Competition - post a photo you've taken of nature >>

GCSE B2 OFFICAL UNOFFICIAL BIOLOGY UNIT 2 MARK SCHEME. 9th June 2017

hi guys. here's the long-awaited B2 mark scheme for you to enjoy. Please don't forget to follow me for future mark schemes. (and dont forget to give reps :wink:

). Enjoy!

any corrections, please let me know

1a) Where are epithelial cells found? [1]
in epithelial tissue in lining of stomach, intestine (and maybe skin)

1b) Label the cell animal cell. [2]
A - cell membrane
B - cytoplasm

1c) What is the function of ribosomes? tick one box [1]
protein synthesis

1d) Describe the process of diffusion? [2]
movement of particles down concentration gradient, from high concentration of particles to low concentration of particles.

2) Describe how the student could use the apparatus in Figure 7 to test the hypothesis. In your answer you should include: the measurements necessary
how the student can obtain valid results. [6]
cba to write this out

3a) Explain why it was important to use placebos in this investigation [2]
reduces bias in the investigation as the cyclists won't know one's fake and one's real

3b) One scientist concludes that the more glucose improves athletic performance
Evaluate the validity of method used by the scientists and how the evidence supports the scientists conclusion [4]
evidence shows that with higher blood sugar concentration, the cyclists cycled for 4 hours, and hour longer than compared to session 2 with no glucose in the drink. this shows that more glucose increases athletic performance. The method could have been more valid if the experiment was double blind trial to see the results(not quite sure about the validity part of the question)

3c) explain how increased glucose concentration, increased heart rate and increased breathing rate improves athletic performance. [4]
increased heart rate means more blood pumped faster around the body, and linking with the faster breathing rate, this allows more oxygen to get to the muscles faster. Combined with the increased glucose this results in more respiration for more energy, improving the performance of the cyclists. The oxygen from breathing also break down lactic acid, reducing fatigue, means better performance. The increased breathing also encourages more removal of CO2 from the breakdown of lactic acid(C3H6O3)

4a) Fill in the gap to show the result of Starch breakdown by amylase [1]
starch (+ amylase) ------> ..sugars...........

4b) Suggest two variables the student should control [2]
any two from: same volume of starch/amylase
same concentration of starch/amylase
temperature of solutions(possibly)
- any other suggestions comment below :smile:

4c) Suggest the colour of the iodine solution for pH6 when added at: [2]
1. 4 mins - light brown
2. 6 mins - dark blue.

4d) suggest the time taken to change colour for a test at at pH3 [2]
would not change colour/stays light brown, as pH3 denatures the amylase/amylase does not work in this pH
(reject - 'takes longer as enzyme activity slower)

5a) write down the word equation for photosynthesis [2]
CARBON DIOXIDE + WATER --> GLUCOSE + OXYGEN
(NB - you lose marks for symbol eq)

5b) what was the rate of photosynthesis when 0.04% CO2 concentration? [1]
16 arbitrary units

5c) Work out the percentage change of rate between 0.04% and 0.08% [1]
rate at 0.08%: 20 arb units, rate at 0.04% = 16 units
20-16 = 4, 4/16 x100 = 25%

5bi) Explain the farmer does not use concentration of CO2 any greater than 0.08%? [2]
rate of growth at 0.08% is same as after 0.08%, and there are other limiting factors. (worded this differently in my exam, cant remember how tho)

5bii) Suggest TWO other factors the farmer could change to increase growth [2]
1. temperature
2. light

6a) What is an allele? [1]
alternative form of (the same) a gene

6b) What does recessive mean? [1]
non-dominant version, so 2 required to express the characteristic

6Ci) What does heterozygous mean? [1]
a pair of genes where one is dominant and one is recessive.

