BIOL4 Biology Unit 4 Exam - 13th June 2011

Unofficial markscheme - This is what my answers were, obviously some might be wrong so do tell if so. I’ll try and remember as much of the paper as I can. some of my question titles might be wrong as i cant remember exactly and my answers in this are in slightly less detail so that i don't take up to0 much space haha

ATP Question
1.Tick Boxes
- I ticked all 3 for ATP production. Only photosynthesis and aerobic respiration were ticked for the organelles and electron transport chain bit.
2. Equation
- ADP + Pi + energy = ATP (you didn't need to put energy so don't worry)
3. Two ways in which ATP is useful
- Easily hydrolysed in a one step reaction so immediate energy source
- Released in small, manageable quantities so can be used quickly
4. why is lots of ATP needed for biological processes
- Needed for glycolysis to produce even more ATP
- muscle contraction in movement
- active transport (eg. nutrients in gut)

Productivity question
1. Why is productivity higher in whichever July?
- photosynthesis is an enzyme controlled reaction. the temperature was higher in july so the enzymes had more kinetic energy and could work at a faster rate. so the rate of photosynthesis was greater.
2. Equation
- Net = gross - respiratory losses
3. Why was net productivity higher in august than july
- photosynthesis is an enzyme controlled reaction. temperature lower in august at 18 degrees so enzymes have less kinetic energy so rate of respiration lower so respiratory losses are fewer, therefore net productivity is greater.
4. What could horse do with extra nutrients?
- if excess proteins were available it could use them for muscle growth due to the increased amount of exercise because more energy has been made available to it.
5. Why is more energy used in march?
-more energy used in maintaining a respiration rate to maintain the horse's body temperature.

Anaerobic respiration Q
1. 2 reasons for not doing in pond
-Methane could escape into atmosphere
- anaerobic bacteria produce toxic waste which would kill other aquatic organisms
2. Why was it cooled?
- if it gets to hot the enzymes would get denatured and the process would stop.
3. What would eutrophication do?
- nitrates stimulate growth of algae
- algal bloom which blocks light reaching to plants below and so kills plant life below as there isn't enough light for them to photosynthesise
- bacteria feed on dead matter using oxygen, so other aquatic organisms cant respire and die.
- anaerobic dudes move in and produce toxic waste and nitrates

Populations Questionnn
1. What is birth rate
- amount of births in a population in 1000 ....
2. Describe data
- higher life expectancy in uk for both females and males (stated values)
- higher life expectancy of females in both uk and sudan (stated values)
3. Reasons
- sudan is an LEDC - poor sanitation, healthcare, diet
- a lot more men are sent to war where the chances of dying are much higher than not going to war...

Cat question
1. what in the above data proves that the allele for white fur is recessive
- Both parents have black fur but produce a white fur offpsring. they both must be heterozygous for black fur.
2. Ratio
- 1:1
3. phenotypes
- I cant remember this but it was fairly simple. think i remember one being black for sure. one chocolate. the last was either cinnamon or black i think.
4. genetic cross
- as long as one parent was 'Bbi' and the other 'bbi' you should have been fine. produced two black offspring, on choco and one cinnamon.
5.why was the number of choco cats not as expected?
- predicting the frequency of alleles for the genotypes in offspring is just an estimate. the offspring are completely random so any of the possible genotypes can be formed every time.
6. breeder wanted cats of just chocolate fur - is this possible?
- yes if you have parents of genotypes 'bb' and 'bb' OR 'bb' and 'bbi' ... as the offspring will all be chocolate guaranteed - this question has caused controversy i know so lets not start the debate on this again haha


I will do the rest in a bit as i need some food

Thanks very much for starting this. Im sure i speak for everyone when i say its very useful to be able to compare answers to an unofficial mark scheme. Are you nearly finished compiling the second section? I very much appreciate you spending time doing this. Thank you.

What do we all think on grade boundaries? Around the norm? Or higher or lower? I personally felt like it was a regular paper, no harder than Jan11.

if everyone found it better than jan 2011 then boundaries are gonna be highhhhh

its was 47 for an A then i think. probably 50 this time? maybe more? dunno really...

Well with that said I can't see a massive increase, like more than 2 or 3, it would have to take a massive increase in high results to go up by 5 or so surely?

How many marks was the long question about benzene worth?Was it 4 or 6 marks?

