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BIOL4 Biology Unit 4 Exam - 13th June 2011 Watch

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    (Original post by arvin_infinity)
    Energy is transferred through an ecosystem. Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer. (6 marks)
    When light hits the producer (plant) not all of it is absorbed by the plant as some of it is lost as heat, or is reflected or even it may not be the right wavelength. When the energy is transferred through different stages of the trophic levels, the energy efficiency decreases, as some of it is lost during respiration or in the faeces- as some parts of an organism is not digestible e.g. cellulose. Alternatively some organisms use the energy for growth and repair. Urmm what else is there ?? Thats not enough for 6 marks is it? How many would i get?
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    (Original post by User12399)
    thats becuase this exam is a f-ing piss take! The wording of the questions is annoying as well as the HSW. It is a hard exam don't take it lightly! I resitting after getting a D!
    I know I got a C in AS and was predicted an A!
    Shock of my life :eek:
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    Why does an agricultural ecosystem have a lower species diversity?
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    If anyone could summarise respiration into 5 mark questions that would be seriously helpful as I don't have the foggiest on it :/

    E.g Describe the process of glycolysis, Describe the Krebs Cycle, Describe the process of the electron transport chain.
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    What are all your revision plans for tonight? You going to stay up late tonight to revise...? or Wake up early tomorrow to get a few hours of revision in? Im interested to see what others do. xD
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    (Original post by arvin_infinity)
    Energy is transferred through an ecosystem. Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer. (6 marks)
    1. Light energy is absorbed, re-emitted, reflected.
    2. the light energy that is absorbed is only 2%
    3. Plants use light energy and carbon dioxide to form glucose used as chemical energy for growth/repair respiration.(combustion of ATP as a product of glucose is used for protein synthesis using mineral compounds)
    4. consumer then feeds on producer, cellulose and lignin is insoluble, the consumer uses the organic compounds(chemical energy) as matter for growth and respiratory fuel, energy is lost through respiration and excretion of indigestible matter
    5. secondary consumer eats primary consumer, since the primary consumer is biologically more similar to the secondary consumer less organic matter is lost through excretion and more can be digested therefore more efficient, it loses energy through heat and respiration
    6.skipping to saprobionts/detrivores~the secondary/primary consumer or producer die, the detritus is digested by detritivores(usually invertebrates e.g earthworm) the waste products of the detritivores is decomposed by extracellelur digestion by saprobionts which are micro-organisms, carbon compounds are used for respiration and released as co2 which enters the atmosphere, mineral compounds such as nitrates are turned into nitrates by saprobionts and enters the atmosphere/or nitrifyed by nitrifying bacteria in soil.
    7.and it happens all over again

    Efficiency decreases due to light being reflected, re-emitted, in plants energy is lost through heat and respiration, in consumers energy is lost in reproduction, respiration, heat and excretion of indigestible matter, however energy cannot technically be lost it merely turns into heat energy and leaves the earth which is a open system with respect to energy.
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    (Original post by Rickesh)
    Why does an agricultural ecosystem have a lower species diversity?
    Because plants are grown in a monoculture, that is, one crop/plant species is grown specifically in a field. Weeds are removed by herbicides.
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    (Original post by Lozzah8)
    If anyone could summarise respiration into 5 mark questions that would be seriously helpful as I don't have the foggiest on it :/

    E.g Describe the process of glycolysis, Describe the Krebs Cycle, Describe the process of the electron transport chain.
    Correct me if i'm wrong anyone but:

    Glycolysis is the production of pyruvate from glucose it takes place in the cytoplasm:
    Glucose is converted into triose phosphate by adding a phospate group onto the glucose, which gives two X trise phosphate (i.e. its phosphoylated). This requires ATP. The triose phosphate is then converted to pyruvate, this produces ATP and NADH. The pyruvate then enters the link reaction where it loses a carbon molecule in the form of CO2, which is lost as a waste product, this produces actetate, the acetate is a 2 c molecule, and it binds with co-enzyme A in the Krebs cycle (takes place in the matrix of mitochondria), producing: acetyl co-enzyme A. This binds with a 4c molecule producing a 6c molecule. the 6 c molecule loses 2X co2 and produces NADH and FADH. These go to the mitochondiral membrane, where they lose C and H moleucles, and they're passed down the electron acceptors which are at a lower energy that the previous, the enrgy is used to actively transport the H+ ions into the intermembrane space, there is now a higher conc of H+ ions in the intermembrane space, the H+ ions go down their diffusion gradient through ATPsynthase where ATP is produced, the protons and electrons are accepted by the final acceptor which is oxygen to produce water!!!