6cii) punnet square for AKU disease. Both parents are heterozygous for AKU and do not have AKU. Work out the probability that the child has AKU [4]

Parents alleles: dad - Nn, mum - Nn. The outcome is 25% chance of AKU, with the correct cross identified as AKU - WITHOUT THE INDENTIFICATION, MAX. 2 MARKS)

6di) how many chromosomes are there in a human cell? [1]
46 OR 23 pairs

6dii) the parents do not want to have another child with AKU. They choose to undergo the procedure of embryo cell screening. Below is the procedure........ blah blah . What type of cell division occurs at stages 2 and 3? [1]
MITOSIS

6diii) Suggest one disadvantage of embryo screening [1]
leads to designer babies(bunch of other reasons too so comment below and have good debate :wink:

)

6vi) Suggest one advantage of embryo screening. [1]
reduces medical costs/child has easy life/stops disease spreading in human population

7a) What is a species? [2]
population of organisms with similar genes that can interbreed to produce fertile offspring

7b) how do fossils provide evidence that species has evolved? [2]
fossils are remains of organisms and show how organisms have changed over time. It shows the similarities between them and organisms today

7c) Speciation 6 marker (you do not know how relieved I was when i saw this, but kinda piss*d off cuz there were 2 6 markers) [6]
geographical isolation of population of the bird, and there were some variations among them due to mutations in DNA, causing some to be unable to fly. Environments either side were different and the non-flying birds may not have had to fly. These would've survived and others may have been eaten by dinosaurs and become extinct. By natural selection these would have passed common characteristics and mutated genes/alleles to offspring. Over many generations the process of speciation repeats and newer birds have common characteristics, but also cannot fly eg. emu and ostrich.

(edited 6 years ago)

Scroll to see replies

Reply 1

JamiePaine

Thank you! 46/60 for me, what about everyone else?

Reply 2

3317752

Original post by JamiePaine

Thank you! 46/60 for me, what about everyone else?

above 50 lol.

Ty sm for this

for this six marker was it sampling along a transect or random sampling? because i wrote random and half of my year wrote along a transect :frown:

Reply 5

Ewanross10

Original post by 12ishikakumar

for this six marker was it sampling along a transect or random sampling? because i wrote random and half of my year wrote along a transect :frown:

Either can be used

Reply 6

12ishikakumar

Original post by ewanross10

either can be used

oh thank god

Reply 7

mahmed69

Original post by 12ishikakumar

Ty sm for this

No problem. Happy to help 🙂

Posted from TSR Mobile

Reply 8

Gabzinc

This and the other UMS give me varying results... this one says I got 53 marks, the other says 48. Nonetheless I found the exam really difficult, although other found it easy. High grade boundaries, it seems :frown:

Reply 9

mahmed69

Original post by Gabzinc

This isnt ums aha. Ums is uniform mark scheme, its whats given to u on results day. Im happy to say that this one is more reliable. Ive reviewed the spec. And this is the detail you need. Good luck!

Posted from TSR Mobile

Reply 10

Gabzinc

Original post by mahmed69

By UMS I meant unofficial mark scheme, I was just too lazy to type the whole thing out at the time :P

Reply 11

mahmed69

Original post by Gabzinc

By UMS I meant unofficial mark scheme, I was just too lazy to type the whole thing out at the time :P

Oh 😁 Sorry. My bad ahah, not too good with abbreviations 😂

Reply 12

richageorge

I've been waiting for this, thank you so much, what a legend

Reply 13

Gabzinc

Original post by mahmed69

4d) suggest the time taken to change colour for a test at at pH3 [2]
would not change colour/stays light brown, as pH3 denatures the amylase/amylase does not work in this pH
(reject - 'takes longer as enzyme activity slower)

6diii) Suggest one disadvantage of embryo screening [1]
leads to designer babies(bunch of other reasons too so comment below and have good debate :wink:

)

Hi there! Me again. I suggest that you can add to a disadvantage (ethical objection) of embryo screening that it involves the disposal of/destruction of embryos.

Also, the colour will be dark blue as the starch is not broken down by the amylase, so the iodine will react with the starch.

Reply 14

3317752

Original post by Gabzinc

finally someone lol. It only changes when the starch breaks down.

Reply 15

mahmed69

Original post by Gabzinc

Yeah hi, umm for the embryo one that should be fine. even along the lines of 'destruction of human life' will get you the mark so. Also im not too sure about the starch one because it says that oncce the starch breaks down, the colour changes. again i could be wrong. the web says 'The test cannot be performed at very low pH due to the hydrolysis of the starch under these conditions'.

thanks for the insight :wink:

(edited 6 years ago)

Reply 16

asdasdfdsgffd

Original post by JamiePaine

Thank you! 46/60 for me, what about everyone else?

what grade would this be roughly?