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Biology Practical notes!!

Discussion in 'International A And AS Level' started by libra94, Apr 18, 2011.

  1. libra94

    libra94

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    i have some notes for biology practicals, i would like to share it here :D hope it helps! :)
    GRAPHS!
    1.the value which is varying is always on the y-axis while the constant value is on the x-axis.
    2.no unbroken lines
    3.it must be neat and thin
    4.the points can be joined using a ruler or by hand
    5.do not draw beyond the plotted points.
    6.blobs or centre points more than 1mm are NOT acceptable
    7.if zero is present in the reading, ur graph MUST pass through zero.
    8.label both axis!
    9.use appropriate units
    10.use appropriate scale
    11.use sharpened pencil to plot
    12.plot the dots within circles, of equal sizes, must be clear and not too big.

    SOURCES OF ERRORS!
    1.temp nt controlled
    2.pH not controlled or nt measured accurately
    3.difficulty in judging the colour.
    4.difficulty in having the same time
    5.inaccuracy in preparing serial dilution
    6.inaccuracy of equipment, fr e.g. pipette/syringe
    7.too short time.
    8.evaporation of the solution which can cause the concentration to change.

    LIMITATIONS OF ERRORS!
    1.measure the volume accurately using syringe with narrow range of calibration
    2.repeat more times at each pH/conc./temp
    3.use range of pH/conc./temp
    4.accurate specific measuring devices
    5.use colorimeter to measure the degree of colourness.
    6.use buffer to control pHs
    7.use of water bath/thermostat to control temp
    8.use thermometer to measure the temp.
    9.thermostatically controlled environment.
    10.repeat with each conc.
    11.volume of the sample(e.g. enzyme/substrate) must be the same..cuz as volume increases, conc also increases
    12.keep only one factor different, and all others must be the same.

    Reliability.....take minimum of 3 readings!
    repeat with mre pH/conc/temp
    and find out their mean
    Accuracy.....seing electronic thermostat
    use of pippettes instead of measuring cylinders

    KEY
    1)read the whole question till the end
    2)decide number of readings to take
    3)don't go for more or less than 3 readings per conc/vol of any ques.
    4)make a table
    5)write down the UNITS in each coloumn of the table...e.g. conc/cm^3 , temp/°C

    MICROSCOPY!!!

    1)propotion of thickness must be correct.
    2)draw the organelles where u see them, dont just draw anywhere within the cell! never draw what u know.
    3)whenever u see the plant cells, draw the cell walls.
    4)IN PLAN DIAGRAMS, NO DRAWING OF ANY CELLS, AND NO SHADING...if u'll do either of them, u'll lose the whole mark!!
    5)when asked to draw 2 cells, draw the ones that are easiest to draw. and dont draw more then 2 cells!
    6)fraw the adjacent (touching) cells.
    7)drawing should be large, unshaded.
    8)in plan diagrams show the relative thickness of each layer.
    9)draw the exact shape, if its oval or round or has wavy outlines
    10)label the diagram...simplest thing to label is cytopasm, nucleus and cell membrane.
    11)if its a trachea cell, then label goblet cells, cilia, blood vessels, muscular tissue, cartilage cells (lacunae)
    12) when asked to compare 2 diagrams....make a table (drawing a table itself has 1 mark!)....put atleast one similarity

    ERRORS IN MESUREMENTS!

    1)irregular in shape
    2)difficulty in focusing
    3)preperation is squashed

    and yeahhhh one more thingg, the values must be whole numbers!!! e.g if its 8.5mm u round it off to a whole number which is 9!!
     
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  3. hassam

    hassam

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    thank you very much...these r some file from revision book of cambridge AS biology
     
  4. hassam

    hassam

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  5. hassam

    hassam

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    i request from planet master or moderators to kindly make this topic STICKY !!!
     
  6. hassam

    hassam

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    WHAT IS antigenic concealment...?..
     
  7. libra94

    libra94

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    its when the antigen conceals (hides) itself, and cannot be recognised by the body's immune response
    e.g. in malaria, the plasmodium protoctist stays in the RBCs or the liver cells, therefore cannot be recognised by the immune system
    also, in cholera, the bacteria conceals itself in the intestine, and cannot be recognised by the immune system.
     
  8. hassam

    hassam

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    there was a practical abt counting no. of stomata ...hav u performed dat
     
  9. hassam

    hassam

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    MAKING TABLES
    iNDEPENDENT Variable in the first column....and observations or dependent variables in other columns.....
    in question 1 of exam..two kinds of questions cn be set....one involving quantitative observations like most enzyme experiments and other involving qualitative observations like food-tests...as far as observations for qualitative data are concerned...these will include most probably color changes during course of investigation...so a likely error for these experiments cn be difficulty in judging b/w different colors with your improvement being the use of colorimeter to measure color intensity.....
     
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  10. princesszahra

    princesszahra

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    thanks alot!!
     
  11. hassam

    hassam

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    princess...cn u help me out with o/n paper 34 2010 practical questiion 1..cnt understand wat shud be observations
     
  12. Banglarbagh

    Banglarbagh

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    hassam bro do u kno from where i can download cambridge as chemistry revision guide, if u kno pls sahre the link.
     
  13. hassam

    hassam

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    i searched it a lot hte other day bt cud not find any torrent or file share link
     
  14. hassam

    hassam

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  15. MaidaMunaf

    MaidaMunaf

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    thank u so much the notes are realy helpful
     
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  16. libra94

    libra94

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    yr welcome :)
     
  17. libra94

    libra94

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    is may/jun 09 p32 the one u r talking abt??
     
  18. princesszahra

    princesszahra

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    what was wrong in that practical??what thing u didnt understand?
     
  19. hassam

    hassam

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    well i ll chek it again and then tell u
     
  20. hassam

    hassam

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    wat the hell was that......??
     
  21. libra94

    libra94

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    i have no idea :!: :x
     

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