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 ECOLOGY : FIELD TRIP TO CORREZE

COLLECTING ABIOTIC DATA ALONG A TRANSECT

In ecology it is important to collect information on the various abiotic factors that will influence the living organisms being studied.

First you must decide on which factors are the most significant. There is no point in measuring everything. You may also be limited by the instruments at your disposal.

Materials

Tape measure or string marked in metres

TI Graphing Calculator with DataMate program installed
CBL2 interface

Any of the following probes:

  • Temperature probe
  • Light probe
  • Humidity probe
  • Conductivity probe
  • Flow rate probe

Starting the DataMate Program and setting up

  1. Use the following steps to start the DataMate program on your calculator:
    Press , then press the calculator key for the number that precedes DATAMATE. Press . (For T1 73, 82 and 83 press ). An introductory screen will appear, followed by the main screen.
  2. Plug one of the probes into channel CH 1 on the CBL2 interface.
  3. Start the DataMate program. Press to reset the program. DataMate will detect the probe and display the current sensor reading.

 

  1. Press : SETUP and using the cursor buttons, or (be patient it’s a bit sluggish!)
    Select MODE press (scroll up to get to the last item on the menu).

  1. In the SELECT MODE menu press : EVENTS WITH ENTRY.
  2. Press : OK to return to the main screen.

Collecting data
  1. Set the probe in position for measurement, take care that you are not influencing the measurement.

  2. Select : START to begin data collection. Press to record your measurement. Then enter the distance (0m at the beginning of the transect). Press again.
  3. Move to the next position and press . Then type in the distance (e.g. 2m). Press again and you will find the calculator producing an autoscaled scattergram of the measurements.

  1. Continue to take measurements at intervals. They do not have to be regular interval, especially where there is a significant change in the environment (e.g. passing from shade into sunlight)
  2. You may stop data collection at any time by pressing the key. Remember for line graphs you should have at least 5 data points (10 is even better). When you stop data collection you well see the complete auto-scaled graph.
  3. To store your data, if you are satisfied with it, return to the main screen by pressing .
    Press 5: TOOLS, then select 1: STORE LATEST DATA RUN. This stores the data in lists. In this case distance in L1 and the abiotic factor (e.g. soil temperature). will be in L2 with a copy of it in L3.
    To check this press : QUIT, then , then and then select 1:EDIT…You will see a spread sheet with your data in it in L1, L2 (and L3).

Collecting data from more than one probe

You may plug up to three probes in channels 1, 2 and 3 (e.g. temperature, humidity and light). However, you will not see a graph appear as you carry out Events with Entry. Otherwise the procedure is the same.

At the end to see a graph of data from each channel you will have to select the channel you want.

You may even plot the data of one channel against another. This is especially useful if you want to see if there is a relationship between the abiotic factors. (Link to Comparing the Relationship between two Abiotic Factors).

Analysing the data

  1. Describe the overall shape of the line set out by the scattered points on the graph. (Is it linear or curved? Which way does the trend go?)
  2. Use the cursor keys or to examine the data points at each of the distances along the transect.
    Does the data follow the trend you expected?
  3. If you find a difference between your measurements and those expected, there are two possibilities, either there is an error in the experiment or your prediction is incorrect.
    Search for possible sources of error. List as many sources of error as you can find.
  4. If there is time, repeat the investigation trying to eliminate or minimise, as much as possible, the errors in the experiment.
MOST IMPORTANT Storing your data in the calculator’s archive

If you do not do this your data will be lost. The next time you use a spread sheet the data in L1, L2 etc. will get compressed.

Archiving frees up RAM memory so that you can continue recording more data. Archiving data will remove it from the RAM memory but it will not stop it from being over-written when new data is recorded. It needs to be renamed.

To rename a list of data (e.g. L1)

  1. Select the list to be stored by pressing then then
  2. Open the LIST menu by pressing then LIST and select OPS using the cursor
     
  3. Descend the menu using the cursor to B: L press and type in a code name for the list. It must start with a letter so press the green key and chose a letter. Your list name can consist of one letter and four figures (try today’s date)

To archive or un-archive a list variable (L1) using a Memory Management editor:
  1. Press then MEM to display the MEMORY menu.
  2. Select 2:Mem Mgmt/Del... to display the MEMORY MANAGEMENT/DELETE menu.
  3. Select 4:List... to display the LIST menu.
  4. Press to archive L1. An asterisk (*) will appear to the left of L1 to indicate it is an archived variable.
    To unarchive a variable in this screen, put the cursor next to the archived variable and press     . The asterisk will disappear.
  5. Press then QUIT to leave the LIST menu.

© Paul Billiet 2004