AQA BIOL2 Biology Unit 2 Exam - 26th May 2011

Pm me a model answer regarding tissue fluid? It's the one thing I think I would struggle with if it came up for 6 marker ! <3

Is this all we need to know about fish?

- The pharynx is lowered, and pressure decreases inside the fish's mouth, so water is drawn in.
- The pharynx then closes and pressure is high in the mouth, so water is forced out past the gills over the operculum.
- Gills have many filaments and lamallae to increase surface area for efficient gas exchange.
- The counter current system improves gas exchanges because blood travels in the opposite direction of water. This means that blood always has a lower oxygen concentration than the water, so the oxygen will diffuse into the blood.

Can anyone add to that or is that all we need to know?
Thanks

Is this all we need to know about fish?

- The pharynx is lowered, and pressure decreases inside the fish's mouth, so water is drawn in.
- The pharynx then closes and pressure is high in the mouth, so water is forced out past the gills over the operculum.
- Gills have many filaments and lamallae to increase surface area for efficient gas exchange.
- The counter current system improves gas exchanges because blood travels in the opposite direction of water. This means that blood always has a lower oxygen concentration than the water, so the oxygen will diffuse into the blood.

Can anyone add to that or is that all we need to know?
Thanks

Yes that's pretty much it. Although you may want to add during inspiration when the mouth opens the pharynx is lowered due to muscle contractions and this also increases the volume of the chamber. But aside from that it looks fine

Looks pretty good to me, I probably wouldn't even mention the pharynx myself just that water is drawn in and forced out over the gills ^^

what are the coronary arteries? D:

Is the cohesion, in cohesion tension theory, caused by hydrogen bonds or Van der Waals'?
cos the text book says hydrogen, but i'm sure my teacher told us it was Van der Waals' :/

and could someone try explain root pressure to me?

thanks!

what are the coronary arteries? D:

Is the cohesion, in cohesion tension theory, caused by hydrogen bonds or Van der Waals'?
cos the text book says hydrogen, but i'm sure my teacher told us it was Van der Waals' :/

and could someone try explain root pressure to me?

thanks!

Looks pretty good to me, I probably wouldn't even mention the pharynx myself just that water is drawn in and forced out over the gills ^^

are they not just the Vena Cava, and the Aorta? otherwise i'm stuck too :/

pretty sure it's Hydrogen bonds (they are technically Van der Waals, but it's definitely h bonds.

When the casparian strip prevents water from entering via apoplast pathway, the water switches to symplast.
The salts in the endodermis are actively transported into the xylem and this makes a force which helps draw water up the plant. The force is root pressure.

Hydrogen bonds. Save van der waals for Chemistry :P

You may just want to add that due to the endordermal cells actively transporting ions and salts into the xylem, the water potential of the xylem is lowered and therefore water moves into the xylem via osmosis

ive never been taught about the pharynx i hope that doesnt come up

oh yeah, so what does root pressure do then?

ive never been taught about the pharynx i hope that doesnt come up

sorry it's not really clear.
So originally it's ii,
then this become Ii iI (during sc replication, the strands separate and become I, i, i and I which are joined by free nucleotides all 15N)
becoming : II, Ii, iI, II
this then becomes
II, II, II, Ii, iI, II, II II
8 results!

Sorry late reply, was revising som philosophy and ethics too