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    (Original post by jimmy303)
    1.)Explain how grazing prevents succession. Suggest why grasses can survive being grazed upon, but smaller woody plants and shrubs cannot.

    Succession is prevented as grazing stops the amount of growth of plant species needed to alter the environment, e.g. through the deomposition of matter that would not have been eaten. Grasses survive as their growth rate is fast enough between grazing to survive, whereas other plants cannot, and so don't photosynthesise, can't respire etc.

    2.) I was recently conducting a study into the investigation of the colour found under the wings of eagles. The recessive allele 'q' codes for the production of a purple pigmentation under the wing. The dominant allele 'p' codes for the formation of green pigmentation under the wing.

    A.)Define in terms of expression in the phenotype
    i) Dominant allele - This allele affects the phenotype when present and 'represses' a recessive allele in heterozygous genotypes.
    ii.) Recessive allele - This allele is expressed only if no dominant allele is present, i.e. in recessive homozygous genotypes.
    iii.) Codominance - both alleles affect the phenotype of a heterozygous genotype, and neither is dominant over the other. For example, alleles A and B are codominant and, together, produce blood type AB.
    iv.) Hierarchy of dominance - a form of animal social structure in which a linear ranking exists. each animal is dominant over those below it and submissive to those above it in the hierarchy - Why did I have to answer this?

    B.) Explain why we cannot directly determine the genotype of an eagle with a green pigmentation. Suggest how we could determine the genotype.

    An eagle with green pigmentation could be either heterozygous dominant (pq), or homozygous dominant (pp). A genetic cross between the eagle with a green pigmentation and an eagle with a known genotype (i.e. homozygous recessive (qq) could be carried out. If any offspring present the phenotype of purple pigmentation then the green pigmented parent was heterozygous. If none were produced, the parent was likely to be homozygous dominant.


    I remember deducing that there were 333 eagles in the population I was studying. I remember recapturing 143 on the second week I was there, and I recognised 46 from before - theoretically speaking?

    Ci) Suggest how I recognised them. You marked them the first time around, e.g. with a leg tag.
    ii) How many did I originally capture? eurgh... let me find that calculator. 333 x 46 = 15318. 15318 / 143 = 107.11 (so 107.)
    iii) What presumptions did I make when estimating the population size. There was no migration in and out of the population. No reproduction, deaths and births in the population. Marking did not affect behaviour or survival of the birds. And finally that random mixing occured between the marked and unmarked birds within the population.

    My data shows that 224 of the eagles had green pigmentation under their wings. Using this, suggest how many heterozygous individuals are there in the population. 224 / 333 = 0.67 = P squared. Square root = 0.82. P + Q = 1. 1 - 0.82 = 0.18 = Q. 2PQ = frequency of heterozygous individuals. 2 x 0.82 x 0.18 = 0.295. 0.295 x 333 = 98-99 heterozygous individuals.
    Although I enjoyed the challenge (and most likely got one or two wrong), I don't think many people would bother to answer such a long winded question for the sake of revision.

    My question:

    Define Directional Selection. If you can, explain why the curve on the graph moves to the right and why some new alleles appear on the extreme side that is becoming advantageous.
    You got most of it right buuuuut....!
    1.) Woody plants grow from top/grass grows from bottom/auxin.
    2.) You've presumed that eagles with green pigmentation are pp! Mwahaha!

    I think longer structured questions are more fun!
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    (Original post by jimmy303)
    Define Directional Selection. If you can, explain why the curve on the graph moves to the right and why some new alleles appear on the extreme side that is becoming advantageous.[/B]

    When environmental conditions change, so will the phenotypes needed for survival. Within any population there will be a spread of phenotypes available some individuals will fall to either extreme of the mean. Natural selections selects for individuals on one of the extreme to be the ones that are more likely to survive, reproduce and pass on their alleles than other individuals i.e. on the other extreme...so the mean moves to the side of the advantageous extreme. It changes the characteristic of the population. New alleles, I don't know what you mean....but 'new' alleles = mutation caused by changes to the base sequence in the DNA of organisms.


