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					Unit 1
    Investigating an Ecosystem
   Ecosystem – made up of habitats, populations and
   Habitat – is the place where organism lives in an
   Population – is the number of individuals of the same
    species in an ecosystem
   Community – is all the population of different species
    in an ecosystem in an ecosystem
   Ecological Niche – the role an organism plays within
    the community
   Biotic Environment – Disease, Predators, competition,
    availability of food
   Abiotic Environment – Light intensity, temperature,
    rainfall, pH, flow rate
    Quadrat Experimental Errors
 10 quadrats may be too small a number to give a fair
 Some of the type of plant being considered may be
  partly inside and partly outside the quadrat
Minimising Errors
 Large numbers of quadrats
 As long as everyone counts the sameway
 Make sure the sampling is random
                                                 50   cm²
 Estimate number of daisy
 Number of quadrats 800 ÷ 0.25 =3200
 Daisy in field = 725 x 3200 = 23200               40
 Yarrow in field = 11.08 x 3200 = 35456   20   800 cm²
 Clover in field = 3 x 3200 = 9600
    Pitfall Traps
 Used to trap small animals moving across the surface of
  the soil or leaf matter
 The animals fall into the trap and is unable to climb out
 Examples; beatles, worms, woodlice
 You can not sample animals with wings
Experimental Errors
 Numbers of animals may not be representative of an
  ecosystem as a whole
 Birds my eat trapped animals
 Animals may eat each other
Minimising Errors
 Set up several traps
 Disguise the opening with lid e.g. Leaf
 Check traps regulary
Line Quadrat/ Transect
 Used to sample the distribution of
  species in for example a forest or a
 A line is placed from the start to the end
 A quadrat is placed every few meters
 The number of species are counted
 To make more reliable, more quadrats
  are taken
    Tulgren Funnel
  Used to remove tiny organisms form the soil sample
 They move down and away from the hot, dry conditions
   created by the light bulb
 Fall through the sieve and die
Experimental Errors
 Numbers may not be representative
 Soil maybe too thick and may still contain many organisms
   at the end of the experiment
 Sieve mesh may be too fine and some animals may fail to
   fall through
Minimising Errors
 Set up several tunnels
 Make layer on surface of soil thinner keep trap set up for
   longer period of time
 Use mesh with larger size of holes
    Tree Beating
 Use a stick and tray to catch small animals
 Then use a potten then in jars for examination
Experimental Errors
 Numbers many not be representative
 Some organisms may miss the trap or drop off or
  fly away
 Some animals may not be dislodged by the
Minimising Errors
 Take several samples beat several branches and
  pool results
 Use large tray with raised edges
 Examine branch after beating and use blunt
  instruments to collect remaining animals
    Pond Nets
  The pond nets are used to capture small animals living in
 The net is moved rapidly through the water catching
   animals which are quickly transferred to screw top jars
   containing pond water
Experimental Errors
 Numbers may not be representative
 Small animals may escape through the holes in the mesh
 When investigating the bottom of the pond some animals
   in the net may have been caught from the water near the
   surface as the net is passed through
Minimising Errors
 Take several samples form several net and pond results
 Choose net with fire mesh
 Rotate the handle of the net to close opening on the way
   down and back up
Identifying Organisms
 Use simple keys or checklists to identify
Biological Keys
 Way of identifying organisms using a
  series of paired statements or a branched
  diagram based on their characteristics
Measuring Abiotic factors
 Use a light meter
 Point it at the same of the light
 Read the results off the scale
Flow Rate
 Drop a ball or something that floats into the river
 Measure how long it takes (in seconds) to travel one meter
 Use a moisture meter
 Insert probe into the ground
 Read results off the scale
 Use a pH meter
 Insert the Probe in the ground
 Read results off the scale
Sources of Error
 Shadow of user falls over the sensor
 Prevent by ensuring user are well back from the
Flow Rate
 The river flows at different rates across it’s width
 Prevent by taking several readings across the river
 Moisture from previous reading effects the probe
 Prevent by wiping the probe before and after using
 The pH from a previous reading affects the probe
 Prevent by wiping the probe before and after use
Abiotic factor affect the
distribution of an Organism
 Some plants grow well in bright sunlight (trees) others grow
  better in the shade (Bluebells)
 Some fish like fast flowing water. Others like still water
 Some plants grow well in damp soil . Others grow in well
  drained soil
 Some plants like acidic soil (low pH). Others like alkali soil
  (high pH)
Measuring Abiotic Factors
 When we measure abiotic factors we wouldn’t simply take one
  measurement and assume that was it
 We would take a number of measurements At different spots
  and calculate an average
 This makes the results more reliable
 The cells and bodies of plants and animals decay
  by the action of soil bacteria's and fungi – these
  are often called decomposers
 In the food chain the arrow represents the flow of
 Food Chain
Primary Producer 1st
Primary Consumer 2nd
Secondary Consumer 3rd
Tertiary Consumer 4th
   Primary Producer Grass
                                 Primary Producer Phytoplankton

