1. Sampling techniques and population growth

2. What is sampling?
Taking a small part of the ecosystem to estimate population size
Taking more and/or larger samples will give you a better estimate than less and/or smaller samples

3. Types of sampling Type of sampling What is it? When is it used?
Benefits of technique
Drawbacks of technique
Quadrats
Squares of a determined 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 strip laid across area to be studied. Organisms that lay along strip are counted
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 organism abundance.
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

4. Examples of quadrat use
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

5. Examples of transect use
A typical transect diagram shows the topography of the land and labels features. It also notes the organism types along the line
Quadrats and transects can be used together to create an overall idea of the ecosystem

6. Examples of mark and recapture
Cicada 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

7. Population dynamics The study of change in population size over time.
Requires more than one sampling event

8. Factors affecting population size
Birth rate (eg. 55 per year)
Death rate (eg. 104 per year)
Migration rate – includes immigration (moving into 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]
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9. Population grown Positive result = population growth
Zero result = zero population growth
Closed population = no migration (maybe due to isolation)
Open population = migration occurs

10. Activities
Glossary: sampling, quadrat, transect, mark recapture, population dynamics, birth rate, death rate, migration rate, closed population, open population, zero population growth
Quick Check pg 487
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