Download Biodiversity

Biodiversity
Recall the definition of SPECIES from the
topic Classification
Write the key ideas in bullet points on white
boards
OBJECTIVES
• To define key terms
• To explain how biodiversity can be considered
at different levels
• To discuss current estimates of global
biodiversity
HABITAT
Write the definition of habitat onto one of your
glossary cards from the last lesson
Which has a greater biodiversity?
Low diversity
High diversity
Definition of biodiversity
from an OCR mark scheme
• The existence of many different species
– Interspecific variation
• with a wide range of different alleles
– Genetic intraspecific variation
• that live in many different habitats/ ecosystems
– Variation in habitats
(in purple: different levels of biodiversity)
Tropical rainforests
These ecosystems have
the highest biodiversity
of any ecosystem on the
planet.
Estimating global biodiversity
• Catalogue of life by
– Species 2000
– Integrated Taxonomic Information System
– All Species Foundation
Estimating global biodiversity
• Not accurate because
–
–
–
–
–
May not have found all
New species being found all the time
Continuing evolution and speciation
Species becoming endangered & extinct
Habitats which are difficult to access
Sampling
OBJECTIVES
• Explain the importance of sampling
• Describe how random samples of plants and
animals can be taken
Theory of sampling
If we want to work out the biodiversity of an
area then we need to find out how many of
each type of organism there are present
This can be a bit of a challenge if you bear in
mind that there might be hundreds of
thousands of mites per square metre, not to
mention the millions of bacteria
In practice
Obviously, it’s not practical to count everything
so we take a sample to estimate the
abundance of each organism present
Sampling
• Study a small section of the habitat
• Multiply the number of individuals of each
species to estimate the number in the whole
habitat
• gives us quantitative data to calculate
biodiversity.
• more valuable than qualitative data, which
merely tells us what is present
Randomness
To remove any influence of bias
Systematic:
Taking samples at regular intervals
Random
Using random number tables to plot coordinates
within a habitat.
– with tape measures or,
– if the area is large, GPS coordinates
How should your quadrat be placed
in the study area?
RANDOM
SYSTEMATIC
For example
Random sampling of plant
populations can be done using
a quadrat by marking out 2
axis with a tape measure then
using random numbers to
chose which coordinates to
sample at.
Disadvantage: could miss trends
as only gives overall data
Using a random number table
Click here to see
a random
number table
How many quadrats?
Running mean – gaining a representative sample
Quadrat no.
No. of different
species
Running mean
no. sp/no. quadrats
1
2
3
4
10
20
9
17
10
15
13
14
5
6
12
10
13.6
13
7
8
9
21
15
13
14.1
14.3
14.2
10
14
14.2
The number of
quadrats needed in
this case = 7
Making notes
• Make BRIEF bullet point notes on how plants
are sampled from page 195
• And a spider diagram on sampling animals
pages 196-197
• The next slides will be shown at the end of the
session to confirm if your notes are accurate
Sampling plants
• Using random quadrats
• Using a transect
Using quadrats
•
•
•
•
Usually 50 cm to 1m2
Generate pairs of random numbers
Identify the plants
Measure abundance
– AFCOR scale (not quantitative)
• (abundant, common, frequent, obvious, rare)
– Estimate percentage cover with
• gridded quadrat
• Point frame
Measuring abundance
• AFCOR scale (not quantitative)
– (abundant, common, frequent, obvious, rare)
• Estimate percentage cover with
– gridded quadrat
– Point frame with 10 needles
• Used 10x in each quadrat
• Each plant touching needle wil have 1% cover
• Can have several plants & bare ground touching needle
Using a transect
• A line of rope or tape measure across a
habitat
• For a large habitat
• Methods:
– Interrupted line transect
• Record plants touching line at set intervals
– Interrupted line transect
• Use quadrat at set inervals
– Continuous belt transect
• Move a quadrat along the line
Sampling animals
• Large animals
– observe NOT trap
– Look for signs
• Droppings
• Undigested food
• Burrows
• Smaller animals
– Can be trapped
Trapping animals
• Sweep netting – for low vegetation
– Use with pooters
• Tree beating
• Pitfall traps
– With water or scrunched up paper
– Sheltered from rain
• Tullgren funnel
– Light drives animal downwards through different-sized
meshes
• UV light trap at night
– With collecting vessel containing alcohol
Homework
Bullet point 2 methods
Method 1) How you would use a square quadrat and random
coordinates to sample 2 areas of the school field, 1 in light
and 1 in shade, to see which had more daisies. You may be
able to actually do this if the weather is OK!
Method 2) How you would use a point quadrat and transect to
see if the percentage cover of daisies increased or decreased,
with distance from a hedge.
Alternative homework
• Answer Qs:
– 3 to 5 on Activity Sheet 30
– 1 to 5 on Activity Sheet 31
Measuring Biodiversity
OBJECTIVES
• Describe how species richness and evenness
can be measured
• Use Simpson’s Index of Diversity
• Outline the significance of this Index
Measuring biodiversity
Species richness = the number of species present
- qualitative survey
Species evenness = a measure not just of the number of species
present but of the relative abundance of each.
- quantitative survey
• Look at Table 1 on page 198
• Compare the species richness and species evenness
Surveying frequency of plants
• Counting number of plants per unit area
– For larger plants
• Estimating percentage cover
– For smaller plants like grasses and herbs
Recording
percentage
cover
• Look down on the quadrat from above and
estimate the percentage cover occupied by each
species (e.g. species A - D).
• Species often overlap and there may be several
different vertical layers.
• Percentage cover may therefore add up to well
over 100% for an individual quadrat.
Measuring density of small animals
• Large animals - observe
• Small animals
– Using the Mark-Recapture technique
• Soil animals
– Take soil sample and sift through
• Aquatic animals
– Use net
– Sift through mud
Mark-and-recapture
• Trap a sample of animals
– Count = C1
• Mark them without causing harm, release
• Re- capture
– Count = C2
• Those already marked in the re-capture
– Count = C3
Calculating the total population
Can you think of how you can use these counts
to estimate the total population?
Total population = (C1 x C2)/C3
Simpson’s Diversity Index
• Takes into account species richness and
evenness
• Copy the formula from page 199, indicating
what each part of the formula means
SDI = 1 – [∑ n 2]
N
Significance of the Index
• High value
– Diverse habitat
– A small change may affect only one or a few
species
– the effect on habitat is likely to be small
• Low value
– A habitat dominated by a few species
– A small change affecting dominant species could
damage or destroy the habitat