Poll: What do you think the 6 marker will be?
Embryonic Stem cells/Genetic disorders (16)
29.09%
Mitosis and Meiosis (11)
20%
Speciation (13)
23.64%
Quadrats and Transects (6)
10.91%
Limiting factors of photosynthesis in the greenhouse (9)
16.36%
IsaacIIV
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made a few changes:

UNOFFICIAL MARK SCHEME AQA GCSE BIOLOGY UNIT 2
CREATED BY THATGIRLX
(with help from IsaacIIV)


1a) heat is given off by the lamp, how can this problem be solved?
• A glass sheet or glass is placed between the pondweed and lamp to deflect or absorb the heat. OR a water bath (1)
1b) Explain the relationship between distance from lamp, and bubbles given off per minute.
• As the distance increases the oxygen bubbles given off decrease. At 10 and 15cm, the oxygen bubbles remain at 84 meaning that it is no longer the limiting factor (1)
1c) What was preventing photosynthesis?
• Carbon dioxide, concentration or temperature (1)


2a) QWC question: explain the structure and function of a leaf?
• waxy cuticle - reflect UV radiation
• mesophyll - spongy for gas exchange
• xylem + phloem - transport of water and nutrients
• Epidermal tissue - protection, retain shape?
• palisade cells - primary source of photosynthesis
• stomata + guard cells - gas exchange




Enzymes section
1) Explain the relationship between amount to trypsin and rate of reaction?
• As the percentage of trypsin increases, the rate of reaction increases from 0.1 to 0.6. They are directionally proportional to each other. (2)
2) Forgotten question...
• 0.6 or 6% forgot.. (1)
3) Why did the manufacturers use 0.5% trypsin at 35 degrees C?
• It was better for manufacturers to use 0.5% with 35 degrees because 35 is the optimum temperature. So less money is used to maintain higher temperatures for no reason AND because less money is spent on the enzymes which are very costly, a compromise between the two.(4)
4) Why are protease used in the manufacture of baby foods?
• Enzymes are used in baby foods as proteases as they can break down the protein to amino acids. This allows the baby to digest the food easily (3)
5) How is one other enzyme used in industry?
• BIOLOGICAL DETERGENTS: Proteases and lipases are used in industry to remove stains from clothing.
• SLIMMING FOODS: Isomerase can be used to convert glucose syrup into fructose syrup. Fructose is sweeter so less can be used compared to glucose. (3)
• Converting starch to sugar


Mitochondria section
1) Label part A of the plant cell?
• Part A was a mitochondria (1)
2) What chemical reaction takes place here? (I think)
• respiration
3) Explain how oxygen gets to part A?
• Oxygen diffuses from an area of high concentration in the blood to an area of low concentration in the cell. It moves down the concentration gradient through a partially permeable membrane. (4)
4) How do part a and ribosomes work together to produce enzimes.
• Ribosomes produce proteins. They get the energy to do this by Part A the mitochondria respiring to supply energy. They put amino acids in a specific order to form an enzyme (3)


Meiosis section
1) What does this diagram show?
• The diagram showed meiosis (1)
2) Where are the male gametes found?
• Testes (1)
3) How many chromosomes are found in gametes
• 23 (1)
4) Why are there this number?
• They must be 23 so that the gametes produced by meiosis can fuse at fertilisation to produce the full set of 46 whilst causing variation in the offspring. (2)


Genetic variation section:
1) What is a dominant allele?
• A dominant allele is one which is expressed over recessive even if only one is present (1)
2) How can you tell that person B is heterozygous?
• Had children both with + without disorder
3) What genotype was person A?
• Heterozygous! Dd. (1)
4) How can you tell it isn't a recessive disorder?
• You could tell that it was not a recessive disorder because there were no carriers without the disorder (1)
6) Work out the chance of person c+d's child having the disorder?
•50% - drawn genetic cross (4)
7) Why can stem cells be used to treat disorders?
• Stem cells can be made to differentiate to any cell. Therefore can treat the disorder (2)
8) Why is it preferable to take stem cells from umbilical chords rather then embryos?
• Taking cells from skin have no ethical issues / not harmful / optional / volunteers / does not result in death of embryo. (1)


