Ecosystems and Sustainability

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Ecosystems and Sustainability

• Unit 1
• Communication, Homeostasis and Energy

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Ecosystems

• Module 3 Ecosystems and Sustainability

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Learning outcomes

• Define the term ecosystem.
• State that ecosystems are dynamic systems.
• Define the terms biotic factor and abiotic
  factor, using named examples.
• Define the terms producer, consumer, decomposer
  and trophic level.
• Describe how energy is transferred though
  ecosystems.

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Keywords

• Ecology
• The study of how whole communities of living
  organisms interact with each other and with their
  environment.
• Ecosystem
• A relatively self-contained, interacting
  community of organisms, and the environment in
  which they live and with which they interact.
• Habitat
• The place where an organism lives

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Keywords

• Population
• The number of individuals of the same species,
  living in the same place at the same time.
• Community
• All the organisms, of all the different species
  living in a habitat.
• Niche
• The role of an organism in the ecosystem.

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Themes of ecological systems

• Flow of energy
• Energy flows
• into an ecosystem from outside
• through an organism in the ecosystem
• leaves the ecosystem
• Recycling of materials
• Matter cycles round an ecosystem, where some
  atoms are reused over and over again by different
  organisms.

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Biotic factors

• Biotic factors involve other living organisms
• Feeding of herbivores on plants
• Predation
• Parasitism
• Mutualism
• competition

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Abiotic Factors

• Abiotic factors involve the non living components
  of the environment
• Temperature
• Light intensity
• Oxygen concentration
• Carbon dioxide concentration
• Water supply
• pH
• Availability of inorganic ions
• Edaphic features
• Atmospheric humidity
• Wind speed

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Energy Flow in Ecosystem

• Living organisms need a constant supply of energy
  to drive metabolic reactions and to stay alive.

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Food Chains and Food Webs

• A food chain shows the way in which energy flows
  from producer to consumers
• Arrows indicate the direction that the energy
  flows
• Oak tree? caterpillar ? great tit ? sparrowhawk
• Each position along the food chain is called a
  trophic level

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Food Web

• A food web shows all the different
  interrelationships between many food chains.

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Decomposers

• The role of decomposers in the ecosystem is to
  feed on detritus
• Detritus is organic matter in dead organisms and
  waste material
• Decomposers include
• Bacteria
• Fungi
• Detritivores
• Earthworms etc

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Energy Losses along the food chain

• When energy is transferred from one form to
  another, some energy is always lost as heat

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Photosynthetic efficiency

• Less than 3 of sunlight is converted to chemical
  energy
• Sunlight missing leaves
• Reflection of light
• Transmission of light
• Not all the light absorbed is used for
  photosynthesis

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productivity
1o primary

• Productivity
• rate at which the plant converts light energy
  into chemical potential energy
• Gross 1o Productivity (GPP)
• total quantity of energy converted by plants in
  this way
• Net 1o Productivity (NPP)
• energy which remains as chemical energy after
  plants have supplied their own needs in
  respiration

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Losses between plants and primary consumers

• Only about 10 of the energy in plants gets
  passed on to the animals that eat them.
• half of the chemical energy in plants is used by
  the plants themselves (respiration)
• not all the parts of the plants are eaten
• not all the parts eaten are digestible
• energy loss as heat from digestive system as food
  is digested

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Question time!!

• Classify each of these features as biotic or
  abiotic
• The speed of water flow in a river
• The density of seaweed growing in a rock pool
• The oxygen availability on a high altitude
  mountainside
• Energy losses from mammals and birds tend to be
  significantly greater than from other organisms.
  Suggest why this is.

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Learning Outcomes

• Outline how energy transfers between trophic
  levels can be measured.
• Discuss the efficiency of energy transfers
  between trophic levels.
• Explain how human activities can manipulate the
  flow of energy through ecosystems.

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Measuring Energy Transfer

• Pyramid of biomass
• Area of the bars is proportional to the dry mass
  of all the organisms at that trophic level
• Pyramid of energy
• Bars represent energy available
• Organisms are burned in a calorimeter and the
  amount of heat energy released per gram is worked
  out.

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Manipulating energy transfer

• Net Primary productivity (NPP) is the difference
  between primary productivity and respiratory head
  (R)
• NPP is the rate of production of biomass
  available for heterotrophs
• By manipulating environmental factors, humans can
  increase NPP.

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Increasing NPP

• Increasing light levels
• Increase water availability
• Maintain a constant temperature
• Provide the correct nutrients required for
  photosynthesis and growth
• Pest control
• Disease control
• Remove competition

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Improving secondary productivity

• Manipulating the energy from producer to consumer
• Harvest animals before adulthood
• Treat with steroids
• Selective breeding
• Treat with antibiotics
• Maintain constant temperature
• Limit movement
• Supply food
• A balance needs to lie between animal welfare and
  efficient food production.

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Succession

• Gradual change in a community over a period of
  time

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Learning outcomes

• Describe one example of primary succession
  resulting in a climax community.

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Keywords

• Succession
• Pioneer community
• Climax community
• Seral stages
• Sere

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Succession

• Succession
• Gradual directional change in a community of
  organisms over time
• its unidirectional
• Primary succession
• Original area has no soil or living organisms
  present
• Secondary succession
• Following disturbance of the area, soil is
  present.

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Succession

• New land is formed on the Earths surface at
  river deltas, at sand dunes and from cooled
  volcanic lava.
• When new land is exposed it is invaded and
  colonised by plants, a sequence of communities
  develops over time by Primary succession
• Secondary succession is the colonisation of an
  area that has been previously occupied and become
  barren.

