Mayfly distribution coursework

In this investigation you are looking at the distribution of two families of mayfly in relation to current. Look that the sheet on swimmers and clingers for the general idea of how freshwater invertebrates are adapted to current.

Heptageniidae are flattened and their adaptations include ‘hiding ‘in the boundary layer on the surface of rocks (see swimmers and clingers sheet), claws on their legs and the orientation of the legs. One species has the first gill modified as a sucker.

Baetidae are active swimming mayflies. They have a streamlined teardrop shaped body, they sit up in the current on their legs and use their tails to orientate themselves into the current.

Freshwater invertebrates are usually samples by a technique known as kick sampling. This has to be carried out for a standard length of time and the effort also standardised.

Upland steams usually have a riffle and pool sequence. The speed the flow varies. In this investigation you are going to investigate the distribution of these two families of mayfly in relation to current.

You need to consider.

• How you are going to measure the abundance of the mayflies.
• How you are going to measure the speed of the current.
• How you are going to select your sample sites.
• What other factors might affect the distribution of the mayfly species.
• As these other factors cannot be controlled how can they can be measured to see if they too are having an effect.
• How you are going to treat the data statistically. There are two possible approaches, a correlation analysis or an analysis that compares the means of two samples (see flow diagram on a separate sheet). You need to think carefully about how you are going to analyse the data when designing the experiment.

At this stage you need to produce a detailed plan of your investigation. You also need to state which statistical test(s) you are going to carry out and why made that choice.