Quadrat section
1) Explain how the scientist could make the experiment more valid?
• They could use a larger sample size
2) explain why the scientists method were not valid?
• They had to make sure the quadrates were randomly placed (the transect must have been placed anywhere in the woodland, not specifically where they think they would get best results) (2)
2) Explain why the plants in the bright forest grew more flowers than the plants in the dark forest?
The plants in the light can photosynthesise more, meaning growing more compared to the rest (2)
3) Forgotten question?
11 I think, forgot! (1)
4) How could the scientists test their hypothesis?
To test their hypothesis they could place similar sized plants of the same species in both light and dark conditions within the lab, and compare the growth.
5) Why did plants group A grow more flowers?
How plants produce more flowers i have no idea? More photosynthesis occurs, so more glucose produced for growth?(2)


Speciation section
1) Define the term 'species'?
• A species is a group of organisms with similar characteristics who can interbreed to produce fertile offspring (2)
2) Explain why the two plant groups can no longer interbreed even though they were once the same plant species?
• The two groups were separated + isolated; by a geographical barrier (e.g. ocean). Genetic variation occurred, and due to different environments, natural selection occurred differently, the 2 groups became so different that speciation occurred + they cant't interbreed anymore.
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meeeeee7
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#562
THIS WAS SO HARD


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Midnight1811
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#563
(Original post by ThatGirlx)
What grade was 34?
& don't worry, stay positive!
The unofficial mark scheme is what I think the answers were, I didn't take this exam, just my first time. But I did take b1, c1 and p1 which is why I made a mark scheme for this because I sort of know what keywords the examiners are looking for
Yeah I got a B last year. After I thought I got a C haha so hopefully I got a B.
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ThatGirlx
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#564
(Original post by IsaacIIV)
made a few changes:

UNOFFICIAL MARK SCHEME AQA GCSE BIOLOGY UNIT 2
CREATED BY THATGIRLX
(with help from IsaacIIV)


1a) heat is given off by the lamp, how can this problem be solved?
• A glass sheet or glass is placed between the pondweed and lamp to deflect or absorb the heat. OR a water bath (1)
1b) Explain the relationship between distance from lamp, and bubbles given off per minute.
• As the distance increases the oxygen bubbles given off decrease. At 10 and 15cm, the oxygen bubbles remain at 84 meaning that it is no longer the limiting factor (1)
1c) What was preventing photosynthesis?
• Carbon dioxide, concentration or temperature (1)


2a) QWC question: explain the structure and function of a leaf?
• waxy cuticle - reflect UV radiation
• mesophyll - spongy for gas exchange
• xylem + phloem - transport of water and nutrients
• Epidermal tissue - protection, retain shape?
• palisade cells - primary source of photosynthesis
• stomata + guard cells - gas exchange




Enzymes section
1) Explain the relationship between amount to trypsin and rate of reaction?
• As the percentage of trypsin increases, the rate of reaction increases from 0.1 to 0.6. They are directionally proportional to each other. (2)
2) Forgotten question...
• 0.6 or 6% forgot.. (1)
3) Why did the manufacturers use 0.5% trypsin at 35 degrees C?
• It was better for manufacturers to use 0.5% with 35 degrees because 35 is the optimum temperature. So less money is used to maintain higher temperatures for no reason AND because less money is spent on the enzymes which are very costly, a compromise between the two.(4)
4) Why are protease used in the manufacture of baby foods?
• Enzymes are used in baby foods as proteases as they can break down the protein to amino acids. This allows the baby to digest the food easily (3)
5) How is one other enzyme used in industry?
• BIOLOGICAL DETERGENTS: Proteases and lipases are used in industry to remove stains from clothing.
• SLIMMING FOODS: Isomerase can be used to convert glucose syrup into fructose syrup. Fructose is sweeter so less can be used compared to glucose. (3)
• Converting starch to sugar


