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8/8/2019 Mark scheme P2 (structure)
1/5
2
BIOLOGY
SECTION A
PAPER 2 [4551/2]
No. Marking Criteria / Sample Answers Marks
1 (a) (i) Gills 1
(ii) Tracheal system 1
(b) P : Filaments
Q: Spiracles
1
1 2
(c) (R is ring of chitin which) support the tracheal / prevent the tracheal
from collapsing.
1
(d) Diagram 1.1(b):
P1: The filament have numerous thin-walled lamellae to maximise
the surface area for gaseous exchange.
P2: The gill filaments have thin membrane and covered by a net
work of capillaries to transport respiratory gases.
P3: The surface of the gills is moist which allows the gases to be
dissolved.
Any 1P 1
Diagram 1.2(b)
P1: The large number of tracheoles provides a large surface for the
diffusion of gases.P2: Tip of tracheoles have thin permeable walls and contain fluid in
which respiratory gases can dissolve.
P3:Terminal ends of the tracheol remains moist which allows the
gases to be dissolved.
Any 1P
1
(e) (i) P1:( The gaseous exchange process occurs over the whole body
surface in an Amoeba sp) through simple diffusion.
P2:Higher concentration of oxygen in the water surrounding causes
oxygen to diffuse into the Amoeba.
P3:Higher concentration of carbon dioxide in the cell causes carbondioxide to diffuse out of the Amoeba.
Any 2P
1
1
1
2
(ii) S: Contractile vacuole 1
(iii) P1: Freshwater is hypotonic to the cytoplasmic fluid of Amoeba sp .
P2: Water diffuses into the cell and fill the contractile vacuole by
osmosis
P3: When the contractile vacuole is filled with water to its maximum
size, it contracts to expel its content from time to time.
Any 2P
1
1
1
2
8/8/2019 Mark scheme P2 (structure)
2/5
3
No. Marking criteria/ Sample answers Mark
2 (a) (i) Osmosis 1
(ii) P1 : Sucrose solution is hypertonic / more concentrated.
P2 : Water diffuse from distilled water into the sucrose solutionP3 : The level of sucrose solution in the capillary tube stop rising
at the equilibrium stage / the concentration inside and outside
of the visking tubing is the same / the amount of water
diffuse into and out from the visking tubing is the same.
Any 2 Ps
1
11 2
(b) F- Sucrose molecules are too large
E- The visking tubing is a semi permeable membrane/
which only allows certain substances to pass through.
1
1 2
(c) (i) Y : crenation
Z : haemolysis
1
1 2
(ii) P1- Solution Z is hypotonic compare to red blood cell.
P2- Osmosis occur
P3- water leaves/ diffuses into the cell
P4- Red blood cell expand/ swell and burst.
Any 3P
1
1
1
1
3
(iii) F : No
P1 : Plant cell consists of cell wallP2 : Cell wall is made up of cellulose
// Cell wall able to withstand the pressure.
Any 2
1
11 2
Total 12
8/8/2019 Mark scheme P2 (structure)
3/5
4
No. Marking criteria/ Sample answers Mark
3 (a) (i) Absorption / Simple diffusion / facilitated diffusion 1
(ii) F1 thin wall/ one cell thick
E1 increase rate of diffusion of digested food/ nutrients
F2 large surface area/ has microvilli
E2 increase rate of absorption of digested food/ nutrient
F3 has a network of capillaries/ blood vessels
E3 to transport the absorbed nutrients
Any F + E
1
1
1
1
1
1
2
(b) P: hepatic portal vein
Q: lymphatic/lymph vessel/ duct
1
1 2
(c) P1: Deamination.// The amino group is removed (from amino acid)/
converted to ammonia .
P2: (Ammonia) is converted to urea.
P3: urea will be excreted through the kidneys.
Any 2 Ps
1
1
1 2
(d) L1: A major energy reserve in the body//
L2: (phospholipids are) components of the plasma membrane//
L3: Lipids is used as a respiratory substrate//
L4: Excess fats are stored in adipose tissues (under the skin, aroundinternal organs)
Any 1L
A1:Amino acids are used in protein synthesis//
A2:For repair and production of new protoplasm/growth and repair//
A3:Used in the formation of enzymes/ some hormones/protein part of
haemoglobin/ antibodies
Any 1A
G1:Glucose is used as the main respiratory substrate// It is oxidised to
release energy (water and carbon dioxide)//
G2:Excessive glucose is converted to glycogen// Blood glucose level rise / increase.
Any 1 G
1
1
1
1
1
1
1
1
1
3
(e) P1: Diabetes mellitus // Blood sugar level increases// Hyperglycemia
P2: Excess glucose cannot be converted to glycogen.
1
1 2
Total 12
8/8/2019 Mark scheme P2 (structure)
4/5
5
No. Marking criteria/ Sample answers Mark
4 (a)
Both arrows correct 1
(b) A Pulmonary artery
B Pulmonary vein
1
1 2
(c) F : Contraction of ventricle / heartE1: generates a (high) pressure
E2 : (to) propel/ force / pump the blood flow from the heart/ ventricle to
vessel A
Any two
11
1 2
(d)(i) Coronary artery 1 1
(ii) P1: Cut the supply of O2/ nutrients to the heart muscle
P2: causing chest pain / angina / heart attack / myocardial infarctionReject Heart problem
1
1 2
(e) (i)
(ii)
P1: platelets break down and release chemicals
P2: to cause platelets to stick to each other
P3: platelets clump together to form a plug to prevent blood loss .
P4: released thrombokinase and other clotting factors
Any 2P
P1 : Fibrinogen is soluble, fibrin is insoluble / not soluble
P2 : Fibrin able to form fibres / meshwork / thread to trap
blood cells, fibrinogen is not able to do so.
1
1
1
1
1
1
2
2
Total 12
8/8/2019 Mark scheme P2 (structure)
5/5
6
No. Marking Criteria / Sample Answers Marks
5 (a) (i) (Transfer/flow of) energy 1
(a) (ii) F : Phytoplankton is an autotrophic organism.P1 : Able to absorb light energy / consists of chloroplast.
P2 : synthesis their own food / carry out photosynthesis
Any 2
11
1 2
(b) F1 : population of small fish increases
P1 : no shark feed on small fish // shark is the predator
F2 : population of plankton decreases
P2 : more small fish feed on the plankton
F3 : Eventually the population of small fish decreases
Any 3
1
1
1
1
1 3
(c) F : Commensalism
P1 : Shark is the host / neither gain any benefit nor harmed.
P2 : Remora benefits
P3 : Remora obtain protection / food / transport from the shark.
Any 3
1
1
1
1 3
(d) P1 : Fertilizer washed away by rain water into the lake
P2 : Nutrient / minerals content in the lake increase.
P3 : alga bloom / alga grow rapidly in the lake.
P4 : eutrophication occur.P5 : Oxygen content in the lake decrease / drop
P6 : Fishes die / population decrease
Any 3 P
1
1
1
11
1 3
Total 12