Wrong thread This is BIOL4 not CHEM4

Hardy Weinberg Question

1.Calculation
- 4%
2.What does hardy about the frequency over 10 generations
- that the frequency of the alleles in the population won't change
3. Use probability and chance
- there is a probability of 5% or less that the change in allele frequency is due to chance. therefore we reject our null hypothesis that the frequency of alleles wont change. (not sure about this, can someone back me up if they put something similar,cheers)
4. What type of selection is this
- Stabilising selection
- The recessive allele has decreased in frequency. it was at the extreme of the range of alleles as the hardy calculation proved it was only present in 4% of the population. with a further decrease it means that alleles closer to the middle of the range are being selected for, hence its stabilising.


Mites Question (cant remember many of these question so i'll try my best.)

1.Why was the data selected at random
- to remove bias from the experiment. It allows us to form a valid correlation between numbers of mites and successful breeding chicks. (not sure about 2nd point)
2.Describe the data and does it agree with the statement that more mites decrease successful breeds???? (think that was the question)
- with small increases in mites the amount of successful breeds fluctuated at around 80.
- with a large increase in mites (170), the number of successful breeds decreases to 42 from 86 at 15 mites.
- However, without further data we cannont conclude that an increase in mites does cause a decrease in successful chicks.
3. State a null hypothesis
- there is no significant statistical difference between the numbers of mites present and the amount of successful chicks.
4. Spearmans showed a negative correlation between mites and successful chicks what does this mean?
- That an increase in mites does not effect the number of succesful chicks. (is this right?) ...
5. Describe the data in the graph
- For tits with large oil glands, many of the points are close or touching the line of best fit. However, for tits with small oil glands, few points are close to the line or touching it. However, overall there is a slight positive correlation.
6. Does measuring oil gland size increase reliability?
- yes because different tits have different sizes of oil glands and therefore we are removing this variable from the experiment. (dunno if this is right) ....
7. Mites eat pathogenic bacteria and fungus, how could this effect tits and their breeding?
- tits are less likely to contract pathogenic disease or fungus infection so less energy is used to fight them off and more energy can be used for reproduction and breeding behaviour. therefore the numbers of successful breeds are likely to increase.


The big 3 Questions

1. How is nitrogen made available to plants for growth
- microorganisms digest the dead organic matter via extra-cellular digestion
- in doing so they release ammonium ions into the soil
- the ammonium ions are converted into nitrates, via nitrites by nitrifying bacteria
- the nitrates can be used for protein synthesis or synthesis or nucleic acids in the plants.

(i also then mentioned how they make co2 available to the plants through respiration but i dont think it was relevant) ....

2. How does the CO2 concentration change though deforestation and burning of vegetation
- Plants and treed use CO2 for photosynthesis
- their net rate of photosynthesis is greater than their net rate of respiration so they remove CO2 from the atmosphere
- by destroying them there are less plants and trees photosynthesising and so less uptake of CO2 so and increased amount of CO2 in the atmosphere
- Burning of the vegetation released the carbon compounds in them in the form of CO2 (combustion), which also increases the amount of CO2 in the atmosphere
- However, the destruction of plants and trees removes niches/ habitats so many species die out or move out
- therefore there are few respiring organisms so less CO2 is released to the atmosphere in that respect
- However, overall the amount of CO2 would increase in the area.

3. How does CO2 get used in plants for synthesis of organic compounds?

- CO2 combines with RuBP via enzyme Rubisco
- forms 6C compound which splits into 2 3C glycerate phosphate molecules
- GP reduced into 2 triose phosphate molecules via products of light dependent reaction
- ATP provides energy, reduced NADP provides hydrogen (both products of light dependent)
- TP converted into useful hexose sugars, eg. glucose
- 5 out of 6 TP molecules are used to reform RuBP so the cycle can be started again.



Can someone tell me what they think i've got in the hardy and mites question please? (i didn't like the mites one at all - think it went really bad for me).... had little timeeee.

cheers,

For the spearman rank question i thought it said that the value was negative. Explain why.
so i just wrote negative correlation >.<

and for the length of oil gland i said it wont be reliable because surface area to volume ratio is not taken into account...a oil gland could be long but has a small volume; a oil gland can be short but have a large volume "/

and i wrote directional not stabilising...

and i wrote that it was random so that bias is eliminated and a statistical test can be calculated lol

not sure though "/

negative correlation is probably fine!

I don't this that measuring surface are to vol ratio for the oil glands was a concern, because the size will relate in general to how much oil it produces and i think thats what they wanted to take into account. greater size, more oil produced. and size may refer to surface area to vol ratio who knows? ...


and why did you put directional selection?

im not sure "/

uhm...because only one phenotype was selected against...the freq of recessive was decreasing.
nothing was stated that the freq of dominant was decreasing so i just said it was directional...
because if it was stabilising both extremes [dominant and recessive] will be selected against?



what do you reckon the grade boundaries will be...reading your answers i think i got like a C at the moment >.<
what did you get in Jan 2011?