   Primary Consumer Cows
                                 Primary Consumer Zoo Plankton

   Secondary Consumer
                                 Secondary Consumer Small Fish

                                 Tertiary Consumer Pike
   Tertiary Consumer Worms

                                 Top Carnivore Osprey
   Top Carnivore Eagle
90% of energy is lost Thourgh;
 Movement
 Respiration
 Urine/ Faeces
 Heat
 Not all the animal is eaten
 Reproduction
Birth and Death Rate
                           Under ideal conditions No
                           shortage of food, shelter. Lack
                 Limited   of predators then the population
                 Growth    shows uncontrolled growth

                                    Birth rate is high
                                   Death rate is low
                                  Factors limiting population Growth
                                   Shortage of food and water
                                   Lack of shelter/ space
                                   Predators
                                   Toxic waste
                                   Disease
               A – slow increase as the population is
                small to start with
               B – large increase as more individuals
        c      C – Growth slows e.g. Lack of food

            Population Growth
    b        Growth rate = birth rate – death rate
             Birth rate greater than death rate =
               population increases
             Birth Rate less than death rate =
               population decrease
             Stable population = death rate equal to
               birth rate
   food
 Water
 Space        Stronger
Plants         survive
 Light        weaker
 Moisture
               species die

 Nutrients
 Root space
To investigating the effect of competition between radish and cress seeds
We put cotton wool in three plastic cups with a bit of water in one cup we put 100
Cress seeds and 100 radish seeds. In another we put just 100 radish seeds and
in another cup we put just 100 cress seeds and then left them to grow for 5 days
at 24º
Results %                  Number of seeds            Showing Successful
Cup                        No. Of Radish growth       No. Of Cress growth
            A                          96                         67
            B                          94                       Absent
            C                       Absent                        89

 Radish is clearly the top competitor out of the radish and the cress
Cycling of Nutrients
   Nutrients are;
   Chemical substance which care needed for living things to
    stay alive
   Nitrogen
   Oxygen
   Mineral Salts
   Carbon Dioxide                                           Nutrients in
                           Nutrients in living               dead bodies
   Water
                             Organisms                         and waste

                         ed by
                         living                                  Decomposed
                                                                 by Bacteria
                                            Nutrients in the     and fungi
Nitrogen Cycle
Growth and development
 Proteins
 Nucleic acid
 Other Cellular compounds
Several Process
Nitrogen Cycle
Control and Management
The main areas in which pollution occurs
Identify the source
Part of       Main source of     Example             Possible Control
environment   pollutant
Air           Industrial         Smoke,              Smoke scrubbers
                                 containing SO²      Fume filters

Land          Human, industrial, Rubbish, Human      Recycling, Burn
              Waste              waste

