A level Biology: Post your doubts here!

[thats_me]

Q38)
Since the sun is more intense during the summer than the winter, this must be
curve B. During the winter most plant and animal life will be very limited as many have died and therefore
the nutrients are more in winter than summer, curve A. This leaves curves C and D. Since primary
consumers feed on producers, there should be more producers than consumers, hence curve C is correct.

Q40 )
Statement A is valid since in ecosystem Y the dominant
producer is large and woody, so would not be easily consumed. Statement B is valid since there is a smaller
fluctuation of temperature in marine aquatic ecosystems and also there is less oxygen. Statement C is also
valid, since with lower energy losses between trophic levels the ecosystem X can support more trophic
levels. Therefore the answer is statement D.

Got it! Thankyouu!
Could you check q 39 http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s13_qp_13.pdf
Isn't this the same question, or am I missing something:/
Why is the ans D here & not B?

 

[ZaqZainab]

Thanks a lot
In Q20.....I believe that 2 is not correct as complementary base pairing doesn't occur in TRANSLATION ! that is way my answer was only 1,3and 4
soo ? how they say its correct ?

i am sorry to say this but complementary base pairing does occur in TRANSLATION
'where mRNA codons are matched through complementary base pairing to specific tRNA anticodons.'
check out wikepidea http://en.wikipedia.org/wiki/Translation_(biology)

 

[ZaqZainab]

Got it! Thankyouu!
Could you check q 39 http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s13_qp_13.pdf
Isn't this the same question, or am I missing something:/
Why is the ans D here & not B?

statement 4 is suppose to be correct there is more tropical levels in X
the energy loss is more but energy is suppose to reach the last consumer
so if only the producer makes more energy the last consumer will get enough energy

 

[Mohammed salik]

Thank you soooooo much

You Are Welcome !!

 

[thats_me]

statement 4 is suppose to be correct there is more tropical levels in X
the energy loss is more but energy is suppose to reach the last consumer
so if only the producer makes more energy the last consumer will get enough energy

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w13_qp_12.pdf q40
Sooo why is it an invalid suggestion here?

 

[ZaqZainab]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w13_qp_12.pdf q40
Sooo why is it an invalid suggestion here?

lol i should go and die
if i was answering them separately i would be like X has less O2 if more Photosynthesis takes place the O2 will increase

 

[Mohammed salik]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w13_qp_12.pdf q40
Sooo why is it an invalid suggestion here?

This Looks Really Messed Up... its Exact same Question!!!

 

[thats_me]

This Looks Really Messed Up... its Exact same Question!!!

Yess:/

lol i should go and die
if i was answering them separately i would be like X has less O2 if more Photosynthesis takes place the O2 will increase

I still don't get it:/ why are the answers different again?

 

[Mohammed salik]

Yess:/

I still don't get it:/ why are the answers different again?

I will try..
Only According to this Question 39.. =D
There are more Trophic Levels meaning more Energy is there To reach those Tropic levels . More energy means Faster rate of Photosynthesis.!

 

[ZaqZainab]

I think there is something wrong with the MS i have seen some mistakes before too

 

[Mohammed salik]

I think there is something wrong with the MS i have seen some mistakes before too

Probabaly...!

 

[joanna omar]

The need of transport system in Plants ? (5 marks )

 

[thats_me]

The need of transport system in Plants ? (5 marks )

Unicellular organisms have a large surface area to volume ratio which is efficient enough for a specific transport system
In lager more complex organisms cells maybe to widely separated from each other & from their external environment
So specialised long distance transport system which can move substances more rapidly become necessary
(Materials are generally moved by a mass flow system which is as a result of pressure difference between 2 points
Animals are able to move materials by the contraction of muscles but plants rely only on mechanisms such as evaporation,active transport & osmosis)

 

[MÁťT PŭמҚ]

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w13_qp_53.pdf
o/n 2013 paper 5 3 question 2 (a) iii
how to calculate the rate? :/

 

[VelaneDeBeaute]

You're sayying exactly the opposite thing bro :/ In the book its written clearly that facilitated diffusion takes place across channel proteins and active transport thru carrier proteins.:/

Channel proteins. ION CHANNELS. (What more does it require to make a connection?)
Also, per se I checked the book. There's no lingo there labeling channel proteins to exclusively facilitated diffusion. There is however only a statement that says active transport happens through carrier proteins but as I wrote already, active transport occurs through both types of proteins.
Here's more of an 'intellectual' answer for what you're asking.

I could go into discussion for this but exams are closing up so I'd say bring out some other important questions rather than wasting time with this debate which might carry a mark or two in the actual paper.

 

[VelaneDeBeaute]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w13_qp_53.pdf
o/n 2013 paper 5 3 question 2 (a) iii
how to calculate the rate? :/

Mean distance moved (as given in diagram) = 25 mm
Time = 30 minutes OR 0.5 hour
Rate = 25/0.5 = 50 mm/h

 

[kitkat <3 :P]

Channel proteins. ION CHANNELS. (What more does it require to make a connection?)
Also, per se I checked the book. There's no lingo there labeling channel proteins to exclusively facilitated diffusion. There is however only a statement that says active transport happens through carrier proteins but as I wrote already, active transport occurs through both types of proteins.
Here's more of an 'intellectual' answer for what you're asking.

I could go into discussion for this but exams are closing up so I'd say bring out some other important questions rather than wasting time with this debate which might carry a mark or two in the actual paper.

so it means that facililtated diffusion and active transport both take place in channel proteins and in carrier proteins only active transport takes place? sorry but i just want to have a clear concept if u dont mind answering

 

[VelaneDeBeaute]

kitkat <3 :P I don't mean to be rude or anything, but I posted it a few pages ago. Here it is again.

'Transport proteins' refer to the membranal proteins that help in the movement of substances across the membrane. They can be divided into two types:
1. Carrier proteins: The proteins that assist in facilitated diffusion or active transport processes, for moving substances like glucose etc.
2. Channel proteins: The proteins that provide a 'channel' for ions or other small molecules to be exchanged across a membrane. These are specific for specific substances. For instance, you may have heard of 'sodium channels' (allow movement of Na+ ions only) etc.

 

[kitkat <3 :P]

kitkat <3 :P I don't mean to be rude or anything, but I posted it a few pages ago. Here it is again.

thanks alot for quoting it i didnt see it or i think i forgot

 

[MÁťT PŭמҚ]

Mean distance moved (as given in diagram) = 25 mm
Time = 30 minutes OR 0.5 hour
Rate = 25/0.5 = 50 mm/h

Thnkx