AQA A2 Biol4 January 2012 pre- exam discussion

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thank you.! in jan 11 q)2c how would you get to the answer? dont understand

16 percent rhesus negative. Rhesus positive is dominant allele, so rhesus negative is reccessive allele.

so q^2 = 0.16
so q = 0.4

heterozygous is 2pq
you already have q so you just need p and as p + q =1.0
p => 1-0.4 = 0.6
so heterozygous is 2*0.4*0.6 = 0.48 = 48%

(edited 12 years ago)

Reply 1581

eemooz

Original post by SpringNicht

Fertilisers are leached from farm land into lakes. Numbers of algae increase (algal bloom) and this decreased light transmission through water. Plants at the bottom of the lake cannot photosynthesise and die. Algae also die and sink to the bottom of the lake. Numbers of saprophytic bacteria increase in the lake due to the increase in dead organic matter so the biochemical oxygen demand increases. This lowers the O2 concentration in the water so marine animals eg fish die.

Ooh thanks :smile:

Btw one more thing, is saprophytic bacteria the same as saprobiotic bacteria? :s-smilie:

Reply 1582

SpringNicht

Original post by eemooz

Ooh thanks :smile:

Btw one more thing, is saprophytic bacteria the same as saprobiotic bacteria? :s-smilie:

Yes

Reply 1583

eemooz

Original post by SpringNicht

Yes

thanks!!!

Reply 1584

AckyWackyBacky

Original post by nasira372

-Nitrates leach into the sea, resulting in algae growth
-Light prevented from reaching plants
-Plants cant photosynthesis so they die
-Increased number of bacteria
-Bacteria respire so less oxygen
-Fish die

good summary cheers :biggrin:

Reply 1585

AckyWackyBacky

Question 7 will be a little bitch as usual!

Looking forward to Q8, hoping its a kind mark reaper for us :P
Someone give me a topic that will prbably come up!
Cramming is a sport im rather good at!

Reply 1586

gpostleth

I'm off to get a good nights sleep. Can't wait to check this tomorrow after sixthform and see how many questions I got wrong!
Good luck guys

Reply 1587

SpringNicht

Original post by AckyWackyBacky

Question 7 will be a little bitch as usual!

Looking forward to Q8, hoping its a kind mark reaper for us :P
Someone give me a topic that will prbably come up!
Cramming is a sport im rather good at!

My teacher was saying you can tell who revised a lot from those who didn't by seeing if they do better in question 8 or 7, LOL.

I'd say respiration is a pretty safe bet (and its not too long, always a plus!)

Reply 1588

AckyWackyBacky

Im a boss at remembering diagrams, but i swear to god I hope they dont pull an ecological one on me, its such a picky subject!

Does anyone else find AQA a little too nitty gritty on the HSW?

Reply 1589

F1's Finest

im gonna hit the bed now (sound wrong i know but basically im gonna sleep :tongue:

)

my mum said she's gonna wake me up early like 5am (because even my alarm clock doesn't wake me up!) so i can start revising till 7.00, where i then leave my house......... why don't you guys sleep now?

Reply 1590

AckyWackyBacky

I could never revise at 5am!

I like to feel proper tired before I sleep, or i dont get a good night :P

I crash/feel drowsy at about 11am anyway which is after exam time so thats alright i suppose haha

Reply 1591

casio1

Hi,,

can someone please explain to me how one can see if a condition is sex-linked?

and I would appreciate a good'ol summary of succession. :smile:

Thank you guys,,,, Wish everyone the best for tomorrow!

Reply 1592

Mathematix

I look forward to these exams xD

I blag my way through because I can usually work out good responses to the how science works questions.

That being said, I should be able to answer the ones in question 8 fairly well :smile:

Aren't the boundaries only like 45/75 for an A or something anyway if its an average paper?

Reply 1593

AckyWackyBacky

Last thing, can anyone tell me

The total yeild of ATP in aerobic respiration?
Whats in glycolysis in terms on "on the spot ATP produced" and potential ATP in reduced NAD etc
Also in krebs/ETC :P

Reply 1594

F1's Finest

Original post by AckyWackyBacky

lol, yeah, im gonna eat weatabix coz the pack said slow releasing energy. so ill be good for the exam.....

my brain seems to fresh in the morning, especially 30 minutes into the start....... loads of things are going through my brain right now! like going to sleep!!

anyway bye guys

Reply 1595

Mathematix

Original post by AckyWackyBacky

Last thing, can anyone tell me

The total yeild of ATP in aerobic respiration?
Whats in glycolysis in terms on "on the spot ATP produced" and potential ATP in reduced NAD etc
Also in krebs/ETC :P

Total yield varies between textbooks/sources but it's usually either 32 or 36, they won't ask for it without giving you data to work it out from.

In glycolysis there is a NET production of 2 ATP (2 is used in turning glucose into tp but 4 created in turning tp into pyruvate) and there is 2 NADH formed.

In link there is 1 NADH formed (but happens twice for every one glucose)

In krebs there is 3 NADH, 1 FADH and 1 ATP (but happens twice for every one glucose)

In ETC the NADH and FADH are used to produce ATP by giving up their H (but this is where the discrepancy lies, some say 3 ATP per NADH and 2 ATP per FADH but others 2.5 and 1.5 per etc)