My reasons for stabilising are that the recessive allele was at one extreme of the range of alleles present. (it was 4% from hardy weinberg) ... and then it said that the frequency decreased even more... so the extreme was being selected against which would mean alleles towards the middle were being favoured for. so its stabilising.

but i see where you're coming from for directional too... so i dunno really.

I wouldn't go solely by my answers as i may have got some wrong lol. I reckon we will be looking at the highest boundaries yet - probably 50 for an A if not more. 47 was an A in january and they were high boundaries! plus there will be a lot more retakers this time round who need to do well so are likely to have revised more who knows? its all bad news though haha. what do you think they will be?

looking at my answers what do you think ive got overall? the other part is a page or two back btw.

i thought it was definately easier that Jan 2011....so maybe higher than 47 for an A?
But i hope not...i need as much ums as possible >.<

How many marks do ppl think for an A* in jan it was 52/75 soo it could be say 55/75 that's my best bet. But it couldn't be as high as 60/75=A* do you reckon? cos it seems although people thought it was easier than the jan one, they have made silly mistakes. So that would be taken into consideration.
I have a couple of doubts, you know the anaerobic digester question, where it said state 2 advantages of using this inside of dumping waste in a pond, would you get the marks for saying:
- the methane released can be used as a fuel
- the waste (or summet) that is released during digestion can be used a natural fertiliser.
Also the next bit why did the system need coolling down, I put:
To allow for the anaerobic bacteria to carry on digesting the organic compounds, as the accumulation of the heat would stop the action of the bacteria.
But I didn't mention anything about enzymes, so would I get at least 1 mark out of the 2?

Hardy Weinberg Question

1.Calculation
- 4%
2.What does hardy about the frequency over 10 generations
- that the frequency of the alleles in the population won't change
3. Use probability and chance
- there is a probability of 5% or less that the change in allele frequency is due to chance. therefore we reject our null hypothesis that the frequency of alleles wont change. (not sure about this, can someone back me up if they put something similar,cheers)
4. What type of selection is this
- Stabilising selection
- The recessive allele has decreased in frequency. it was at the extreme of the range of alleles as the hardy calculation proved it was only present in 4% of the population. with a further decrease it means that alleles closer to the middle of the range are being selected for, hence its stabilising.


Mites Question (cant remember many of these question so i'll try my best.)

1.Why was the data selected at random
- to remove bias from the experiment. It allows us to form a valid correlation between numbers of mites and successful breeding chicks. (not sure about 2nd point)
2.Describe the data and does it agree with the statement that more mites decrease successful breeds???? (think that was the question)
- with small increases in mites the amount of successful breeds fluctuated at around 80.
- with a large increase in mites (170), the number of successful breeds decreases to 42 from 86 at 15 mites.
- However, without further data we cannont conclude that an increase in mites does cause a decrease in successful chicks.
3. State a null hypothesis
- there is no significant statistical difference between the numbers of mites present and the amount of successful chicks.
4. Spearmans showed a negative correlation between mites and successful chicks what does this mean?
- That an increase in mites does not effect the number of succesful chicks. (is this right?) ...
5. Describe the data in the graph
- For tits with large oil glands, many of the points are close or touching the line of best fit. However, for tits with small oil glands, few points are close to the line or touching it. However, overall there is a slight positive correlation.
6. Does measuring oil gland size increase reliability?
- yes because different tits have different sizes of oil glands and therefore we are removing this variable from the experiment. (dunno if this is right) ....
7. Mites eat pathogenic bacteria and fungus, how could this effect tits and their breeding?
- tits are less likely to contract pathogenic disease or fungus infection so less energy is used to fight them off and more energy can be used for reproduction and breeding behaviour. therefore the numbers of successful breeds are likely to increase.

Can someone tell me what they think i've got in the hardy and mites question please? (i didn't like the mites one at all - think it went really bad for me).... had little timeeee.

cheers,

negative correlation is probably fine!

I don't this that measuring surface are to vol ratio for the oil glands was a concern, because the size will relate in general to how much oil it produces and i think thats what they wanted to take into account. greater size, more oil produced. and size may refer to surface area to vol ratio who knows? ...


and why did you put directional selection?

I put directional selection as well. Stabilising selection indicates action against BOTH extremes, whereas directional selection indicates only one extreme being acted against. So surely it is directional because ONLY the recessive allele is being acted against?

yeh you're answer makes sense im probably wrong mate. ....

although also, how does it make sense in terms of extremes as there is only one extreme, being recessive? cause dominant and heterozygous both code for the same phenotype.