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Edexcel Biology IGCSE 2B Unofficial Mark Scheme 10th June 2016 watch

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    Tell me the questions which I'm missing out - I'll add them in. Thanks for the rep.

    1.a)
    Respiration. (1)

    1.b)
    [Insect] pollination. (1)

    1.c)
    Producer and consumer. (2)

    1.d)
    Advantages of brushing hairs twice before closing:
    Ensures the insect is there hence can catch it for a source of food hence energy for respiration.
    Plant is efficient as it prevents wasting of energy by closing trap when no insects are present. (2)

    1.e)
    Protease enzyme pepsin etc. (1)

    1.f)
    Issue with microbes entering plant:
    Can cause disease hence cause plant to die.
    Can use up all the nutrients etc. by decomposing the food ingested by the plant. (2)

    1.g)
    Lack of teeth decreases rate of digestion due to no mechanical digestion which would increase the surface area of the food for the enzymes to act upon to increaser rate of chemical digestion. (2)

    1.f)
    Factors effecting rate of digestion:
    Optimal pH for enzyme activity increasing the rate of chemical digestion.
    Optimal temperature for enzyme activity increasing the rate of chemical digestion due to increase ke or enzyme and substrate hence more successful collisions where substrate and active site align to produce product.
    Size hence biomass of insect. Increase in biomass = increase in material to break down hence takes longer. (4)

    2.a)
    Fish have different amounts of nitrogenous excretory products because they may be different species, have eaten different quantities and type of food etc. (1)

    2.b)
    Eutrophication when organic matter is leached into aquatic environment, decomposers e.g bacteria decompose the matter, releasing high concentration of nutrients and mineral ions hence algal bloom (rapidly growing algae population). Hence algae at surface block light from reaching algae at bottom of river/lake hence can't photosynthesise hence die hence large biomass which is decomposed by bacteria, using all the oxygen in the water, hence lack of oxygen for respiration in fish hence fish kill.

    (Maybe) Could also talk about the ammonia being converted into nitrates and then hence amino acids and protein hence increasing growth and obviously the death of plants hence producers have negative effect on food chain. Main points however are above. (5)

    2.c)
    Increase in immunity to disease as an immune response is launched where lymphocytes create antibodies for the antigens of the foreign cell/pathogen. Once the specific antibody has been made, it is replicated and hence bind to the antigens and destroy the cell. Phagocytes engulf them via phagocytosis and break the cell down with digestive enzymes. This helps prevent disease and spread of disease, preventing death and hence contributing to growth as the antibodies remain in the blood at a low level and can be quickly replicated when infected with the actual disease. (4)

    3.a)
    Independent variable is the type of plastic. (1)

    3.b)
    72.3 x 0.4 = 28.9 cm. (2)

    3.c)
    Reliable as repeats (equivalent) were used as he used 10 trays for each and hence average, used a variety of different independent variables and grew the plants for a long enough time (3 months). Helps to factor the anomalous results. (2)

    3.d)
    Abiotic factors:
    Temperature.
    Type of soil.
    Concentrations of CO2 and O2 for photosynthesis and respiration. (3)

    3.e)
    Why the black sheet resulted in faster growth:
    Black is a good absorber of thermal radiation from the sun hence increases temperature to the optimal temperature for enzyme activity hence increase in photosynthesis and respiration rate.
    Also prevents other organisms getting into soil and taking nutrients hence decreases competition. Also helps prevent growth of weeds etc. (4)

    4.a)
    Increase in gestation period resulted in an increase in female mass on average. (1)

    4.b)
    Roe as it had the same mass as the Silo (can't remember name but it started with an S) but it had a longer gestation period. This difference in can only be explained as it took a longer time for the same growth and development due to mitosis etc. to get to the same mass as a result of no development during a few months of this period. (3)

    4.c)
    Placenta. Embryo hence foetus is connected to it via the umbilical cord. It allows the transfer of substances between the mother's and baby's blood as the blood can't mix as they may have different blood types. This transfer is done by the maternal and umbilical vessels. Substances for growth and development etc. are transferred from mother to baby/embryo i.e glucose, salts, oxygen, hormones etc. and waste products to the mother i.e CO2, urea and water. (4)

    5.a)
    11 and 0. (2)

    5.b)
    .125 (1)

    5.c)
    Arteries narrow due to build up of cholesterol hence constricts flow of blood hence less glucose and oxygen delivered to cells hence cells can't respire (aerobically) hence cells die hence muscle decay. Could talk about lactic acid and anaerobic respiration. (5)

    6.a)
    7mm. (1)

    6.b)
    Retinal cells in the back of the eye. (1)

    6.c)
    The pupil dilates to allow more light to enter the eye as the antagonistic radial muscles contract and circular muscles relax, allowing the diameter of the pupil to expand. (3)
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    I believe it was (insect) pollination rather than (wind) pollination, as it asked why the insects were needed. Also I put secondary consumer instead of just consumer - do you think it will count? Also for 6b I just got retina. What was the answer for 'suggest why the black sheet meant the plant grew faster' (or something like that)
    Overally I defo found this paper easier than paper 1 but then again I think I made a lot of mistakes and strange answers
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    uuu
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    Fish vaccination.
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    (Original post by conradliebers)
    Tell me the questions which I'm missing out - I'll add them in.