Fresh water   Industrial,        Sewage,             Less fertilizer,
              Agricultural       Fertilizers         decompose by
Sea           Oil tankers,       Oil, Radioactive,   Sealing waste, no
              getting wash out   waste, heat         dumping,
              nuclear                                alternative energy
              PowerStation                           soucre
 Fuels – Adverse Effects
Coal/ Oil/ Gas
 Emits SO² and so it causes acid rain
 Emits CO² so increase grenhouse effects
 Waste has to be disposed safley
 There is a risk of acidents
 Radiation is harmful to living things- this increases the risk of cancer
Renewable Energy
Wind, Tidal, Solar power
 Clean
 Will run out
 Easily accessible
 Often depends on weather
 Look ugly
 Energy is dilute, in other words, very spread out
Acid Rain
How to Stop acid rain
 Scrubbing the fumes
 A scrubber contains a slurry of limestone
  which removes

 Fuel burns operate at lower
  temperatures and produces less toxic
  gas nitrogen dioxide
 Treat the disease symptoms e.g. Adding
 Organic waste
   Microorganisms (bacteria) in the sewage, eat the
    sewage as an energy source.
   Multiply
   They use up all the oxygen
   Oxygen organisms can not survive
   Organisms that don’t need oxygen flourish
Level of       No          Very High High        Low          No
population     Pollution   Pollution Pollution   Pollution    Pollution
Oxygen Level   Very High   Very Low     Low      High         Very High
Most common    Stonefly    Rat-tailed   Water    Shrimp.      Stonefly
Animals        Nymph.      Maggot.      Louse.   Caddis fly   Nymph.
collected      Mayfly      Sludge       Blood    larva.       Mayfly
               Nymph.      Worm.        Worm.                 Nymph.
Poor                Reason             Effect                  Possible Solution
Management                                                     or Improvements

Overuse of          Over harvesting    Pesticides pollute      Use alternative
fertilisers and     of crops, leaves   rivers                  pest control
chemical            soil short of                              Biodegradable
pesticides          nitrates                                   chemical
Use of grain to     Humans eat too     Overweight              Eat less meat
feed                much meat          Poor Diet               Eat more
domesticated                                                   Vegetables
Growth of cash      Poor countries Unable to feed              Supply tools and
crops by            grow cash crops population                 technology without
developing          to buy tools and Import food – debt        economic strings
countries instead   technology for
of the food crops   development
Overgrazing of      Livestock main     Overgrazed plants die Economic acid
grassland           source of wealth   Increase in desert      developing rogation
                    in developing      areas. People – poorer, schemes
                    countries          malnutrition, disease
Indicator Species
 Lichens are sensitive to sulphur dioxide
Mossy Lichen = Clean Air
Crusty Lichen = Polluted Air
Indicator Species        Appearance of Lichens SO² Concentration
Crusty Lichens Only      Crusty                High
Crusty and Leafy         Leafy                 Medium
Crusty, Leafy and some   Shrubby               Low
Crusty, Leafy, Shrubby   Hairy                 Very Low
and hairy
Agriculture and Forestry
 Agriculture and Forestry carry out many
  practices to control the ecosystem to
  produce more crops, beasts and trees.
 Minimising the growth and survival of
  other species e.g. Scarecrows protects
  crops but prevents birds from obtaining
 Plough, fencing and hedging
 Draining
 Fertilising – manure protects the
  structure of the soil by adding humus.
  Overuse of chemicals fertilisers destroy
  the structure of the soil
 Pesticides and weed killers – build up to
  toxic levels in the food chain
   Draining

   Laying of new roads

   Deer fencing
    Crop Rotation
 If a farmer plants out his field with certain crop.
  That crop will take out certain nutrients from the
 If he continues to do this year after the soil will
  eventually become deficient of certain nutrients
 To overcome this he uses a system called Crop
  Rotation. Crop rotation allows the soil to recover
 He also includes crops like clover or legumes
  which are able to fix nitrogen – enriching the soil

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