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Examples of ecosystems include a woodland, pond, ... Cockle. Sycamore. Dandelion. Giraffe. Gold finch. Mackerel. Seaweed. Spider. Sea Urchin. Venus Fly Trap ... – PowerPoint PPT presentation

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Title: The%20Biosphere

The Biosphere
  • Investigating an Ecosystem

Mr G Davidson
Investigating an Ecosystem
  • Examples of ecosystems include a woodland, pond,
    loch, moor etc..
  • An ecosystem includes all the living things,
    their non-living surroundings and the factors
    which affect their lives.
  • Factors in the ecosystem related to living things
    are called Biotic Factors.

Investigating an Ecosystem
  • Examples of these are the amount of food,
    disease, the amount of grazing and hunting.
  • Non-living factors in the ecosystem are called
    Abiotic factors.
  • Examples of these are temperature, moisture and

Investigating an Ecosystem
  • The place where an organism lives is called a
  • There are many habitats within an ecosystem.
  • E.g. in a woodland there are many layers and
    within these layers many different habitats such
    as trees, leaves (dead and alive), shrubs,
    bushes, soil, etc..

Using a Quadrat
  • We could find out exactly what is living in a
    particular ecosystem by collecting and counting
    all the organisms.
  • This would be difficult and would take a long
  • However, we can get some idea of the amount and
    kinds of living things in an ecosystem by taking
    a sample.

Using a Quadrat
  • In order to sample plants (and slow moving
    animals) we can use a quadrat.
  • A quadrat marks off a small piece of ground of
    known area so that different plants present
    within this sample can be identified and counted
    or their area of cover estimated.
  • This sample gives us an idea of the number and
    kind of organism present in the whole area.

Using a Quadrat
  • The quadrats we use are 0.25m2 and sub-divided
    into 25 smaller squares each 100cm2.
  • The quadrat is placed randomly on the ground.
  • The number of small squares containing the plant
    we are interested in are counted.
  • This is called the abundance estimate.

Other sampling Techniques
  • Pitfall traps are used to trap small animals
    moving across the surface of the ground.
  • Sweep netting is used to catch small animals
    living in vegetation.
  • Potato traps can be used to attract small
    animals, particularly snails and slugs.

Pitfall Trap
Other sampling Techniques
  • Pond nets are used to catch animals living in
  • Tullgren funnels are used to remove tiny
    organisms from soil samples.
  • Pooters are used to capture small insects.

Pond Net
Tullgren Funnel
Estimating Total Numbers
  • We can estimate the total numbers of organisms
    living in a certain area.
  • We need to calculate the area we are sampling.

Estimating Total Numbers
  • We need to estimate numbers using the quadrat.
  • We then calculate an average number of organisms
    per quadrat.
  • We then work out how many quadrats fit into the
    specified area and multiply this number by the
    average number of organisms per quadrat.

Estimating Total Numbers
  • Calculate the area of this field.
  • Length times breadth.

Estimating Total Numbers
  • We now know the area of the field is 15 x 40
  • We now need to sample the field by using the
    quadrat , say 10 times.
  • The quadrat is then placed randomly in 10
    different spots in the field, and the number of
    plants counted.
  • Suppose we are measuring daisies.

Sampling Daisies
The quadrats are placed randomly and the number
of daisies in each are counted.
Sampling Daisies
  • The results are collected and recorded.
  • We then calculate the average number of daisies
    per quadrat.
  • Add up the number of daisies column and divide by
    the number of sites.

Quadrat Number of daisies
1 7
2 15
3 9
4 2
5 12
6 0
7 13
8 6
9 10
10 16
Sampling Daisies
  • In this case the total number of daisies sampled
    was 90.
  • The number of sites was 10.
  • Therefore the average number of daisies per site
    is 90 10 9 daisies
  • We now need to work out how many quadrats fit the

Sampling Daisies
  • The field is 600m2 and there are 4 quadrats to
    each 1m2.
  • Therefore, the field is 600 x 4 2400 quadrats.
  • If there are, on average 9 daisies per quadrat,
    this means there are 9 x 2400 21 600 daisies in
    the field.
  • A good estimate.

Estimating Total Numbers
  • Here is one for you to try on your own.
  • This time we are estimating the number of worms
    in a field.
  • Here are the results.

Quadrat No. of Worms
1 6
2 7
3 2
4 9
5 12
6 5
7 7
8 6
9 8
10 8
Estimating Total Numbers
How did you do?
  • Average number of worms per quadrat?
  • Answer 7 worms per quadrat.
  • Total area of field?
  • Answer (50 x 40) (25 x 15) 1625m2
  • Total number of quadrats in field?
  • Answer - 1625 x 4 6500 quadrats
  • Total number of worms?
  • Answer 6500 x 7 45 500 worms

Factors Affecting Distribution
  • There are many different factors in an ecosystem
    which affect the lives of organisms.
  • The factors are also responsible for the
    distribution of the organisms, i.e. where they
  • Some of these factors the abiotic factors are
    easy to measure, e.g. light, moisture,

Measuring Abiotic Factors
  • We can measure light using a Light meter.
  • Make sure you dont cast a shadow on the meter or
    you will get a false reading.

Measuring Abiotic Factors
  • We can measure moisture using a moisture meter.
  • Carefully push the probe vertically into the soil
    to a depth of approximately 4cm.

Measuring Abiotic Factors
  • When we measure abiotic factors, we wouldnt
    simply take one measurement and assume that was
  • We would take a number of measurements at
    different spots, and then calculate an average.
  • This makes our results more VALID.

Line Transect
Line Transect
  • In this example the light intensity would
    decrease as you move from site 1 to 10.
  • The moisture readings would increase as you move
    from site 1 to 10.
  • Therefore, the distribution of plants are
    different i.e. there are likely to be more
    daisies at site 1 than site 10.
  • Likewise there are likely to be more woodlice at
    site 10 than at site 1.

Scientist studying Distribution of Organsims
Identifying Organisms
  • Its all very well counting organisms or
    collecting organisms.
  • Not all of them will be familiar to us.
  • In order to identify unfamiliar organisms, we
    would use a key.
  • There are different kinds of key.
  • We will use 2 kinds.
  • Branching Keys
  • Paired statement keys.

Branching Keys
Branching Keys
  • When using a branching key you must always start
    at the top.
  • If you follow the line of the key, you will be
    given a choice to make.
  • Study your organism and make the appropriate
  • If your organism is in the key, you should
    eventually finish at its name.

Paired Statement Keys
  • Paired statement keys work in the same way as
    branching keys.
  • At each stage you are given a choice.
  • Make the appropriate choice and go to where you
    are asked to go.
  • Again, if the organism is present, you should end
    up with a name for it.

Paired Statement Key
  • Single leaf go to 2
  • Several leaflets go to 6

2. Leaf with prickles HOLLY Leaf with no
prickles go to 3
3. Leaf edge with lobes go to 4 Leaf edge
with no lobes go to 5
4. Lobes sharp pointed SYCAMORE Lobes
rounded OAK
5. Leaf with smooth edge BEECH Leaf with
serrated edge ELM
6. Leaflets in fan shape HORSE
CHESTNUT Leaflets in pairs go to 7
7. Leaf edge serrated ROWAN Leaf edge
plain ASH
  • The paired statement key is more manageable as it
    tends not to spread itself out as much.
  • The branching key is more pictorial and usually
    easier to use.
  • Try building your own keys for the following
    organisms. (Branching and Paired Statement!)

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