Transcript 1.5 a study of an ecosystem

Chapter 6: A Study of an
Ecosystem
Leaving Certificate Biology
Higher Level
Study of an Ecosystem
• Broad Overview of a Selected Ecosystem
• Observation and Scientific Study of a Selected
Ecosystem
• Organism Distribution
• Choice of Habitat
• Organism Adaptations
• Organism Role in Energy Transfer
• Analysis
A Broad Overview of a Selected
Ecosystem
• Choose your ecosystem and visit it
• Suitable ecosystems:
– hedgerow
– stream
– rock pool
– rocky seashore
– old wall
– small woodland
– small meadow
– freshwater pond
– waste land
– an overgrown garden
– soil
– peatland
– grassland
Broad Overview of a Selected
Ecosystem
• “Select and visit one ecosystem”:
• Hedgerow:
– Physical properties:
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Acts as a boundary to the field
It is a large hedgerow
Provides good protection from the weather
It can be classed as a very small woodland area
– General presence of life:
• Flora: many trees and shrubs, plants, and grasses
• Fauna: herbivores, birds and predators
Observation and Scientific Study of a
Selected Ecosystem
• “Identify any five fauna and any five flora using
simple keys”:
– Fauna:
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Beetles
Butterflies
Hoverflies
Snails
Ladybirds
Hare
Foxes
Badgers
Hedgehog
Mice
– Flora:
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Hawthorn
Blackthorn
Gorse
Blackberry bramble
Fuschia
Holly
Rowan (Mountain ash)
Ash saplings
Hazel
Willow
Observation and Scientific Study of a
Selected Ecosystem
• “Identify a variety of habitats within the selected
ecosystem”:
– There are a number of habitats in the selected
ecosystem of the hedgerow
– Each habitat is simply a measured subsection of the
hedgerow – for example every 5 m of the hedgerow
along with, for example, 5 m of the field either side of the
hedge
– Identifying a range of habitats from the hedgerow
involves choosing habitat areas at random and mapping
them
Ecology Apparatus
• “Identify and use various apparatus required
for collection methods in an ecological study”
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Mammal trap
Pitfall trap
Cryptozoic trap
Beating tray
Pooter
Nets (to include – sweep net, insect net, plankton net
or fish net)
– Direct search
– Tullgren funnel
Ecology Apparatus
• Traps:
– Mammal trap
• Bait attracts small mammals into box
• Once they enter the trap door prevents exit
Ecology Apparatus
• Traps (continued):
– Pitfall trap
• Involves simple can or plastic up embedded in the ground and
covered to prevent water entering
• Bait is sometimes used
Ecology Apparatus
• Traps (continued):
– Cryptozoic trap
• Shelter trap involving a piece of old wood, a log, or
a large stone
• Small animals like slugs and woodlice hide under a
cryptozoic trap during periods of inactivity
Ecology Apparatus
• Beating tray:
– Hold under tree
or bush
– Shake the tree
or bush
– Insects fall onto
tray and can be
identified
Ecology Apparatus
• Pooter:
– Device ecologists use
to pick up small
objects, like insects
– Like a miniature
vacuum cleaner with
your lungs working as
the engine
Ecology Apparatus
• Nets:
– Sweep nets, insect nets, plankton
nets:
• Have a lightweight aluminium frame
• The net bags usually have curved
tips to help prevent insects escaping
• Sweep net usually have a 5-sided
frame designed to give a better
sampling sweep than circular frames
• Plankton nets are long and very light
designed to
Ecology Apparatus
• Tullgren funnel:
– Used for both dry and wet
extraction of soil organisms from
soil samples
– A soil sample is placed in the
removable upper part of the
funnel
– Heat and light from the lamp
creates a temperature gradient
of approximately 14°C in the soil
sample
– This stimulates the downward
movement of soil arthropods,
and similar organisms, through
the gauze to a receiver attached
to the base of the funnel
Organism Distribution
• Use qualitative and quantitative surveys of
plants and animals in your ecosystem
– Qualitative survey:
• Record of presence/absence of organism
– Quantitative survey of flora and
stationary/slow-moving fauna:
• Subjective estimate – educated guess which is
inaccurate
• Objective estimate – accurate (two methods)
– Quadrats
– Transects
Organism Distribution
• Objective estimation: Quadrats
– Squares with sides of either 1, 0.5, or 0.25 m
– Thrown randomly in habitat over shoulder
– Two measurements taken with quadrat:
• Percentage cover: estimate of the ground in quadrat
covered by each species of interest
• Frequency: chance of finding a named species with
any one throw of the quadrat
– Limitations:
• Animals can move fast and not remain in the quadrat
