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BIOL4 Biology Unit 4 Exam - 13th June 2011 watch

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    (Original post by Stratos)
    Could someone outline eutrophication for me(and for yourself as revision of course)

    What I got down here is;

    1. Leaching of inorganic fertiliser into lake/river
    2. Algae grows rapidly
    3. Algae die but there's so much of it that bacteria strive as they decompose the algae
    4. Bacteria use up oxygen in water, oxygen concentration decreases
    5. Fish and aerobic organisms die due to low oxygen concentration
    6. bacteria decompose detritus, reducing the oxygen concentration even more
    7. random thought 'anaerobic bacteria infest the water possibly?'
    I would go with :

    1) Leaching of water-soluble inorganic fertiliser allows algae to grow. Algal blooms occur.
    2) This blocks out sunlight, thus not allowing plants to photosynthesise and they die.
    3) Saprobiotic micro-organisms or decomposers digest on this dead material, and to do they need energy and so respirate. They use up o2 dissolved in the water
    4) Fish die, and anaerobic micro-organisms then can survive, releasing toxins/hydrogen sulfide which kills more fish/plants.

    Hope that helps
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    (Original post by Stratos)
    Could someone outline eutrophication for me(and for yourself as revision of course)

    What I got down here is;

    1. Leaching of inorganic fertiliser into lake/river
    2. Algae grows rapidly
    3. Algae grow at the surface and so become densely populated killing plants and algae at lower levels because of lack of lightAlgae die but there's so much of it that bacteria strive as they decompose the algae
    4. Leads to an increase in saprobiotic microorganics which feed on dead material however they create a demand for oxygenBacteria use up oxygen in water, oxygen concentration decreases
    5. Fish and aerobic organisms die due to low oxygen concentration
    6. bacteria decompose detritus, reducing the oxygen concentration even more
    7. random thought 'anaerobic bacteria infest the water possibly?'Yeah, anaerobic bacteria increase due to less competition from aerobic bateria but they decompose releasing more nitrates and toxic waste making water putrid.
    Made a few corrections in bold.
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    Out of 75 what is roughly an A?
    Let's get some questions rolling....
    What is meant by co-dominance?
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    (Original post by Stratos)
    Could someone outline eutrophication for me(and for yourself as revision of course)

    What I got down here is;

    1. Leaching of inorganic fertiliser into lake/river
    2. Algae grows rapidly
    3. Algae die but there's so much of it that bacteria strive as they decompose the algae
    4. Bacteria use up oxygen in water, oxygen concentration decreases
    5. Fish and aerobic organisms die due to low oxygen concentration
    6. bacteria decompose detritus, reducing the oxygen concentration even more
    7. random thought 'anaerobic bacteria infest the water possibly?'





    P+Q=1 In this case P and Q indicate allele frequency
    P^2+Q^2+2PQ=1 P and Q are the respective homozygous genes of the alleles and 2PQ is the heterozygous gene.

    - soluble nitrates from fertiliser are leached into nearby water source (eg. pond or river)
    - nitrates stimulate algal growth and an algal bloom occurs on the surface of the water
    - this prevents light from reaching plants below, so they die as they are not able to photosynthesis
    - microorganisms digest the dead organic matter and in doing so aerobically respire, removing oxygen from the water
    - the increase in respiring microorganisms leads to a decrease in the dissolved oxygen levels in the water
    - fish and other aquatic organisms cannot respire sufficiently due to the lack of dissolved oxygen and so die
    - anaerobic organisms increase as there is no competition. they feed on the dead matter and in doing so produce nitrates and toxic waste.
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    Thanks for the corrections guys I feel confident on eutrophication now ^__^.
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    (Original post by Thepupil)
    If it asks about population or genotype then its p or q squared. Think it as the genotype/population have the alleles already and say R/r is your alleles. RR = p squared and rr = q squared.

    If it's asking about allele frequency its on about p + q = 1 and it is not squared.

    If they ask about genotype/populations its going to ask about heterozygous genotypes
    cheers mate
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    chap 8 i find the hardest, dont kno about u lot?
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    (Original post by Rickesh)
    Out of 75 what is roughly an A?
    Let's get some questions rolling....
    What is meant by co-dominance?
    Alleles are equally dominant and both are present and expressed in the phenotype..