Mitochondria section
1) Label part A of the plant cell?
• Part A was a mitochondria (1)
2) What chemical reaction takes place here? (I think)
• respiration
3) Explain how oxygen gets to part A?
• Oxygen diffuses from an area of high concentration in the blood to an area of low concentration in the cell. It moves down the concentration gradient through a partially permeable membrane. (4)
4) How do part a and ribosomes work together to produce enzimes.
• Ribosomes produce proteins. They get the energy to do this by Part A the mitochondria respiring to supply energy. They put amino acids in a specific order to form an enzyme (3)


Meiosis section
1) What does this diagram show?
• The diagram showed meiosis (1)
2) Where are the male gametes found?
• Testes (1)
3) How many chromosomes are found in gametes
• 23 (1)
4) Why are there this number?
• They must be 23 so that the gametes produced by meiosis can fuse at fertilisation to produce the full set of 46 whilst causing variation in the offspring. (2)


Genetic variation section:
1) What is a dominant allele?
• A dominant allele is one which is expressed over recessive even if only one is present (1)
2) How can you tell that person B is heterozygous?
• Had children both with + without disorder
3) What genotype was person A?
• Heterozygous! Dd. (1)
4) How can you tell it isn't a recessive disorder?
• You could tell that it was not a recessive disorder because there were no carriers without the disorder (1)
6) Work out the chance of person c+d's child having the disorder?
•50% - drawn genetic cross (4)
7) Why can stem cells be used to treat disorders?
• Stem cells can be made to differentiate to any cell. Therefore can treat the disorder (2)
8) Why is it preferable to take stem cells from umbilical chords rather then embryos?
• Taking cells from skin have no ethical issues / not harmful / optional / volunteers / does not result in death of embryo. (1)


Quadrat section
1) Forgotten question?
•They had to use a large sample size
2) explain why the scientists method were not valid?
• They had to make sure the quadrates were randomly placed (the transect must have been placed anywhere in the woodland, not specifically where they think they would get best results) (2)
2) Explain why the plants in the bright forest grew more flowers than the plants in the dark forest?
The plants in the light can photosynthesise more, meaning growing more compared to the rest (2)
3) Forgotten question?
11 I think, forgot! (1)
4) How could the scientists test their hypothesis?
To test their hypothesis they could place similar sized plants of the same species in both light and dark conditions within the lab, and compare the growth.
5) Why did plants group A grow more flowers?
How plants produce more flowers i have no idea? More photosynthesis occurs, so more glucose produced for growth?(2)


Speciation section
1) Define the term 'species'?
• A species is a group of organisms with similar characteristics who can interbreed to produce fertile offspring (2)
2) Explain why the two plant groups can no longer interbreed even though they were once the same plant species?
• The two groups were separated + isolated; by a geographical barrier (e.g. ocean). Genetic variation occurred, and due to different environments, natural selection occurred differently, the 2 groups became so different that speciation occurred + they cant't interbreed anymore.
Thank you Isaac


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Midnight1811
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#565
Whats the best way to revise past papers if I dont know the full syllabus. The same could be be said for maths. Do I just go through past papers ? What happen if I donto understand how to answer the question ? I'm proper confused
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Zawarkhan786
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#566
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#566
For the first question, can 'light intensity' be accepted as an answer?
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ThatGirlx
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#567
(Original post by Zawarkhan786)
For the first question, can 'light intensity' be accepted as an answer?
No because the first question was asking how the lamp can be prevented from giving off heat to the pondweed
So it had to be something like put a glass sheet or bowl around it


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ThatGirlx
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#568
I dont understand how everyone has written water bath for the first question :s how can you put it in a water bath, the pondweed was already in a water bath as plants need water to grow... Just because the answer on a specimen paper was waterbath doesn't mean this is automatically waterbath


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NightStrider
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#569
(Original post by IsaacIIV)

2) explain why the scientists method were not valid?
I don't remember this question at all, but I remember a question asking how they could make them more valid
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IsaacIIV
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#570
(Original post by NightStrider)
I don't remember this question at all, but I remember a question asking how they could make them more valid
That is probably one of the many questions i'de forgotten, i'll add it in..
I didn't actually write most of this mark scheme... i just added any questions i could remember in. Best ask ThatGirlX if she's certain about that question.

