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

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Reply 2420

VigneshSB

Original post by PoorLoser

can someone help me on June 2010 Question 5d please (both parts)

thanks!

i) Well, the gamete would contain three chromosomes, 1 from each homologous pair.

ii) There are two possible chromosomes for each of the three 'positions' in the gamete, so there are 2*2*2 possible combinations = 8 combinations

Reply 2421

Sorro10

If anyone needed pdf here it is, in-case you missed it on the last page.

BIOL2 Topic Analysis new.pdf145.2KB

Reply 2422

doctordee

If anybody has any last minute questions or are confused on any topics feel free to private message me.
I'd be more than happy to go through things with you.
Good luck guys!

Reply 2423

VigneshSB

Original post by Suzanna5678

What's chiasma

Chiasmata are the points where chromatids cross over.

Reply 2424

Suzanna5678

Original post by doctordee

If anybody has any last minute questions or are confused on any topics feel free to private message me.
I'd be more than happy to go through things with you.
Good luck guys!

Are you doing a predicted paper??

Reply 2425

hannah2101

I would say to look more at topics that haven't come up in the past few years... e.g. tissue fluid hasn't come up a lot at all however it was a 6 mark question in June 2012 so it's unlikely it'll come up in this one or if it does it will only be a couple of marks.

Reply 2426

LiamDaly

Original post by BingTaoBing

Guys...

why are the grade boundaries for an A so low? I mean, on Jan2010, the boundary was 52/85, which is about 62%...It just seems pretty unbelievable. I don't have a teacher so I can't ask anyone else!

Because AQA like to troll with shrimp questions

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Reply 2427

Suzanna5678

Original post by doctordee

If anybody has any last minute questions or are confused on any topics feel free to private message me.
I'd be more than happy to go through things with you.
Good luck guys!

Could you please do a 6 mark response on mass transport and circulatory system of a mammal

Reply 2428

LiamDaly

Can someone post 6 marker for fish gas exchange? Want to make sure I've got similar points

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Reply 2429

doctordee

Original post by Suzanna5678

Are you doing a predicted paper??

You messaged me this already.
I can't because I have been very ill all weekend but I can answers any questions or help that people need.

Reply 2430

Sumi Prakash

Could someone tell me the purpose of the casparian strip please?

Reply 2431

Pataiiii

Original post by philippawright

Yeah but i'm sure we were told even if it is water, if it doesnt cross a partially permeable membrane it cant be counted as osmosis, its just diffusion? aahhh so confused!

It's known as capillarity which is how water moves via the apoplastic pathway. Capillarity is the movement of water due to the cohesive properties of water through the cell walls of the root cortex cells.

Reply 2432

PR11NCE

Original post by doctordee

If anybody has any last minute questions or are confused on any topics feel free to private message me.
I'd be more than happy to go through things with you.
Good luck guys!

PLEASE do the predicted paper.

Reply 2433

Suzanna5678

Original post by doctordee

You messaged me this already.
I can't because I have been very ill all weekend but I can answers any questions or help that people need.

Okay hope ya feel better soon

Reply 2434

Manni

Original post by Simran Mars Foster

Environmental variation
Root pressure
Independant assortment
Organs
Enzyme inhibitation

Haven't come up a lot

Whats independent assortment regarding?

Reply 2435

EmilyC96

Original post by Suzanna5678

What's chiasma

the same as crossing over i think

Reply 2436

Bixel

Original post by hannah2101

A six mark question came up on tissue fluid in June 2012 so I don't think it will come up again this year!

I bet AQA will be nasty and give us it again! Haha, they seem to like giving similar questions, and they just change a few words :P

Reply 2437

laithmo96

Does anyone know how much ums each unit holds and how much we need to get an A,B thanks!

Reply 2438

ImAz

Original post by Sumi Prakash

Could someone tell me the purpose of the casparian strip please?

It's water resistant, so it redirects water from them apoplastic to the symplastic pathway.
I think this means that the plant can regulate what's coming into it, and stops any chemicals/toxic substances from entering

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Reply 2439

Sapphire123

Original post by Dinvan

Could some explain how artioles are adapted to their function?

Also what is tissue fluid and how does it return to the circulatory system?

Would greatly appreciate the help!!

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Your arterioles carry blood from the artery's to the capillaries under lower blood pressure than the capillaries. They have no valves as the blood pressure is still high. The elastic layer is thinner than the arteries because they are under less pressure. The muscle lining is thinner as well.

Tissue fluid is the fluid that bathes cells in tissues. It contains substances like oxygen, amino acids and glucose, and receives materials like co2. It is therefore used as a means of exchange between the body and the cells.

Its formed in your blood plasma. Your hydrostatic pressure (that is formed from the movement of blood through the arteries, to the arterioles to the capillaries) is used to force tissue fluid out of the blood plasma. The pressure can only force small molecules out of the blood plasma so proteins remain behind. This process is known as ultrafiltration.

Once your tissue fluid has exchanged materials with the cells it bathes it must be returned to the circulatory system. It can do this through the capillaries. When the tissue fluid leaves the capillaries the water potential of the capillaries is reduced, so water can then re enter the capillaries by osmosis down its concentration gradient. The other way it can be returned is through the lymphatic system. The contents of the lymphatic system cannot be moved by the beating of the heart but are moved by hydrostatic pressure and/or muscle contractions that squeeze lymph vessels.

Hope that helped! :smile: