AQA BIOL2 ~ 21 May 2012 ~ AS Biology

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Reply 1380

cuckoo99

your spec is sooo similar to ours ( AQA Human Biology) minus the plants and add evolution in and human adaptations

im scared i havent done enough revision please pray for me

Reply 1383

Waki

All of this xylem, apoplast, symplast stuff is starting to confuse me..
In some places it mentions you have to say about the casparian strip, others it doesnt.

What questions could we be asked on just to do with xylem
And the mark scheme answers to go with it please.

Reply 1384

EffKayy

Original post by dongonaeatu

im scared i havent done enough revision please pray for me

lol, k.

Reply 1385

W4L1Y

Could someone explain antiobotic resstant and what is an antibiotic? :confused:

Reply 1386

Mocking_bird

Original post by britash

I'm confused myself. I'll tell you my understanding, maybe you can tell me where i'm wrong :smile:

Human cell. Meiosis..
So a diploid cell has 46 chromosome (or is it pairs.... O.o)
Then at meiosis 1, the homologous chromosomes pair up.. so doesnt it double?
Then still at meiosis 1, you have crossing over, and then you get 1 chromosome in each cell (it divides)
Then at meiosis 2... the chromatids from the chromosome move apart, so you have 1 chromatid in each cell (a gamete)... (how many chromosomes are here then..?)

Like how many chromsomes (or pairs..!?!?) are at each bit..?

Okay here we go, i hope this helps :smile:

(may need to open it in a new window as its fairly big so will get shrunk by tsr)

Spoiler

(edited 11 years ago)

Reply 1387

britash

Original post by Mocking_bird

Okay we go, i hope this helps :smile:

(may need to open it in a new window as its fairly big so will get shrunk by tsr)

Spoiler

Theres 8 chromosomes in each cell.. O.o?
How come its like... just 2 in a cell in the text book..
I thought it was lkke this :

i'm so confused O.O

Reply 1388

username890104

Original post by britash

Theres 8 chromosomes in each cell.. O.o?

No, that is a template. Imagine M_B having to draw the real number of chromosomes.

Reply 1389

Dorkins

Original post by totw

What do we need to know about tissue fluis and the lymphatic vessels for this exam? :confused:

- Hydrostatic pressure is high in the arteriole (artery) end of the capillary
- This forces water out and into the tissue fluid (glucose, ions and other solutes also leave the capillary. Proteins in the blood plasma are too big to leave the capillaries)
- Because the water content decreases, the concentration of blood protein increases. This reduces the water potential inside the capillary
- By the time the blood is at the venule (vein) end, the water potential is low enough that water moves back into the capillary via osmosis

- Not all of the water is reabsorbed. The remaining tissue fluid enters the lymph vessels
When it's inside the lymphatic system, it's called lymph
- The lymph travels to the lymph nodes, where it filtered and cleaned up
- The cleaned lymph then rejoins the circulatory system at the vena cava

Reply 1390

Mocking_bird

Original post by Tullia

No, that is a template. Imagine M_B having to draw the real number of chromosomes.

I'm not really sure how to explain this anymore,
Can you try Tullia? :tongue:

Reply 1391

EffKayy

Original post by Mocking_bird

I'm not really sure how to explain this anymore,
Can you try Tullia? :tongue:

Do we have to know ethical issues surrounding the use of antibiotics? o_O

Reply 1392

Mocking_bird

Original post by britash

Theres 8 chromosomes in each cell.. O.o?
How come its like... just 2 in a cell in the text book..
I thought it was lkke this :

i'm so confused O.O

Actually I think I get where you're confused now (maybe)

In a human cell there would be 46, but i couldnt be bothered drawing 46 :tongue:

I think you're confusion is interphase.
In your first cell, its a single stranded chromosome. In the second cell, it shouldnt be 4 single stranded chromosomes, it should be 2 double stranded chomosomes (2 chromatids joined by a centromere).

I have a diagram in my book if you want me to scan it in.

Reply 1393

The Assassin

Original post by EffKayy

Do we have to know ethical issues surrounding the use of antibiotics? o_O

Possibly. I believe the CGP guide mentions it so it's likely the could give a question in an unfamiliar context.

Reply 1394

holliezilph

can anyone explain what tissue fluid is and what is its purpose?

Reply 1395

George_

Err, I've only started revising today because of other exams. :/

So far I've done: Transport in Organisms, Meiosis, Mitosis, Classification. But I dunno what else to do! How to revise so much stuff?!

Reply 1396

britash

How many chromosomes are there before meiosis 1
during meiosis 1, meiosis 2...?

Because I thought it was 2n
then it doubled to 4n at interphase
Then at meiosis 1, after crossing over and independent segregation when it separates to daughter cells it goes to 2n
Then at meiosis 2, this goes from 2n to n...

I dont know if this is right.. but then.. how many choromsomes are 4n, 2n and n... thats whats confusing me :/