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OCR 21st Century Biology - B7 and Ideas in Context

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Hey, can anyone explain this past paper question to me cos i am really confused...

(B7, june 2009 paper, question 3)
Rachel wants to find the percentage of biomass in a soil sample here is the data she collected:

Soil sample - 150g
Soil after drying 80 degrees - 140g
Soil after heating 200 degrees - 110g

Calculate the percentage biomass in her soil sample of 150g.

The answer is 20%, but i have no idea how to get this and why. HEEELPP!!

Reply 41

username504651

Original post by Alexandra82

I need help on this too!

Reply 42

bethanyd

I'm kicking myself because I left my textbook at school and all I have to revise from over the half term is the specification, the past papers and my notes from the topic :/ So I decided to make my own textbook, but as the specification is really slimmed down, it's quite annoying having to google everything if my notes aren't great. Makes me regret not taking better notes :/

Reply 43

Adamtemps1

Original post by Alexandra82

140g-110g = 30g
30g/150g x 100 =20%

Reply 44

Aidn

Original post by Alexandra82

Biomass is organic material, most of the water is gotten rid of at the 80 degrees stage.. So to work out the biomass you have to take into account the TOTAL amount of soil after the water has been taken, and the amount that's left AFTER 200 degrees.. 140-110 = 30g / 150g x 100 = 20% like the person said above.. :biggrin:

Reply 45

Maat

what does everyone think will come up??
i have no idea what to revise!!!

Reply 46

Problematique

I think Biology's easier to get your head around than the other 2 but the actual exam papers are a lot harder. The grade boundary is so much higher as well :frown:

Reply 47

Azzy G

1. What is meant by the term 'Biodiversity'?

2. Why is it important for a habit to have large numbers of plant and animal species living in it?

3. If one species disappears from a habitat, what effects could this have?

4. If there were 600 invasive species noted in Europe in 1982, how many are there estimated to be now?

5. For what reasons might species be introduced to an area intentionally?

6. By what means might species be introduced to an area unintentionally?

7. The ruddy duck and harlequin ladybird are described as 'agressive' species. What is meant by this?

Reply 48

Azzy G

8. Looking at maps, the harlequin ladybird was most mainly found in the SE England in 2004.

a) From this, where does it seem most likely to have come from?
b) By what means could it travel?
c) How would you compare the rate of invasion between 2003-2006?

9. How can biodiversity be reduced by introducing more species into a habitat/area/ecosystem?

10. Without a license, animals and plants may not be taken from one country to another and so it is regulated. What sort of species can be carried without anyone being aware of it, and in what form?

11. In what ways can invasive species cause £12 billoin worth of damage?

12.

a) What is Biological control of species?
b) Give two examples of a species controlled by their natural predators.

13. What non-biological methods are often used to control:

a) Insects
b) Weeds/plants

Reply 49

Azzy G

Original post by lizz-ie

I have created this thread for discussion of the upcoming Biology exam on the 13th of June, since I plan to start revising it as soon as Physics is over! Does anyone have any questions they've been given for the Ideas in Context on 'Alien Invaders?'

You should edit your first post and put all the questions people suggest in the thread so we could all compare answers and stuff ;D + it makes it easier to see the questions :smile:

Reply 50

Aidn

Biology B7 CGP Resources for you guys :P It took a long time to scan and upload so please use them!

(edited 11 years ago)

Reply 51

Aidn

Here's the next few:

Reply 52

Aidn

And the last two, good luck with revision guys!

And the additional page 82 I forgot..

(edited 11 years ago)

Reply 53

Alexandra82

Original post by Aidn

Thanks

But the reason i got confused was that i thought water evaporated at 100 degrees, not 80? and also, does that mean that the biomass in the soil is burnt up at 200 degrees, so the 110 grams that is left is just soil?

Reply 54

Aidn

Original post by Alexandra82

Thanks

Yes, you're right, but I think they try to either put you off or just have made a genuine mistake from the obvious 100 degrees.. Not really sure ¬_¬

Reply 55

Liam2404

Hi guys, I've not used this before so if this totally messes up i apologise, basically I've 2 of my 3 science exams and I've been panicking ever since. I'm aiming for A*'s in Biology and Chemisty, and an A in Physics, however I'm seriously starting to doubt if its still achievable. C7 didnt go so well, Physics went quite good, and i already struggle with B7. So i was wondering if anyone could make an estimate or tell me if i could still achieve my grades based on the marks I've already got and my prediction for the P,C and B 7 exams.
In Chem I've got:
C1,C2,C3 - 45/50 - A*
C4,C5,C6 - 45/50 - A*
COURSEWORK - Im not to sure, but its definatley, 35-36/40 -A*
C7 - Im not sure whether I've reached the A* boundary for the exam because i paniced and messed up, i think I'll have a strong - middle grade : A
Does this still mean i can achieve an A*?

In Bio I've got:
B1,B2,B3 - 41/50 - A (but i have retaken (although that didn't go to well either))
B2,B3,B4 - 46/50 - A*
COURSEWORK - 38/40 - A*
B7 - I think ill get a high A or a low A*
Can i still achieve an A*

In Physics I've got
P1,P2,P3 - 41/50 - A
P4,5,6 - 35-36/50 - B (did pretty bad, but i revised alot and i doubt i could do much better)
COURSEWORK - 33-34/50 A*
P7 - I think it went surprisingly well, i actually think i could have got an A*, but more likely a strong A
Can i still get an A in Physics, and if i achieve an A* in P7 is there a chance of an A* overall, or does p1-6 pull me down to far.

Any help is greatly appreciated, good luck in B7 :smile:

Reply 56

Azzy G

^ Are you sure 34/40 in physics cw is A*? I got the same my teacher said it was an A

Reply 57

Aidn

Original post by Liam2404

In Chem I've got:
C1,C2,C3 - 45/50 - A*
C4,C5,C6 - 45/50 - A*
COURSEWORK - Im not to sure, but its definatley, 35-36/40 -A*
C7 - Im not sure whether I've reached the A* boundary for the exam because i paniced and messed up, i think I'll have a strong - middle grade : A
Does this still mean i can achieve an A*?

In Bio I've got:
B1,B2,B3 - 41/50 - A (but i have retaken (although that didn't go to well either))
B2,B3,B4 - 46/50 - A*
COURSEWORK - 38/40 - A*
B7 - I think ill get a high A or a low A*
Can i still achieve an A*

Ok, I only study OCR Biology and Chemistry so that's why i'm only doing these two..

Chemistry
UMS for an A* overall = 270/300
UMS you already have = 45 + 45 + (92 around about) = 182
For C7 you need (around about) = 270 - 182 = 88 UMS (This is a very high A)

Grade boundaries A* it's looking like for the unit exams but your coursework is only going to give you 2 UMS give or take.. Therefore, for C7 you'll need at least 88/89 UMS to get your A*.

Biology
UMS for an A* overall = 270/300
UMS you already have = 41 + 46 + (98 around about) = 185
For B7 you need (around about) = 270 - 185 = 85 UMS (This is a mid-A)

Your coursework mark is impressive but your unit marks are looking bad in terms of getting an A*, these balance out in your favour though so you'll only need about 84/85 UMS to maintain the A*, well done!