Biology; Chemistry; Physics: Post your doubts here!

[AAAYY***]

As yo9u may know, epidermal cells are the outer most layer of a leaf.... so its basic function is to protect the various cells(like spongy/palisade mesophyll cells) and thus lets thus lets them conduct their function easily; photosynthesis!! -------> this is the main reason!!

Is there something else after "and question"???

Hope it helps!!!

thankyou

 

[AAAYY***]

As yo9u may know, epidermal cells are the outer most layer of a leaf.... so its basic function is to protect the various cells(like spongy/palisade mesophyll cells) and thus lets thus lets them conduct their function easily; photosynthesis!! -------> this is the main reason!!

Is there something else after "and question"???

Hope it helps!!!

btw how did you prepare for sci subjects am appearing in oct session only few days left and am still stuck to how i should do pastpaper along with revision

 

[AAAYY***]

when mentioned state in biology what one should right is they have to mention only a single line or what ????

 

[Zuhsid]

btw how did you prepare for sci subjects am appearing in oct session only few days left and am still stuck to how i should do pastpaper along with revision

Well m not gonna lie to you..... i only prepared for one month, did not do many past papers, 3 years max.......
what i feel should be the case is clearing your concepts, some topics are hard, some are easy, take a topical past paper book and solve the topic which you are confused in or you find hard, even if you dont do others!!! Make notes while doing past papers, for every question in which you think your answer was even slightly wrong!!!
AND ALWAYS consult the syllabus, take every point individually coz there would alot of things not mentioned in a single book!!!!
Also surf the net for various problems!!!
Clear your head of any doubts, we, including me are regular XPC members and are always here for help, dont hesitate asking!!!
This all got my A*s alhamdullillah!!!

Hope it helps!!1

 

[Zuhsid]

when mentioned state in biology what one should right is they have to mention only a single line or what ????

An extremely precise answer...... not more than 1-2 line(1 line preferably)...... if you have time/space write a single word example(in a more than 1 mark questioon), but even that is not necessary......... But more commonly, this used for one word answer-questions!!!

 

[AAAYY***]

any tips for phys atp graphs

 

[Zuhsid]

any tips for phys atp graphs

Well m not sure what to tell about them... they are quite simple..... the normal rules apply like the independent thing is on the x-axis and dependent on the y-axis..... plot the graph with CROSSES..... and see what is written in the question(read it thoroughly), like if its written "smooth curve" or "line of best fit"...... in the smooth curve thing, make sure the line is continuous and no sharp edges on the edges/curves.... in the line of best fit.... make the line such that the maximum points pass through BUT more importantly, the number of marks above the line SHOULD BE EQUAL to number of marks below it!!!

Other than that, anything specific you want to know???

 

[Salman Shah Jee]

Hye!! Can anyone explain budding and grafting(reproduction in plants).......i m nt getting it!!!!!!!!!!
any link will also be helpfull....thnkx

 

[Mustafa Abbasi]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s12_ms_11.pdf
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s12_qp_11.pdf

Had a doubt in question 5 :
5 A hard stone hits the ground and comes to rest almost immediately.
As the stone hits the ground, what is the direction and the size of the force acting on the ground?
A downwards and equal to the weight of the stone
B downwards and larger than the weight of the stone
C upwards and equal to the weight of the stone
D upwards and larger than the weight of the stone

Now, initially i thought A was the answer. My confusion is that all of us know that"for every action there is equal + opposite reaction" so in case the force acting on ground was same as weight of stone, then the ground would exert equal force upwards on the stone which would balance the upwards and downwards(weight) forces on the stone and so stone wont bounce back and come to rest immediately . However, in the Mark Scheme B is Written Correct but if B was ans, then the force acting on ground would be greater than weight of stone meaning ground would exert same force upwards on stone therefore the resultant force on the stone would be UPWARDS and hence it would bounce so why is B correct(i want clear ans).... Thank You for ur Help guys.

 

[usama321]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s12_ms_11.pdf
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s12_qp_11.pdf

Had a doubt in question 5 :
5 A hard stone hits the ground and comes to rest almost immediately.
As the stone hits the ground, what is the direction and the size of the force acting on the ground?
A downwards and equal to the weight of the stone
B downwards and larger than the weight of the stone
C upwards and equal to the weight of the stone
D upwards and larger than the weight of the stone

Now, initially i thought A was the answer. My confusion is that all of us know that"for every action there is equal + opposite reaction" so in case the force acting on ground was same as weight of stone, then the ground would exert equal force upwards on the stone which would balance the upwards and downwards(weight) forces on the stone and so stone wont bounce back and come to rest immediately . However, in the Mark Scheme B is Written Correct but if B was ans, then the force acting on ground would be greater than weight of stone meaning ground would exert same force upwards on stone therefore the resultant force on the stone would be UPWARDS and hence it would bounce so why is B correct(i want clear ans).... Thank You for ur Help guys.

