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Biology Practical notes!!

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Djlucifer

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libra94 said:
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!!
Click to expand...
heyyyyyyyyyy when did u give ur a levels
 
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Aishaox

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i know i am a little late but i wanted some help. i am going to take my AS cie for biology in 2 months and still i am having difficulties in using the microscope. microscopes at our school have 4 objective lens namely: 100x, 4x, 40x, 10x. our teacher told us to use either 40 or 10 times one. now i cannot set or view my slide on 40x lens at all. whereas i manage to view the specimen under 10 times lens easily. if theres anyone who has already taken their exam can they confirm that we would be given choice in what lens we are using or is it absolutely necesary to use any one particular lens??
 
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Aishaox

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i know i am a little late but i wanted some help. i am going to take my AS cie for biology in 2 months and still i am having difficulties in using the microscope. microscopes at our school have 4 objective lens namely: 100x, 4x, 40x, 10x. our teacher told us to use either 40 or 10 times one. now i cannot set or view my slide on 40x lens at all. whereas i manage to view the specimen under 10 times lens easily. if theres anyone who has already taken their exam can they confirm that we would be given choice in what lens we are using or is it absolutely necesary to use any one particular lens??
 
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Aishaox

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i know i am a little late but i wanted some help. i am going to take my AS cie for biology in 2 months and still i am having difficulties in using the microscope. microscopes at our school have 4 objective lens namely: 100x, 4x, 40x, 10x. our teacher told us to use either 40 or 10 times one. now i cannot set or view my slide on 40x lens at all. whereas i manage to view the specimen under 10 times lens easily. if theres anyone who has already taken their exam can they confirm that we would be given choice in what lens we are using or is it absolutely necesary to use any one particular lens??
 
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Aishaox

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i know i am a little late but i wanted some help. i am going to take my AS cie for biology in 2 months and still i am having difficulties in using the microscope. microscopes at our school have 4 objective lens namely: 100x, 4x, 40x, 10x. our teacher told us to use either 40 or 10 times one. now i cannot set or view my slide on 40x lens at all. whereas i manage to view the specimen under 10 times lens easily. if theres anyone who has already taken their exam can they confirm that we would be given choice in what lens we are using or is it absolutely necesary to use any one particular lens??
 
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sunstar

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filza94 said:
Ok Duh we're getting urease & urea tomorrow in Bio 33, Now what wud be the Improvements, Sources of error & Limitations for the experiment below?
Enzyme Concentration

In this investigation, we will examine what happens to the rate of a reaction when the amount of enzyme is reduced. We will use urease, an enzyme that converts urea to ammonia. The ammonia causes the pH of the water to increase (it becomes more basic). You will be able to tell when a reaction occurs because the urea solution also contains a pH indicator that is becomes yellow in acid but turns red when the solution becomes basic.

The object of this experiment is to measure the amount of time it takes for the solution to turn red if less enzyme is used.

C1. Create a hypothesis regarding the the amount of urease and the rate of reaction of Urea.

C2. Obtain four test tubes and add 2 cm of urea to each.

C3. Label three of these tubes 1 through 3; the remaining tube will not be used; it will serve as a control.

C4. Have your lab partner start timing as you add 15 drops of urease to tube #1 and then swirl the tube until it changes to a red color. Record the amount of time that it took for the urease to change to a red color.

C5. Add 5 drops of urease to tube #2 and then swirl the tube until it changes to a red color. Record the amount of time that it took for the urease to change to a red color.

C6. Add 1 drop of urease to tube #3 and then swirl the tube until it changes to a red color. Record the amount of time that it took for the urease to change to a red color.

C7. Record your results in the answer sheet.

C8. Did using less enzyme produce a reaction?

C9. What was the effect of using less enzyme in your experiment? If your experiment did not work as expected, what should have happened?

C10. In general, what happens to the rate of reaction as the amount of enzyme is decreased?

C11. Do your results support your hypothesis? Explain.
Click to expand...


Any suggestions for V2 pls?? :S
I would appreciate your help please
 
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Aliza Jade

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hi does anyone knw what we might be getting tomorrow for variant 33.
Plz Plz reply
 
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