A2 Biology Unifying Concepts past paper - help!

Doolally

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Several groups of discs cut from spinach leaves were placed in test tubes of water. The discs all sank to the bottoms of the tubes. The tubes were each placed at a measured distance from a lamp.....

Suggest why the experiment recorded the time taken for 5 discs to float rather than time time taken for all of them to float (2)

The experiment was repeated by putting spinach leaf discs into water that had been boiled for several minutes and cooled in the abscene of air. None of the discs floated. Explain why. (2)

(ok, i know these 2 are pretty basic...but im hangover and my minds not working properly!)

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Explain why blood pressue is important for kidney function (2)

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Explain why two very simliar species are not expected to occur together in the same community (2)

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Thanks so much to anyone that can help!

1. Cause otherwise, data might be skewd due to 1 disk not floating at all. (due to handling errors, so thus causing erronous results)

2. Probably lack of 02?

3. High bp = higher filtration rate etc etc

4. Interspecific competition, so eventually 1 species will die out/move

Reply 2

I'm so scared of the UC exam! Haven't seen any past papers yet though. 2776 seems to have answered your questions!

Reply 3

GH

SiAnY

I'm so scared of the UC exam! Haven't seen any past papers yet though. 2776 seems to have answered your questions!

Actually I'm not too sure of why the spinach disks float? Any ideas on it?

Or why it doesn't float when O2 has been removed.

Reply 4

oxymoron

7

2776

Actually I'm not too sure of why the spinach disks float? Any ideas on it?

Or why it doesn't float when O2 has been removed.

The discs float because Oxygen is produced as a product when the discs photosynthesise. As oxygen is less dense than water and it gets trapped in the discs, they float (provided the leaves are photosynthesising faster than they are respiring)

When the water is boiled ... the CO2 is removed so the leaves can no longer photosynthesise as CO2 is a necessary reactant. Therefore, no O2 is produced and the leaves do not float.

Reply 5

OP

awh wow thanks people...really helped!
I'm now going to be really cheeky and ask for more help :P hehe
Its for one of those long questions (8 marks for content, 1 mark for QWC) and its about the nitrogen cycle:

"Discuss whether it would be desirable for the environment and whether it would be economically practicable to run a dairy farm without any of the inputs W, X, Y,Z"

W=cattle food
X=organic manure
Y=synthetic fertliser
Z=synthertic fertiliser

.....I didn't even know practicable was a word! I thought it was a typo and they just meant practicle....I can see this exam is gunna go GREAT!

Oh, and also, what are two nitrogen containing compounds, other than proteins and amino acids that are found in plants?

Thanks!

Reply 6

oxymoron

7

Doolally

Oh, and also, what are two nitrogen containing compounds, other than proteins and amino acids that are found in plants?

Thanks!

DNA and ATP (or even NADP) are two other Nitrogen containing compounds found in plants

With the other question, are Y and Z supposed to say the same thing?

Reply 7

OP

oxymoron

DNA and ATP (or even NADP) are two other Nitrogen containing compounds found in plants

With the other question, are Y and Z supposed to say the same thing?

Thanks! Yeah, they do say the same thing on the diagram...Y is pointing to "ammonium ions" and Z is pointing to "nitrates". (also, W is pointing to nitrogen compounds in the bodies of cattle, and X is poitning to dead organic matter)

Reply 8

Uh oh, i hate the nitrogen cycle and all that crap. Mehhhhhhhhhhhhhhhhh.

Reply 9

OP

SiAnY

Uh oh, i hate the nitrogen cycle and all that crap. Mehhhhhhhhhhhhhhhhh.

Me too! Infact, i hate all of biology. Grrr, why did i choose bloody Biology..should of dropped it!!

Reply 10

Doolally

Me too! Infact, i hate all of biology. Grrr, why did i choose bloody Biology..should of dropped it!!

Hehe. I have a strange relationship with biology, :biggrin:

. I hated it at GCSE and got a B and i don't know why i chose it for A-level! But i'm dropping English Language to give me more time to concentrate on biology and my geog and socio courseworks. I hate biology in lessons because it's so confusing, though i have a nice teacher this year. :smile:

I go home and realise i've forgotten everything we learnt that day! But then when i've learnt something properly it's so...satisfying! Don't ya think? :smile:

Reply 11

OP

SiAnY

Hehe. I have a strange relationship with biology, :biggrin:

. I hated it at GCSE and got a B and i don't know why i chose it for A-level! But i'm dropping English Language to give me more time to concentrate on biology and my geog and socio courseworks. I hate biology in lessons because it's so confusing, though i have a nice teacher this year. :smile:

I go home and realise i've forgotten everything we learnt that day! But then when i've learnt something properly it's so...satisfying! Don't ya think? :smile:

Yeah, i know what you mean! I rememeber when i actually bothered to learn my AS stuff properly for the exams in June and it did feel good, especially for stuff i was interested in like the HHD module..transport I didnt mind either. It was Foundation i struggled with that i took in January, and i only just got a B on that (63/90)..but to be fair i didnt really revise for that..it was the xmas season..too much going out! But i suprised myself loads and got one mark off an A for overall A/s and will retake foundation again in Jan.....But UC exam is reaaaally scaring me now!

Reply 12

hihihihi

yup, have you finished the Central Concepts module already?

Reply 13

GH

What module is this? BYB5? BYB4?

Reply 14

2776

What module is this? BYB5? BYB4?

Nope, because it's OCR. I'm guessing BYB5 etc are either AQA or Edexcel?

Doolally

HHD module..transport I didnt mind either. It was Foundation i struggled with that i took in January, and i only just got a B on that (63/90)..but to be fair i didnt really revise for that..

Ooh, i was kind of the opposite! I revised for Foundation LOADS over the Xmas hols (lol i was sad, k? :biggrin:

) and got an A (77/90) which i never expected in a zillion years! Transport - exam was ok i thought, got a B though. HH&D - thought the exam was HELLish and got an A. Biology is barmy. Yah. :biggrin:

hihihihi

yup, have you finished the Central Concepts module already?

I haven't, don't know if Doolally (Sian) has...but, no, I haven't started any UC past papers or anything. Occasionally my teacher will ask synoptic questions in lessons though.

Reply 15

OP

hihihihi

have you finished the Central Concepts module already?

No...but we're not doing it till June which means we arent in a rush, so for some reason, we had a random week on synoptic skills. We've done Photosyntheis, populations and interactions, control, corrdination and homeostasis, and are half way through energy and resp.

SiAnY

Ooh, i was kind of the opposite! I revised for Foundation LOADS over the Xmas hols (lol i was sad, k? :biggrin:

)

Not sad...just sensible! Trying to understand translation/transcription with a clear heard was bloody hard enough but with a hangover was never going to work!

SiAnY

and got an A (77/90) which i never expected in a zillion years!

Well done! I can see someone will be getting some frantic PM when i attempt to revise for my resit this Jan! hehe :tongue:

SiAnY

Biology is barmy. Yah. :biggrin:

Agreeeeeeed!

Ooo i got my ucas letter today Sian! Went on track..no offers :frown:

I'm so bloody impatient!

Reply 16