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Succession - definition

• The gradual replacement of one plant community by
  another over a period of time, through a series
  of seral stages, starting with the pioneer
  community and ending with a climax community.

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The pioneer community

• The first plants to colonise an area are pioneer
  plants, which are adapted to survive in difficult
  conditions.
• These are usually mosses or grass
• As they grow these plants change the
  environmental conditions until they are no longer
  the best suited.
• Better adapted plants start to colonise.

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Look at the photographs
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Question

• Suggest and explain what happens to each of the
  following during the process of succession.
• The number of different species in the community
• The quantity of biomass per unit area

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Summary

• Plants colonise an area, they change it in such a
  way that they are no longer the best adapted to
  survive there and are out competed, new plants
  then colonise the area.

Pioneer community
Climax community
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• In the early stages of succession, abiotic
  factors are important in determing what can
  survive.
• Availability of water
• Availability of nutrients in the soil
• Wind exposure

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Primary Succession
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Human Intervention

• Clearing of deciduous woodland for
• Agriculture
• Conifer forestry
• Human settlement
• Intensive grazing by sheep can deflect succession
  from a forest climax community to grassland.
• A deflected climax community is known as a
  plagioclimax

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Learning Outcomes

• Describe how the distribution and abundance of
  organisms can be measured, using line transects,
  belt transects, quadrats and point quadrats.

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Studying Succession

• We can use the distribution of the communities in
  space on the ground to show us what they look
  like at different times during a succession
• Examples
• Retreating glacier (Glacier Bay, Alaska)
• Sand dunes

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Sampling

• Plant and animal communities can be sampled using
• Point quadrats
• Quadrats
• Transects
• Transects are the best way showing succession

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Using transects to study succession

• Line transect
• Record what is touching the tape
• Belt transect
• Quadrats are placed alongside the tape
• Continuous belt transect
• Record along the whole length of the tape
• Interrupted belt transect
• Record at intervals along the tape

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Measuring Species

• Distribution
• Presence or absence of each species
• Abundance
• Estimate or count the number of individuals
• Percentage cover

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Estimating population size
Mean number of individuals of the species in each
quadrat
Population size of a species

Fraction of the total habitat area covered by a
quadrat
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Nutrient Cycling
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Learning outcomes

• Describe the role of decomposers in the
  decomposition of organic material.
• Describe how micro-organisms recycle nitrogen
  within ecosystems

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• Nutrient cycling
• Provides elements for
• metabolic processes
• Constructing organic molecules
• Decomposition
• Provides mineral and nutrients for metabolism

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Decomposers and Detritivores

• Decomposers
• Bacteria and fungi
• Absorb organic nutrients from dead organisms and
  waste from living organisms, converting them into
  inorganic molecules
• Detritivores
• Organisms living in or on the soil that feed and
  gain nutrients from detritus.

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Decomposition

• Breakdown of dead organic matter with release of
  inorganic nutrients into surrounding soil

decomposition
Litter
Humus
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Rate of decomposition

• Factors
• Type of organic matter present
• Number and types of decomposers and detritivores
• Environmental conditions
• Temperature
• O2 content
• moisture

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Nutrient cycling
Nutrients in environment
photosynthesis
decomposition
producers
decomposers
feeding
decomposition
consumers
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The carbon cycle
Carbon dioxide In the air (CO2)
photosynthesis
respiration
Combustion (burning)
feeding
Carbon compounds in plants
Carbon compounds in animals
Fossil fuels Coal, oil, gas, peat
decay
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The Nitrogen Cycle
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The Nitrogen Cycle

• Most nutrient cycles have two components
• Geochemical
• Biological
• Cycling of Nitrogen
• Nitrogen fixation
• Assimilation
• Ammonification
• Nitrification
• denitrification

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Nitrogen Fixation

• Nitrogen gas converted to nitrogen-containing
  compounds.
• Three ways all require energy
• Lightning
• nitrogen oxygen ? oxides of nitrogen
• Industrial processes
• Haber process combine hydrogen and nitrogen to
  form ammonia
• Fixation by micro-organisms

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Fixation by microorganisms

• Free-living nitrogen fixers
• Bacteria reduce nitrogen to ammonia
• Used to manufacture amino acids
• Nitrogen rich compounds released when die and
  decay.

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• Mutualistic nitrogen fixers
• E.g. Rhizobium
• Live in root nodules of leguminous plants
• Nitrogenase converts N2 to NH4 using H and ATP
• Requires anaerobic conditions (leghaemoglobin)
• Plant uses ammonium ions to make amino acids

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Assimilation

• Nitrogen assimilated in the form of ammonium ions
• Nitrate ions reduced to nitrite ions and then
  ammonium ions.
• Animals assimilate nitrogen in the form of protein

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Ammonification

• Production of ammonium-containing compounds
• E.g urea, protein, nucleic acids and vitamins
• Decomposers feed on these releasing ammonia

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Nitrification

• Two stages
• Oxidation of ammonium ions to nitrites
• Nitrosomonas
• Oxidation of nitrites to nitrates
• Nitrobacter

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Denitrification

• Anaerobic denitrifying bacteria
• Reduce soil nitrates into nitrogen gas
• NO3- ? NO2- ? N2O ? N2

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Nitrogen Cycle
Nitrogen in atmosphere (N2)
assimilation
Nitrogen-fixing bacteria in root nodules of
legumes
Denitrifying bacteria
Plants
animals
Nitrates (NO3-)
Decomposers (aerobic and anaerobic bacteria and
fungi)
Nitrobacter
ammonification
Nitrification
Nitrites (NO2-)
Ammonium (NH4)
Nitrosomonas
Nitrogen-fixing soil bacteria