteins.
• In animals, proteins are vital for muscle
  function.
• In plants, nitrogen is important for growth.
• The largest store of nitrogen is in the
  atmosphere in the
• form N2.
• Approximately 78 of the Earths atmosphere is N2
  gas.
• Nitrogen is also stored in oceans, and as organic
  matter in soil.
• Smaller nitrogen stores are found in terrestrial
  ecosystems and
• waterways.
• Nitrogen is cycled through processes involving
  plants
• Nitrogen fixation
• Nitrification
• Uptake

See page 78
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Nutrient CyclesThe Nitrogen Cycle (continued)

• Nitrogen fixation is the conversion of N2 gas
  into compounds containing nitrate (NO3) and
  ammonium (NH4)
• Both nitrate and ammonium compounds are usable by
  plants.
• Nitrogen fixation occurs in one of three ways
• In the atmosphere - lightning provides the energy
  for N2 gas to react with O2 gas to form nitrate
  and ammonium ions.
• Compounds formed by these ions then enter the
  soil via precipitation
• This only provides a small amount of nitrogen
  fixation.
• In the soil - nitrogen-fixing bacteria like
  Rhizobium in the soil convert N2 gas into
  ammonium ions
• These bacteria grow on the root nodules of
  legumes like peas.
• The plants provide sugars, while bacteria provide
  nitrogen ions.
• In the water - some species of cyanobacteria also
  convert N2 into ammonium during the process of
  photosynthesis.

See pages 78 - 79
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Nutrient CyclesThe Nitrogen Cycle (continued)

• Nitrification occurs when certain soil bacteria
  convert ammonium.
• Ammonium is converted into nitrates (NO3) by
  nitrifying bacteria.
• Ammonium is converted to nitrite (NO2), which is
  then converted to nitrate.
• Nitrates enter plant roots via uptake
• These nitrogen compounds compose plant proteins.
• Herbivores then eat plants, and use nitrogen for
  DNA and protein synthesis.
• Nitrogen is returned to the
• atmosphere via denitrification.
• Nitrates are converted back to N2
• by denitrifying bacteria.
• N2 is also returned to the
• atmosphere through volcanic eruptions.

See page 80
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Nutrient CyclesThe Nitrogen Cycle (continued)

• Excess nitrogen dissolves in water, enters the
  waterways, and washes into lakes and oceans.

• The nitrogen compounds eventually become
  trapped in sedimentary rocks, and will not be
  released again until the rocks weather.

See page 81
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Nutrient CyclesThe Nitrogen Cycle (continued)

• Human activities can also affect the nitrogen
  cycle.
• Due to human activities, the amount of nitrogen
• in the ecosystem has doubled in the last 50
  years.
• Burning fossil fuels and treating sewage releases
  
• nitrogen oxide (NO) and nitrogen dioxide (NO2).
• Burning also releases nitrogen compounds that
  increase acid precipitation in the form of nitric
  acid (HNO3).
• Agricultural practices often use large amounts of
  nitrogen-containing fertilizers.
• Excess nitrogen is washed away, or leaches, into
  the waterways.
• This promotes huge growth in aquatic algae
  eutrophication
• These algal blooms use up all CO2 and O2
• and block sunlight, killing many aquatic
  organisms.
• The algal blooms can also produce neurotoxins
  that
• poison animals.

See pages 82 - 83
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Nutrient CyclesThe Phosphorous Cycle

• Phosphorous is essential for life processes in
  plants and animals.
• Phosphorous is a part of the molecule that
  carries energy in living cells.
• Phosphorous promotes root growth, stem strength
  and seed production.
• In animals, phosphorous and calcium are important
  for strong bones.
• Phosphorous is not stored in the atmosphere.
• Instead, it is trapped in phosphates (PO43,
  HPO42, H2PO4) found in rocks and in the
  sediments on the ocean floor.
• Weathering releases these phosphates from rocks.
• Chemical weathering, via acid precipitation or
  lichens, releases phosphates.
• Physical weathering, where wind, water and
  freezing release the phosphates.
• Phosphates are then absorbed by plants, which are
  then eaten by animals.
• Weathering doesnt occur until there is geologic
  uplift,
• exposing the rock to chemical and physical
  weathering.

See pages 83 - 84
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Nutrient CyclesThe Phosphorous Cycle (continued)

• Humans add excess phosphorous to the environment
  through mining for fertilizer components.
• Extra phosphorous, often long with potassium,
  then enters the ecosystems faster than methods
  can replenish the natural stores.

• Humans can also reduce phosphorous supplies.
• Slash-and-burning of forests removes
  phosphorous from trees, and it then is
  deposited as ash in waterways.

