AQA Biol 4 unofficial Markscheme

Futuremedic2096

ps1265A

Yup, here is what I've made:

a) Initially both high
Death rate decreases first, followed by birth rate
Then both low

b) Low at first, then increases, then remains stable (sigmoidal)

c) 6.33

d) Less women smoke, ideas about better lifestyle, drinking drugs
--------
a) R

b) Saprobiotic microorganisms break down proteins to amino acids, amino acid converted into ammonium compounds (Extracellular digestion, secretion of enzymes) - ammonification

c) Fetility increases, less denitrifying bacteria because less oxygen, so more nitrates in soil. More aerobic conditions, more nitrification

d)
1. Monoculture leads to reduced INTERspecific competition
2. Morw nitrogen-fixing bacteria present
3)add, removes different nutrients, as they use different nutrients
--------
a) KJm-2year-1

b) Pioneer species makes conditions less hostile, so nitrate concentration increases, more used for proteins in plants, explains why biomass increases, more plants, greater variety, more specific plants

b) Decreases because climax community, increased INTERspecific competition for light, fewer less dominant species photosynthesise, reduced biomass

c) Stays constant because climax community, net prod = gross prod - resp losses, Gross productivity and net productivity are almost the same

a) Pyruvate, decarboxylation, dehydrogenation, combines with coenzyme A
Reduces NAD to NADH

b) Insert fancy enzyme name - binds to enzyme brings about conformational change, tertiary structure of active site shape changed, new active site complementary to acetylcoezyme A

c) Competitive inhibitor, less acetylcoezyme A binds, reduces rate of production of 6 carbon compound

d) Lactate increases H+, affects enzyme activity/causes fatigue, or it is oxidised to Pyruvate and then glycogen and can be used as an energy source
LCtate converted to pyruvate and this is used in aerobic respiration, high atp yield.
------
a) Volume of oxygen produced per unit time.
This asked what to measure, time, volume, mass

b) CO2 concentration and concentration of algae(argument about light intensity)

c) More CO2 absorbed, less CO2 In solution, increases pH. As photosynthesis occurs

d) Wavelength corresponds to green light, light reflected, reduced rate of light dependent reaction, reduces products, glycerol etc, less growth
------
a) Both expressed in the phenotype if hetero

b) Males only have one allele as it's on x and they only have one x
Black male black female ginger female tortoise shell (don't quote on sexes)

c) 1:1:2

d) 0.90

e) Increases because homozygous recessive decreases. Dominant increases, recessive decreases (dependent on which way round, I can't recall)
-------
7
a)
Keep salty - representative of the environment,
Several times - There maybe variation in the type/number of fungus between different plants-ensures representative

b)
Good:
- All showed a decrease
- One decreased by almost 40
Bad
- Overlap with control
- Overlap within fungus
Don't know effect on yield and such like

c) Comparison + to show that effect was due to fungus

d) Increase temperature, evaporation, reduces amount of water, same salt. reduced water potential

e) Bacteria computers with fungus for food resources/out competes, less plant biomass eaten by fungus. Change growth in plant, competition will reduce it's growth won't be due to bacteria

f) High salt, lowers water potential, water moves out of plant by osmosis.
Alternative less, insufficient osmosis

--------
8
a)
- Geographical isolation
- Variation due to mutation
- Different selection pressures
- Differential reproductive success
- Pass on allele
- Increase in frequency of allele
No interbreeding to form fertile offspring

b)
- Capture
- Mark with non toxic non conspicuous marker
- Release, give enough time to evenly spread amongst population
- Recapture and count number of marked
- Use formula

c)
Daytime - Increase in light intensity and temperature, rate of photosynthesis is greater than respiration, so net uptake of CO2, concentration decreases

Nighttime - ONLY respiration, no photosynthesis, net CO2 production, increases CO2

High above ground - more leaves, more photosynthesis, decrease CO2

Below ground - light doesn't reach plants, decease photosynthesis, high CO2 concentration

(edited 8 years ago)

Reply 1

Miles97_X

1

[QUOTE="Futuremedic2096;56756061"]

ps1265A

Yup, here is what I've made:

Thank you!! :biggrin:

x

Reply 2

Futuremedic2096

OP

8

Mostly the work of ps1265A

Reply 3

SamuelSingleton

13

just a suggestion but something i cleared up with my teacher: for the question on acetylcoenzyme a and enzyme in krebs cycle, my teacher told me that oxaloacetate (however it's spelt) is combined with acetlycoA, therefore wouldn't be non-competitive inhibition, it's part of the induced fit model as 1 part binds to the enzyme it causes the confirmational change so the other part is complementary to acetylcoA
(but just a suggestion i have no idea it could be right or wrong)

