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Biology graph - dot to dot?

Discussion in 'Science' started by pookyrobin, May 21, 2010.

  1. Dot to dot is the term used but it is actually centre of the cross to centre of the cross. didn't mean to confuse.
    As mentioned previously the guidance to plot dot to dot (centre of the cross to centre of the cross being a more cumbersome albeit more accurate phrase) is from the Institute of Biology book Biological Nomenclature
     
    samlloyd73 likes this.
  2. This whole issue of dot-to-dot vs. LOBF was raised in a department meeting at my school. Our Biology teacher said that when he went to a training day run by examiners (CIE Board) he was also told to do dot-to-dot for all of the same reasons given by previous posters.
    I was surprised about this but now we all teach this to the students that when they do Bio questions they should do dot-to dot and for all other questions they should do LOBF (all where appropriate, of course). It was a little bit confusing at first but they got used to it (a bit like when we told them that in Science lines could be curves (of best fit) unlike in Maths).

     
  3. ScienceGuy

    ScienceGuy Established commenter

    I have had the delight of teaching some pupils for both AS biology and AS chemistry this year (both OCR spec A). Explaining to them that in their Biology coursework tasks they should draw a dot to dot graph (having previously been banned from doing so at GCSE) but should continue to draw lines of best fit in chemistry was fun.
    The precise guidance for biology is
    "Straight lines should join points. A smooth curve is only drawn if there is reason to believe that intermediate values fall on the curve."
     
  4. lunarita

    lunarita Senior commenter

    But surely there is often reason to believe that?
    Are dot-to-dots the norm because it's easier to have a general rule than for pupils to have to decide each time?
     
  5. ScienceGuy

    ScienceGuy Established commenter

    Part of what we teach the pupils also comes down to exam board requirements. For OCR, it is very hard to get all the marks for graphs with a line of best fit. Consequently we teach the pupils the method which will allow them to achieve the most marks. Whether this is desirable or not is another discussion!
     
  6. Couldn't remember at all what I did at school in the old days before the subject science was invented (I really am very old) and the National Curriculum and its statements for SC1 etc. I don't have any of my old books but have rooted out reprints from my previous life in research. Dot to dot! European Journal of Biochemstry circa 1985 (told you I was old). So i reckon biologists always did dot to dot until the invention of science when physicists decided the rules for SC1. There must be some people that remember the old 10 point scale. It was when I first went into teaching; my published papers scored around Level 4.

     
  7. I agree that in many cases it should be oint to point. In Cambridge IGCSE the recommendation is dot to dot (actualy cross to cross), for the reasons mentioned above. For my Pharmocokinetics module for my Masters degree ot was also point to point. Certainly no free-hand trend lines should ever be drawn for linear relationships, instead the equation should be used.However, for curved line graphs I always tell my students to do dot to dot then discuss the overall trend, even draw the trend-line in with a dash.
    So for those immediately disparaging the teacher referred in your original post: oop!

     
  8. OK. I guess this would have helped. I looked up the Report on the Examination for the first set of ISAs on the AQA site.
    http://web.aqa.org.uk/qual/newgcses/science/new/bio_materials.php?id=03&prev=03
    "In GCSE Science AQA has always asked centres to instruct candidates to use a line of best fit
    rather than dot to dot lines. The new ISAs are no different.
    However, the Institute of Biology expresses the view that in certain circumstances a dot-to-dot
    line is the most appropriate. Candidates should not be penalised if, in the professional opinion
    of the teacher and in that particular case, the joining of dot-to-dot is appropriate in biological
    experiments
    [my italics]. If this is the case then the work should be annotated to that effect."
     
  9. lunarita

    lunarita Senior commenter

    Interesting. So, if they draw a dot to dot when it's apporopriate, great.
    But what about the many occasions whenit isn't? I take it they're not penalised then either?
     
  10. As a moderator when marking at gcse its classed as a no no but at alevel it is allowed in line with institute of biology guidelines. generally its a curve of best fit.
     
  11. If I understand the report I quoted above (three posts back); at GCSE it's ok to do dot to dot for biology results if appropriate. Not physics, not chemistry. What an appropriate case is, I'll leave to the biologists.[​IMG]
     
  12. not according to edexcel this year I argued this point in line with a level marking but they said definately a no for gcse.
     
  13. lunarita

    lunarita Senior commenter

    I have to say, this discussion hasn't done much for inter-disciplinary harmony in our department today.
     
  14. Sorry. [​IMG] It used to be scientists vs mathematicians that caused the problems with graphs and LBF. We have different depts so do our own stuff. I guess it the problems caused by one-size-fits-all = "Science" = chemistry+biology+physics.
     
  15. lunarita

    lunarita Senior commenter

    Don'tworry. We physicists tend to be a bit arrogant and scornful of our <strike>stamp collector</strike> biologist colleages anyway.
     
  16. bogstandardcomp

    bogstandardcomp New commenter

    I had this same discussion witth the physicists in our dept., The example that came to mind on that occasion was in ecology. If you plotted the distrubition or nos of a particular plant species along a transect you are very unlikely to get a straight line or any type of curve. Here is an elk distribution example I just googled. The relationship/pattern is quite easy to see.
    http://www.google.co.uk/imgres?imgurl=http://www.nps.gov/archive/crla/elk/fig1.jpg&imgrefurl=http://www.nps.gov/archive/crla/elk/elk3.htm&usg=__CWOfD0kql-WCie3FX9XEEPskoxw=&h=373&w=500&sz=14&hl=en&start=9&um=1&itbs=1&tbnid=uyb6mhGQWLMJnM:&tbnh=97&tbnw=130&prev=/images%3Fq%3Decology%2Btransect%2Bchart%26um%3D1%26hl%3Den%26sa%3DN%26tbs%3Disch:1

    As for GCSE, just tell the kids what the exam board wants.
     
  17. As always [​IMG]
     
  18. Hmm. Got me clambering on a chair to reach the highest shelf in my study where all my University notes are collecting dust. Digging through the yellowed, fragile pages I found many examples of graphs, including transect data, with all the points plotted but with a LOBF showing the trend. These were written up in the second half of that wondrous decade known for ever as "the Sixties". 1985? Wet behind the ears, new fangled ideas!
    Seriously, when trying to help our pupils scrape every last possible mark lest they fall below a grade boundary by just one, it is becoming rather confusing!
     
  19. Mangleworzle

    Mangleworzle Star commenter

    I dimly remember an AQA training session about ISA's where we told that dot-to-dot was acceptable.
     
  20. Agree with above; OCR are quite happy with dot to dot on biology graphs.
    This makes sense to me:
    When to connect the dots? If each point in the series is obtained from the same source and is dependent on the previous values (e.g. a plot of a baby's weight over the course of a year, or of muscle strength on successive contractions as a muscle fatigues), then the points should be connected by a line in a dot-to-dot fashion. If, however, the series represents independent measurements of a variable to show a trend (e.g. mean price of computer memory over time; a standard curve of optical density vs. solute concentration), then the trend or relationship can be modeled by calculating the best-fit line or curve by regression analysis. Do not connect the dots when the measurements were made independently.

    from http://abacus.bates.edu/~ganderso/biology/resources/writing/HTWtablefigs.html
    This all reminds me of a long joke about horse racing and physicists.
     

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