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

  • View Poll Results: Are you resitting this unit?
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    (Original post by jessplease)
    what do we need to know about the blood system in unit 2?
    Mainly about the veins/cappilaries/arteries Also haemoglobin / it's saturation curve.
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    thankss, under mass transport on the specification its only got the definition of it, do you think thats all we need to know?
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    Argh, the UMS vary so much! Jan 2011 63 Raw = 140 UMS. June 2010 73 raw marks = 140 UMS!
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    Why don't we start questioning each other like we did on the BIO1 thread? It really helps!
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    (Original post by Insanity514)
    Why don't we start questioning each other like we did on the BIO1 thread? It really helps!
    what's the phospholipid bilayers function?
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    ^ isnt that unit 1?

    Acts as a barrier to water soluble substances but
    allows lipid soluble molecules to pass through.
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    (Original post by Insanity514)
    Why don't we start questioning each other like we did on the BIO1 thread? It really helps!
    We've been doing that already

    here, answer

    Describe the adaptations of an insect for efficient gas exchange. (6)


    Describe the adaptations of a plant for efficient gas exchange. (6)
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    can anyone remember all the questions
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    i soo want to do well on this one!
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    I reckon I can nail this exam, it is just the DNA/Genes that I need to learn everything else is absolutely fine. much better than unit 1 this unit is like 80% learning how stuff works
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    (Original post by SteveCrain)
    We've been doing that already

    here, answer

    Describe the adaptations of an insect for efficient gas exchange. (6)


    Describe the adaptations of a plant for efficient gas exchange. (6)
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    Wow I think I'll just answer the first one

    Insects have a ventilation mechanism called air sacs. These air sacs produce short bursts of oxygenated air and pump them to cells for quick respiration. Spiracles close during the contraction of air sacs to stop air escaping. Also the tracheole tips in insects provide a large surface area for oxygen to diffuse across meaning the rate of diffusion increases. The tips of the tracheoles are also filled with fluid meaning that oxygen can dissolve in it before it diffuses again making the rate of diffusion faster. The tracheoles also directly penetrate the cells in an insect and so oxygen and air is directly delivered to each cell and so the rate of diffusion is quicker. The insect also has a waxy skin layer so that water vapours cannot diffuse out of its surface and so this means less useful gases are lost to the environment.

    EDIT also the cells of an insect actively use oxygen in respiration thereby maintaining a diffusion gradient...

    Anything to add? I hate insects lol
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    you could also say that during vigorous exercise insects respire anaerobically, producing lactic acid. this reduces the water potential of of the tissue causing water in the tracheoles to move into the tissue - this increases the rate of diffusion in places where oxygen is required the most xD

    adaptations of a plant for efficient gas exchange:

    Stomata allow diffusion of gases in and out of the leaf, spongy mesophyll layer provides a large surface area for diffusion of gases increasing the rate of gas exchange, palisade mesophyll cells contain many chloroplasts, so CO2 is used up, creating a concentration gradient into the air space. Plants need to balance CO2 intake for photosynthesis with water loss by transpiration, otherwise they will become dehydrated - when guard cells lose turgor they close the stomata, limiting water loss. Waxy cuticle, hairs around stomata, sunken stomata all help limit water loss...

    Was this in a paper? If so which one? Struggling to find 6 points there and not sure if they want to hear about the xerophytic adaptations... what have i missed?
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    (Original post by Insanity514)
    Wow I think I'll just answer the first one

    Insects have a ventilation mechanism called air sacs. These air sacs produce short bursts of oxygenated air and pump them to cells for quick respiration. Spiracles close during the contraction of air sacs to stop air escaping. Also the tracheole tips in insects provide a large surface area for oxygen to diffuse across meaning the rate of diffusion increases. The tips of the tracheoles are also filled with fluid meaning that oxygen can dissolve in it before it diffuses again making the rate of diffusion faster. The tracheoles also directly penetrate the cells in an insect and so oxygen and air is directly delivered to each cell and so the rate of diffusion is quicker. The insect also has a waxy skin layer so that water vapours cannot diffuse out of its surface and so this means less useful gases are lost to the environment.

    EDIT also the cells of an insect actively use oxygen in respiration thereby maintaining a diffusion gradient...

    Anything to add? I hate insects lol
    You sure air sacs are on the syllabus?
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    (Original post by SteveCrain)
    You sure air sacs are on the syllabus?
    For AQA yeah they are. Its the ventilation mechanism in Insects.
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    (Original post by Insanity514)
    For AQA yeah they are. Its the ventilation mechanism in Insects.
    Taken from the only AQA endorsed book:

    "Ventilation. The movement of muscles in insects can create mass movements of air in and out of the tracheae, This further speeds up the exchange of respiratory gases."

    No air sacs for insects.
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    Im so dreading this exam!
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    (Original post by STARMissyB)
    Im so dreading this exam!
    Likewise!! I so KNOW that im gonna forget something major!
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    (Original post by Insanity514)
    For AQA yeah they are. Its the ventilation mechanism in Insects.
    But all we need to know is that insects have a ventilation method called Ventilation, or, the mass movement of muscles, which replaces air in the tracheae and tracheoles
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    (Original post by SteveCrain)
    But all we need to know is that insects have a ventilation method called Ventilation, or, the mass movement of muscles, which replaces air in the tracheae and tracheoles
    I dunno we got taught about air sacs as wel
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    What does it mean appreciate the tentative nature that can be drawn relating to the causes of varitation in the spec?
 
 
 
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