Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta

AQA BIOL2 Biology Unit 2 Exam - 26th May 2011 watch

  • View Poll Results: Are you resitting this unit?
    YES!
    28.62%
    NO!
    71.38%

    Offline

    2
    ReputationRep:
    (Original post by Jorgeyy)
    Yea I posted after that I understood that method but I was trying to explain WHY to the guy that it occurs like that

    Thanks though, would be very useful if I didn't know ^^
    Is it always 2^ no chromosomes? I haven't been taught that lol
    Offline

    12
    ReputationRep:
    (Original post by nasira372)
    Plant adaptations for water loss are stomata in pits to trap air. This reduces the water potential

    This is what is says in my notes. Water potential of what though???
    It decreases the concentration gradient for osmotic movement of water, the diference in water potential between the air trapped around the stomata and the in the stomata itself will be reduced
    Offline

    0
    ReputationRep:
    (Original post by Kandy_Kain_94)
    So basically you can afford to lose 20 marks and still get an A?
    on one paper the mark out of 85 for an a was 54!
    Offline

    1
    ReputationRep:
    (Original post by Jorgeyy)
    Yea I posted after that I understood that method but I was trying to explain WHY to the guy that it occurs like that

    Thanks though, would be very useful if I didn't know ^^
    Oh!!...Apologies

    I just wanted to answer as its one of the very few things I know
    Offline

    2
    ReputationRep:
    (Original post by Unbiased Opinion)
    I know, and when people say the answers to things and you didn't get that. Sucks bad. :p:

    Ouch. :hugs: I've got Ethics in the morning, I haven't revised it much at all, need to do some before I go to bed. Ah well it'll be done in 24 hours.
    Yeahh but i'd want to know so i'd know what to expect at results... Thats even worse all essay writing good luck to you I don't finish till friday i have chemistry but i am soo fed up of revision right now. :argh:
    Offline

    0
    ReputationRep:
    if any1 needs help on bio 2, just pm on me and we can actually chat on skype
    i wanna help all u noob biologists in unit 2 lol

    just pm me if u want to leet me kno
    Offline

    0
    ReputationRep:
    For a question asking about gas exchange in insects...

    • Respirartory gases enter and exit through pores called spiracles
    • These are closed most of the time to prevent water loss
    • Spiracles lead to tracheae which are tubes where the gases travel along, and into even smaller ones called tracheoles
    • Numerous thacheoles mean bigger surface area
    • Short diffusion pathway for the gases to cells
    • Increases diffusion
    • Diffusion gradient occurs because respiring gases produce carbon dioxide and concentration of oxygen decreases as it becomes used up.
    • So oxygen diffuses along conc. gradient from atmosphere to tracheae, tracheoles and into cells. (and the opposite for carbon dioxide)
    • Ventilation occurs by mass movement of air when the insect's muscles contract, this makes the rate of diffusion faster.


    Anything wrong or missing?
    Please could anyone give the points for a question about tissue fluid?
    Offline

    0
    ReputationRep:
    (Original post by EffKayy)
    Is it always 2^ no chromosomes? I haven't been taught that lol

    2^ of pairs of chromosomes

    As previously stated, humans is 2^23 not 2^46

    The most that will come up will require 2^3 or something probs so you can systematically work it out since this isn't a maths exam..

    The worst math you'll find is standard deviation or index of diversity

    remember d = N(N-1) / sum of (sigma) n(n-1)
    Offline

    1
    ReputationRep:
    (Original post by Kaylaleigh)
    It decreases the concentration gradient for osmotic movement of water, the diference in water potential between the air trapped around the stomata and the in the stomata itself will be reduced
    So the water cant move out because there is no gradient so transpiration is reduced. Think I understand now
    Offline

    2
    ReputationRep:
    "The students plotted the distance moved by the air bubble against time on a graph. Describe how they could use the graph to calculate the mean rate of water uptake."

    I have no idea o_O
    Anybody know the answer? I don't know what paper the question came from so can't look up the answer scheme myself. We literally did nothing on potometers and they seem to come up on the majority of papers D:
    Offline

    9
    ReputationRep:
    (Original post by cherri3)
    Yeahh but i'd want to know so i'd know what to expect at results... Thats even worse all essay writing good luck to you I don't finish till friday i have chemistry but i am soo fed up of revision right now. :argh:
    I know what you mean... I would hate to ever think I'd done well then not. That's never happened to me but that would be awful!

    Haha, thanks. I'd rather Bio was in the morning but ahh well.

    I have Chem on Fri then French on the 6th, joy. :p: Tomorrow is my 1st exam. Dw, revision will be done soon, no more for like 7 months!
    Offline

    13
    ReputationRep:
    (Original post by iguess)
    For a question asking about gas exchange in insects...

    • Respirartory gases enter and exit through pores called spiracles
    • These are closed most of the time to prevent water loss
    • Spiracles lead to tracheae which are tubes where the gases travel along, and into even smaller ones called tracheoles
    • Numerous thacheoles mean bigger surface area
    • Short diffusion pathway for the gases to cells
    • Increases diffusion
    • Diffusion gradient occurs because respiring gases produce carbon dioxide and concentration of oxygen decreases as it becomes used up.
    • So oxygen diffuses along conc. gradient from atmosphere to tracheae, tracheoles and into cells. (and the opposite for carbon dioxide)
    • Ventilation occurs by mass movement of air when the insect's muscles contract, this makes the rate of diffusion faster.


