Transcript Ecology Calculations

Ecology Calculations
Dominican College, Griffith Ave
Quantitative Analysis
Numbers!!
Our Habitat
The Rocky Seashore
The Rocky Seashore
Description:
Sitting on the boulders facing the sea, we
mark off a section of the seashore 20m
wide and 50m towards the sea
The total area is 1000m2
The Rocky Seashore
Making a Map:
On a sheet draw a rectangular box, 20cm
wide by 50cm long
This represents your habitat at a ratio of
1cm:1m
Put in the direction
The Rocky Seashore
Making a Map:
Put in main parts of what you see
These include rock pools, large
boulders/rocks, large quantities of named
algae…..
MAKE A KEY
Equipment
•
•
•
•
Mammal trap
Pitfall trap
Insect net
Pooter
• Quadrat
• Grid Quadrat
Method 1 –
Capture/Recapture
Used for Animals
Capture/Recapture Cntd.
The Pitfall Trap
As we are on a rocky seashore, the type of
animal I have selected is the rough
periwinkle which is found on the upper
seashore.
The upper seashore will not flood (except
during a storm/lunar high tide)
Capture/Recapture Cntd.
The Pitfall Trap
Dig a hole and insert a jar
The jar should be at sand level
Put a flat stone over the lid of the jar
Using two pebbles, ensure that the flat
stone has a gap to allow rough periwinkles
fall into the jar
Capture/Recapture Cntd.
The Pitfall trap
Set up a number of Pitfall Traps on the
upper seashore
Leave for 24 hours
Inspect the jars after 24 hours and count
and mark the rough periwinkles
Capture/Recapture Cntd.
The Pitfall trap
Marking the Rough Periwinkles:
• Mark with a non-toxic paint (Not to harm
the animal)
• Mark on the underside (To protect it from
predators)
• Mark with a temporary paint (So that it
clears quickly to prevent predation)
Capture/Recapture Cntd.
The Pitfall trap
Release the rough periwinkles in the
vicinity and re-set the pitfall traps.
After another 24 hours, check the traps
and count the number of rough
periwinkles, noting also the number which
have a paint mark on them
Capture/Recapture Cntd.
The Pitfall trap
Calculations:
Total Population
=
No. caught on 1st visit x No. caught on 2nd visit
No. of marked animals recaptured on the 2nd visit
Capture/Recapture Cntd.
The Pitfall trap
Calculations:
Sample Answers
• No. caught and marked on 1st visit = 20
• No. caught on 2nd visit
=15
• No. of marked animals caught on 2nd visit = 5
• Total population = 20 x 15 = 60
5
Method 2 – Percentage
Frequency
Percentage Frequency
Throw Ten Quadrats (1m X 1m)
FREQUENTLY MARKS COVER NUMBERS
Percentage Frequency
If Present, Tick Yes
• If Absent, Tick No
• Calculate the fraction, then the percentage
FREQUENTLY MARKS COVER NUMBERS
Percentage Frequency
FREQUENTLY MARKS COVER NUMBERS
Percentage Frequency
Calculations:
Sample Answers For Bladder Wrack
• Found in 7 out of 10 quadrats
• Hence 70 % Frequency
FREQUENTLY MARKS COVER NUMBERS
Method 3 – Percentage
Cover
Percentage Cover
• A grid quadrat is used.
• This is 1m X 1m divided into 100 squares
which is 1m2 in area
• Some quadrats may be 0.5m X 0.5m divided
into 25 squares, which is 0.25m2
• Great care must be taken to read any data that
you may have to use in a question
FREQUENTLY MARKS COVER NUMBERS
Percentage Cover
FREQUENTLY MARKS COVER NUMBERS
Percentage Cover
• We select 10 ‘hits’
on every quadrat
• A pen is placed at
this point and if it
touches an
organism it is
recorded as a “hit”
for that organism
FREQUENTLY MARKS COVER NUMBERS
Percentage Cover
FREQUENTLY MARKS COVER NUMBERS
Percentage Cover
Calculations:
Sample Answers For Bladder Wrack
• Found in 34 ‘hits’ from a potential of 100
• Hence 34 % Cover
FREQUENTLY MARKS COVER NUMBERS
Method 4 – Population
Density
Population Density
The number of each plant in each quadrat is
counted and recorded and then
extrapolated as per the whole habitat
Population Density
Population Density
We found that there were 1.9 bladder
wracks per 1m2
As there is 1000m2 in the habitat, we can
find the density by saying:
If we have 1.9 bladder wracks per 1m2,
then we should have 1900 per 1000m2
Method 5 – Distribution
A) -
Distribution
We use a line transect:
Unfurl a 50m rope marked at 1m intervals
from the upper shore to the lower shore
Note the organism that ‘touches’ the ‘mark’
B) -
Population Distribution
We use a belt transect:
Unfurl two 50m ropes marked at 1m
intervals from the upper shore to the lower
shore, with a separation of exactly 1m2
In essence this is now 50 X 1m2 quadrats
Name these, 1 to 50
B) -
Population Distribution
We use a belt transect:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 ……………
To Lower
Shore
50
B) -
Population Distribution
Take the populations of the organisms
chosen
Graph these
B) -
Population Distribution
Section 2 – Calculation Errors
Calculation Errors
No. caught on 1st visit x No. caught on 2nd visit
No. of marked animals recaptured on the 2nd visit
Getting the formula incorrect
Calculation Errors
The use of a quadrat that ISN’T 1m2
The use of a quadrat that ISN’T 1m2
The use of a quadrat that ISN’T 1m2
Calculation Errors
EG. 1 - Percentage Cover:
A grid quadrat 0.5m X 0.5m, was thrown
10 times in a habitat of 3600m2.
25 hits are taken in each quadrat
Quadrat 1 2
No.
No. Hits
11 5
for Bladder
Wrack
3
4
5
6
7
8
0
0
0
23 21 2
9 10
9 9
Calculation Errors
EG. 1 - Percentage Cover Cntd.
How many ‘hits’ did you get?.................80
How many potential ‘hits’ were there…250
As a fraction, this is 80
250
As a Percentage, 80 * 100
250
=
32%
Calculation Errors
EG. 2 - Population Density:
A Grid quadrat 0.5m X 0.5m, was thrown
10 times in a habitat of 3600m2.
25 hits are taken in each quadrat
Quadrat 1 2
No.
No. Hits 11 5
3
4
5
6
7
8
0
0
0
23 21 2
9 10
9 9
Calculation Errors
EG. 2 - Population Density:
Find the population per 1m2 and
extrapolate
Calculation Errors
EG. 2 - Population Density:
80 in 10 quadrats, so the number of
Bladder wracks per 1m2 is
Calculation Errors
EG. 2 - Population Density:
NOT 8 per 1m2
Because the 10 quadrats do not amount to
10m2
Because each quadrat is only 0.25m2
Calculation Errors
EG. 2 - Population Density:
80 in 10 quadrats (0.25 m2),
So, 80 in 25m2
So the number per 1m2 is 3.2
Calculation Errors
EG. 2 - Population Density:
But we’re not finished yet!!
• 3.2 per 1m2
• (3.2 X 3600) in 3600m2
• Answer = 11520 in habitat