    1.a)
    Respiration. (1)

    1.b)
    [Wind] pollination. (1)

    1.c)
    Producer and consumer. (2)

    1.d)
    Advantages of brushing hairs twice before closing:
    Ensures the insect is there hence can catch it for a source of food hence energy for respiration.
    Plant is efficient as it prevents wasting of energy by closing trap when no insects are present. (2)

    1.e)
    Protease enzyme pepsin etc. (1)

    1.f)
    Issue with microbes entering plant:
    Can cause disease hence cause plant to die.
    Can use up all the nutrients etc. by decomposing the food ingested by the plant. (2)

    2.a)
    Fish have different amounts of nitrogenous excretory products because they may be different species, have eaten different quantities and type of food etc. (1)

    2.b)
    Eutrophication when organic matter is leached into aquatic environment, decomposers e.g bacteria decompose the matter, releasing high concentration of nutrients and mineral ions hence algal bloom (rapidly growing algae population). Hence algae at surface block light from reaching algae at bottom of river/lake hence can't photosynthesise hence die hence large biomass which is decomposed by bacteria, using all the oxygen in the water, hence lack of oxygen for respiration in fish hence fish kill.

    (Maybe) Could also talk about the ammonia being converted into nitrates and then hence amino acids and protein hence increasing growth and obviously the death of plants hence producers have negative effect on food chain. Main points however are above. (5)

    3.a)
    Independent variable is the type of plastic. (1)

    3.b)
    29.2 cm. (2)

    3.c)
    Reliable as repeats (equivalent) were used as he used 10 trays for each, used a variety of different independent variables and grew the plants for a long enough time (3 months). (2)

    3.d)
    Abiotic factors:
    Temperature.
    Type of soil.
    Concentrations of CO2 and O2 for photosynthesis and respiration. (3)

    6.a)
    7mm. (1)

    6.b)
    Retinal cells in the back of the eye. (1)

    6.c)
    The pupil dilates to allow more light to enter the eye as the antagonistic radial muscles contract and circular muscles relax, allowing the diameter of the pupil to expand. (3)
    f-or trophic level I put a number so for example: trophic level 1 (for producer)
    -I also put pH for question 3d)
    -question 3c) average of results
    -2a) on top of what you put i think (not sure) you can talk about different metabolism/digestive system as different species.

    the placenta question is missing and the cholesterol in artery question

    can you please remind me what was the question for 1b)
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    (Original post by gcsemusicsucks)
    I believe it was (insect) pollination rather than (wind) pollination, as it asked why the insects were needed. Also I put secondary consumer instead of just consumer - do you think it will count? Also for 6b I just got retina. What was the answer for 'suggest why the black sheet meant the plant grew faster' (or something like that)
    Overally I defo found this paper easier than paper 1 but then again I think I made a lot of mistakes and strange answers
    the black sheet felt more like a physics question......
    the majority of answers in my grade talked about: -retains heat /black absorbs heat/ reduces heat loss. -prevents water from evaporating and mineral ions from evaporating. And some rarer ones like prevents loss of nitrogent/nitrates from denitrifying bacteria or prevents other plants from growing (and competition for food) as it blocks sunlight. Not sure about the last two though
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    (Original post by Pedaly7)
    f-or trophic level I put a number so for example: trophic level 1 (for producer)
    -I also put pH for question 3d)
    -question 3c) average of results
    -2a) on top of what you put i think (not sure) you can talk about different metabolism/digestive system as different species.

    the placenta question is missing and the cholesterol in artery question

    can you please remind me what was the question for 1b)
    Great haha literally all those points I wrote additionally as well but forgot to write them. Im not sure you'd get the mark for putting a number.

    1.b) Why do other plants need to attract insects?
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    (Original post by gcsemusicsucks)
    I believe it was (insect) pollination rather than (wind) pollination, as it asked why the insects were needed. Also I put secondary consumer instead of just consumer - do you think it will count? Also for 6b I just got retina. What was the answer for 'suggest why the black sheet meant the plant grew faster' (or something like that)
    Overally I defo found this paper easier than paper 1 but then again I think I made a lot of mistakes and strange answers
    I literally don't know why I wrote that. I wrote insect pollination in the exam and meant to write it on the mark scheme but my hands did something weird on the keyboard.

