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AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011 watch

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    (Original post by Destroyviruses)
    Omg your doing medicine at birmingham! You'll get to go the the queen elizabeth hospital itss sooo lovely and the underground floor is called -1!!!And I've got an offer at bham tooo for chemistry.
    I am (if i managed to get AAA... )! I know, I really hope I'm there later this year.

    (Original post by Destroyviruses)
    Aw, sorry! You sound so nice and unsnobby! I thought you were a girl!
    I'll take that as a compliment :P.

    (Original post by Destroyviruses)
    I'm going to type this essay please mark it! Using the descriptors attached on the mark scheme at the end of the paper. Its so rubbish!

    Don't laugh.

    Question: Mean temperatures are rising in many parts of the world. The rising temperatures may
    result in physiological and ecological effects on living organisms. Describe and explain
    these effects.

    Increase int emperature is dealt with by living organisms in a variety of ways. Animals are seperated into two groups when considering thermoregulation. There are ectotherms and endotherms.

    Ectotherms will be greatly affectced by increase in heat as they get most of their heat from the enviroment. It will cause them to spend more time in the shade to prevent overheating.This may affect their ability to succesfully predate therefore decrease their chance of survival.Their enzymes will work faster so more metabolic activities such as protein synthesis occurs. This will require more energy which is difficult in the dark.

    Endotherms are able to control their temperature to an extent. The skin receptors will send impulses to the heat loss centre in the hypothalamus ,which sends impulses to the arteriaoles to dialate,hair to flatten and sweat glands to produce sweat which causes loss of heat through evaporation this keeps the blood cool. The blood is also kept cool as more of it is at the surface if the skin increasing surface area over which heat can be radiated out.

    Increase in temperature can also have numerous ecological effects. it can decrease habitats of animals adapted to living in the cold such as polar bears.As polar ice melts there is less space over which polar bears and mate and live.This will increase selection pressures of polar bears better adapted at living in the ocean.

    There will also be selection pressures within the plant community.Plants adapted to living in warmer conditions will be favoured,this is called directional selection. Plants that are adapted have features such as thin leaves to prevent water loss as the surface area to volume ratio is small. The main problem for plants is lack of water.

    Plants that are used for crops will decrease in yeild ,this will affect energy pyramids because all energy in energy pyramids enters by plants. This will cause a great reduction in energy transfered to higher tropic levels.The number of tropic levels of energy pyramids may also decrease because energy transfer is inefficient between levels.

    Plant yeilds will decrease because more of the energy assimilated will be used in respiration rather than stored.This is because the movement of enzymes will be faster as heat provides kinetic energy so more reactions occur per unit of time, these reactions require ATP which can only be produced through respiration.


    Please stop laughing!
    I actually think that the essay covers most of what you would want to/need to talk about and seems to do it in sufficient detail IMO.

    Ideas for other things to add (i think?):

    - I think you sort of mentioned this but biodiversity reduction and knock on effect of distruption of food chains.

    - Denaturation of enzymes and maybe some more about how ectotherms would have a greater geographical range as a result of more thermal energy avalilable in environment where it wasn't before.

    - Could also mention the spread of tropical diseases which could effect the food chain, biodiversity etc.

    I'm not really sure what else to add because you got most of the key points, very well done.
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    Going to start posting revision notes from memory as it should help me revise and might help others...

    Revision Notes for Feedback Mechanisms

    Control Mechanisms -

    - Homeostatic control of any system involves a series of steps:

    1) The set point or desired level at which the system operates (the norm)

    2) A receptor which detects any deviation from the set point (norm)

    3) A controller which coordinates infromation from various sources.

    4) An effector which carries out the corrective measure required to return the system to its set point (norm).

    5) A feedback loop which informs the receptors of changes to the system brought about by the effector. If this information was not fed back then the receptor would continue to stimulate the effort leading to over-correction.

    Negative feedback -

    - It's feedback that causes the corrective measures to be turned off.

    - The system returns to its original level.

    An example of negative feedback: (temperature regulation)

    1) If the temperature of the blood rises then thermoreceptors in the hypothalmus transmit nerve impulses to the heat loss centre, also located in the hypothalmus.

    2) It in turn transmits nerve impulses to the skin (the effector)

    3) Vasodilation, sweating and lowering of body hairs all reduce body temperature.

    4) If the fact that the blood temperature had returned to the set point was not fed back to the hypothalmus then it would continue to stimulate the skin to lose body heat.

    5) This would cause the body temperature to fall below normal and could lead to hypothermia.

    6) In practice cooler blood returning from the skin passes through the hypothalmus and thermoreceptors detect the blood temperature is at its set point and stop transmitting nerve impulses to the heat loss centre.

    7) The heat loss centre stops transmitting nerve impulses to the skin and so vasodilation, sweating etc stop.

