Chapter 54: Ecosystem Ecology IB Biology Review Definitions

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IB Biology Review

• Chapter 54 Ecosystem Ecology

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Definitions

• Ecosystem
• Consists of all the abiotic factors in addition
  to the entire community of species that exist in
  a certain area
• May contain many different communities
• Ecosystem Ecology
• The emphasis is on energy flow and chemical
  cycling among the various biotic and abiotic
  components

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Vocabulary

• Biomass
• the dry weight of organic matter comprising a
  group of organisms in a particular habitat
• Organic Elements
• organic compounds are those which contain carbon
  and are biological in origin
• Inorganic Elements
• inorganic elements do not usually contain carbon
  and are considered to be of a mineral, not
  biological, origin

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Ecosystems Two Major Concepts

• 1. Energy Flow
• continual supply
• 2. Chemical Cycling
• finite supply
• Where does almost all the energy come from?
• The Sun!

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Energy Flow in Ecosystems is Described by Two
Laws

• First Law of Thermodynamics
• energy cannot be created or destroyed, only
  transformed
• as in transformation/conversion of solar energy
  into chemical energy through photosynthesis
• Second Law of Thermodynamics
• energy transformation/conversions are never 100
  efficient (excess energy often lost as heat)
• which is why 90 of energy is lost between
  trophic levels

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Primary Production

• Gross Primary Production
• total amount of light energy converted to
  chemical energy by plants per unit time
• measured in Joules/m2/yr
• Net Primary Production
• Gross Primary Production minus the energy used by
  primary producers for respiration
• It is usually biomass that we can more easily
  measure. It is sometimes used as a surrogate
  (replacement) for energy since energy is harder
  to measure.

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Review of Trophic Structure
3rd Order Consumers
2nd Order Consumers
1st Order Consumers
Producers
Plants
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Review Why does the energy pyramid look like it
does?

• Energy transfer between trophic levels is never
  100 efficient. Only 10-20 of energy is
  transferred
• How is the other 90 of energy lost?
• Heat loss through cellular respiration
• Not all organisms in lower trophic levels are
  consumed
• The whole mass of the prey is not assimilated
  into the predators body
• Energy lost through the metabolic processes of
  the prey before they are consumed

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Biomass Structure

• Is the Biomass structure similar to the Trophic
  structure or not?
• Yes.
• Since only 10 of energy can be transferred to
  higher levels, there is not as much energy to
  support many large individuals
• Since energy is hard to measure, the biomass
  pyramid is often used in place of the energy
  pyramid

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Chemical Cycling Described by One Law

• Law of Conservation of Matter
• Matter cannot be created or destroyed
• This means all the atoms available to organisms
  must be recycled in the ecosystem
• How are chemicals and atoms recycled?
• Decomposers (bacteria and fungi) break down waste
  and matter
• They return nutrients and atoms to the ecosystem
• Why are decomposers vital to the ecosystem?
• Without them, producers would run out of minerals
  and chemicals
• Which means the ecosystem would collapse!

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Chemical Recycling Carbon Cycle

• Be able to reproduce this cycle, including
  biological importance, forms of carbon available
  to life, reservoirs, and key processes

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How are humans altering the Carbon Cycle?

• Adding more carbon dioxide to the ecosystem by
• burning fossil fuels
• Destroying natural carbon sinks, such as
• trees (by deforestation)
• grasslands (by development and urban sprawl)
• fossil fuel reservoirs (by burning them)

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Greenhouse Effect

• The Greenhouse Effect
• occurs when certain molecules like carbon
  dioxide, methane, sulfur, and others reflect and
  retain heat from the earths surface
• Is the greenhouse effect a good thing?
• Yes! If it did not occur, the Earth would be
  frozen and there would be no life!
• However, too much of the greenhouse effect can
  overheat the planet!

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How are humans amplifying the greenhouse effect?