Having said that, i think i remember the question more as:
We're told of the scientist method in which the scientist selectively choose areas of woodland and count the organisms there, why is this not a valid method of sampling an area?
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ThatGirlx
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#571
(Original post by NightStrider)
I don't remember this question at all, but I remember a question asking how they could make them more valid
Yes, that was the question. I didn't add in the questions Isaac did. The answer was what it said in the unofficial mark scheme: large sample size, random placing of transect/quadrat etc.


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ThatGirlx
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(Original post by NightStrider)
I don't remember this question at all, but I remember a question asking how they could make them more valid
Oops my answer wasn't clear. The question was about how they could make the experiment more valid. Not what is written in the unofficial mark scheme


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NightStrider
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(Original post by IsaacIIV)
That is probably one of the many questions i'de forgotten, i'll add it in..
I didn't actually write most of this mark scheme... i just added any questions i could remember in. Best ask ThatGirlX if she's certain about that question.

Having said that, i think i remember the question more as:
We're told of the scientist method in which the scientist selectively choose areas of woodland and count the organisms there, why is this not a valid method of sampling an area?
The thing is I only remember the paper asking how could they make it [more] valid, not why it wasn't valid and ThatGirlX appears to agree with me.
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NightStrider
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(Original post by ThatGirlx)
Yes, that was the question. I didn't add in the questions Isaac did. The answer was what it said in the unofficial mark scheme: large sample size, random placing of transect/quadrat etc.


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Oh, and I said they ought to standardise the counting method - i.e. everything which is half in doesnt count and they should place the transects and quadrats randomly
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ThatGirlx
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(Original post by NightStrider)
Oh, and I said they ought to standardise the counting method - i.e. everything which is half in doesnt count and they should place the transects and quadrats randomly
Yep that's right!
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ThatGirlx
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#576
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#576
(Original post by IsaacIIV)
That is probably one of the many questions i'de forgotten, i'll add it in..
I didn't actually write most of this mark scheme... i just added any questions i could remember in. Best ask ThatGirlX if she's certain about that question.

Having said that, i think i remember the question more as:
We're told of the scientist method in which the scientist selectively choose areas of woodland and count the organisms there, why is this not a valid method of sampling an area?
Oh the question was asking how can they make their experiment or results more valid
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NightStrider
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#577
(Original post by ThatGirlx)
Yep that's right!
Awesome
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IsaacIIV
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#578
UNOFFICIAL MARK SCHEME AQA GCSE BIOLOGY UNIT 2
CREATED BY THATGIRLX
(with help from IsaacIIV)


1a) heat is given off by the lamp, how can this problem be solved?
• A glass sheet or glass is placed between the pondweed and lamp to deflect or absorb the heat. OR a water bath (1)
1b) Explain the relationship between distance from lamp, and bubbles given off per minute.
• As the distance increases the oxygen bubbles given off decrease. At 10 and 15cm, the oxygen bubbles remain at 84 meaning that it is no longer the limiting factor (1)
1c) What was preventing photosynthesis?
• Carbon dioxide, concentration or temperature (1)


2a) QWC question: explain the structure and function of a leaf?
• waxy cuticle - reflect UV radiation
• mesophyll - spongy for gas exchange
• xylem + phloem - transport of water and nutrients
• Epidermal tissue - protection, retain shape?
• palisade cells - primary source of photosynthesis
• stomata + guard cells - gas exchange