Reply 4

alanconnel

4

isnt it 5.95 %? i worked out difference which is 5 but then divided it by 84 instead of 79 or were you meant to divide by 84 instead of 79

Reply 5

alanconnel

4

Original post by Futuremedic2096

Mostly the work of ps1265A

ratio 1:1:1:1

Reply 6

alanconnel

4

Original post by alanconnel

ratio 1:1:1:1

you had 4 different phenotypes XbXg, XbXb, XbY, XgY

Reply 7

ALevelBro

2

Any idea on the grade boundaries? I hope 50% puts you at an A, at least?

Reply 8

Futuremedic2096

OP

8

Original post by SamuelSingleton

just a suggestion but something i cleared up with my teacher: for the question on acetylcoenzyme a and enzyme in krebs cycle, my teacher told me that oxaloacetate (however it's spelt) is combined with acetlycoA, therefore wouldn't be non-competitive inhibition, it's part of the induced fit model as 1 part binds to the enzyme it causes the confirmational change so the other part is complementary to acetylcoA
(but just a suggestion i have no idea it could be right or wrong)

Yeah I wrote exactly the same as you, word for word. it's mostly other guys work with my editing I overlooked this
Indeed it is Induced fit
I've changed accordingly

(edited 8 years ago)

Reply 9

Futuremedic2096

OP

8

Original post by alanconnel

you had 4 different phenotypes XbXg, XbXb, XbY, XgY

That's genotypes
It's undecided whether phenotype accounts for gender,

Reply 10

Futuremedic2096

OP

8

Original post by ALevelBro

Any idea on the grade boundaries? I hope 50% puts you at an A, at least?

38/75 would be an E or scraping a D I'm afraid

Reply 11

ALevelBro

2

Original post by Futuremedic2096

38/75 would be an E or scraping a D I'm afraid

F*ck's sake lol.

Reply 12

alanconnel

4

Original post by Futuremedic2096

That's genotypes
It's undecided whether phenotype accounts for gender,

look at mark scheme for question 13C

https://bbbdc07516fb33dd48861fc5209437d38b800f68.googledrive.com/host/0B1ZiqBksUHNYb1RsOVBqZE9rMXM/Set-A/8%20Inheritance%20&%20Selection%20MS.pdf

its decided.

Reply 13

rachaelharri

Half of this makes me really happy, the other half makes me wanna cry...

Reply 14

Futuremedic2096

OP

8

I'd just like to say something, let's all keep pleasant towards each other, we tried our best to make this accurate as possible but it's not reflective of an aqa mark scheme
And surprise surprise we two a2 students GET THINGS WRONG

Reply 15

Alex_fcxt

For 2b, it's not ammonification.. They said in question name 'other' process from the one shown.. You had to mention nitrogen fixation! And I got 5.92% for difference in percentage of females to males... You had to use the age of two from when 50% still alive so from 50,000 people

Reply 16

Bustamove

19

Thanks for making this, it's definitely reassured me... I probably lost a max of 15 marks... Hopefully can still scrape an A...
Btw, thanks for helping me out with the nitrogen ceycle before the exam in the bio 4 thread :smile:

Reply 17

Futuremedic2096

OP

8

Original post by Alex_fcxt

For 2b, it's not ammonification.. They said in question name 'other' process from the one shown.. You had to mention nitrogen fixation! And I got 5.92% for difference in percentage of females to males... You had to use the age of two from when 50% still alive so from 50,000 people

I believe the context of the question didn't allow you to put fixation but I won't argue with you

It depends whether you took the age as 80 or not
I took females as 84 and males as 79.5 so got similar to you
There will be a range on MS

Reply 18

Pro xi

what was the answer for the hardy wienburg q?

Reply 19

Sanjaypatel13

1

Original post by Futuremedic2096

I believe the context of the question didn't allow you to put fixation but I won't argue with you

It depends whether you took the age as 80 or not
I took females as 84 and males as 79.5 so got similar to you
There will be a range on MS

I believe the guys right.. The question did say OTHER then the one shown (it showed ammonification)
Btw is that all the questions? And do you have a blank paper from today? I wanted to know the amount of marks available for each question:/

AQA Biol 4 unofficial Markscheme

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