Biology A2 Paper 4 Thread (1st June 2011)

[mury456]

heyy,

post up your biology paper 4 questions here preferably with a attachment
and find help

your guesses,

basically evrything paper 4,

Lets make sure we ace this paper

Best of luck revising,
cheers

 

[mury456]

Points for Benefits of Bio Diversity

To keep stable and maintain the Ecosystem
To keep many diverse gene pools in populations
To keep organisms from becoming extinct
To provide possible future medicines
To encourage ecotourism
Ethically all species deserve to live


if I helped remember to THANK

 

[mury456]

How Penicillin works ?

Penicillin inhibits the active site of the enzyme Peptidase, because of this Peptidoglycon chains cannot link.
This cause cell wall of bacteria to weaken.
As a result of this the turgor of the cell becomes to much for the weakened cell wall to bear
this causes lysis of the cell.


Hope I helped ... If I did remember to THANK me !

 

[mury456]

This is the best revision guide right now
it gives a quick detailed view of the whole portion
hit attachmnt and download


Remember to hit the THANKS button if I helped you out

 

[angelgurl]

mury...........is this the mary jones revision guide? because my computer is taking hours to download it and i have tht already

 

[UMAR100192]

chek this out: s-cool.co.uk
the notes are shorter and contain nearly everything...

 

[mury456]

mury...........is this the mary jones revision guide? because my computer is taking hours to download it and i have tht already

yes it is ... I mentioned the name of the book in the post ...
well if you already have that ... blast me with your questions ...
I will get some revision and you your answers

 

[Fauziya]

can u tell me about natural and artificial selection??? :fool: :O:

 

[mury456]

can u tell me about natural and artificial selection??? :fool: :O:

Natural Selection :

In evry population of species any individual can reproduce more then the required number of children to maintain the population so like 2 rabbits can produce GHAZILLION youngs ( I ddnt actualy know how many youngs a rabbit produces in one life time ) so this would cause over population.
But naturally that cannot happen other wise the world would be full of rabbits !!
so many aspects act as the selective pressure on the population like disease, predation ( predators eating rabbits ), the competition for food, competition for mating, ect. Some alleles present in the gene pool will be more adaptable to the surrounding and thus they will survive, and when they survive they reproduce so passing on their alleles to young ones. In simple terms the FIT get to pass on their genes and the UNFIT die out.

Check out Darwinian theory.

Artificial Selection :

It is the choice of human by which plants and animals are allowed to breed. Like farmers breed cows that are docile and yield more milk so after a few generations all the cows they own would be docile and would yield more milk. It is the same as natural selection with only the difference that Humans act instead of nature.



Hope I helped remember to hit the THANKS Button

 

[mury456]

Watch this video to get a basic idea about gel electrophoresis ...
I heard a clue that it might be important this year !


http://www.youtube.com/watch?v=0x2Lh5Rq8e0

 

[Fauziya]

write a short note on the Plant growth regulators.

 

[mury456]

write a short note on the Plant growth regulators.

Lets start with

Auxin :
Remember it stops plant growth. It is produced in area where cell division is taking place like a bud on a growing shoot. This is also know as apical dominance

Gibberellin :
Remember it promotes plant growth, it is also known as GA. Most of the GA is produced by genes in the plants. Lack of GA causes short plants. Its mostly found right after germination.

Abscisic Acid :
AKA plant stress hormone or ABA. Its is a hormone secreted when plants living conditions get tough such as very dry or very cold or very hot. It is made in the leaves. It makes the leaves flaccid and stomata close, its response time is fast and is not effected by any genetic variations.

Hope I helpd Remember to THANK

best of luck

 

[el_nino9]

now i know almost everything is covered in the revision guide, but this cellular respiration flowchart(attached) is kinda helpful too.

 

[mury456]

good work

 

[el_nino9]

good work

Thanks!

 

[el_nino9]

Anyone having difficulties understanding the Na-K pump or the entire excretion part of the syllabus should definitely check out Khanacademy tutorials on the topic.http://www.khanacademy.org/video/the-kidney-and-nephron?playlist=Biology

 

[zwitterion7]

I need notes on the entire co-ordination chapter. Can you please post.

 

[Maniizm]

viewtopic.php?f=26&t=8330&start=10#p91351
Yep khan academy is the best for Biology! i understand waaaaay better

 

[desolator619]

can someone explain action potentials to me? like how they travel along a nerve or whatever :'(

 

[beacon_of_light]

Actional potentials are all those chemical messages travelling along thousands of neurones. In response to a stimulus, particular receptors are activated and if the stimulus is really strong , the reseptor potential would overshoot threshold level and result in an action potential. Now how actually a stimulus is converted into an action potential is all becuz of Na+/K+ channels. Na+ are higher in conc. outside the cell while K+ are higher inside the cell. And then you know when an actional potential starts, prior to that Na+ channels open and Na+ move into the axoplasm causing depolarising the axon membrane (making the inside of membrane more positive than the outside). When potential difference across w.r.t inside reached +50mV, Na+ close and K+ channels open.K+ diffuse out causing repolarisation of the axon membrane...
And now how is the impulse travelling along the neurone. Since the membrane is covered with Schwaan cells, depolarisation can not occur other than at the node of ranvier so successive depolarisation of the membrane and saltatory conduction play a major role... Action potentials jump from node to node!
Hope that helps