Biology P3 Tips 02

note: I'm using Vika's account (again) since i'm too lazy to make one =_=, for those who failed to guess who am I, I wont tell ^.^

Hey ho, next for the tips.
Did this the day before chemistry practical.
This time I'm going to list a compilation of things to remember about errors and improving-the experiment-questions in biology practicals and just a bit of comments on those labelled drawings and how to draw them.

Q1 part 02:
Error identification and countermeasures
This is it, the valuable list of improvements which I have listed and categorized for the sake of convenience. You can deduce what error they represent by yourself, its pretty obvious.

1. Common Improvements (applicable for almost all kinds of experiment)

• Repeated readings
  
• Keep the temperature constant
• Keep the pH constant
• Same amount of time
• Constant concentration
• Constant volumes of reactants and reagents
  

2. Improvements on tests with serial dilution (like Benedict Dilution and Enzyme Inhibitor test)

• Use colorimeter to identify colour difference more accurately
• Increase range of dilution
• More accurate use of equipments

3. Improvements on potato strip tests

• Thickness and/or width of the strips should be same
  
• Use strips from the same potato
• Weigh the strips
• Increase length of strips

4. Improvements on bubble count experiment

• Measure the volume of the bubbles produced

5. Errors that you cannot improve (haha..), i think you can write these on the sources of error questions.

• Difficult to put enzyme at the same time (in Enzyme Inhibitor serial dilution)
• Inaccurate serial dilution
• Volume of Benedict added is not exactly the same

6. Errors involving measurement of lengths on cells/diagrams etc, that ocassionally pop out on question 2 (these are..real)

• Not viewing the ruler from the right angles / Parallax error
• Thickness of ruler lines affects the reading
• Difficult to focus both ruler and specimen at same time

Well that's basically almost everything I know on errors. Yes, I know and have noticed some unclear or funny things on the list above, like 'Difficult to focus both ruler and specimen at same time' and 'Thickness of ruler lines affects the reading', but these are taken from marking schemes, so its all real. Cambridge sure has its own ways of doing (or marking) things...

Next I'd like to comment on drawing with labels on question 2. On the subject of drawing things that you see on the light microscope, what I've noticed from the marking scheme is that it generally speaks about the drawings should have the right orientation, shape and proportional sizes (like a red blood cell should be smaller than a white blood cell). No shadings or colouring is allowed. Make sure your label lines do not intersect each other. And the lines on your drawing should be clean and continuous (like drawing a smooth plasma membrane). Just a simple and clear drawing is good.

This is all for the second part of the p3 tips. I hope you can benefit from it. Dont panic and try to remember all the things on errors I wrote.. Instead focus on two to three things that you dont know yet or that you find easy to remember, since the questions on errors usually only ask for 2 or 3 points.

Ok then guys, good luck on chemistry and Vika's tips are awesome, hands down.