CW
22-Mar-22
Ecology and Ecosystems 3
LO: To understand the use of
quadrats in sampling.
Starter:
Is this food web
complete?
Is this data clearly
presented?
RECAP Keywords & Definitions
Ecosystem –
Population –
Interdependence –
RECAP Keywords & Definitions
Ecosystem – The living and non-living things in a
particular area
Population – The number of individuals of a
particular species
Interdependence – The idea that all organisms
rely on each other to survive
in an ecosystem.
NEW Keywords & Definitions
Sample–
Unbiased –
Adaptation –
Community –
Niche –
Estimate–
Abundance–
Distribution–
Keywords & Definitions
Representative sample– small area reflecting the whole
Unbiased – not chosen to be more or less populated
Adaptation – characteristic that gives fitness
Community – the organisms in one area
Niche – a particular part of a habitat for a species
Estimate– an approximation, eg of the population size
Abundance– how many there are, eg % cover of a plant
(not the same as the number of plants- too hard to see!)
Distribution– where the organisms are, eg evenly
distributed, patchy, irregular…
We’d like to know everything…
It would take too long to
learn everything… and we’d
destroy it! A scientific study
takes samples to get a valid
estimate of the habitat, or at
least some aspects of it.
Scientists use standard methods
3,000kJ
A quadrat is a simple square of fixed area used to
take a SAMPLE of a habitat/ ecosystem. There must
be MULTIPLE samples, distributed in a VALID way.
Eg at random, if the distribution of organisms is also
random. On the left the survey is parallel to the
waterline- a randomised investigation can be done.
An evenly distributed community
can be surveyed by this sort of
random sampling method. A few
quadrats are selected at random
coordinates. The data is used to
CALCULATE the total population.
If the distribution of plants is
not random, perhaps because
there is a gradient in a nonliving factor, then we do a
TRANSECT (line transect)
instead- we’ll do this next
lesson. The samples are taken
at regular intervals.
Some individual plants will cross the boundaries of the
sample area. You could count on the EAST and SOUTH, but
not the N or W.
Data table for a grid quadrat
Quadrat
CoCount
ordinates grass
Count
daisy
Count
dandelion
Count
plantain
Count
other
Count
bare soil
1
2
3
4
5
Here is one kind of table for collecting data. It could be used with
a quadrat that doesn’t have small squares in it, so you have to
estimate the % cover by eye. This takes practice! You can do this
with a friend, and record the mean value of your estimates.
Data table for open quadrat
Quadrat
Co% grass
ordinates
% daisy
%
dandelion
%
plantain
% other
% bare
soil
1
2
3
4
5
Here’s another kind of table for collecting data. It could be used
with a quadrat that doesn’t have small squares in it, so you have
to estimate the % cover by eye. This takes practice! You can do
this with a friend, and record the mean value of your estimates.
Additional
facts
about
quadrats
Calculate the population of each
species in 100m2
Average cover of grass in one quadrat = n
Area of one quadrat (grid) = 0.5 x 0.5 = 0.25m2
Cover of grass in each sq m = 4 x n
Cover in 100m2 = 100 x 4 x n
Repeat calculation for your remaining species types.
Evaluate your findings!
Discuss the whole activity- what do you learn about
your study habitat, and what questions remain?
RECAP Keywords & Definitions
Sample–
Unbiased –
Adaptation –
Community –
Niche –
Estimate–
Abundance–
Distribution–
POSTSCRIPT: Bee good 