    8) The cooling of the body to its normal temperature causes the switching off of the effector and hence it's an example of negative feedback.

    - There are separate negative feedback mechanisms for regulation of departures from the norm in each direction giving a greater degree of homeostatic control.

    Another example of negative feedback (control of blood glucose):
    Fall in blood glucose concentration:

    1) If there is a fall in the concentration of blood glucose then alpha cells in the islets of langerhans in the pancreas produce the hormone glucagon.

    2) Glucagon causes the converstion of glycogen to glucose and glyconeogenisis in the liver.

    3) The blood glucose concentration returns to normal.

    4) This blood is circulated back to the pancreas where the alpha cells detect the change and stop producing glucagon. (negative feedback)

    Rise in blood glucose concentration:

    1) If the level of glucose in the blood rises insulin is produced by beta cells in the pancreas.

    2) Insulin causes an increase in the uptake of glucose by cells and its conversion into glycogen and fats.

    3) The resulting fall in blood glucose causes insulin production to be turned off. (negative feedback)

    Positive Feedback -

    - It occurs when feedback causes the corrective measures to remain turned on.

    - It causes the system to devaiate even further from its original level.

    Example of positive feedback:

    1) Stimulation of neurones causes an influx of sodium ions.

    2) The influx causes the permeability of the neurone to sodium ions to increase and so more sodium ions enter which further increases the permeability of the neurone allowing ions to enter rapidly.

    3) This results in a very rapid build up of action potential allowing an equally rapid response to a stimulus.

    - Positive feedback occurs more often when control systems break down.

    Control of the oestrous cycle -

    - The menstrual cycle is a type of oestrous cycle where the lining of the uterus is shed along with some blood between each cycle.

    - 2 hormones are released from the pituitary gland (which lies at the base of the brain):

    FSH (follicle stimulating hormone) - which stimulates the development of follicles in the ovaries, which contains eggs, and stimulates the follicles in the ovaries to produce oestrogen.

    LH (luteinising hormone) - which causes ovulation to occur and stimulates the ovaries to produce of progesterone from the corpus luteum.

    - The other 2 hormones are produced in the ovaries:

    Oestrogen - causes the uterus lining to build up again after menstruation and stimulates the production of LH from the pituitary gland.

    Progesterone - maintains the uterus lining in readiness to receive a fertilised egg, it also inhibits the pituitary gland producing FSH.

    The Menstrual cycle -

    1) It begins when the uterus lining is shed along with some blood (days 1-5)

    2) From day 1 the pituitary gland releases FSH into the blood causing follicles in the ovaries to develop and mature. Each follicle contains an egg.

    3) The growing follicles secrete small amounts of oestrogen into the blood. These low levels of oestrogen inhibit the pituitary gland from producing LH and FSH. (negative feedback)

    4) As the follicles grow the produce more oestrogen. The oestrogen level increases until around day 10 it reaches a critical point where it stimulates the release of FSH and LH by the pituitary gland (positive feedback).

    5) There is a surge in FSH/LH production. The surge in LH causes one of the follicles in the ovaries to release its egg. This is called ovulation and occurs at day 14.

    6) After ovulation the LH stimulates the empty follicle to develop into a structure called the corpus luteum which secretes progesterone and small amounts of oestrogen.

    7) Progesterone maintains the thick lining of the uterus and inhibits the pituitary gland releasing FSH/LH.

    8) If the egg is not fertilised the corpus luteum degenerates and so no longer produces progesterone.

    9) With less progesterone the uterus lining is no longer maintained and so breaks down (menstruation). Less progesterone also means FSH release is no longer inhibited.

    10) FSH release therefore resumes and the cycle repeats itself.
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    (Original post by hiyarearl)
    I am (if i managed to get AAA... )! I know, I really hope I'm there later this year.



    I'll take that as a compliment :P.



    I actually think that the essay covers most of what you would want to/need to talk about and seems to do it in sufficient detail IMO.

    Ideas for other things to add (i think?):

    - I think you sort of mentioned this but biodiversity reduction and knock on effect of distruption of food chains.

    - Denaturation of enzymes and maybe some more about how ectotherms would have a greater geographical range as a result of more thermal energy avalilable in environment where it wasn't before.

    - Could also mention the spread of tropical diseases which could effect the food chain, biodiversity etc.

    I'm not really sure what else to add because you got most of the key points, very well done.
    Thank you so much!I was quite disappointed with it!
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    Hi, guys. I've attached this mindmap of all the alevel bio topics, it's kinda tailored to me though so I've missed out some stuff, I thought i'd remember.

    But I was thinking, maybe, everyone could use this to put coloured lines to join topics that link. For the synoptic essay! I spent all day making it yesterday!

