A level Biology: Post your doubts here!

[memyself15]

outline the behaviour of chromosomes during meiosis?
RYT now i want to essentaily kill the examiner who is preparing ms :evil: ......wat nonsense is this.....which textbook of the world says that crossing over occurs during METAPHASE.........
reference o/n 2010 p42

doesn't crossing over occurs in prophase? :Search:

 

[M95Caire]

Re: biology: biological molecules question..please help :/

why there is only hydrogen bond in cellulose and there are no hydrogen bonds in glycogen and starch? :S:S:S

Who said so ? as far as I'm concerned both glycogen and starch have hydrogen bonds within their structure to hold them in a helical shape . Also cellulose have hydrogen bonds , cross links between parallel/neighbouring microfibrils.

 

[hemant1]

hey i need help in biology practicals...do u have any guess questions for variant 33???? plz post

 

[M95Caire]

Yeah i need to know too, if u are informed bout anyth please message me!

 

[smileaka2012]

me too any guesses about the biology practical variant paper 33??????????????????????????????????????????????????????????????

 

[sweetiepie]

Biology slides and notes
viewtopic.php?f=26&t=11206

Biology Serial Dilation
viewtopic.php?f=7&t=5229

 

[rz123]

http://www.xtremepapers.com/CIE/Interna ... _qp_11.pdf

plz anyone help me explain the right option for 3rd and 14th mcq in this ppr m/j 2010 p11 (3rd ans is C, 14th is A)

 

[anahita16]

3.
The large scale with divisions far apart is the stage micrometer and the small one below is the eyepiece graticule.
40 subdivisions of the eyepiece correspond to one stage micrometer division, i.i, 0.1mm.
1 subdivision would correspond to 0.1/40 = 0.0025 mm
Radius of field of view=50 subdivisions of eyepiece=0.0025*50=0.125mm=0.125*100μm=125μm
Area=πr^2=π × 125 × 125
Ans C

14. In a cold winter, the temperature of the water could have fallen to below 4°C. In summer, the water starts to warm from the liquid surface to below. Water on the surface warms up to 4°C first, becoming heavier than the 0°C water or so beneath it as water is heaviest at 4°C(max density). So the 4°C water falls and the 0°C water rises, bringing with it dissolved minerals. From this, the 3rd statement becomes true-water contains dissolved minerals, so water is a solvent. The other two statements have little relevance here.

That's as far as my understanding goes. Hope it helps u a bit!

 

[rz123]

^Thank you so much anahita16 , it helped in 3 but this is not 14th mcq answer!!!! 14th one is about graph of enzyme activity u wasted ur time n energy on wrong mcq.

 

[holychalice]

@rviboy - the 14 the question - the y axis is the time taken for the reaction to complete thus if the enzyme denature at 50C then it will take the maximum time or probably the reaction wont occur .. thus A is the answer as in D the reaction continue after 50C to 60C
hope its clear

 

[anahita16]

Ooops i answered number 11. Sorry!

 

[babycry]

Guys... I need help on question 22..2010 November..paper 11

Link is ..

http://www.xtremepapers.me/CIE/index.ph ... _qp_11.pdf

thanks is advance

 

[rz123]

^^^thanks holychalice!! clear!

 

[smileaka2012]

no seriously any guesses ??????????? Biology practical paper 33???????????? 8 Nov ???????????????????
BTW EID MUBARAK!!!!!!!!!!!!!!!!! :Yahoo!:

 

[anahita16]

Guys... I need help on question 22..2010 November..paper 11

Link is ..

http://www.xtremepapers.me/CIE/index.ph ... _qp_11.pdf

thanks is advance

Uracil will pair only with adenine. If uracil is present, thymine will be absent. In sample 3, we can see that if uracil is pst, C is abs, meaning C is thymine.
Thymine pairs with adenine. In samples 1, 2 and 4, we can see that thymine(C) pairs best with B. So adenine is B.

 

[rz123]

Ooops i answered number 11. Sorry!

No problem i got that 1! Thanks anyway!

 

[babycry]

Guys... I need help on question 22..2010 November..paper 11

Link is ..

http://www.xtremepapers.me/CIE/index.ph ... _qp_11.pdf

thanks is advance

Uracil will pair only with adenine. If uracil is present, thymine will be absent. In sample 3, we can see that if uracil is pst, C is abs, meaning C is thymine.
Thymine pairs with adenine. In samples 1, 2 and 4, we can see that thymine(C) pairs best with B. So adenine is B.

You're the besttt ..thanks a loooot..

 

[JmCullen]

URGENT!!!

I have this question about ecology.

Q: base on a food web, why is it hard to draw a biological pyramid?

 

[mrpaudel]

GUys, i didnot understand the line "Even widths ......." the under lined one.....

 

[mrpaudel]

and..this is the ms for that question..