    Discuss differential reproductive success
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    When certain individuals in a population have an advantage over another, differential reproductive success occurs. The advantageous individuals are more likely to survive and pass on their alleles. Allele frequency changes to reflect an increase in the advantageous allele.





    4i.) Complete the following equation-
    NADH + ___________ -> ________ + Lactate (2)
    ii.) What is the difference between Lactate and Lactic acid? (2)
    iii.) The IUPAC name for Lactic acid is 2-hydroxypropanoic acid. Draw this molecule clearly showing ALL bonds. Label the chiral carbon with a *. (3)
    iv.) Explain using enzyme theory, why only one enantiomer of this molecule forms naturally within the body. (3)
    v.) Did lactate form in this experiment as a result of anaerobic respiration? If not, then what did form? Suggest how you can test for what formed. (5)
    vi.) Suggest a way of discovering if any energy is released from this process. (2)
    ________________________________ ________________________________ ___________
    5.) The following answer was given by Ted in the BIOL4 Unit exam.
    Outline the process of Glycolysis.

    During Glycolysis, glucose is phosphorylated using ATP and this activates the glucose. The glucose then splits into two molecules of Glycerate-3-Phosphate. Two molecules of ATP are used in this process. NADP comes along and is oxidised to NADPH, while GP is reduced to Pyruvate. We get 4 molecules of ATP from glycolysis, 2 from each GP.

    The examiner was not impressed with Aleem’s answer. Point out and correct Ted’s mistakes. (4)
    Give your own answer to this question. (7)

    Mark Scheme-
    Spoiler:
    Show


    4.
    i) Gap 1 = Pyruvate (1) Gap 2 = NAD (1)
    ii) Lactate is an ION.(1) Lactic acid dissociates to Lactate in solution. (1)
    iii)
    All bonds clearly shown (1)
    Alcohol group on second carbon (1)
    Chiral Carbon marked correctly (1)
    Ignore bond angles. Penalise missing (O-H) bond once only. Allow mirror structures/enantiomer.

    iv) Enzymes have a specific tertiary structure(1) and hence a specific active site(1). Can only accommodate one form of enantiomer due to opposing 3D structure (1).
    (Accept ‘specific amino acid sequence/polypeptide chain)

    v.)No(1). Ethanol(1) and Carbon Dioxide formed(1).
    Ethanol- H+/KCr₂O₇ (1) OR heat (1)
    (Allow one only)
    Carbon Dioxide- Lime water test(1) OR Bicarbonate indicator solution(1)
    (Allow one only)
    (Ignore incorrect observations if given)

    vi.) Use a thermometer (1) to record heat energy change/ enthalpy change (1).
    (17 MAX)


    5.)
    Corrections-
    Activated Glucose splits into two molecules of TP not GP.(1)
    NADP in photosynthesis. NAD in respiration. (1)
    NAD is reduced to NADH and TP is oxidised to Pyruvate (GP used in question, but addressed above).(1)
    Net gain of 2 molecules of Glycolysis.(1)

    Answer-
    Outline the process of Glycolysis-
    1.) 2 molecules of ATP used to phosphorylate/activate glucose.
    2.) Activated glucose splits into two molecules of Triose Phosphate
    3.) Two molecules of NAD are reduced to NADH
    4.) Triose Phosphate oxidised to Pyruvate.
    5.) Two molecules of ATP formed also.
    6.) Above 3 answers x2.
    7.) Net gain of 2 ATP molecules.
    Penalise references to GP or NADP/NADPH.
    (11 MAX)

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    4i.) Complete the following equation-
    NADH + Pyruvate -> NAD+ Lactate (2)
    ii.) What is the difference between Lactate and Lactic acid? (2)The same just named difrently as 'ate' is the new ending for acids
    iii.) The IUPAC name for Lactic acid is 2-hydroxypropanoic acid. Draw this molecule clearly showing ALL bonds. Label the chiral carbon with a *. (3)
    We dont need to know this but it will have 3 carbons and a carboxylic acid (COOH) group on it
    v.) Did lactate form in this experiment as a result of anaerobic respiration? If not, then what did form? Suggest how you can test for what formed. (5)
    vi.) Suggest a way of discovering if any energy is released from this process. (2)
    Using Q=mcdeltaT and seing if the reacion is endothermic/exothermic
    5.) The following answer was given by Ted in the BIOL4 Unit exam.
    Outline the process of Glycolysis.