    Have fun revising!
    Attached Files
  1. File Type: docx mindmap 2.docx (30.3 KB, 238 views)
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    (Original post by bethalex)
    i've barely done anything so far, feel really bad bout it, i'm kinda freaking out about the essay aswell, does anyone have a big list of mark schemes for all the different titles there has been, if so it would be really helpful to me, thank you

    i don't think we got taught anything about cystic fibrosis either:/
    Do you want all the different titles there have been? Or the actual mark schemes because I have the titles, and different things to write about for each one, but not easy to transfer onto here.
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    I'm so confused about some questions on the specimen paper. I don't get the electrophoresis question (9b)at all!! How does partial digestion end up with more fragments!!

    Also the Last part of question 10. How does low uptake proof that its active transport!!!!!!!!!!!
    So annoyed!
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    (Original post by Jackbruce)
    apologies for posting again, would really like to know!
    I think the questions are only in the books, alot of them are from past papers so try looking for some in energy and ecosystem papers of the past spec on the AQA website.
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    (Original post by parallal)
    That's a good idea. That should be helpful.

    I haven't actually but if I can find someone to mark one or two that would be great. I've got two booklets on writing synoptic essays from my biology teacher. And one of them has a long list of essay topics.
    Have you done the specimen paper?
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    (Original post by cobra2k10)
    Links to the AQA website for the specimen BIOL5 paper + mark scheme as the files are too large to be uploaded! Just click on the "Specimen papers and mark schemes" tab and scroll down.

    http://web.aqa.org.uk/qual/gce/scien...&prev=&tabid=1
    Hi, have you done the specimen paper?
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    Re: Last part of question 10.
    The reason it proves it's active transport is because this is a process requiring energy (diffusion etc being passive) therefore if no uptake happens once the fungi is dead, uptake is being controlled by a process needing energy (lack of energy once dead lol) so therefore it is active transport.
    hope this helps!
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    I did the specimen paper and got 77/100, which based on last years grade boundaries works out at 140/140 UMS
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    (Original post by billst13)
    I did the specimen paper and got 77/100, which based on last years grade boundaries works out at 140/140 UMS
    well done! i havent even done it yet, i want to save it until close to the exam seeing as there are only two practice papers :mad:
    need to get an A in this exam oh dearrr :afraid:
    have you done alot of revision?
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    2 practice papers?! Where's the other one? I've revised heavily on coordination, muscle contraction, homeostasis, need to do all the DNA Tech and transcription stuff, oh and synoptic revision
    I've got my unit 4 resit on monday though (got 74/100 UMS so need to get that up to around 85ish) then I only need around 90ish UMS from unit 5...
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    (Original post by billst13)
    2 practice papers?! Where's the other one? I've revised heavily on coordination, muscle contraction, homeostasis, need to do all the DNA Tech and transcription stuff, oh and synoptic revision
    I've got my unit 4 resit on monday though (got 74/100 UMS so need to get that up to around 85ish) then I only need around 90ish UMS from unit 5...
    June 2010 and the specimen paper.
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    thanks! I'm getting stuck into it now!
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    Just finished June 2010 paper. I got 65/100 but I didn't do the essay so I'm relatively happy with that! How is everyone comparing? Do I need more revision still?
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    (Original post by billst13)
    I did the specimen paper and got 77/100, which based on last years grade boundaries works out at 140/140 UMS
    Awesome I got 73 out of 100. Or 71 depending on wether you agree that the last question about how IAA is uptaken by the fungus has a dumb answer.
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    (Original post by Destroyviruses)
    Could I find them booklets online? I need help! "hiyarearl" said she'd mark mine maybe she'd mark yours too. Or I could mark yours if i get this dumb mindmap finished.
    I don't think so. It's a mash up of synoptic essay information from different sources and I don't know the sources (sorry). Nah, that's ok. I went in to school today and asked my teacher to mark it. Should get it back by Friday.
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    (Original post by Destroyviruses)
    Have you done the specimen paper?
    Yeah, my class had to do it in "exam conditions" last week. I got a low C....
    but I have studied a whole lot more since then.
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    I have a question regarding control of the menstrual cycle... I'd really appreciate an answer!

    Ok, so in terms of positive feedback my book states this:

    Oestrogen stimulates the pituitary to release LH (when in high concentraion, which i fully understand)

    LH stimulates the ovary to release more oestrogen (???)

    Oestrogen further stimulates the release of LH and so on

    I do not understand how LH stimulates the ovary to release more oestrogen? Before reading this, all I was aware of was that LH stimulates the formation of the corpus leutum which releases progesterone. I did not know that LH simulates the release of oestrogen? I know that oestrogen stimulates the release of LH but not the other way around.

    Eep, help, confussiiiooonnn!
 
 
 
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