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*Biology Paper 5 tips*

M

Marks&Spencers

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I'm sorry if this might seem like a stupid question but, when dealing with x2 values, t values, standard errors and deviations, how many significant figures should we write our answers to? Is there a specific number?
 
knowitall10

knowitall10

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narutogirl said:
No matter how the exam turns out to be, I want to thank everyone esp knowitall10
This is my last IGCSE exam ever and XP was a big part of that IG experience.
:oops: Good luck everyone, keep the curve low :p
Click to expand...

Thank you very much narutogirl you've played a huge role too :) If it weren't for your smart questions, I myself would never have learnt... All the best to you too!! (y)
 
nishithini

nishithini

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can you p
knowitall10 said:
Organism Growth:
  • source: corn syrup, glucose, protein, low grade NH3
  • never write nutrient broth
  • mention 2 examples at least
  • same amount or conc of nutrient broth to the two sets of specimen
  • the nutrient supply must be kept constant
  • mention flow rate through fermenter
  • For batch culture: note the amount of time the organism is left in the fermenter
  • keep in mind the O2 supply, temperature, pH
  • sterility of the fermenter is very important [so that no other organism grows and acts as a competitor]
  • sterility is important in both batch and continous culture- in fact, every time you set up a batch culture, sterility must be mainatained
Planning Questions:

  • decide what the experiment is on (like diffusion, osmosis, photosynthesis)
  • use the same apparatus; describe what you're going to vary and what must be kept constant- decide which is the dependant and independant variable (eg light intensity? CO2 conc? or gas produced?)
  • how will you vary (count bubbles? use gas syringe?)---always ask yourself: is it a comparison
  • units--same volume, same mass, same concentration
  • What are the constants? How will you keep them constant?
  • give brief discription of the steps; if time is required, BE SPECIFIC.
  • inference: in some exps you need a control, but don't write anything which isn't required otherwise
  • precautions (FREE MARK!!!)
Reliability:

> give time for caliberation
(Calibration time is adjusting time)
>Repeat 3 times to be certain that the results are consistent-do not change the parameter
>large sample size
Why repeat?
  • increases the certainty that the results are consistent
  • so that anomalous results can be removed
  • permit variance from mean
  • to take an average
Accuracy:

  • means measuring in a reliable manner. Eg
  1. weighing scale
  2. thermometer
  3. verneir caliper
  4. measuring cylindrer
  5. gas syringe
  • use of a buffer solution to maintain pH
  • using sol of known conc (by serial dilution)
  • comparing colors of sol by a colorimeter
  • larger number of known conc
  • washing syringes and pipettes
  • mixing and stirring for uniformity to prevent settling of suspension
  • in microscopy: eye-piece graticule
  • to measure the surface area, the specimen is placed on a grid, where the full squares, half or more than half are taken into consideration
  • FILTERING AND CENTRIFUGING: the suspension spins and the more dense sinks at the bottom
Control:

  • in an exp with living organisms, the control must be a dead organism
  • whatever factor is being used in the question is emitted from the control
  • For counting chromosomes and making them visible, the growing regions of the plant are cut
  • cut surface of the specimen
  • chromosomes are counted by placing cut surface under a high power light microscope(with high magnification)
  • How to make chromosomes visible?
  • > add dye/stain them
  • > Examples of dyes:
  1. methylene blue
  2. aceto-carmine
  3. aceto-orcein
So that's all that was dictated to me, I hope it is helpful inshAllah! :)
Click to expand...

can you please provide us with chemistry paper 5 notes too?! it will be a great help
and thank you very much for helping e with this bio p5 :)
 
perky1

perky1

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can you explain oct/nov/53 q1 b(i concentrations part



knowitall10 said:
Organism Growth:
  • source: corn syrup, glucose, protein, low grade NH3
  • never write nutrient broth
  • mention 2 examples at least
  • same amount or conc of nutrient broth to the two sets of specimen
  • the nutrient supply must be kept constant
  • mention flow rate through fermenter
  • For batch culture: note the amount of time the organism is left in the fermenter
  • keep in mind the O2 supply, temperature, pH
  • sterility of the fermenter is very important [so that no other organism grows and acts as a competitor]
  • sterility is important in both batch and continous culture- in fact, every time you set up a batch culture, sterility must be mainatained
Planning Questions:

  • decide what the experiment is on (like diffusion, osmosis, photosynthesis)
  • use the same apparatus; describe what you're going to vary and what must be kept constant- decide which is the dependant and independant variable (eg light intensity? CO2 conc? or gas produced?)
  • how will you vary (count bubbles? use gas syringe?)---always ask yourself: is it a comparison
  • units--same volume, same mass, same concentration
  • What are the constants? How will you keep them constant?
  • give brief discription of the steps; if time is required, BE SPECIFIC.
  • inference: in some exps you need a control, but don't write anything which isn't required otherwise
  • precautions (FREE MARK!!!)
Reliability:

> give time for caliberation
(Calibration time is adjusting time)
>Repeat 3 times to be certain that the results are consistent-do not change the parameter
>large sample size
Why repeat?
  • increases the certainty that the results are consistent
  • so that anomalous results can be removed
  • permit variance from mean
  • to take an average
Accuracy:

  • means measuring in a reliable manner. Eg
  1. weighing scale
  2. thermometer
  3. verneir caliper
  4. measuring cylindrer
  5. gas syringe
  • use of a buffer solution to maintain pH
  • using sol of known conc (by serial dilution)
  • comparing colors of sol by a colorimeter
  • larger number of known conc
  • washing syringes and pipettes
  • mixing and stirring for uniformity to prevent settling of suspension
  • in microscopy: eye-piece graticule
  • to measure the surface area, the specimen is placed on a grid, where the full squares, half or more than half are taken into consideration
  • FILTERING AND CENTRIFUGING: the suspension spins and the more dense sinks at the bottom
Control:

  • in an exp with living organisms, the control must be a dead organism
  • whatever factor is being used in the question is emitted from the control
  • For counting chromosomes and making them visible, the growing regions of the plant are cut
  • cut surface of the specimen
  • chromosomes are counted by placing cut surface under a high power light microscope(with high magnification)
  • How to make chromosomes visible?
  • > add dye/stain them
  • > Examples of dyes:
  1. methylene blue
  2. aceto-carmine
  3. aceto-orcein
So that's all that was dictated to me, I hope it is helpful inshAllah! :)
Click to expand...
 
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