Physics, Chemistry and Biology: Post your doubts here!

[AAnsarii]

i also need help in may/june 1998 Q.36 i did it correct C but imnot sure why, can anyone plz explain it.

when d water seeps 4m land 2 rivers, it carries d nitrate ions wid it, thus increasing water pollution(coz of growth of bacteria, etc..). hope dat's d ryt qn
n btw, i dnt hv d missing qns

 

[AAnsarii]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_w04_qp_1.pdf q6. hw r u supposed 2 noe dat chloroplasts have starch, isn't it in vacuoles?
also, qn 27

 

[Abu mota]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_w04_qp_1.pdf q6. hw r u supposed 2 noe dat chloroplasts have starch, isn't it in vacuoles?
also, qn 27

Q.6 photosynthesis occurs at the chloroplasts
Q.27 it is B, this is the definition of development

 

[AAnsarii]

w02 ms1?

 

[AAnsarii]

Q.6 photosynthesis occurs at the chloroplasts
Q.27 it is B, this is the definition of development

but vacuoles do contain starch?

 

[Abu mota]

but vacuoles do contain starch?

no, they contain cell sap, sugars, salts, but they dont have starch, dont overthink the questions

 

[Besterlinks]

I know you don't need it now, but still

 

[The sun]

for MJ 2004

Q29 ans is C

30cm3 is used up which is oxygen which makes up 21% of the air
The rest is nitrogen c02 watervapour and noble gases.. these all are 79%

So if 21% = 30cm3

then how much is 100% ( all the volume of the oxgen and other gases)

Do cross multiplication u will get 142 (this is because 21% is only an estimate it might vary) so 150cm3 is the most reasonable answer so choose it

thnx alot for ur help

 

[JOEJOE]

ur welcome

 

[L.V.D]

http://www.bbc.co.uk/schools/gcsebitesize/science/21c_pre_2011/food/harmfulchemicalsrev3.shtml
herbicides kill unwanted weeds
pesticides kill pests(as d name suggests)http://en.wikipedia.org/wiki/Pesticide{this includes almost all of them}
n insecticides kill insects

thanks but how do they affect other organisims around them

 

[JOEJOE]

Some pestecides affect plants

 

[Rahma Abdelrahman]

THANK U SOOOOOO MUCH.......CAN U PLZZZZZZZZZZ EXPLAIN THE OPENING AND CLOSING OF GUARD CELLS IN MORE DETAILS (LIKE WHEN DO THEY OPEN AND WHEN DO THEY CLOSE IN GENERAL I KNOW NOTHING ABOUT IT SO PLZZZZZZ HELP) AND FOR NUMBER 8 - UR LABELING R CORRECT BUT THERE IS NO CHOICE "FROM W TO Y" THE XYLEM IS THE DARKER CELL RIGHT???????? THANKSSSSSS AGAIN

Why do stomata open?
They open in favourable conditions such as high light intensity and optimum temperature to absorb maximum CO2 for maximum photosynthesis.
How do they open?
When the rate of water uptake by the plant is high, the cells become turgid, right? And so are guard cells but instead of becoming just turgid, they curve allowing stomata to open.
What makes the guard cells curve?
This is because the guard cell has thicker inner walls than the outer walls, causing the unequal pressure on both walls and hence the curvature.

For the xylem Q., I believe xylem should be the darker one, but here we should only know that water leaves through stomata, which leaves no other option but B.

Hope this helps!
And, you are most welcome!

 

[JOEJOE]

Mashallah.. ur good Rahma

 

[Rahma Abdelrahman]

Mashallah.. ur good Rahma

Thank yooooouuuuuuuuuuuuu !!!!!!!!!!
That's a real compliment !!!!!!!

 

[always-smile :)]

wont d green clr b absent coz there's no light?

for 2 reasons the first is that the allel for green found is absent and the second is that its in the dark

 

[AAnsarii]

thanks but how do they affect other organisims around them

sm stay in d food chain, they accumulate, increasing by evry step..
crops r saved when pests intending 2 eat them r killed, maybe dat should help
sorry im not of much aid

 

[AAnsarii]

when there's no cell membrane, no osmosis occurs?

 

[Rahma Abdelrahman]

when there's no cell membrane, no osmosis occurs?

Yes, because osmosis only occurs through a partially permeable membrane. ( Recall the definition! )

 

[AAnsarii]

plz xplain air pressure during breathing...txt bk is

 

[Rahma Abdelrahman]

plz xplain air pressure during breathing...txt bk is

During breathing IN, external intercostal muscles contract, internal intercostal muscles relax, diaphragm contracts moving downwards, the rib cage moves up and out pulling the lungs and thus increasing their volume. And as in Physics, pressure is inversely proportional to volume so an increase in volume decreases pressure, this forces air INTO the lungs from high to low pressure to even out the pressure difference. During breathing out the reverse happens!
Hope this helps !