    Anything wrong or missing?
    Please could anyone give the points for a question about tissue fluid?




    Explain how tissue fluid is formed and how it may be returned to the circulatory system? (6 marks)

    There is a high hydrostatic pressure at the arteriole end of the capillary, due to heart contraction.

    This pressure causes filtration of plasma containing (glucose, hormones, amino acids, water) to pass out of the permeable capillary wall. The filtered plasma forms tissue fluid which surrounds body cells.

    Large plasma proteins and red blood cells are too large to fit through the gaps so remain in the capillary.

    They dissolve and lower the water potential of the fluid inside the capillary. So water moves back into the capillaries by osmosis at the venous end of the capillary where there is a low hydrostatic pressure.

    Because the process is slow, there will be excess tissue fluid. This enters the lymphatic vessel and is now called Lymph. The lymphatic system returns the lymph back to the blood.
    Offline

    0
    ReputationRep:
    (Original post by iguess)
    For a question asking about gas exchange in insects...

    • Respirartory gases enter and exit through pores called spiracles
    • These are closed most of the time to prevent water loss
    • Spiracles lead to tracheae which are tubes where the gases travel along, and into even smaller ones called tracheoles
    • Numerous thacheoles mean bigger surface area
    • Short diffusion pathway for the gases to cells
    • Increases diffusion
    • Diffusion gradient occurs because respiring gases produce carbon dioxide and concentration of oxygen decreases as it becomes used up.
    • So oxygen diffuses along conc. gradient from atmosphere to tracheae, tracheoles and into cells. (and the opposite for carbon dioxide)
    • Ventilation occurs by mass movement of air when the insect's muscles contract, this makes the rate of diffusion faster.


    Anything wrong or missing?
    Please could anyone give the points for a question about tissue fluid?
    At the start of the cap[capillary bed there is high pressure due to heart contraction (closer to the heart)

    This causes ultra filtration, so small molecules pass through capillary (i.e amino acids) and form the tissue fluid

    proteins too large to fit through the capillary by ultra filtration so remain, therefore plasma has low water potential

    As water potential is lower in capillary,water moves back into the capillaries by osmosis.

    Anything missing anyone?
    Offline

    0
    ReputationRep:
    find gradient of the curve of best fit?
    Offline

    1
    ReputationRep:
    (Original post by iguess)
    For a question asking about gas exchange in insects...

    • Respirartory gases enter and exit through pores called spiracles
    • These are closed most of the time to prevent water loss
    • Spiracles lead to tracheae which are tubes where the gases travel along, and into even smaller ones called tracheoles
    • Numerous thacheoles mean bigger surface area
    • Short diffusion pathway for the gases to cells
    • Increases diffusion
    • Diffusion gradient occurs because respiring gases produce carbon dioxide and concentration of oxygen decreases as it becomes used up.
    • So oxygen diffuses along conc. gradient from atmosphere to tracheae, tracheoles and into cells. (and the opposite for carbon dioxide)
    • Ventilation occurs by mass movement of air when the insect's muscles contract, this makes the rate of diffusion faster.


    Anything wrong or missing?
    Please could anyone give the points for a question about tissue fluid?
    The trachea is lined with Chitin which is impermeable to gases. I think you covered everything else!
    Offline

    0
    ReputationRep:
    (Original post by parallal)
    With antibiotic resistance that's basically just natural selection right?
    There's variation in the population. Mutation occurs which results in an allele with resistance to a certain antibiotic. The bacteria with the advantageous allele will survive antibiotic treatment and those without will die. The ones who survive can grow and reproduce, pass on the advantageous allele and its frequency will increase. The antibiotic will become less effective. The gene to resistance can be passed on by either horizontal gene transmission between bacteria of different species or by passing it along to offspring by vertical gene transmission.

    Does that sound about right to you?
    Yay well done just remember that horizontal gene transmission takes place by conjuation or you'll lose a mark as it is underlined in the mark scheme.
    Offline

    1
    ReputationRep:
    (Original post by Twigleheight)
    "The students plotted the distance moved by the air bubble against time on a graph. Describe how they could use the graph to calculate the mean rate of water uptake."

    I have no idea o_O
    Anybody know the answer? I don't know what paper the question came from so can't look up the answer scheme myself. We literally did nothing on potometers and they seem to come up on the majority of papers D:


    they can draw a line of best fit and find the gradient of that line. I think that sounds right/
    Offline

    0
    ReputationRep:
    (Original post by Nugard123)
    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
    erm, this isn't in the NT book?
    Offline

    0
    ReputationRep:
    Is 60 something nearly a 100 ums out of 85?? no wayy
    Offline

    0
    ReputationRep:
    What does having hollow xylem vessels which die soon after they are made so all the organelles are lost mean?! Why is this useful?!
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: March 14, 2018
Poll
Do you agree with the proposed ban on plastic straws and cotton buds?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.