Some biology practical doubts

[narutogirl]

Different.

And that's why, you don't rely on guesses, you rely on God.

Anyways, may Allah expand our breasts for us all and ease our ways for us all and guide us all to the straight way, Ameen, ya Arhamar-Rahimeen.

Going to bed; see you later guys.

very well said...ISA everything is fine, I hope you don't get the lab on fire or something..ISA we all do good ^__^

im not worrying im showing concern i have a rough drawing from mr.c i told jazz i'd bring it tomorrow but it's totally not accurate..we'll see

hmm okay ^_*

 

[perkypearl]

anybody got any good lung slides? they're soo weird...cant figure them out :\

http://nhscience.lonestar.edu/biol/respiratory/alveoli.htm

 

[sarahnafea]

very well said...ISA everything is fine, I hope you don't get the lab on fire or something..ISA we all do good ^__^



hmm okay ^_*

if ur still awake check google images it's a tad bit more helpful !

 

[ony]

how many repeats do we have to do and is it important to them or is ONE enough?

 

[narutogirl]

how many repeats do we have to do and is it important to them or is ONE enough?

I think for u to be on the safe side do atleast 3 if they ask about the time and one if they ask about the color..but i am not quite sure :/

You don't have to actually repeat just showing the examiner that you repeated would be enough, because sometimes trials are important to calculate means and rates ^_^

 

[Capricedcapri]

Guys em stuck with the dilutions....any suggesti0ns?

 

[The Munchkin]

Its actually based on what the practical involved, exactly. For example, if you were measuring the color change of, say, Iodine, you would commonly make an error in judging the color - and its improvement could be using a colorimeter. If you were cutting potato pieces; then all the pieces were not uniformly cut, etc. and its improvement could be using a micrometer or a cork borer to cut it to same length.

Beware of writing factors affecting all solutions equally as 'errors' - such as temperature, pH, evaporation of water from the containers (if unlidded/uncovered) etc. These may work in some cases, where they don't affect all solutions/etc. equally, but not when they do so. Use your head here and be careful.

When preparing serial dilutions using syringes, there could be an air bubble trapped in the syringe, or the solutions not accurately prepared. This could be avoided by using a pipette or a more accurate measuring device.

Things which often work as improvements are using a wider range of concentrations of enzyme/substrate/independent variable, and taking more replicates for each concentration.

But it all depends on what the actual procedure is.

Hope that helps!

That helps alright!! Thank you so much !!

 

[The Munchkin]

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 similarityMAKING 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.....
i have some notes for biology practicals, i would like to share it here 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.

Thank you very much!!!!

 

[Saad (سعد)]

Paper went well Al-Hamdulillah... though I screwed up in one place... and in another two I may have screwed up, I dunno yet...

 

[lionkill3r]

i screwed up the actual lenght part i for go to divide image lenght by magnification
Other than nthat all fine except for 2 anomalous values for first question experiment

 

[Capricedcapri]

Awesum paper! Hoping for the best...fingers crossed!

 

[salmank]

guys will the examiner deduct any mark for not drawings the cells in alveolar wall diagram,,???????????

 

[Capricedcapri]

i dun think so dat v were askd to draw the cells......it was just the alveoli..i guess

 

[The Munchkin]

Biology Practical Variant 34 :

Do we need to label the vein and the artery ??
if we do, how many marks does it worth??

 

[Melancholy]

I wrote variant 32... As the % of Enzyme decreased (i used the dilutions of 1%; 0.1%; 0,01%; 0,001%; 0,0001%), the time taken to reach the end point DECREASED Too!!! This was not what I was expecting" Can you please share your results?

 

[blabla]

Biology Practical Variant 34 :

Do we need to label the vein and the artery ??
if we do, how many marks does it worth??

i didnt because it wasnt asked in the question. i just labelled the muscle wall :\

 

[Saad (سعد)]

Biology Practical Variant 34 :

Do we need to label the vein and the artery ??
if we do, how many marks does it worth??

No, you weren't supposed to label them. Just the smooth muscle in the artery. Never label more than what's asked, they may even deduct marks for that.

i dun think so dat v were askd to draw the cells......it was just the alveoli..i guess

You were supposed to draw the cells in the 'large drawing' of the alveoli. You were supposed to show the individual cells and the nucleus - but, of course, no shading or anything. That's because the word they specifically used was 'drawing', not 'plan diagram'.

 

[Capricedcapri]

R u sure? I mean u draw the inner cells onli if the word " label" is used....n frm wich school were u btw me in fsd 2....

 

[Saad (سعد)]

R u sure? I mean u draw the inner cells onli if the word " label" is used....n frm wich school were u btw me in fsd 2....

LGS.

I dunno, but that's what I understood, and I confirmed it here with another student and she also said that we were supposed to draw the cells and label the nucleus.

 

[Saad (سعد)]

wow!
all papers?

Excuse me? o.o;