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Biology BY2 unofficial mark scheme 1st June 2015

{These are the answers that I remember}

Family, (the genus listed), (the species listed)

Closely related where top two (stating genus in brackets and species FULL NAME)

Mechanical digestion= mouth and stomach
Lipase production= pancreas
Protein digestion= stomach
End of carbohydrate digestion= duodenum

Arrow to where tapeworm found= small intestine

Why tapeworm found here?= small intestine is sight of food absorption and thus where most nutrients found, so tapeworm absorb nutrients across body surface

Bile salts emulsify lipids making tiny droplets which increase surface area for lipase action in digestion

Alveoli in microscope= many alveoli have large surface area relative to the body and are thin and permeable allowing oxygen to diffuse as short diffusion path. Alveoli also covered by extensive network of capillaries which cause oxygen from alveolus to diffuse to blood and carbon dioxide vice versa.

Mammal ventilation expiration= external intercostal muscles relax, diaphragm relax, thorax move inward and downward, volume of thorax decreases and pressure in thorax increases as air moves out of lungs

Mammal need ventilation= mammal have a small surface area to volume ratio due to their size and specialised organs causing long diffusion path and ventilation being required for gas exchange

Root hair=thin and large surface area with a lower potential allowing osmosis to occur

Plant tissue for carbon isotope= Phloem tissue (because of translocation in phloem)

Carbohydrate found= sucrose

Radio isotope labelling film= translocation of sucrose and amino acids from leaves to growing parts of plants (not certain of this)

Annelid proof of translocation= (no clue so just guessed) A and B both one hour and translocation to growing parts

Calculation= add 1+2.5=3.5hrs 3.5*60=210minutes 210/cm=cm per minute (think it was the other way around)

Apoplast and symplast= apoplast is cell wall to cell wall and symplast is cytoplasm to cytoplasm or plasmadesmata

How does endodermis build up root pressure in xylem= endodermis cells consist of a waterproof substance called Suberin to form casparian strip which blocks apoplast pathway, allows symplast pathway and causes mineral ions to be actively transported into xylem and water to be transported to xylem via osmosis creating water potential gradient which builds up root pressure causing water to move upwards

Sino atrial node function= transmits electrical impulses across atria causing them to contract simultaneously and impulse is sent down to AVN

Purkinje fibres function= carry electrical impulse sent from AVN and to bundle of his, and send these to base of ventricles which contract base upwards

Pressure seconds on graph = 0.6s and 0.3s (guessed)

Letters on graph= B, D, A (guessed)

Why blood doesn't flow from left ventricle back to left atrium= because of the bicuspid valves which prevent the back flow of blood back to the left atrium by closing the valves

Ten marker=
haemoglobin=
-haemoglobin is pigment found in red blood cells
-haemoglobin structure quaternary consists of 4 polypeptide chains of two alpha and two beta
-haemoglobin in mammal carried in blood vessel where closed circulatory system
-in mammal, haemoglobin loaded with oxygen in lungs where partial pressure is high and unloads oxygen in muscle tissue where partial pressure is low
-partial pressure and oxygen saturation represented in oxygen dissociation curve (drawn) which has sigmoidal shape
-llama and lug worm in environments with low oxygen concentrations, llama has more red blood cells to compensate for this and lugworm pumps water from bellow to get dissolved oxygen, both have low affinity of oxygen
-when exercise partial pressure decreases considerably, myoglobin required
-carbon dioxide combines with haemoglobin to form carbamino haemoglobin
(edited 8 years ago)

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Parasites do not use their suckers to obtain nutrition, they use it to hold onto the gut (along with hooks). They diffuse the pre-absorbed food through their bodies.

Purkinje fibres only pick up the impulse at the apex, at the bottom of the bundle of His.

Evidence for bi-directional flow was that radioactive carbon was found both above and below the leaf that was provided with radioactive carbon dioxide.

Just a few minor points I could think of :smile:
Reply 2
Avatar for SalmanOrange
SalmanOrange
OP
Original post by Sophie_Lester
Parasites do not use their suckers to obtain nutrition, they use it to hold onto the gut (along with hooks). They diffuse the pre-absorbed food through their bodies.

