Investigating Populations: Quadrats/Transects Flashcards
What is abundance?
Abundance is the number of individuals of a species in a given area
What are the two sampling techniques used to study habitats?
Random sampling and systematic sampling
When random sampling is used, what mechanism is used to study the habitat?
When systematic sampling is used, what mechanism is used to study the habitat?
When random sampling is used, a frame quadrat or point quadrat is used
When systematic sampling is used, a belt transect is used
What is a point quadrat?
A point quadrat consists of a horizontal bar supported by two two legs. At set intervals,along the horizontal bar are ten holes, through which a long pin is dropped. Each species touching the pin is recorded
What is a frame quadrat?
A frame quadrat is a square frame divided by sting or wire into equally sized subdivisions. It is a more suitable option due to its compact and transportation abilities
What are the three factors that affect the use of quadrats?
1) The size of the quadrat used
2) The number of small quadrats that need to be recorded within a study area
3) The position of each quadrat within a study area
How does the size of the quadrat used affect the use of a quadrat?
Depending on the size of the plants/animals being counted and how they are distributed within an area, different quadrat sizes will be used
Larger species will use larger quadrats
A large number of small quadrats will produce more representative results than a small number of large quadrats
How does the number of small quadrats that need to be recorded within a study area affect the use of a quadrat?
The more small quadrats used within a study area, the more reliable the results produced are. The balance between reliability of results and time available needs to be maintained. The more species being studied, the greater the number of quadrats required to produce more reliable results for a valid conclusion
How does the position of each quadrat within the study area affect the use of a quadrat?
To produce statistically significant results, random sampling must be used
How is sampling at random conducted?
1) Two long tape measures are laid out at right angles, along two sides of the study area
2) A series of coordinates are obtained by using random numbers taken from a table or generated by a computer
3) A quadrat is then placed at the intersection of each pair of coordinates and the species within it are recorded
What are the two ways abundance of plant, non - motile or slow moving animals measured?
Abundance is measured through frequency and percentage cover
What is frequency?
What is a strength of using frequency?
What is a limitation of using frequency
Frequency is the likelihood that a species will appear in a quadrat.
Frequency is useful when it is hard to count a species, providing a quick idea of present species and determining their general distribution within an area
Frequency does not provide information on the density and detailed distribution of a species
What is percentage cover?
What is a strength of using percentage cover?
What is a limitation of using percentage cover?
Percentage cover is an estimate of the area within a quadrat that a particular plant species covers
Percentage cover is useful for species that are particularly abundant or difficult to count, data can be collected rapidly and individual plants do not need to be counted
Percentage cover is less useful where organisms occur in several overlapping layers