If the stone had been lying on the table, we would have considered only the weight of the stone. But as it is falling, it has kinetic energy, and when it hits the ground, the earth has to provide resistance to the kinetic energy of the stone to stop it as well as the weight. It's the same concept as if a car hits a wall at 10 km/h and another at 20km/h. The force on the wall would be greater by the second car

It's most probably related to momentum.

 

[raynalist]

Grafting involves joining a portion of a certain plant to the corresponding part of another plant of a closely related variety.For e.g:grafting a variety of rose onto another rose variety.
The variety which is desirable is called the scion.This is a piece of the rose system bearing buds but no leaves.To minimise water loss by transpiration.One end of the scion is securely attached to the corresponding end on the other plant called the stock.The leafy shoot of the stock is cut and discarded.When the graft has bee done it may be covered to reduce water loss and protect from pest.The xylem and phloem of the stock provide water and food to the scion.The buds on the scion develop into new shoot bearing flowers or fruits of its kind.

 

[Salman Shah Jee]

thnx bro..........

 

[Deadly Orchid]

How to effectively answer questions in biology? (both sections)

 

[irfan.kheerdali]

can someone tell me tecniques to get an A* in o level Biology,physics and chemistry.

 

[Zuhsid]

Just read the main course book thoroughly....but more importantly, take the syllabus and cover each point seperately and thoroughly...... and use the notes given on this site, to study topics you find you lack in or dont have enough information about after solving questions(links below)......... in the end, you should do past papers, i would prefer topical, and do the topics you find hard to understand/solve.....
And we, XPC members, are online extremely frequently, so ANYTHING at all that you find confusing, ask us, post in threads, but dont hesitate!!!

https://www.xtremepapers.com/community/threads/all-notes-o-level-0r-igcse-a-level.4866/
https://www.xtremepapers.com/community/threads/biology-chemistry-physics-post-your-doubts-here.9672/​

https://www.xtremepapers.com/community/threads/o-level-notes-center.11138/​

This applies to all 3!!​

 

[irfan.kheerdali]

Suggest and explain the effect on a plant shoot of a large number of aphids feeding at
the same time over a period of several weeks. [7 pts](biology o level)

 

[irfan.kheerdali]

Suggest and explain the effect on a plant shoot of a large number of aphids feeding at
the same time over a period of several weeks. [7 pts](biology o level)

 

[irfan.kheerdali]

Just read the main course book thoroughly....but more importantly, take the syllabus and cover each point seperately and thoroughly...... and use the notes given on this site, to study topics you find you lack in or dont have enough information about after solving questions(links below)......... in the end, you should do past papers, i would prefer topical, and do the topics you find hard to understand/solve.....​

And we, XPC members, are online extremely frequently, so ANYTHING at all that you find confusing, ask us, post in threads, but dont hesitate!!! ​

​

https://www.xtremepapers.com/community/threads/all-notes-o-level-0r-igcse-a-level.4866/​

https://www.xtremepapers.com/community/threads/biology-chemistry-physics-post-your-doubts-here.9672/​

https://www.xtremepapers.com/community/threads/o-level-notes-center.11138/​

This applies to all 3!!​

Thanks very much

 

[Zuhsid]

Suggest and explain the effect on a plant shoot of a large number of aphids feeding at
the same time over a period of several weeks. [7 pts](biology o level)

The aphid will consume the pants amino acids, so less protein can be made, and this new protoplasm would be hard to make and thus stunted growth. It would take glucose, and ither carbohydrates, so plant would not be able to respire properly and thus less energy produced may weaken and kill the plant, as t would not be able to pollinate or keep itself warm etc. It may also allow introduce pathogenic foreign bodies into the plant through its hibiscus, thus would not be able to survive!!!

You can use the marking schemes for there questions as well!!!

 

[irfan.kheerdali]

Explain how it is possible that parents with different blood groups are able to produce
only children with blood groups different from themselves?[5 pts](biology o level)

 

[Zuhsid]

Explain how it is possible that parents with different blood groups are able to produce
only children with blood groups different from themselves?[5 pts](biology o level)

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_w12_ms_21.pdf