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

Original post by myah_94

No, sorry it's page 162

It’s not the clearest question I’ve ever seen (the wording “Within each variety...” is confusing)
but I assume they are looking for:

•

prevent inbreeding which could ultimately lead to homozygosity for many characteristics

•

preserve the existing variety (or even increase it?) bycrossing different genotypes.

(edited 11 years ago)

Reply 184

I've attached a question in the doc below that I don't really understand, can someone explain it thanks :colondollar:

Tissue fluid.docx

Reply 185

http://www.thestudentroom.co.uk/showthread.php?t=2212505&p=41970257

Original post by Sophie1994

I've attached a question in the doc below that I don't really understand, can someone explain it thanks :colondollar:

Tissue fluid.docx

I guess they’reare after the fact tissue fluid forms at the arterial end of a capillary so long as:
net hydrostatic pressure inside capillary > in surrounding tissue fluid

In this example inside capillary = + 5.2 – 3.15
=2.05
surrounding tissue = + 0.45 – 0.35
=0.1
pressure differential = 2.05 – 0.1
(which forces
fluid out of capillary)

= 1.95

(edited 11 years ago)

Reply 186

BobTheBuilder94

2

Original post by liquid394

by all means :smile:

.

Describe and Explain the process of Semi-conservative replication.

Sorry been putting this q off for a few days, this is just from my jan exam memory...

DNA Helicase unzips the double helix (DNA) into two single stranded poly nucleotides. Free complementary bases (roaming around) attach to the 2 single stranded DNA polynucleotide strands- which act as template strands. This forms 4 single polynucleotide strands, DNA polymerase (enzyme) is used to join the polynucleotide strands together into 2 double helixes.

Explain the cohesion-tension theory

Reply 187

User944645

2

If anybody wants revision notes, mine are here :smile:

Reply 188

Original post by biology911

I guess they’reare after the fact tissue fluid forms at the arterial end of a capillary so long as:
net hydrostatic pressure inside capillary > in surrounding tissue fluid

In this example inside capillary = + 5.2 – 3.15
=2.05
surrounding tissue = + 0.45 – 0.35
=0.1
pressure differential = 2.05 – 0.1
(which forces
fluid out of capillary)

= 1.95

Yep I understand the part where the hydrostatic pressure inside the capillary must be higher than outside in the tissue fluid also that water potential must be more negative for tissue fluid formation.

The aspect which confuses me is the calculation bite... :tongue:

because at least, I worked out the difference in hydrostatic pressure in the capillary and in the tissue fluids then took it away from the difference in water potential and arrived at 1.95

so I did 5.2-0.45=4.75 (difference in HP)
then -3.15-(-0.35)=-2.8 (difference in water potential)

Final step -> 4.75-2.8= 1.95

... the thing is my calculations looks dodgy and I know it looks incorrect and how it arrived at the right answer I don't understand :ashamed2:

(edited 11 years ago)

Reply 189

Original post by Sophie1994

Yep I understand the part where the hydrostatic pressure inside the capillary must be higher than outside in the tissue fluid also that water potential must be more negative for tissue fluid formation.

The aspect which confuses me is the calculation bite... :tongue:

because at least, I worked out the difference in hydrostatic pressure in the capillary and in the tissue fluids then took it away from the difference in water potential and arrived at 1.95

so I did 5.2-0.45=4.75 (difference in HP)
then -3.15-(-0.35)=-2.8 (difference in water potential)

Final step -> 4.75-2.8= 1.95

... the thing is my calculations looks dodgy and I know it looks incorrect and how it arrived at the right answer I don't understand :ashamed2:

I think you’re methodology looks better than mine!
(1) You’ve worked out the overall pressure differential thatwould send water out (4.75)
(2) Then you’ve worked out the effective Ψdifferential that would draw water in (-2.8)
(3) Putting these together, you found the resultant pressureto be 1.95. Brilliant.

Reply 190

Original post by biology911

I think you’re methodology looks better than mine!
(1) You’ve worked out the overall pressure differential thatwould send water out (4.75)
(2) Then you’ve worked out the effective Ψdifferential that would draw water in (-2.8)
(3) Putting these together, you found the resultant pressureto be 1.95. Brilliant.

Haha thanks even though I got the answer I'm unsure of the last step. From the calculations I got 4.75 and -2.8.

I thought I would do 4.75 - (-2.8)= 7.55 since is always the biggest take away the smallest but this gives me 7.55.. this is the part I'm don't understand, or it is because is water potential so I just ignore the negative signs and turn the number into positive?

Reply 191

Original post by Sophie1994

Haha thanks even though I got the answer I'm unsure of the last step. From the calculations I got 4.75 and -2.8.

I thought I would do 4.75 - (-2.8)= 7.55 since is always the biggest take away the smallest but this gives me 7.55.. this is the part I'm don't understand, or it is because is water potential so I just ignore the negative signs and turn the number into positive?

Ah I see what you mean. I treated it like algebra where I was just putting a positive integer with a negative integer and let them fight it out! That’s all I’ve got.

Reply 192

Original post by biology911

Ah I see what you mean. I treated it like algebra where I was just putting a positive integer with a negative integer and let them fight it out! That’s all I’ve got.

Haha, yep, I'll definitely try that out if I come across another question like this. :cool:

Reply 193

F1's Finest

21

You don't need to work out pressure, It's not in the spec.

Reply 194