CIE IGCSE Biology Alternative to Practical

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for the dye i put cut the stem and then put dye into water and place the stem into the dyed water. Leave for 5 mins and then cut open the stem to see where the red dye is. That is the xylem. Repeat for accuracy. Wear goggles.

Reply 21

123Master321

https://drive.google.com/file/d/0B108wb6vqF_8ZWxsRzJwcl9td3M/view
https://drive.google.com/file/d/0B108wb6vqF_8bEdLM3FxSkxMQWc/view

h part iv) might help it was investigating the effect of pH on enzyme activity, here the control was boiling the enzyme and in the exam it was alcohol concentration on enzyme activity, it's quite similar

Reply 22

123Master321

Original post by SalopJack

didn't you have to talk about the microscope

Reply 23

123Master321

Original post by CIEBioloysifh

For the control I said use water instead of hydrogen peroxide. I found the last question stupid as I said water with dyed water and then talked about translocation and the transpiration stream. The drawing was dumb as hell, where were the food tests?

It was a describe style question, surely you shouldn't need to use any theory

Reply 24

GCSE DEMOLISHER

Original post by suht

I know it was stupid no food tests, nothing on arthropods and the diagram was like nothing we've ever done. As for the last question I just test for water using copper sulfate crystals to identify where the thing they wanted us to identify was

There were some easy marks to be won, so overall it wasn't too bad. There was a lot of measuring in mm and a bar chart which only measured 2 things; before and after the alcohol. The vascular bundle drawing was difficult and I can't draw anything so it was quite difficult for me to adapt the drawing even though is understood what was in it. The grade boundaries are low for these papers so don't worry. (Last year it was 25 out of 40 for an A).

Reply 25

Zx12r1

For the last question I put out plant in red dye (eosin) solution and leave for 1-2 days. Then cut open at middle of stem and place cut section in microscope and red stained section xylem and cells are not densely packed and unstained area around it is phloem and it is more densely packed.

For the drawing I thought by individual cell not to draw one xylem and one phloem so I drew the individual cells but labelled the xylem vessel, how may marks would I lose for this?

For oxygen counting method innacciracy I put can e miscounted and for the improvement use gas syringe ? Is this right

Reply 26

123Master321

Original post by Zx12r1

For your last point, I did past papers and the mark schemes were like it was because the size of the bubbles might be different. But your point might be fine

and gas syringe is correct

Reply 27

123Master321

Original post by Zx12r1

It was in bold so you might lose a mark or two if you are unlucky

Reply 28

DJShaji

Original post by Zx12r1

I went a different route and talked about the red dye being 'eosin'. Pour 20cm^3 of eosin into a beaker and place a cut plant so that the stem lies in the beaker. Make sure humidity is low, light intensity is high( to open stomata) and carbon dioxide and temperate should be optimum so that transpiration can take place. After a while the water should move up the plant. :/

eugh.....How does one forget about a gas syringe. I can't believe that. I wrote about inverting the test tube and putting into a water bath - like this:

What did you get for the source of error

Reply 29

SalopJack

Original post by 123Master321

didn't you have to talk about the microscope

possibly but i didn't oops

Reply 30

CIEBioloysifh

I'm pretty sure I wouldn't get the marks for the control for saying "Use water instead of hydrogen peroxide", what do you guys think? Also I talked about dying water, then watering with dyed water and then waiting for a couple of days and cutting open the stem. How many marks will I have lost?

Reply 31

SalopJack

Original post by DJShaji

What did you get for the source of error

Bubble size could be different

Reply 32

Zx12r1

What did you get for the source of error

I think there may be two answers I put it may be susceptible to miscounting with the oxygen bubbles as it said that a few years ago in a mark scheme for a similar question

Another answer that my friends put was the volume of oxygen bubbles varies

Reply 33

Zx12r1

Original post by DJShaji

What did you get for the source of error

I think there may be two answers I put it may be susceptible to miscounting with the oxygen bubbles as it said that a few years ago in a mark scheme for a similar question Another answer that my friends put was the volume of oxygen bubbles varies

Reply 34

Igcseexams101

I think you had to talk about how the water would move up the xylem and under the microscope the xylem would be stained and the phloem would not, that's how you could tell what was in the vascular bundle

Reply 35

123Master321

Original post by CIEBioloysifh

i'm not sure but I thought the whole of the last question was microscope preparation

Reply 36

CIEBioloysifh

It definitely involved talking about dye, however, I think that the dye molecules would be too big to pass through the root cells. I'm not sure. I need some help .-. I regret not talking about boiling the potato as I don't think water is right instead of hydrogen peroxide. Welp, help.

Reply 37

examhater44

Original post by 123Master321

For your last point, I did past papers and the mark schemes were like it was because the size of the bubbles might be different. But your point might be fine

and gas syringe is correct