    And yes for the secondary consumer, retina part maybe as it said where in the eye.
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    (Original post by conradliebers)
    Great haha literally all those points I wrote additionally as well but forgot to write them. Im not sure you'd get the mark for putting a number.

    1.b) Why do other plants need to attract insects?
    ok cool and do you know how many points the insect question was on
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    (Original post by Pedaly7)
    ok cool and do you know how many points the insect question was on
    1 mark.
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    I can't remember which question but one about genetic diagrams, another about blood clots and one about the placenta with the deers
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    (Original post by conradliebers)
    Tell me the questions which I'm missing out - I'll add them in.

    1.a)
    Respiration. (1)

    1.b)
    [Insect] pollination. (1)

    1.c)
    Producer and consumer. (2)

    1.d)
    Advantages of brushing hairs twice before closing:
    Ensures the insect is there hence can catch it for a source of food hence energy for respiration.
    Plant is efficient as it prevents wasting of energy by closing trap when no insects are present. (2)

    1.e)
    Protease enzyme pepsin etc. (1)

    1.f)
    Issue with microbes entering plant:
    Can cause disease hence cause plant to die.
    Can use up all the nutrients etc. by decomposing the food ingested by the plant. (2)

    2.a)
    Fish have different amounts of nitrogenous excretory products because they may be different species, have eaten different quantities and type of food etc. (1)

    2.b)
    Eutrophication when organic matter is leached into aquatic environment, decomposers e.g bacteria decompose the matter, releasing high concentration of nutrients and mineral ions hence algal bloom (rapidly growing algae population). Hence algae at surface block light from reaching algae at bottom of river/lake hence can't photosynthesise hence die hence large biomass which is decomposed by bacteria, using all the oxygen in the water, hence lack of oxygen for respiration in fish hence fish kill.

    (Maybe) Could also talk about the ammonia being converted into nitrates and then hence amino acids and protein hence increasing growth and obviously the death of plants hence producers have negative effect on food chain. Main points however are above. (5)

    3.a)
    Independent variable is the type of plastic. (1)

    3.b)
    29.2 cm. (2)

    3.c)
    Reliable as repeats (equivalent) were used as he used 10 trays for each, used a variety of different independent variables and grew the plants for a long enough time (3 months). (2)

    3.d)
    Abiotic factors:
    Temperature.
    Type of soil.
    Concentrations of CO2 and O2 for photosynthesis and respiration. (3)

    3.e)
    Why the black sheet resulted in faster growth:
    Black is a good absorber of thermal radiation from the sun hence increases temperature to the optimal temperature for enzyme activity hence increase in photosynthesis and respiration rate.
    Also prevents other organisms getting into soil and taking nutrients hence decreases competition. Also helps prevent growth of weeds etc. (4)

    6.a)
    7mm. (1)
    e6.b)
    Retinal cells in the back of the eye. (1)

    6.c)
    The pupil dilates to allow more light to enter the eye as the antagonistic radial muscles contract and circular muscles relax, allowing the diameter of the pupil to expand. (3)
    for 3b) i thought it was 29.28 which i rounded to 29.3 since the results had one decimal place. I did 73.2/1000 and multiplied the result by 400
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    (Original post by Pedaly7)
    for 3b) i thought it was 29.28 which i rounded to 29.3 since the results had one decimal place. I did 73.2/1000 and multiplied the result by 400
    No, I forgot the calculation but the answer was like 29.21 or 29.23 and hence you rounded down. I checked with people on this as well.
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    (Original post by conradliebers)
    No, I forgot the calculation but the answer was like 29.21 or 29.23 and hence you rounded down. I checked with people on this as well.
    to get 29.2 you must have done 73/1000 rather than 73.2. 73/1000 x 400 would give 29.3 whereas 73.2/1000 x 400 would give 29.28 (29.3)
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    No it did equal 29.28. 400 / 1000 = 0.4
    0.4 X 73.2 = 29.28
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    Hi guys what was the 29.2 cm question?
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    How did people find it?
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    (Original post by Pedaly7)
    to get 29.2 you must have done 73/1000 rather than 73.2. 73/1000 x 400 would give 29.3 whereas 73.2/1000 x 400 would give 29.28 (29.3)
    I honestly can't remember what I put down now. Maybe it was 29.3 but I can't remember.
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    why do i remember getting 28.9?
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    (Original post by Abodee1)
    why do i remember getting 28.9?
    You are right as well as me, I thought there was something wrong with it. Other people said it was 73.2 but it was 72.3 so it was 28.92 hence 28.9. Thanks.
 
 
 
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