    Question: Describe nitrogen fixation
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    (Original post by Rickesh)
    Out of 75 what is roughly an A?
    Let's get some questions rolling....
    What is meant by co-dominance?
    http://store.aqa.org.uk/over/stat_pd...OUND-JAN11.PDF
    http://store.aqa.org.uk/over/stat_pd...OUND-JAN10.PDF

    Hope this helps

    Codominance - both alleles are expressed in the phenotype
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    (Original post by Thisisj)
    hi can you please explain 5b on the jan 2011 paper pleaseeeeeeeeeeeeeeeeeeeeeee
    use the equation:

    net = gross - respiratory losses

    then re-arrange to get, gross = net + respiratory losses.

    on the graph the net rate for medium light intensity at 20 degrees is around 2.4

    then look at the straight line below the light intensity lines (this refers to the respiration rate) ..... now read off the graph its value at 20 degrees, but remember to read from the left hand sides graduations as they are the ones relevant to respiration. it should read around 0.35 .... so the anwer is around 2.75
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    (Original post by INeedToRevise)
    Alleles are equally dominant and both are present and expressed in the phenotype..

    Question: Describe nitrogen fixation
    nitrogen fixing bacteria (eg. rhizobium) convert nitrogen gas in the atmosphere into ammonia. they form a mutualistic relationship with plants by providing them and the ecosystem with usable nitrogen, and in turn the plants give them carbohydrates.
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    (Original post by SK-mar)
    use the equation:

    net = gross - respiratory losses

    then re-arrange to get, gross = net + respiratory losses.

    on the graph the net rate for medium light intensity at 20 degrees is around 2.4

    then look at the straight line below the light intensity lines (this refers to the respiration rate) ..... now read off the graph its value at 20 degrees, but remember to read from the left hand sides graduations as they are the ones relevant to respiration. it should read around 0.35 .... so the anwer is around 2.75
    knew the formula, still flopped it

    i hope hardy equation comes up again lol
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    (Original post by Rickesh)
    Out of 75 what is roughly an A?
    Let's get some questions rolling....
    What is meant by co-dominance?
    Probably no more than 60% raw marks, but that depends on the paper really.
    Codominance- when neither allele is dominant or recessive, so both are expressed in the phenotype usually as a mixture e.g. pink flowers from codominant red and white colour alleles.
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    (Original post by kingsmod1)
    knew the formula, still flopped it

    i hope hardy equation comes up again lol
    don't worry i flopped it the first time too, its frustrating when you realise how you went wrong though! Yeh i hope hardy comes up, but i hope its a decent question. i sometimes get confused with hardy but fingers crossed for tomorrow!
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    Hoping hardy weinberg equation dosnt come up again, i can NOT do it to saave my life. Hahahaha
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    Questions I want to come up; photosynthesis, respiration, succession, carbon cycle, nitrogen cycle, anything to do with genetics and eutrophication, If I get those questions it will be a guarantee A, anything to do with the more annoying part of ecology=
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    (Original post by INeedToRevise)
    Alleles are equally dominant and both are present and expressed in the phenotype..

    Question: Describe nitrogen fixation
    Nitrogen fixation is a way that nitrogen in the atmosphere becomes available to plants. Nitrogen fixing bacteria in the soil, convert the nitrogen in the atmosphere into ammonium ions. These are subsequently oxidised by nitrifying bacteria to nitrites, and again to nitrates, which can be actively transported into the plants' roots.

    Alternatively, some plants, such as legumes, have nitrogen-fixing nodules on their roots, allowing the plants to get the nitrates they require
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    (Original post by SK-mar)
    use the equation:

    net = gross - respiratory losses

    then re-arrange to get, gross = net + respiratory losses.

    on the graph the net rate for medium light intensity at 20 degrees is around 2.4

    then look at the straight line below the light intensity lines (this refers to the respiration rate) ..... now read off the graph its value at 20 degrees, but remember to read from the left hand sides graduations as they are the ones relevant to respiration. it should read around 0.35 .... so the anwer is around 2.75
    Yhh i got this wrong in jan .. i get it now though , thankyou.
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    (Original post by Stratos)
    Questions I want to come up; photosynthesis, respiration, succession, carbon cycle, nitrogen cycle, anything to do with genetics and eutrophication, If I get those questions it will be a guarantee A, anything to do with the more annoying part of ecology=
    Apart from succession, same for me. I find succession so fiddly to talk about. If chapter 5 comes up, I'll cry my way through the questions.
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    Nitrogen fixation is when the nitrogen in the atmosphere is converted into, firstly nitrite ions by an oxidatio reaction, then into nitrate ions again through oxidation. The nitrifying bacteria do this reaction, in aerobic conditions. Or some bacteria live in the roots of plants in nodules, they give the plant nitrate ions, for growth and the plant must give the bacteria carbohydrates in a mutualisitc relationship.
    Is that right?
 
 
 
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