Investigating Populations Flashcards
What is the abundance
The number of individuals of a species In a given space
What are the two types of quadrant
A point quadrant
A frame quadrat
What’s a point quadrat
Consists of a horizontal bar supported by two legs. A set intervals along the horizontal bar are ten holes, through each of which a long pin may be dropped. Each species that touches the pin is recorded
What’s a frame quadrat
A square frame divide by string or wire into equally sized subdivisions. The quadrat is placed in different locations within the area being studied. What he abundance of each species within the quadrat is recorded
It is often designed so that it can be folded to make it more compact for storage and transport
What are the three factors to consider when using quadrats
Size of the Quadrat to use- will depend on the size of the plays or animals being counted and how they are distributed within the area
The number of sample quadrat s to record within the study - the larger the number of samples the more reliable the results will be.
The position of each quadrat within the study area - to produce statistically significant results a technique called random sampling must be used
How do we do random sampling
- Lay out two long tape measures at right angles, along two sides of the study area
- Obtain a series of coordinates using a random numbers from a generator
- Place a quadrat at the intersection of each pair of coordinates and record the species within it
How do we do systemic sampling along belt transects
- Stretching a string or take across the ground Ina straight line
- A frame quadrat is laid down alongside the line and the species within it recorded
- It’s then moved it’s own length along the line and the process is repeated
- This gives a record of species in a continuous belt
What is frequency
It’s the likelihood of a particular species occurring in an quadrat
Gives a quick idea of the species present and their general distribution within an area (e.g. grass)
What is percentage cover
Is an estimate of the area within a quadrat that a particular species covers
Useful when a species is difficult to count
It is quick however doesn’t count overlapping
What is necessary to obtain reliable results
Large sample size - many quadrats are used and the mean of all the samples is obtained
The larger the number of samples, the more representative of the community as a whole will be the results
What’s the formula for estimated population size in mark release recapture
Estimated population size = total no. Of individuals caught in 1st sample x total no. Of individuals caught in 2nd sample / number of marked individuals in 2nd sample
Describe the mark release recapture test
- Capture a sample of species using an appropriate technique
- Mark them in a harmless way
- Release them back into their habitat
- Wait a week, then take a second sample from the same population
- Count how many of the second sample are marked. You can use the equation to estimate population size
What assumptions does the recapture release technique rely on
The marked sample has had enough time and opportunity to mix and in with the population
Population has a definite boundary so that there is no immigration into or out emigration out of the population
The marking hasn’t affected the individuals chance of survival and the marking itself is still visible
No changes in population sizes due to births, deaths and migration during the period of study
