biology paper 1 doubts

[athaan]

i

I don't get how to do this.
Please help.
Thanks..

it has been stated from the question, that the net productivity of the producer is 1.8%.
but the actual energy the herbivore [primary consumer] receive is only 0.75%.
therefore, the proportion is 0.75/1.8, the ratio of energy received to energy sent.

 

[athaan]

Nov 09. ques 13
Please explain why the answer is A and not C?
thanks..

can you specify the variant? :0

 

[Irfan1995]

Nov 09. ques 13
Please explain why the answer is A and not C?
thanks..

Every single order of protein structure affects the shape of a protein (including the active site of an enzyme).

Take it this way: with sickle cell anemia, one of the polar amino acids is replaced by a non-polar one. This changed the primary structure. Since the new amino acid is non polar, it can't make any hydrogen bonds, so the secondary structure is ruined. Also, since the new amino acid is non polar, it has to face the centre of the molecule, not outside, so the polypeptide has to refold to do that - tertiary structure ruined. Now the entire beta polypeptide chain cannot interact with the other three in the same way anymore - quaternary structure changed.

 

[xtremeforums]

can you specify the variant? :0

Variant 1....

 

[♥Яαηõõşḧ♥]

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Each of the following events takes place during mitosis.​

1 centromeres divide
2 chromatids move to opposite poles of the cell
3 chromosomes line up along the equator of the spindle
4 chromosomes uncoil
5 two chromatids are joined by a centromere
In which order do the events take place?
first to last

A

1 2 4 5 3​

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B 3 1 2 4 5​

C 4 5 3 1 2

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D
5 3 1 2 4

can someone please help me,,, why is the answer D not C ???​

 

[xtremeforums]

Every single order of protein structure affects the shape of a protein (including the active site of an enzyme).

Take it this way: with sickle cell anemia, one of the polar amino acids is replaced by a non-polar one. This changed the primary structure. Since the new amino acid is non polar, it can't make any hydrogen bonds, so the secondary structure is ruined. Also, since the new amino acid is non polar, it has to face the centre of the molecule, not outside, so the polypeptide has to refold to do that - tertiary structure ruined. Now the entire beta polypeptide chain cannot interact with the other three in the same way anymore - quaternary structure changed.

Thankyou so much! Great explanation!

 

[♥Яαηõõşḧ♥]

​

​

​

​

Each of the following events takes place during mitosis.​

1 centromeres divide
2 chromatids move to opposite poles of the cell
3 chromosomes line up along the equator of the spindle
4 chromosomes uncoil
5 two chromatids are joined by a centromere
In which order do the events take place?
first to last

A

1 2 4 5 3​

​

B 3 1 2 4 5​

C 4 5 3 1 2

​

​

​

​

D
5 3 1 2 4

can someone please help me,,, why is the answer D not C ???​

sorry i can type it again if its confusing

 

[InnocentAngel]

To find the greatest change in % saturation of Hb, move 1 small square to the right along the x-axis, and see the corresponding change on y-axis. This change is greatest where the graph is steepest, in the B region.

Mercii

 

[Z.S.M]

sorry i can type it again if its confusing

which year is it?

 

[Irfan1995]

sorry i can type it again if its confusing

During prophase, the chromosomes coil and condense, and they don't uncoil until the end of telophase.
In prophase, the two chromatids are still held together by a centromere (5). After that, metaphase pulls all the chromosomes to the metaphase plate (imaginary line drawn through the perpendicular bisector of the centrioles) (3). In the beginning of anaphase, the spindle fibres break the centromere (1) and pull each chromatid to the opposite pole of the cell (2). As mentioned near the end, the chromosomes uncoil after telophase (4) which is followed by cytokinesis.

 

[♥Яαηõõşḧ♥]

june 2012 variant 2 question 17

 

[♥Яαηõõşḧ♥]

During prophase, the chromosomes coil and condense, and they don't uncoil until the end of telophase.
In prophase, the two chromatids are still held together by a centromere (5). After that, metaphase pulls all the chromosomes to the metaphase plate (imaginary line drawn through the perpendicular bisector of the centrioles) (3). In the beginning of anaphase, the spindle fibres break the centromere (1) and pull each chromatid to the opposite pole of the cell (2). As mentioned near the end, the chromosomes uncoil after telophase (4) which is followed by cytokinesis.

thank u sooooo much !!! i finally get it =)

 

[InnocentAngel]

Please help :

 

[xtremeforums]

Can somebody please post may june 2012 papers?
thanks!

 

[Taci12]

I don't get how to do this.
Please help.
Thanks..

Walaikum salaam! The question asks for the proportion of net productivity passing on from the producers to the primary consumers.
Hence you can ignore the 4.0% from the producer as it represents the gross productivity. Likewise, the 2.3 % is irrelevant .The value of the net productivity passing from producers to primary consumers is 0.75%.
Moreover, 1.8% is the total energy passing from the producers. So the proportion is 0.75/1.8.
You can think of the net productivity as the effective or net energy transfer and the gross productivity as the total amount of energy passing from one trophic level to the next.
Hope I helped!

 

[xtremeforums]

Please help :View attachment 18196

because the habitat of the tree is not mentioned. The tree "provides" a habitat for other organisms, yet again, another role of the tree, i.e. its niche.

 

[Irfan1995]

Please help :View attachment 18196

Yes, you're right. A habitat is where an organism lives. But if the tree carries out phtotosynthesis and absorbs water etc..., then it is more than "just a habitat". They're describing for you the role of the tree in the ecosystem which is its niche. ONE of its roles may be that it is a habitat, but that's not all. Makes sense?

 

[Taci12]

Can somebody please post may june 2012 papers?
thanks!

http://olevel.sourceforge.net/papers/9700/
Voila!

 

[athaan]

Please help :View attachment 18196

The paragraph talks more about the tree itself rather than its surrounding, and the roles of the tree. Therefore it's the niche.

Can somebody please post may june 2012 papers?
thanks!

olevel.sourceforge.net

 

[Twinks05]

http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_w10_qp_12.pdf

Does anyone know why the answer to question number 9 is D??