    Let me know if thats okay :P
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    (Original post by tehsponge)
    Because plants are grown in a monoculture, that is, one crop/plant species is grown specifically in a field. Weeds are removed by herbicides.
    And is that why they have less competition in comparison to a natural ecosystem? Because an agricultural ecosystem isnt allowed to reach climax community? whereas a natural one does?
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    (Original post by Stratos)
    1. Light energy is absorbed, re-emitted, reflected.
    2. the light energy that is absorbed is only 2%
    3. Plants use light energy and carbon dioxide to form glucose used as chemical energy for growth/repair respiration.(combustion of ATP as a product of glucose is used for protein synthesis using mineral compounds)
    4. consumer then feeds on producer, cellulose and lignin is insoluble, the consumer uses the organic compounds(chemical energy) as matter for growth and respiratory fuel, energy is lost through respiration and excretion of indigestible matter
    5. secondary consumer eats primary consumer, since the primary consumer is biologically more similar to the secondary consumer less organic matter is lost through excretion and more can be digested therefore more efficient, it loses energy through heat and respiration
    6.skipping to saprobionts/detrivores~the secondary/primary consumer or producer die, the detritus is digested by detritivores(usually invertebrates e.g earthworm) the waste products of the detritivores is decomposed by extracellelur digestion by saprobionts which are micro-organisms, carbon compounds are used for respiration and released as co2 which enters the atmosphere, mineral compounds such as nitrates are turned into nitrates by saprobionts and enters the atmosphere/or nitrifyed by nitrifying bacteria in soil.
    7.and it happens all over again

    Efficiency decreases due to light being reflected, re-emitted, in plants energy is lost through heat and respiration, in consumers energy is lost in reproduction, respiration, heat and excretion of indigestible matter, however energy cannot technically be lost it merely turns into heat energy and leaves the earth which is a open system with respect to energy.
    Is that what the mark scheme says lol ?

    What is the difference between agricultural and a natural ecosystem?
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    (Original post by Abby :))
    What are all your revision plans for tonight? You going to stay up late tonight to revise...? or Wake up early tomorrow to get a few hours of revision in? Im interested to see what others do. xD
    I'm sleeping at 12 and then revise from 7am till 1pm which is 6 hours of extra revision ^__^.

    So In total I did today from 12pm-11pm+7am-1pm.

    Which is all the revision I ever did.



    (Original post by Rickesh)
    Is that what the mark scheme says lol ?

    What is the difference between agricultural and a natural ecosystem?
    No that's what I thought would be relevant, agricultural ecosystems are in plagioclimax whereas natural ecosystems are in climax community, this is due to the agricultural ecosystem constantly being managed through cropping, harvesting, pest management through herbicides, biological and cultural controls and selective breeding, whereas natural ecosystems allow themselves to be succeeded by faster growing organisms which larger photosynthetic area, and the diversity is much higher in natural ecosystems due to different niches allowing organisms to survive/be supported.
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    Does anyone know how to prove an allele is not on the x chromosome? This is in reference to the Jan 2011 paper :\
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    (Original post by Rickesh)
    And is that why they have less competition in comparison to a natural ecosystem? Because an agricultural ecosystem isnt allowed to reach climax community? whereas a natural one does?
    Yep. Also the effect of limiting factors is reduced by adding fertilisers. Which means productivity is increased.

    More on productivity: However, diseases and parasites can spread quickly through a monoculture which would reduce its productivity as the photosynthesising parts of the plant get damaged/die, so integrated pest control systems are used.
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    (Original post by tehsponge)
    Yep. Also the effect of limiting factors is reduced by adding fertilisers. Which means productivity is increased.

    More on productivity: However, diseases and parasites can spread quickly through a monoculture which would reduce its productivity as the photosynthesising parts of the plant get damaged/die, so integrated pest control systems are used.
    Right okay, in a natural ecosystem dont they use integrated pest control too?
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    (Original post by 04bellot)
    Does anyone know how to prove an allele is not on the x chromosome? This is in reference to the Jan 2011 paper :\
    What does the Jan 11 paper say? I dont remmeber seeing that question lol ?
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    (Original post by Rickesh)
    Right okay, in a natural ecosystem dont they use integrated pest control too?
    There would be no reason to. A natural ecosystem is something like a rainforest. The ecosystem isn't being used for crops.
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    (Original post by Rickesh)
    Right okay, in a natural ecosystem dont they use integrated pest control too?
    I would assume natural ecosystems to be unaffected by humans.



    (Original post by tehsponge)
    There would be no reason to. A natural ecosystem is something like a rainforest. The ecosystem isn't being used for crops.
    I think the book did mention something about conserving ecosystems for biodiversity, and the reason was so that we may use the genes of the large variety of organisms for medical practises and biotechnology or something.
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    (Original post by tehsponge)
    There would be no reason to. A natural ecosystem is something like a rainforest. The ecosystem isn't being used for crops.
    Thats true!
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    Can some go through the key points of Integrated Pest Control.
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    (Original post by 04bellot)
    Does anyone know how to prove an allele is not on the x chromosome? This is in reference to the Jan 2011 paper :\
    I was also having trouble with this...

    I think its to do with that males can only get there Y chromosome from the father... and they HAVE to get the X chromosome from the mother. If the mother has the disease and is homozygous then the child would HAVE to have it... but in the question in Jan '11 the child dosnt... showing it isnt on the x chromosome.

    Hope that makes sense... Thats what the mark scheme said anyways.
 
 
 
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