How was Biology Paper 42

[Amaryllis]

Everything is pre-written ,but with prayers it can be re-written

you are right all what we have to do now is to pray to allah and im sure we'll get what we want and deserve inshallah hope we all get A* and As

 

[pansyflower]

What did you guys write for 8 iii).....the one where the lake got filled up again and all the four different species of desert pupfish were in one lake again

itz abt sympatric speciation

 

[magnesium]

you are right all what we have to do now is to pray to allah and im sure we'll get what we want and deserve inshallah hope we all get A* and As

*ALLAH

 

[ijjukittu]

what we had to write for that Na/K-pump?

 

[mhalvi]

Aoa another repeated question was nov 2003 qs. 4

 

[Ykzimri]

For Q1 (ii)
I wrote that since it was an aquatic plant and after 30 degrees the O2 releases decreases. It means that CO2 is a limiting factor. Meaning the concentration of CO2 decreased in the water after a period of active photosynthesis. As there was less CO2 less photosynthesis and O2 level decreased.
I wrote about transpiration first and then i realised that since it was an aquatic plant there won't be any transpiration

 

[code11]

12

Exactly I did the same.

yar the question told us that 125 has been filtered of the plasma (700) ...so wats the percentage of plasma into the capsule
125/700 * 100
answer is 17.9 %

 

[Rajvinder]

For Question 10: (Section B)

(a) structure of a chloroplast (7)
- biconvex disc
- 3-10 um diameter
- double, membrane/envelope
- internal membrane system
- flattened or fluid-filled sacs/thylakoids
- arranged in stacks/grana
- hold pigments/named pigment
- clusters of pigments
- (membrane of grana) hold ATP synthase
- intergranal lamellae
- stroma/ground substance
- lipids/strarch grains
- contains enzymes of Calvin Cycle/rubisco
- stroma contains ribosomes/DNA
any other valid point such as presence of mRNA, tRNA, proteins, 70S ribosomes, brief detail of photosystems, electron carriers.
You had to mention any seven of the above points, but had to include references to shape, size and contents (internal membrane system + stroma)

(b) adaptation of rice (8)
- low oxygen (availability) in water (when soil is flooded)
- results in anaerobic respiration
- anaerobic respiration produces alcohol
- rice tolerant to alcohol
- because rice has high levels of alcohol dehydrogenase/enzyme that breaks down alcohol
- presence of aerenchyma/air spaces
- in mesophyll/cortex
- formed by cell death
- provides oxygen
- for aerobic respiration/because conditions are anaerobic
- allows escape of ethene/buoyancy/active transport
- stem elongation
- leaves above the surface of water/in contact with air

The syllabus states: candidates should be able to explain how rice is adapted to grow with roots submerged in water in terms of tolerance to ethanol and presence of aerenchyma. Hence, these two points were to be mentioned along with their relevant detail.

for the rice plant we can also describe its adaptations to reduce transpiration due to humid and hot temperatures right ?

 

[rizwaan]

It was the most easiest paper uptill now i think ....Ma paper was aweesome !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

we don't say most easiest but simply easiest.

 

[Analiegh]

for the rice plant we can also describe its adaptations to reduce transpiration due to humid and hot temperatures right ?

No, thats for Sorghum. Completely different.

 

[Rajvinder]

No, thats for Sorghum. Completely different.

I know but can't we use that as leaf adaptations since rice is grown in hot humid countries?

 

[Rajvinder]

and guys if i get 61 for AS total and 65 for P42 and 25 for P52 , what would my grade be ? according to expected GT of this years papers

 

[Analiegh]

I know but can't we use that as leaf adaptations since rice is grown in hot humid countries?

I've never seen marks given to describe rice like sorghum. Specifically what did you write? If you said something like thick cuticle, high sillica content (to reduce silting), leaves coil, etc, then no. This is basically marks given for sorghum and not rice.

 

[Rajvinder]

Heres some answers:

pupfish seperated -> allopatric speciation

when rejoined -> directional selection, survival of the fittest

plasma percentage -> 125/700 x 100

why calcium2+ comes in -> because voltage gated channels open upon depolarization

what does turtles ion channels closing do -> prevents depolarization by keeping ion conc. constant

i said when pupfish rejoined , there is gene flow , over time must adapt to new selection pressures , eventually become phenotypically / genotypically similar. ISit correct? pretty much a reverse answer for the earlier part about when they're seperated.

 

[Rajvinder]

I've never seen marks given to describe rice like sorghum. Specifically what did you write? If you said something like thick cuticle, high sillica content (to reduce silting), leaves coil, etc, then no. This is basically marks given for sorghum and not rice.

owh crap. yea i gave thick cuticle , sunken stomata. But i also said that they have air sacs to supple oxygen , ethanol dehydrogenase to increase tolerance to ethanol produced. And i tried to elaborate on them abit but wasnt sure if it's enough for 8 marks soo i included the cuticle ,stomata points.

 

[Analiegh]

owh crap. yea i gave thick cuticle , sunken stomata. But i also said that they have air sacs to supple oxygen , ethanol dehydrogenase to increase tolerance to ethanol produced. And i tried to elaborate on them abit but wasnt sure if it's enough for 8 marks soo i included the cuticle ,stomata points.

I don't remember what I wrote exactly, but yes those other points are right. When there is no oxygen rice undergoes anerobic respiration which produced ethanol. And rice is ehtnala resistant because there is an abundance of alcohol dehydrogenase. There is an aerenchyma for gas diffusion. Rice elongates when water levels rises due to production of gibberellins i think. Shallow root system for short diffusion of gasses or somehting like that

 

[Rajvinder]

I don't remember what I wrote exactly, but yes those other points are right. When there is no oxygen rice undergoes anerobic respiration which produced ethanol. And rice is ehtnala resistant because there is an abundance of alcohol dehydrogenase. There is an aerenchyma for gas diffusion. Rice elongates when water levels rises due to production of gibberellins i think. Shallow root system for short diffusion of gasses or somehting like that

hmmm with those points i gave you , How many marks you think i could get with what i told you ? Atleast 5 if my elaborations were alright ?

 

[Analiegh]

hmmm with those points i gave you , How many marks you think i could get with what i told you ? Atleast 5 if my elaborations were alright ?

Well to be honest, I only see 2 marks with this. One mark for alcohol/ethanal dehydrogenase and ethanal/alcohol resistance. Possibly maybe one for air sacs.