• Limited by species size, e.g. trees and large animals
Organism Distribution
• Percentage cover: estimated using one of two
methods:
– The area of quadrat covered by each species (five flora)
of interest is estimated as a percentage of the total
quadrat area – not very accurate
– Using a graduated quadrat the total number of squares
(25) is divided by the number of squares (top and right
sides only) touched by the flora of interest (e.g. 10) –
much more accurate
No. of squares touched by flora
10
x 100 =
x 100 = 40%
25
Total no. of squares in grad. quad
Organism Distribution
• Frequency: chance of finding a named species with
any throw
– Record presence/absence of each species with each
quadrat throw – no counting involved
– This method is quick and percentages of organisms can
be calculated easily
– The more throws and frequency checks you do, the more
accurate your end-frequency percentage results will be
– Limitations:
• Dependent on the organism size and quadrat size
• Presumes that organisms are evenly distributed
Organism Distribution
• Transects: used in gradient habitats, e.g. seashore
– Not random – you decide where to place the transect
– Type 1: Line transect:
• Plants/animals touching the string/rope (marked at
regular intervals) are recorded
• Limitations: only samples narrow strip of habitat
– Type 2: Belt transect:
• Two parallel ropes with squares made from 1 m lengths
of ropes attaching the two main ropes together
• Contents studied in same way as normal quadrats and
graduated quadrats: percentage cover and frequency.
• Limitations: same limitations as those of quadrats
Organism Distribution
• Quantitative survey of animals:
– Capture-recapture method is used to calculate the no.
of moving animals in a habitat
– 1st visit: Capture no. of animals of same species, mark
them, and release again
– 2nd visit: Similar no. of animals of same species
captured; some will have marks – they are counted
– Total no. of animals in that habitat can be calculated:
No. of
animals in =
habitat
(#C&M1st)(#C2nd)
#M2nd
Organism Distribution
• Quantitative survey of plants:
– Use one of two methods:
• Frequency: presence/absence recorded as a %
• Percentage cover: approximate % of the area of the
quadrat that is occupied by plant species OR the
number of plants touching top and right sides of
graduated quadrat
Organism Distribution
• Sources of error in studying an ecosystem:
– Human error – especially when estimating frequency
– Changing conditions – seasonal variations
– Accidental discovery – by a walker instead of an
ecologist
– Sample size – more samples, better accuracy
Experiment to conduct a
quantitative study of plants and
animals of a sample area of a
selected ecosystem
• LC HL 2006:
– “Describe how you carried out a quantitative
survey of a named animal in the ecosystem
that you have studied.”
Answer:
• Named animal: snail
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Brief description of the hedgerow was made
An area of the hedgerow was marked off and mapped
Within this particular area 22 snails were collected
Snails were marked with paint and released
One week later, same habitat – 20 snails were
collected and it was found that 9 had the paint marks
– Formula used to get approximate number of snails in
the habitat chosen:
• 22 x 20 = 49
9
– Therefore, there were approx. 49 snails in our habitat
Choice of Habitat
• Study the effects of abiotic factors on the suitability of
an organism to its habitat
• You must study at least 3 abiotic factors:
– pH
– percentage air in soil
– temperature
– percentage water in soil
– light intensity
– percentage humus
– water current
– salinity
– air current
– degree of exposure
– dissolved oxygen
– slope
– mineral content
• Then describe how each of the 3 you chose affects your
ecosystem
Organism Adaptations
• Adaptations are necessary for an organism to
survive new conditions
• Adaptations may be structural, competitive, or
behavioural
• Describe ONE adaptation of an organism you
studied in your habitat
– Snail has a protective shell
– Ladybird has a red covering to warn birds that it is
poisonous to eat
– Blackthorn has thorn to protect its fruits
Organism Role in Energy Transfer
• Identify where each organism in your habitat
is positioned in the food chain/food web
• From the data collected on your field trip
construct a food chain, food web, and
pyramid of numbers
Analysis
• Learn to analyse, assess, and discuss your
results and conclusions
• Is there any relationship between the results
and conclusions of your study and local
ecological issues
• Prepare a portfolio/report/project (no less
than 1,000 words, no more than 2,500
words)