sampling techniques and population growth

8/13/2019 Sampling Techniques and Population Growth

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Sampling techniquesand population growth


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What is sampling Taking a small part of the ecosystem to

estimate population size

Taking more and/or larger samples willgive you a better estimate than less

and/or smaller samples


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Types of samplingType of

sampling

What is it? When is it

used?

Benefits of

technique

Drawbacks of

technique

Quadrats Squares of adetermined

size, placed on

the ground to

be sampled

When the

organisms

you are

counting are

sessile

(immobile)

Simple, can easily

sample many

times. Good for flat

ground

Difficult on

rocky/uneven areas.

Cannot sample fast

moving organisms

Transect Line or striplaid across

area to be

studied.

Organisms

that lay along

strip arecounted

Measuring

change over

time of

topography

From the air

Under the sea

Simple. May be

used to sample

different parts of

the ecosystem.

Shows change in

land as well as

organismabundance.

Can be time

consuming. A width

around the transect

line must be adhered

to. Not good for fast-

moving organisms

Mark and

recapture

Members of

population are

caught,

marked and

released

To count

difficult to see

or fast moving

animals

Can be used for

fast moving

animals.

Very time consuming.

Important to lay traps

that will not just catch

the sick/weak


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Examples of quadrat use http://livingprairie.ca/livinglandscape/qua

drats/quadrat.html?q=1

More than one quadrat is

being used at once to sample

an area of this cave.

Quadrats can be

used under water to

sample the bottom

of the sea/pond etc
http://livingprairie.ca/livinglandscape/quadrats/quadrat.html?q=1http://livingprairie.ca/livinglandscape/quadrats/quadrat.html?q=1http://livingprairie.ca/livinglandscape/quadrats/quadrat.html?q=1http://livingprairie.ca/livinglandscape/quadrats/quadrat.html?q=1


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Examples of transect use

Quadrats and transects can be

used together to create an

overall idea of the ecosystem

A typical transect diagram shows the

topography of the land and labels features. It

also notes the organism types along the line


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Examples of mark andrecaptureCicada marked with white paint. This

study was not a study over time. They

used this technique to simply estimate the

abundance of cicadas in the area

This mark recapture study of

Bull Trout was repeated each

year to show the change over

time of abundance of Bull Trout

in this area


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Population dynamics The study of change in population size

over time.

Requires more than one sampling event


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Factors affectingpopulation size Birth rate (eg. 55 per year)

Death rate (eg. 104 per year)

Migration rate

includes immigration (movinginto the area eg. 20 per year) and emigration

(moving out of the area eg. 31 per year)

Growth rate = (births + immigration) (deaths + emigration) per unit time [eg. A year]

(55 + 20) - (104 + 31)- 60


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Population grown Positive result = population growth

Zero result = zero population growth

Closed population = no migration (maybe

due to isolation)

Open population = migration occurs

sampling techniques and population growth

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