• Humans are adding more greenhouse gases to the
  atmosphere through
• fossil fuel burning
• garbage burning
• deforestation
• development/urban sprawl, which destroys plant
  life
• cattle ranching (produces methane)
• production of nitrogen oxides
• use of chlorofluorocarbons
• water vapor from factories

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Human Impact Depletion of Atmospheric Ozone

• What is ozone and what does it do?
• ozone (O3) is formed when one atom of oxygen is
  added to atmospheric oxygen (O2)
• The role of the ozone is to filter out deadly
  ultraviolet (UV) radiation from sunlight. Without
  this filtering living things would be exposed to
  lethal doses of radiation.
• What is causing the depletion of the Atmospheric
  Ozone?
• chlorofluorocarbons (CFCs) from aerosol cans,
  refrigeration chemicals, etc. released in the
  atmosphere can destroy the ozone layer and reduce
  the filtering capacity of the atmosphere.
• However, since world governments have decreased
  or eliminated production of CFCs, there are signs
  that the ozone layer is replenishing itself.

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The Effects of UV Radiation on living things and
biological productivity

• UV radiation can penetrate living cells and
  damage DNA, thereby disrupting cell function and
  sometimes causing cancer.
• UV radiation can be harmful to phytoplankton and
  other producers, thereby reducing the
  productivity of ecosystems.

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Biomagnification

• Biomagnification
• the process in which toxic chemical substances
  become more concentrated (accumulated) at each
  higher trophic level
• Toxins that most easily accumulate are ones that
  are not broken down by normal metabolic processes
  in living organisms (ex. Heavy metals like Lead,
  mercury insecticides like DDT, industrial
  chemicals like PCBs)
• How does biomagnification occur?
• These toxins tend to accumulate in fatty tissue
  and at high concentrations- disrupt the normal
  metabolism of species, especially those high on
  the food chain. Ex. DDT disrupts the deposition
  of calcium in eagle eggs, causing the eggs to
  break prematurely thereby increasing mortality of
  young eagles.

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Biomagnification

• Classic example
• of DDT crashing eagle populations
• egg shells became thin due to DDT, broke when
  incubated

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1. Explain why the gross production of a species
in an ecosystem is always higher than the net
production. (2 marks)
IB Exam Question

• net production is gross production minus
  respiration
• all species respire

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2. Outline ways in which leaves take part in the
carbon cycle in ecosystems, apart from
photosynthesis. (4 marks)
IB Exam Question

• leaves release carbon dioxide when they respire
• when they are burned/combustion
• carbon passed to decomposers when they die
• carbon passed to detritus feeders from leaf
  litter
• carbon passed to consumers/herbivores in the food
  chain
• carbon removed from the carbon cycle when leaves
  are fossilized/ in carbon sinks such as peat,
  coal, and oil

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3. Explain the effects of depletion of
atmospheric ozone. (4
marks)
IB Exam Question

• ozone (O3) is formed when one atom of oxygen is
  added to atmospheric oxygen (O2)
• the role of ozone is to filter ultraviolet (UV)
  radiation from sunlight
• without this filtering, living things would be
  exposed to lethal doses of radiation
• chloroflourocarbons (CFCs) from aerosol cans,
  refrigeration chemicals etc. released in the
  atmosphere can destroy the ozone layer and reduce
  the filtering capacity of the atmosphere
• since world governments have decreased or
  eliminated production of CFCs, there are signs
  that the ozone layer is replenishing itself

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4. Outline the effects of UV radiation on living
tissues and biological productivity.
(2 marks)
IB Exam Question

• UV radiation can penetrate living cells and
  damage DNA, thereby disrupting cell function and
  sometimes causing cancer
• UV radiation can be harmful to phytoplankton and
  other producers, thereby reducing the
  productivity of ecosystems

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5. Explain the concept of biomagnification.

(5 marks)
IB Exam Question

• Biomagnification is a process in which toxic
  chemical substances become more concentrated
  (accumulated) at each higher trophic level
• toxins that most easily accumulate are ones that
  are not broken down by normal metabolic processes
  in living organisms
• Ex. heavy metals like lead, mercury, insecticides
  like DDT, industrial chemicals like PCBs
• these toxins tend to accumulate in fatty tissue
  and - at high concentrations disrupt the normal
  metabolism of a species, especially those high on
  the food chain
• Ex. DDT disrupted the deposition of calcium in
  eagle eggs causing the eggs to break prematurely
  thereby increasing mortality of young eagles