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AQA BIOL2~3rd June 2013~AS Biology (Now Closed)

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Reply 620

chelley2

What is the difference between independent segregation and independent assortment ? :|

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Reply 621

Nina8

Original post by lauraaaaa

You said meiosis 1 the first time! That's why I was confused! I basically just wanted to know when independent segregation (metaphase?) and crossing over (prophase) occur.

Each chromosome is going to arrange itself with its homologous partner. (Homologous chromosomes are made up of two pairs, one from the mother and one from the father)

I hope you remember a chromosome is made up of two sister chromatids. Each chromatid in one pair will twist around each other, and so breaks off and rejoins with the chromatids of the homologous partner. So imagine it in your head, portions of each chromosome are exchanged. You can get lots of new genetic combinations.

Its called independent segregation because when the chromosomes line up, they do so very randomly. One pair from the countless lined up goes to the daughter cell and you can never predict which other pair goes along with it.

The last bit you need to know is the the gametes fuse randomly during fertilization Each gamete has a different genetic makeup so again variation is increased.

According to the specification thats all in Meiosis.

Reply 622

Scienceisgood

Original post by SonamH

But at higher altitudes, there is less oxygen so the affinity would be higher in order to ensure it can associate oxygen more readily..

Yes, but if it was any higher, cells would die due to not enough oxygen being dropped off due to haemoglobin holding on too tightly to the oxygen.

Think of it this way;
An orphanage is home to dozens of orphans, however, if their carer holds onto them too tightly, they are not doing their job are they because they are not being sent away to homes.

Reply 623

SonamH

Original post by Scienceisgood

Okay, i understand what you're saying but at high altitude, if it cannot associate with oxygen more easily, then what oxygen would it be delivering to the tissues?

Reply 624

username504651

Original post by Sapphire123

ok, thanks because i saw it on the specification, but it failed to mention if it was necessary to be able to draw it or just identify it

My teacher told us to be able to draw it but I'm not sure haha

Reply 625

Scienceisgood

Original post by SonamH

Okay, i understand what you're saying but at high altitude, if it cannot associate with oxygen more easily, then what oxygen would it be delivering to the tissues?

Whatever it could get.
There has to be a compromise. I know there is little oxygen meaning SOME oxygen is being taken up by cells, however, it is better for some oxygen to be taken up and little to be delivered than more to be taken up and none to be delivered.

Understand what I mean?

There has to be a compromise.

Reply 626

pamela124

JW bt do we get given the species diversity index?

Reply 627

IgorYakov

Absolute GODSEND for Unit 2, make sure you know all of it!

http://www.thestudentroom.co.uk/showthread.php?t=2363012

(edited 10 years ago)

Reply 628

JackTheNerd

Original post by pamela124

JW bt do we get given the species diversity index?

Yep

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Reply 629

karenkaur

In how much detail do we need to know about the apoplastic and symplastic pathway? :smile:

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Reply 630

Paulineuh

Original post by karenkaur

In how much detail do we need to know about the apoplastic and symplastic pathway? :smile:

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I guess just as much detail given in your textbook. In the spec they just say "Apoplastic and symplastic pathway" so :dontknow:

I would just learn all of it seeing as its not that much :colondollar:

Original post by chelley2

What is the difference between independent segregation and independent assortment ? :|

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Aren't they the same thing?
:confused:

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(edited 10 years ago)

Reply 631

Jay95

i think im gonna fail :redface:

what is everyones revision plans for biology unit 2?

so far i have made a booklet with exam style answers accirding to the mark scheme in there for topics and questions that come up repeatedly in past papers.

also printed off good simplified notes from online which simplifies the nelson textbook ( :angry:

)

also have the cgp study book (complete course, not the thin one)

gonna go through 5 or 6 chapters per day then when iv gone through it one i will repeat again but then with the mark scheme booklet...

does anyone have suggestions?

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(edited 10 years ago)

Reply 632

Jay95

i really struggle with the math questions so can someone tell me how to do

-percentage increase and decrease

-ratios and proportion questions (not sure what may be asked but a general way to figure it out will be helpful)

thanks!

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Reply 633

chelley2

Original post by Paulineuh

I guess just as much detail given in your textbook. In the spec they just say "Apoplastic and symplastic pathway" so :dontknow:

I would just learn all of it seeing as its not that much :colondollar:

Aren't they the same thing?
:confused:

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I don't have a frigging clue -.-
My teacher tells me one thing the text book tells me the other :|

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Reply 634

Secret.

Original post by chelley2

I don't have a frigging clue -.-
My teacher tells me one thing the text book tells me the other :|

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They are the same :biggrin:

Reply 635

Secret.

Original post by Jay95

1. Change over original. For example:

I had 30 hours played on a game, then few weeks later I had 41.7, what is the percentage increase?

Change would be 41.7 - 30

original is 30

So percentage change is (41.7-30)/30 = 39%

2. If I have a cube that is 5x5 work out the surface area to volume ratio

Surface area = (5x5)x6

Volume = 5x5x5

The ratio asks for surface area to volume so divide surface area by volume

= 6/5:1 (or 1.2:1)
or if asked for a single answer just keep it as 6/5 (or 1.2)

Does that help?

(edited 10 years ago)

Reply 636

kiyubi

Hello everyone!
can someone help me with this Q please
"is cholera toxin an antigen?"
My answer is no, but my friend says yes nd she wrote that in her bio1 exam=/
any suggestions would be appreciated thanks :wink:

Reply 637

chelley2

Original post by Secret.

They are the same :biggrin:

Oh -__- & for months I've been thinking they're completely 2 different things but I knew what independent segregation was i was a bit confused on assortment.
So independent segregation AND independent assortment is when homologous pairs line up together at the cell equator in Metaphase 2 ?Corect :biggrin:

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Reply 638

chelley2

Original post by kiyubi

I'm pretty sure the cholera toxin is a bacterium (prokaryotic cell).
An antigen is a protein that causes an immune response.they're completely two different things :smile:

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Reply 639

Secret.

Original post by chelley2

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Yeah but I don't think we need to be specific when (i.e. we don't need to know about metaphase 2 etc, just meiosis I and meiosis II and the fact that they do line up randomly)