    During Glycolysis, glucose is phosphorylated using ATP and this activates the glucose. The glucose then splits into two molecules of Glycerate-3-Phosphate. Two molecules of ATP are used in this process. NADP comes along and is oxidised to NADPH, while GP is reduced to Pyruvate. We get 4 molecules of ATP from glycolysis, 2 from each GP.

    The examiner was not impressed with Aleem’s answer. Point out and correct Ted’s mistakes. (4)
    Give your own answer to this question. (7)
    mistakes
    NAD is respiration NOT NADP
    Splits into TP not GP
    Only net gain of 2 molecules
    thats all i can find

    Answer
    - glucose activeted by two molecules of ATP
    - splits into 2 triose phosphates
    -2 molecules NAD are reduced
    - two molecules of ATP formed
    - pyruvate is final product


    Yays

    Outline the nitrogen cycle and give details of ALL stages

    Liam Williams xD
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    (Original post by Orihime)
    New alleles, I don't know what you mean....but 'new' alleles = mutation caused by changes to the base sequence in the DNA of organisms.
    Yep, basically the mutations are slightly advantageous and so survive in the population, but are not as common as the alleles with the most advantage, if that makes sense. :p: Basically if you look at the directional selection graph you'll notice that it all shirts right/left (rather than 'squishing' up against one extreme), with some members of the population being taller/shorter (for example) than was possible beforehand.

    (Original post by Hippysnake)
    The examiner was not impressed with Aleem’s answer. Point out and correct Ted’s mistakes. (4)
    I don't think this guy was meant to have two names somehow :p: .

    As to my mistakes, do we need to know about auxins for the AQA exam? :confused:
    The second mistake reminds me to check my answers thoroughly when it comes to the exam to correct those silly awful mistakes, so another learning curve for me! :cool:

    (Original post by Liam227)
    Outline the nitrogen cycle and give details of ALL stages
    We've done this so much it's drilled into my head!!!


    • Plants absorb nitrates (NO3-) from the soil.
    • Plants use the nitrates and compounds from respiration to form amino acids (amongst other things such as ATP and nucleic acids).
    • The amino acids are used to synthesise proteins.
    • The plants are eaten by animals, the proteins digested into amino acids, the amino acids are absorbed and assimilated into animal proteins.
    • Both plants and animals excrete and die, leaving a collection of materials which contain the nitrogen still in organic molecules (e.g. detritus).
    • Decomposers (saprophytes) decay the excretory products and detritus, releasing ammonia (NH3) into the soil - Ammonification.
    • Nitrifying bacteria oxidise the ammonia first into nitrites (NO2-) then to nitrates (NO3-) - nitrification -, which are taken up by the plants.



    Nitrogen-fixing bacteria living free in the soil and in the nodules on the roots of legumes (pod plants such as peas and lentils) fix nitrogen gas - nitrogen fixation- into molecules of ammonia. This adds to the total amount of nitrogen available for use by plants.

    Dentrifying bacteria reduce nitrate to nitrogen gas that escapes from the soil - denitrification. This decreases the amount of nitrogen available to the plants.

    The bacteria use the nitogen-containing compounds for respiration - as a reminder.

