OCR 2010 A2 Biology Unit 2 - Control, Genome and Environment Watch

uer23
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#1361
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Anyone retaking Unit F214 ? Don't think so I'm going to have time to revise for that now, just too much for this Unit. I'm going to have a 9 day period between my last Unit 5 A2 exam and F214 will revise nonstop then.
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InvoluntarySlacker
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(Original post by win2kpro)
:hi:

Some stuff people are on about in this thread make me just want to... - Im leaving this thread for now, gotta focus on F211 first...:

:getmecoat:
Hey.

I'm retaking F211 as well to get a higher grade. Just started revising today and I am shocked how easy it looks. :confused: I can't remember it being this easy.
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Aftermath_Fan
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(Original post by ViolinGirl)
Well, if from your Chi-squared test you get a value that is lower than that present in the critical region for your certain no. of degrees of freedom then you can assume that any differences in observed and expected no's are due to chance, but if you get a value that is higher than the given value in the tables, it is not due to chance, and you have to suggest why this is the case. For example the specific cross that you get may be more similar to 1:2:1, in this case it would show that codominance is occuring.

^^ I can easily explain that but the answer that was on the mark scheme was along the lines "genes are linked, not independently assorted at meiosis 1 etc.. I was wondering how would you knw if this is what you supposed to put down
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ViolinGirl
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(Original post by Aftermath_Fan)
^^ I can easily explain that but the answer that was on the mark scheme was along the lines "genes are linked, not independently assorted at meiosis 1 etc.. I was wondering how would you knw if this is what you supposed to put down
There is no right or wrong answer really. It is asking you to suggest why the expected numbers are different to expected numbers. SO any reasonable explanation. That is why several examples are given in the marksheme.
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win2kpro
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(Original post by InvoluntarySlacker)
Hey.

I'm retaking F211 as well to get a higher grade. Just started revising today and I am shocked how easy it looks. :confused: I can't remember it being this easy.
My thoughts exactly :ashamed: , lets hope we ace the exam?

What did you get first time around?
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InvoluntarySlacker
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(Original post by win2kpro)
My thoughts exactly :ashamed: , lets hope we ace the exam?

What did you get first time around?
Few marks of a B.

You?
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win2kpro
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(Original post by InvoluntarySlacker)
Few marks of a B.

You?
70/90

To better marks in the resit! - :cheers:
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InvoluntarySlacker
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(Original post by win2kpro)
70/90

To better marks in the resit! - :cheers:
Yup. :five:
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smflesh
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(Original post by Tinkerbelle ♥)
As far as I'm aware it does. The release of ADP + Pi is because of the use of ATP
I'm still a bit confused .

I know for definite that ATP is hydrolysed to ADP + Pi to release energy to break the cross-bridges, in order to allow the myosin heads to 'unbend' thus re-enabling them to initiate another power stroke.
Does the ADP + Pi remain on the myosin head until it binds again to actin, which then causes then causes them to dissociate away? Maybe there's some ''left-over'' energy from the hydrolysis of ATP from the previous step?
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TX22
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why is there less energy transfer between producers and primary consumers.
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student92
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(Original post by TX22)
why is there less energy transfer between producers and primary consumers.
Because some energy is lost at each trophic level, which is unavailable to the organisms at the next trophic level. So energy decreases at each trophic level - from producers to primary consumers to secondary consumers and so on. Energy is lost to respiration, heat loss and in faeces, urea (excretion) - which is only available to decomposers.
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student92
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Module 3 - Ecosystems and sustainability

Ecosystems

Ecosystem - all the living organisms and all the non-living components of a specific habitat and their interactions.

Ecosystems are dynamic systems:
- Population sizes change
- A small change affects the other
- e.g. Population of predators increase, then population of prey decreases.

Habitat - a place where an organism lives

Population - all of the organisms of 1 species that live in the same place at the same time and that can breed with each other

Community - the population of a different species that live in the same place at the same time and that can interact with each other

Niche - the role of an organism in its community.
e.g. its position in the food chain, how it interacts with the environment and other species.


Biotic factors - Living organisms effect each other
e.g. predation, disease, food supply.

Abiotic factors - the effects of non-living organisms in an ecosystem
e.g. pH, temperature, CO2/O2 conc.


Producer
- Convert light energy into chemical energy, which is supplied on to the consumer
- Energy is used to convert small, inorganic compounds (H20, CO2) into complex ogranic molecules (AA)

Consumer
- Living organism that feeds off another living organism
- Primary consumers - herbivores - convert energy into animal tissue
- Secondary consumers - carnivores

Decomposers
- Living organisms that feed off dead, organic matter
- Used as a source of energy
- e.g. bacteria, fungi

Trophic level
- The level at which an organism feeds off in a food chain.


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win2kpro
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Anyone got the F211 January Paper? - Rep available
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MadMaths
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Do we need to know what antisense genes are its in the stretch and challenge bit?
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ACDC
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can someone explain how the plant hormone auxin acts as a growth promoter when we're talking about cell elongation(allowing shaded cells to take up more water), but when we're speaking of apical dominance auxin acts as the inhibitor stopping lateral buds from growing. it just seems contradictary.
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Remarqable M
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(Original post by win2kpro)
Anyone got the F211 January Paper? - Rep available
pm your email and i'll send it to you
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Remarqable M
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I have a feeling that gorillas might come up on the exam lol just a feeling, but i suppose chimpanzees could come up or any other primates for that matter :lol:
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ibysaiyan
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LOL nice to see familiar faces around =}
I haven't been around for a week xD
Couldn't resist it.
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uer23
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(Original post by ibysaiyan)
LOL nice to see familiar faces around =}
I haven't been around for a week xD
Couldn't resist it.
lol liar, you're earliest post was 2 days ago. :rofl:
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ibysaiyan
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(Original post by ACDC)
can someone explain how the plant hormone auxin acts as a growth promoter when we're talking about cell elongation(allowing shaded cells to take up more water), but when we're speaking of apical dominance auxin acts as the inhibitor stopping lateral buds from growing. it just seems contradictary.
Okes:
For cell elongation here is what happens:
Photo-tropins which are found around the cell membrane get phosphorylated this causes the flow of auxins sideways the way is not understood fully but two possible scenarios are its either that the phosphorylation causes more photo-tropins to get collected on a particular site or they use more energy.As auxin (IAA)travels sideways they cause a series of changed to their target cell.They attach onto the receptors which causes an increase of H+ ions within the cell,this activates an enzyme which cuts right through the plasmodesmata which causes them to loosen.
=} but in apical dominance auxins work the other way around: They inhibit terminal buds (lateral) so auxin conc. at the top is more and as you go down decreases more buds being inhibited at the top and less and less as you go downwards =}
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