Purkinje fibres only pick up the impulse at the apex, at the bottom of the bundle of His.

Evidence for bi-directional flow was that radioactive carbon was found both above and below the leaf that was provided with radioactive carbon dioxide.

Just a few minor points I could think of :smile:

Yeah I meant absorb, sorry typo. Also, the Purkinje fibres do carry the impulses, search the function on Google
(edited 8 years ago)
how many marks were there when talking about mammals needed a complex ventilation.mechanism ? and did you have to mention sa to volume ratio ?
Reply 4
Avatar for SalmanOrange
SalmanOrange
OP
Original post by sophialouise
how many marks were there when talking about mammals needed a complex ventilation.mechanism ? and did you have to mention sa to volume ratio ?


I think it was 2 or 3 marks, and I guess you would to explain why they would need a complex ventilation. Don't sweat it only one mark hopefully grade boundaries are low
Original post by SalmanOrange
Yeah I meant absorb, sorry typo. Also, the Purkinje fibres do carry the impulses, search the function on Google


They do carry impulses, but not from the AVN, it is picked up from the bundle of His :smile:
Original post by SalmanOrange
I think it was 2 or 3 marks, and I guess you would to explain why they would need a complex ventilation. Don't sweat it only one mark hopefully grade boundaries are low


i put large sa to.volum ratio by accident but then i explained everything.else correctly. hopefully ill only loose 1 mark on that . im hoping the boundaries are around 52 for an A.
Reply 7
Avatar for Z1228
Z1228
2
Was the graph one not 0.2 and then 0.6 and also the phases were A C E?
Reply 8
Avatar for Z1228
Z1228
2
Original post by SalmanOrange
I think it was 2 or 3 marks, and I guess you would to explain why they would need a complex ventilation. Don't sweat it only one mark hopefully grade boundaries are low

Ventilation was 4 and explanation was 2, and Yh usually you do
Original post by sophialouise
how many marks were there when talking about mammals needed a complex ventilation.mechanism ? and did you have to mention sa to volume ratio ?


Think it was two marks :smile:
Original post by Z1228
Was the graph one not 0.2 and then 0.6 and also the phases were A C E?


Yep, I got this too!
Can anyone remember what the question said where we had to name something about photosynthesis site and sucrose?
Original post by Sophie_Lester
They do carry impulses, but not from the AVN, it is picked up from the bundle of His :smile:


Really? Great!! I put that in the exam subconsciously and forgot to go back to put 'from AVN' :biggrin:
Original post by sophialouise
i put large sa to.volum ratio by accident but then i explained everything.else correctly. hopefully ill only loose 1 mark on that . im hoping the boundaries are around 52 for an A.


I hope it's that or even better 50 seeing as last year was 47, really needed this mark to boost some of the silly mistakes I made in by1
Reply 14
Avatar for Z1228
Z1228
2
Original post by Eleanor303
Can anyone remember what the question said where we had to name something about photosynthesis site and sucrose?


Name the tissue which they inject with radioactive carbon and the name of the carbohydrate they transport
Im sure the rate was 0.422222222? Please someone?
Reply 16
Avatar for hprynne
hprynne
2
Original post by jarvisg18
Im sure the rate was 0.422222222? Please someone?

Agreed! Moved up 38 cm in one and a half hours, convert to minutes is 90. Then 38/90! Most people I spoke to also got 0.422222....
Original post by hprynne
Agreed! Moved up 38 cm in one and a half hours, convert to minutes is 90. Then 38/90! Most people I spoke to also got 0.422222....

Awesome! A lot of people I spoke to left it in hours, and some multiplied. At least someone agrees!
(edited 8 years ago)
Reply 18
Avatar for Z1228
Z1228
2
Original post by hprynne
Agreed! Moved up 38 cm in one and a half hours, convert to minutes is 90. Then 38/90! Most people I spoke to also got 0.422222....


Yep 0.42 is correct
I did 90/38 😒😪

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