    My question: :yep:
    Explain how you would attempt an investigation using quadrats. State one way you would increase the reliability of such a method.
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    Explain how you would attempt an investigation using quadrats. State one way you would increase the reliability of such a method.
    Map out the area into a grid using tape measures - coordinate system - generate random numbers using a calculator, computer or random numbers table and convert these numbers into co-ordinates. Place the bottom, left-bottom-hand corner of the quadrat on the intersection of pairs of co-ordinates, take a lot of readings i.e. 10 or more. Sample within the quadrats.Then work out the mean of all the samples and carry out statistical tests such as chi squared.
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    (Original post by Remarqable M)
    Describe the effect on the levels of GP, RuBP and TP of changing the Light Intensity.

    is photosynthesis in the AQA spec?


    Do you have an exam on monday, then?
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    (Original post by Liam227)
    4i.) Complete the following equation-
    NADH + Pyruvate -> NAD+ Lactate (2)
    ii.) What is the difference between Lactate and Lactic acid? (2)The same just named difrently as 'ate' is the new ending for acids
    iii.) The IUPAC name for Lactic acid is 2-hydroxypropanoic acid. Draw this molecule clearly showing ALL bonds. Label the chiral carbon with a *. (3)
    We dont need to know this but it will have 3 carbons and a carboxylic acid (COOH) group on it
    v.) Did lactate form in this experiment as a result of anaerobic respiration? If not, then what did form? Suggest how you can test for what formed. (5)
    vi.) Suggest a way of discovering if any energy is released from this process. (2)
    Using Q=mcdeltaT and seing if the reacion is endothermic/exothermic
    5.) The following answer was given by Ted in the BIOL4 Unit exam.
    Outline the process of Glycolysis.

    During Glycolysis, glucose is phosphorylated using ATP and this activates the glucose. The glucose then splits into two molecules of Glycerate-3-Phosphate. Two molecules of ATP are used in this process. NADP comes along and is oxidised to NADPH, while GP is reduced to Pyruvate. We get 4 molecules of ATP from glycolysis, 2 from each GP.

    The examiner was not impressed with Aleem’s answer. Point out and correct Ted’s mistakes. (4)
    Give your own answer to this question. (7)
    mistakes
    NAD is respiration NOT NADP
    Splits into TP not GP
    Only net gain of 2 molecules
    thats all i can find

    Answer
    - glucose activeted by two molecules of ATP
    - splits into 2 triose phosphates
    -2 molecules NAD are reduced
    - two molecules of ATP formed
    - pyruvate is final product


    Yays

    Outline the nitrogen cycle and give details of ALL stages

    Liam Williams xD

    if you look at a more complete diagrm of glycolysis, i think you'd find that glucose go through many stages to become pyruvate. 2 of these are GP and triosphosphate so in a way, you're both right. But in most textbooks, they just put triosphosphate as the intermediate. just saying
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    Could someone tell me whether you need to know the statistical tests for the exam tomorow. The tests include; chi squared, spearman ranked, etc.

    cheers:eek3:
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    (Original post by eashenn)
    Could someone tell me whether you need to know the statistical tests for the exam tomorow. The tests include; chi squared, spearman ranked, etc.

    cheers:eek3:

    those are for the practical assesments that will follow the exams

    how ever i heard you may need to give either test as an example for a statistical analysis in the test (not too sure though)
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    (Original post by jimmy303)

    My question: :yep:
    Explain how you would attempt an investigation using quadrats. State one way you would increase the reliability of such a method.

    lay 2 tape measures at right angles and generate random coordinates from a table or a computer

    then place the quadrats at each of your randomly generated quadrats and record the species that are present in each of the quadrats

    you can do this either by recording the frequency or the percentage cover of each species.

    a method of increasing accuracy could be increaing the number of randomly generated coordinates to make the results more representative

    question: Name 4 uses for ATP?
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    (Original post by dull)

    question: Name 4 uses for ATP?

