Ecology Calculations Dominican College, Griffith Ave

Ecology CalculationsEcology Calculations

Dominican College, Griffith AveDominican College, Griffith Ave

Quantitative AnalysisQuantitative Analysis

Numbers!!Numbers!!

Our HabitatOur Habitat

The Rocky SeashoreThe 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


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


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

EquipmentEquipment

• Mammal trap

• Pitfall trap• Insect net• Pooter

• Quadrat• Grid Quadrat

Method 1 – Method 1 – Capture/RecaptureCapture/Recapture

Used for AnimalsUsed for Animals

Capture/Recapture Cntd.Capture/Recapture Cntd.The Pitfall TrapThe 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.Capture/Recapture Cntd.The Pitfall TrapThe 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.Capture/Recapture Cntd.The Pitfall trapThe 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


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)


• 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


Calculations:

Total Population =

No. caught on 1st visit x No. caught on 2nd visit

No. of marked animals recaptured on the 2nd visit


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 Method 2 – Percentage FrequencyFrequency

Percentage FrequencyPercentage Frequency

Throw Ten Quadrats (1m X 1m)

FREQUENTLY MARKS COVER NUMBERS


If Present, Tick Yes

• If Absent, Tick No

• Calculate the fraction, then the percentage





Calculations:Sample Answers For Bladder Wrack• Found in 7 out of 10 quadrats• Hence 70 % Frequency


Method 3 – Percentage Method 3 – Percentage CoverCover

Percentage CoverPercentage 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





• 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





Calculations:Sample Answers For Bladder Wrack• Found in 34 ‘hits’ from a potential of 100• Hence 34 % Cover


Method 4 – Population Method 4 – Population Density Density

Population DensityPopulation Density

The number of each plant in each quadrat is counted and recorded and then extrapolated as per the whole habitat



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 Method 5 – Distribution

A)A) -- DistributionDistribution

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)B) -- Population DistributionPopulation 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


We use a belt transect:0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 …………… 50

To Lower Shore


• Take the populations of the organisms chosen

• Graph these


Section 2 – Calculation ErrorsSection 2 – Calculation Errors

Calculation ErrorsCalculation 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


The use of a quadrat that ISN’T 1m2




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 No.

1 2 3 4 5 6 7 8 9 10

No. Hits for Bladder Wrack

11 5 0 0 0 23 21 2 9 9


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= 32%

250


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 No.

1 2 3 4 5 6 7 8 9 10

No. Hits 11 5 0 0 0 23 21 2 9 9



Find the population per 1m2 and extrapolate



80 in 10 quadrats, so the number of Bladder wracks per 1m2 is



NOT 8 per 1m2

Because the 10 quadrats do not amount to 10m2

Because each quadrat is only 0.25m2



80 in 10 quadrats (0.25 m2),

So, 80 in 25m2

So the number per 1m2 is 3.2


EG. 2 - Population Density:But we’re not finished yet!!

• 3.2 per 1m2

• (3.2 X 3600) in 3600m2

• Answer = 11520 in habitat

Documents

Ecology Calculations Dominican College, Griffith Ave