Enzymes section
1) Explain the relationship between amount to trypsin and rate of reaction?
• As the percentage of trypsin increases, the rate of reaction increases from 0.1 to 0.6. They are directionally proportional to each other. (2)
2) Forgotten question...
• 0.6 or 6% forgot.. (1)
3) Why did the manufacturers use 0.5% trypsin at 35 degrees C?
• It was better for manufacturers to use 0.5% with 35 degrees because 35 is the optimum temperature. So less money is used to maintain higher temperatures for no reason AND because less money is spent on the enzymes which are very costly, a compromise between the two.(4)
4) Why are protease used in the manufacture of baby foods?
• Enzymes are used in baby foods as proteases as they can break down the protein to amino acids. This allows the baby to digest the food easily (3)
5) How is one other enzyme used in industry?
• BIOLOGICAL DETERGENTS: Proteases and lipases are used in industry to remove stains from clothing.
• SLIMMING FOODS: Isomerase can be used to convert glucose syrup into fructose syrup. Fructose is sweeter so less can be used compared to glucose. (3)
• Converting starch to sugar


Mitochondria section
1) Label part A of the plant cell?
• Part A was a mitochondria (1)
2) What chemical reaction takes place here? (I think)
• respiration
3) Explain how oxygen gets to part A?
• Oxygen diffuses from an area of high concentration in the blood to an area of low concentration in the cell. It moves down the concentration gradient through a partially permeable membrane. (4)
4) How do part a and ribosomes work together to produce enzimes.
• Ribosomes produce proteins. They get the energy to do this by Part A the mitochondria respiring to supply energy. They put amino acids in a specific order to form an enzyme (3)


Meiosis section
1) What does this diagram show?
• The diagram showed meiosis (1)
2) Where are the male gametes found?
• Testes (1)
3) How many chromosomes are found in gametes
• 23 (1)
4) Why are there this number?
• They must be 23 so that the gametes produced by meiosis can fuse at fertilisation to produce the full set of 46 whilst causing variation in the offspring. (2)


Genetic variation section:
1) What is a dominant allele?
• A dominant allele is one which is expressed over recessive even if only one is present (1)
2) How can you tell that person B is heterozygous?
• Had children both with + without disorder
3) What genotype was person A?
• Heterozygous! Dd. (1)
4) How can you tell it isn't a recessive disorder?
• You could tell that it was not a recessive disorder because there were no carriers without the disorder (1)
6) Work out the chance of person c+d's child having the disorder?
•50% - drawn genetic cross (4)
7) Why can stem cells be used to treat disorders?
• Stem cells can be made to differentiate to any cell. Therefore can treat the disorder (2)
8) Why is it preferable to take stem cells from umbilical chords rather then embryos?
• Taking cells from skin have no ethical issues / not harmful / optional / volunteers / does not result in death of embryo. (1)


Quadrat section
1) Explain how the scientist could make the experiment more valid?
• They could use a larger sample size , randomise locations of quadrates or transects, or regular measuring with quadrates along a transect.
2) Explain why the plants in the bright forest grew more flowers than the plants in the dark forest?
The plants in the light can photosynthesise more, meaning growing more compared to the rest (2)
3) Forgotten question?
11 I think, forgot! (1)
4) How could the scientists test their hypothesis?
To test their hypothesis they could place similar sized plants of the same species in both light and dark conditions within the lab, and compare the growth.
5) Why did plants group A grow more flowers?
How plants produce more flowers i have no idea? More photosynthesis occurs, so more glucose produced for growth?(2)


Speciation section
1) Define the term 'species'?
• A species is a group of organisms with similar characteristics who can interbreed to produce fertile offspring (2)
2) Explain why the two plant groups can no longer interbreed even though they were once the same plant species?
• The two groups were separated + isolated; by a geographical barrier (e.g. ocean). Genetic variation occurred, and due to different environments, natural selection occurred differently, the 2 groups became so different that speciation occurred + they cant't interbreed anymore.
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shibucool
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I found the grade boundaries: http://store.aqa.org.uk/over/stat_pd...OUND-JAN13.PDF

A* - 48
A - 39
B - 30
C - 22
D - 14
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ThatGirlx
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(Original post by shibucool)
I found the grade boundaries: http://store.aqa.org.uk/over/stat_pd...OUND-JAN13.PDF

A* - 48
A - 39
B - 30
C - 22
D - 14
48 for A*
Exactly what I thought ...
Good luck for tomorrow


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