    1. Growth (division), maintenance and repair of cells and organelles
    2. Movement including muscle contraction and the circulation of blood
    3. maintaining body temperature in birds and mammals. Heat that is lost to the environment during respiration must be replaced.
    4. Active transport of ions and molecules against a concentration gradient across plasma membranes


    Question
    : describe what happens and the importance of anaerobic respiration in plants and animals.
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    (Original post by emmachewit)
    1. Growth (division), maintenance and repair of cells and organelles
    2. Movement including muscle contraction and the circulation of blood
    3. maintaining body temperature in birds and mammals. Heat that is lost to the environment during respiration must be replaced.
    4. Active transport of ions and molecules against a concentration gradient across plasma membranes


    Question
    : describe what happens and the importance of anaerobic respiration in plants and animals.
    can you believe no woke up to revise this time around lol
    most of them probably pulled all nighter which is bad.

    ps: i can answer your question on what happens and the importance of anaerobic respiration in animals only

    so here it goes:

    Anaerobic respiration is release of energy in the absence of oxygen.

    Now there are 2 types of anaerobic respiration:

    Note neither of these pathways produce any ATP, but two ATP is made per molecule of glucose by substrate level phosphorylation during glycolysis.

    Lactate fermentation - This is mainly used by animals; this is how it goes

    Reduced NAD is re-oxidised to NAD. Pyruvate is the hydrogen acceptor.
    It acceps hydrogren atoms from reduced NAD. NAD is now re-oxidised and is available to accept more hydrogen atoms from glucose, so glycolysis can continue, generating enough ATP to sustain muscle contraction. The enzyme lactate dehydrogenase catalyses the oxidation of reduced NAD, together with the reduction of pyruvate to lactate.

    In some active tissues like skeletal muscles, although aerobic metabolism takes place but in sustained activity when the oxygen supply can not keep pace with the energy demand, anaerobic respiration supplies the energy continuesly by the breakdown of glucose to lactic acid.
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    haha i know thats just what i was thinking, for every exam i always sleep at 7pm get up at 5am have a coffee then have soup before i set off. If i dont do that i just dont feel right, it drives me crazy when im waiting for an exam and people are falling asleep, its just like what on earth were you thinking!

    I know what you mean, i think doing an allnighter could possibly be the worst thing ever, but i guess it works for alot of people. Im in college till 6pm tonight then i have to revise for chemistry on wednesday. I have a feeeeling tonight may be hard

    p.s do we really need to know anaerobic respiration in that much detail !!!! :O
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    nevermind, after reading your answer for the 100000 time i've finally got my head around it, i think it may be all the coffee
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    (Original post by emmachewit)
    haha i know thats just what i was thinking, for every exam i always sleep at 7pm get up at 5am have a coffee then have soup before i set off. If i dont do that i just dont feel right, it drives me crazy when im waiting for an exam and people are falling asleep, its just like what on earth were you thinking!

    I know what you mean, i think doing an allnighter could possibly be the worst thing ever, but i guess it works for alot of people. Im in college till 6pm tonight then i have to revise for chemistry on wednesday. I have a feeeeling tonight may be hard

    p.s do we really need to know anaerobic respiration in that much detail !!!! :O
    hahe thanks for reminding to make my cup of tea lol

    p.s. check your specification if it doesn't ask you anything more than just the importance of anaerobic respiration then don't write anything about how lactate fermentation works. By the way im doin OCR and the thread revision is ghost town as expected but hopefully some took my advice and slept to wake up early for revision
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    Anaerobic respiration is all about energy demand, if there is isn't enough ATP in the body to sustain cellular activity then the body will resort to
    anaerobic respiration even though the energy released is much lesser than aerobic respiration.
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    ah righteo, well i get it more now, hopefully it will only be like 2 marks so not too worry im just dreading the hardy weinburg equation, i can do it now, but i know when i get in the exam im going to be rubbish at it!!
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    (Original post by emmachewit)
    ah righteo, well i get it more now, hopefully it will only be like 2 marks so not too worry im just dreading the hardy weinburg equation, i can do it now, but i know when i get in the exam im going to be rubbish at it!!
    hey don't feel too bad about the exam, the caffeine will definetly help you and coupled with your good nigh sleep last nite the exam should be no problem

    is your exam in the morning or afternoon?
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    does anyone know what we need to know about human life expectancy in the AQA exam? is it just applying it to pyrimads or is there more too it?
 
 
 
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