See page 85
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How Changes in Nutrient Cycles Affect
Biodiversity

• Any significant changes to any of these nutrients
  
• (C, H, O, N or P) can greatly impact
  biodiversity.
• Carbon cycle changes are add to climate change
  and global warming.
• Slight temperature fluctuations and changes in
• water levels can drastically change ecosystems.
• Changes influence every other organism in those
• food webs.
• Increased levels of nitrogen can allow certain
  plant
• species to out-compete other species, decreasing
  
• resources for every species in those food webs.
• Decreased levels of phosphorous can inhibit the
• growth of algal species which re very important
• producers in many food chains.

See pages 86 - 87
Take the Section 2.2 Quiz
20
2.3 Effect of Bioaccumulation on Ecosystems

• Amphibians (like frogs) live on both land and in
  the water.
• They are also sensitive to chemicals changes in
  the environment.
• They are therefore valuable indicators of
  environmental health.
• Since the 1980s, much of the worlds amphibian
  species have suffered declines in population.
• There has also been alarming increases in
  amphibian birth deformities in that time.
• Many theories attempt to explain these changes,
  including drought, increased UV rays, pollution,
  habitat loss, parasites and diseases.

Amphibians, like this frog, have exhibited
drastic changes since the 1980s.
See pages 92 - 93
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Bioaccumulation

• Bioaccumulation refers to an organism slowly
  building
• up the amount of chemicals in their bodies.
• Many harmful chemicals cannot be decomposed
  naturally.
• These chemicals can be eaten or absorbed, and
  sometimes
• cannot be removed from the body of the organism
  effectively.
• If a keystone species suffers a chemical
  bioaccumulation,
• it can affect every other organism in its far
  reaching niches.
• A keystone species is a vital part of an
  ecosystem.
• Biomagnification refers to the animals at the top
  of the food pyramid receiving huge doses of
  accumulated chemicals.
• At each level of the food pyramid, chemicals that
  do not get broken down build up in organisms.
• When the consumer in the next trophic level eats
  organisms with a chemical accumulation, they
  receive a huge dose of the chemical(s).

See page 94
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Bioaccumulation (continued)

• An example of bioaccumulation in BC is the effect
  of PCBs on the Orca.
• PCBs are a chemical that were used for many
  industrial and electrical applications in the mid
  20th century.
• PCBs were banned in 1977 because of fears of
  their environmental impact.
• PCBs bioaccumulate, and
• also have a long-half life
• (they break down very slowly).
• PCBs will affect the
• reproductive cycles of Orcas
• until at least 2030.

See page 95
The bioaccumulation of PCBs begins with the
absorption of the chemicals by microscopic
plants and algae.
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Bioaccumulation (continued)

• Chemicals like PCBs and DDT are called
• persistent organic pollutants (POPs)
• POPs contain carbon, like all organic compounds,
  and remain in water and soil for many years.
• Many POPs are insecticides, used to control pest
  populations.
• DDT was introduced in 1941 to control mosquito
  populations, and is still used in some places in
  the world.
• Like PCBs, DDT also bioaccumulates
• and has a long half life.
• At even low levels (5 ppm), DDT in
• animals can cause nervous, immune
• and reproductive system disorders.
• ppm parts per million

See page 96
Spraying DDT, 1958
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Bioaccumulation (continued)

• Heavy metals also bioaccumulate.
• Lead, mercury and cadmium of the most polluting
  heavy metals.
• Lead is found naturally at low levels, but levels
  have increased.
• Lead is not considered safe at any level.
• Many electronics contain lead, and must
• be recycled carefully.
• Lead can cause anemia, nervous and
• reproductive system damage.
• Cadmium is also found in low levels naturally.
• Cadmium is used in the manufacture of plastics
• and nickel-cadmium batteries.
• It is toxic to earthworms, and causes many health
  problems in fish.
• In humans, the main source of cadmium exposure is
  cigarette smoke.
• Cadmium causes lung diseases, cancer,
• nervous and immune system damage.

See page 97
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Bioaccumulation (continued)

• Mercury also is found naturally.
• Much more has entered ecosystems through the
  burning of fossil fuels, waste incineration,
  mining and the manufacture of items like
  batteries.
• Coal burning adds 40 of of the mercury released
  into the atmosphere.
• Mercury bioaccumulates in the brain, heart and
  kidneys of many animals.
• Fish bioaccumulate mercury compounds, adding risk
  for any organisms eating fish.
• Reducing the effects of chemical pollution
• By trapping chemicals in the soil, they cannot
  enter the food chains as easily.
• Bioremediation is also used, as micro-organisms
  or plants are used to help clean up, and are then
  removed from the ecosystem.
• The oil industry will often use bacteria to eat
  oil spills.
• Certain natural species are also excellent at
  bioremediation.

See pages 98 - 99
Take the Section 2.3 Quiz