A2 Biology | Post your doubts here

[hassam]

well definition of excretion says removal of waste poducts of metabolism that are toxic (e.g urea) or in excess.....cn u name a product which is excess.....i guess water ll be one.....is co2 also an excess product?

 

[angelgirl:)]

Errors in the MarkScheme??!​

43/O/N/11 Q11 b​

Chiasma formation in metaphase I? Isn't it supposed to be late prophase I?​

41/O/N/10 Q9 a​

Males homogametic? Aren't they supposed to be heterogametic?​

and finally... 43/M/J/10 Q7 c​

Anaerobic respiration in yeast involves ethanal dehydrogenase? Isn't it supposed to be alcohol dehydrogenase?​

So, is it me or they are really making MISTAKES???​

exactly even i was confused with the ethanal dehydrogenase 1...it is suppose to be alcohol dehydrogenase...
Chiasma formation takes place in late prophase I not in metaphase I...

 

[angelgirl:)]

well definition of excretion says removal of waste poducts of metabolism that are toxic (e.g urea) or in excess.....cn u name a product which is excess.....i guess water ll be one.....is co2 also an excess product?

yes it might be...

 

[angelgirl:)]

chek revison guide....its a hundred pages.......http://studyguide.pk/?p=431

y cant i download the notes for bio?

 

[Paradoxical]

Could someone please explain allopatric speciation? And polyploidy in wheat? They both really confuse me! :/

 

[hassam]

Explain the source and importance of removing nitrogenous waste products
from the body.
deamination;
ref. to ornithine cycle ;
ref. to not all urea / produced each day / always some present ;
ref. to urea ;
ref. to creatinine and uric acid ;
and ammonium ions ;
produced in liver ;
continuously / from excess amino acids ;
toxic ;
if allowed to accumulate ;
ref. to potential damage to tissues ;
ref. to not all urea / that produced each day ;
cn someone explain me abt how uric acid cratinine and ammonium ions are excreted ....

 

[ousamah112]

hows prep for bio guys...????

 

[hassam]

hows prep for bio guys...????

normal

 

[smartangel]

chek revison guide....its a hundred pages.......http://studyguide.pk/?p=431

i cant download it..if i click the download option it opens up some warning. help plz?

 

[angelgirl:)]

Could someone please explain allopatric speciation? And polyploidy in wheat? They both really confuse me! :/

allopatric speciation is the geographic speciation of organism where they r totally separated from eachother due to some physical barrier formation b/w the population...so the two population formed r now totally different from eachother and can not interbreed ...
polypoloidy....im not explaining the whole process but its like wen the whole set of chromosomes move to 1 side of the cell during meioses...so 1 daughter cell die due to luck of chromosome but the otherdaughter cell gets the full set of chromosome forming poluypliody... hope this explaination helps u...

 

[Paradoxical]

allopatric speciation is the geographic speciation of organism where they r totally separated from eachother due to some physical barrier formation b/w the population...so the two population formed r now totally different from eachother and can not interbreed ...
polypoloidy....im not explaining the whole process but its like wen the whole set of chromosomes move to 1 side of the cell during meioses...so 1 daughter cell die due to luck of chromosome but the otherdaughter cell gets the full set of chromosome forming poluypliody... hope this explaination helps u...

Oops, I was meant to say sympatric speciation. Thanks for the polyploidy explanation! ^_^

 

[ousamah112]

Oops, I was meant to say sympatric speciation. Thanks for the polyploidy explanation! ^_^

polyploidy is sympatric speciation. In which number of sets of chromosomes is odd and thus that specie can not make gametes and is infertile. so,it is sexually isolated

 

[angelgirl:)]

Oops, I was meant to say sympatric speciation. Thanks for the polyploidy explanation! ^_^

so in sympatric speciation new species may arise due to polyploidy....

 

[omair tahir]

How the action potential is transmitted along a sensory neurone?
I cant properly set my answer according to the marking scheme can somebody help me wid te steps taking place?

 

[user]

Assalamoalaikum wr wb!!!!
angelgirl:)
A biosensor has a layer of immobilized enzyme which catalyses the conversion of glucose to gluconic acid as shown above. A platinum electrode in the biosensor will measure the drop in oxygen concentration, as it is used to make hydrogen peroxide, and generates an electric signal. The size of the electrical signal is proportional to the concentration of glucose in the blood. A digital readout gives the user a digital figure for the glucose concentration. Hence a low reading will give a warning of low blood glucose concentration.
^pretty much the same as the one in the application booklet I guess..

 

[hassam]

polyploidy is sympatric speciation. In which number of sets of chromosomes is odd and thus that specie can not make gametes and is infertile. so,it is sexually isolated

well its not necessary that number of chromosomes is ODD.....and the polyploid organism may well be fertile......bt due to a different chromosome number compared to originl one....it cnt produce a fertile offspring

 

[angelgirl:)]

polyploidy is sympatric speciation. In which number of sets of chromosomes is odd and thus that specie can not make gametes and is infertile. so,it is sexually isolated​

well its not necessary that number of chromosomes is ODD.....and the polyploid organism may well be fertile......bt due to a different chromosome number compared to originl one....it cnt produce a fertile offspring
hmmm i guess u both r right..coz different books explains it in diff..ways...

 

[smartangel]

in the loop of henle..Na and Cl ions diffuse out of the ascending limb into the space between the two limbs. water moves via osmosis frm descending limb into the tissue fluid. Na and Cl ions due to their higher conc move into the descending limb. so how is the tissue fluid more concentrated as we move down towards the bottom of the loop? please clarify...

 

[shyqueen]

explain y genes fo antibiotic resistance r now rarely used as markers in gene technology?

1 risk spread of resistance to other bacteria ;
2 spread of resistance makes the use of antibiotics less effective / AW ;
3 via, conjugation / transformation / uptake of plasmids ; A description
4 via, ‘phage / transduction ; A description
5 ref. R plasmid multiple resistance (MDR) / extreme resistance (XDR)

i dont understand point no 3 , 4 and 5 can anybody explain dis?

 

[ousamah112]

well its not necessary that number of chromosomes is ODD.....and the polyploid organism may well be fertile......bt due to a different chromosome number compared to originl one....it cnt produce a fertile offspring

if one specie has odd numbers of chromosomes it can only be fertile if by chance all the chromosomes go into one cell while meiosis,and other cell remains empty. and yes there is probability of even chromosomes too in polyploidy