Transcript File - Groby Bio Page

Learning Objectives
 Understand how to sample plants and animals
Success criteria
Learners should be able to demonstrate and apply their
knowledge and understanding of:
(b)(i) how sampling is used in measuring the biodiversity
of a habitat and the importance of sampling
(ii) practical investigations collecting random and
non-random samples in the field
To include how sampling can be carried out i.e. random
sampling and non-random sampling (e.g. opportunistic,
stratified and systematic) and the importance of sampling
the range of organisms in a habitat.
Sampling
Why do we sample?
 Important in measuring the biodiversity of a habitat.
 Individuals too numerous to count all in habitat e.g.
bacteria, fungi
 Time consuming to count everything
 Study to investigate effects of humans
 Provide data to give assessments of environmental impact
 Allow us to reduce our impact
Studying Habitats
 When studying a habitat, ecologists will first estimate the
populations of the species living there.
 The abundance of each species can never be known exactly,
but sampling can give reasonably accurate estimates.
 So small samples are studied and then scaled up to fit the
entire habitat.
 Reliability – sampling is never entirely representative:
 Sampling bias
 Chance
Sampling
The approach to sampling can be in one of two ways:
1. Random
2. Non-random
Random Sampling:
This is usually employed when trying to eliminate bias.
Two numbered axis can be laid out over the sample area.
Generation of random numbers provides co-ordinates for
areas to study.
Sampling
Non-random Sampling:
There are 3 main types:
Opportunistic – weakest form of sampling as it may not be
representative of the population.
Stratified – population divided into sub-groups e.g. Males
and females.
Systematic – often carried out using a line or belt transect.
Particularly useful if the environment is changing e.g.
Shoreline.
 Line transect: along large habitat, record
plants touching line at intervals
 Belt transect: move quadrat along line
Sampling plants - Quadrats
 A quadrat is just a fancy square used by biologists/ecologists.
 There’s two types of quadrat:
Frame Quadrat
Point Quadrat
Quadrats
 Three things to consider when using quadrats:
The size of the quadrat:
Depends on the size of species being investigated, or what
kind of groups or colonies the species live in.
2. The number of samples being taken in the area:
The more samples you take in the habitat, the more reliable
the results will be... Depends if time is an issue.
3. The position of each quadrat:
Producing unbiased results within a small time-frame is the
best idea. Random sampling would work well.
1.
A problem that arises during quadrat sampling is the clumping of
plants. To get around this... We measure the ‘mean density’ or
‘percentage cover’ instead.
Using frame quadrats
 Density – counting exact numbers of large plants in a 1m x 1m
quadrat will give density per square metre.
 Frequency – used when individuals of a species are hard to
count. Count the squares within a quadrat to give a
percentage cover (ACFOR scale)
 Percentage cover - used when a species is abundant or
difficult to count, estimated by eye.
 The large the number of samples the more reliable the result.
 Using results to get total population :
 Calculate mean of the individual quadrat results to get an
average per m2.
 Multiply by the total area of the habitat
What about animals?
 What we’ve seen up until now is fine for sampling plant
populations, but studying animals and insects is trickier.
1. A set of animals are caught and then marked in some way.
2. They’re then released back into the community.
3. After a specified length of time, the community is revisited
and the same number or individuals is caught again.
4. The number of marked individuals is counted.
The population size is calculated:
Estimated pop. = Total number of individuals
size
x Total number of individual
in the first sample
in the seconds sample
Number of marked individuals recaptured
Measuring Biodiversity - animals
Give brief descriptions of the methods of collecting
animals
 Sweep netting
 Tree beating
 Pooting
 Pitfall trap
 Tullgren funnel
 Light trap
 Kick sampling
Measuring Biodiversity: Animals
 Nets sweeping the ground
 Trees: knock branches with
stick and collect in plastic
on floor
Measuring Biodiversity: Animals
 Pitfall trap collects small soil
animals
 Tullgren funnel collects small
animals from leaf litter
 Light trap collects flying
insects
Measuring Species Richness
 Number of species present in habitat
 Qualitative survey
 Use sampling techniques best suited to habitat (e.g.
transect, quadrats)
 Walk round see if any species you’ve missed
Measuring Species Evenness
 Measure of abundance of individuals in each



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species
Quantitative surveying
Plants - use sampling techniques measuring
species per unit area or percentage ground cover
With large animals use observation
With small animals can use mark and recapture
method
Species richness and evenness
Habitat X
Habitat Y
Species 1
28
15
Species 2
2
15
Total
30
30
What can you deduce about species richness and evenness
for these 2 habitats?
•Species richness (2) is the same for both habitats
• Habitat Y has a greater species evenness
Measuring abiotic factors
Abiotic factors are the non-living conditions in a habitat
Abiotic factor
Sensor used
Example unit of
measurement
Wind speed
Anemometer
ms-1
Light intensity
Light meter
lx
Relative humidity
Humidity sensor
mgdm-3
pH
pH probe
pH
Temperature
Temperature probe
oC
Oxygen content in
water
Dissolved oxygen probe
mgdm-3
Measuring abiotic factors
Advantages of using sensors:
 Rapid changes can be detected
 Human error reduced
 High degree of precision
 Data can be stored and tracked on a computer
Task
 Complete the task Belt transect in a National Park for
homework