1989 Biology Paper I Marking Scheme

CE BIO 1989 Alex Lam

1. (a) (i) with foot supplied from the corm )

buds develop into aerial shoots )

carry out photosynthesis ) any FOUR ------------------------------------1,1,1,1

storage of excess food in base of stems )

to form daughter corms )

(ii) food storage / pass over unfavorable periods (winter) / perennation ------------------------------1

(iii) No - the stamens / stigma are not hanging out )

- the stigma is not feathery ) any ONE----------------------------------1+1

(iv) A - dries up / withers / falls off ---------------------------------------------------------------------------1

B - forms fruit wall / fruit -----------------------------------------------------------------------------------1

(v) (1) get flowers / new plants more easily / rapidly------------------------------------------------------1

maintain the desired quality of the flowers --------------------------------------------------------1

(2) variation occurs / may give rise to flowers of a better quality ---------------------------------1

Total : 12 Marks

1. (a) (i) Most candidates wrongly stated that during vegetative propagation of a corm, food from the

aerial shoot is passed down to the lateral buds. In fact, excess food is passed down to the

base of the stem to form a daughter corm for storage until the next growing season.

(iv) Some candidates wrongly thought that ovaries will develop into seeds rather than fruit.

(v) Many candidates were unable to point out that sexual reproduction by seeds has the

advantage of variation over vegetative propagation. Quite a number mentioned "to prevent

overcrowding" as an advantage of using seeds to produce new plants for flowers. This is an

advantage from the viewpoint of plant dispersal, not from the viewpoint of gardeners

growing flowers. This is a clear indication of the inability of many candidates to apply simple

biological principles to daily life. Candidates were not aware that genetic variations may give

rise to new varieties which may or may not be better adapted. A considerable number

incorrectly thought that genetic variation will always give rise to better adaptation to the

environment.

Paper I Marking Scheme & Year Report P.1


1. (b) (i) (1) remains relatively constant ----------------------------------------------------------------------------1

(2) mouth temperature approximates to internal temperature )

this indicates that enzyme activity / rate of metabolism

remains relatively constant, irrespective of changes in

external temperature )--------any ONE set 1+1

OR

Mouth temperature is better than skin )

temperature as an indicator of internal temperature )

(ii) (1) Skin temperature drops --------------------------------------------------------------------------------1

(2) vasoconstriction / vessels in skin constricts -------------------------------------------------------1

and less blood / heat is carried to the skin --------------------------------------------------------1

(iii) yes - there is still a temperature gradient / difference

between the skin and the environment ----------------------------------------------------------1+1

Total : 8 Marks

1. (b) (i) Many candidates did not fully understand the "significance" of having a constant mouth

temperature. They were unable to point out that mouth temperature is an indication of

internal body temperature.

(ii) Most candidates could not clearly distinguish the physiological process from either the

structural or the physical process in temperature regulation of the skin. Many candidates

gave “contraction of erector pili muscle” or “goose skin” as the answer, but they failed to

realize that this is not an efficient mechanism for temperature control in humans when

compared with other mammals.

(iii) Many candidates did not appreciate that heat energy always flows from a region of high

temperature to a region of low temperature even in biological systems. Thus in the graph

given in this question, even when the skin temperature was at its minimum, the skin could

still lose heat to the outside room.



1. (c) (i) carbon dioxide ---------------------------------------------------------------------------------------------------1

(ii) (1) to absorb carbon dioxide from the incoming air --------------------------------------------------1

(2) to check that all carbon dioxide from the incoming

air has been removed -----------------------------------------------------------------------------------1

(iii) by putting the plant in darkness for a )

few days before setting up )

destarch the leaves ) any TWO -----------------------------------------------1,1

to ensure that any starch detected )

was formed during the expt. )

(iv) - put the leaf in boiling water for a few minutes ----------------------------------------------------------1

- put the leaf in a cube of alcohol in a hot water-bath --------------------------------------------------1

- put the leaf in water -------------------------------------------------------------------------------------------1

- add iodine solution --------------------------------------------------------------------------------------------1

(v) replace both sodium hydroxide solution and lime

water by water / use any leaf outside the glass bottle -------------------------------------------------1

Total : 10 Marks

1. (c) (iv) In the test for the presence of starch in a leaf after photosynthesis, many candidates wrote

"boil the leaf" without mentioning the medium used for boiling. This was a crucial point in the

experiment. A common language weakness was that they wrote "put iodine" instead of "put

iodine solution" in the test for starch.

(v) In setting up a control experiment, many candidates mentioned using water to replace either

sodium hydroxide solution or limewater instead of both. This signifies another weakness of

many candidates: not being able to critically appraise the experimental techniques used in

biological investigations.



2. (a) (i) A is thick-walled and B is thin-walled -----------------------------------------------------------------------1

valves present in B but absent in A -------------------------------------------------------------------------1

(ii) C is thin-walled (one cell thick) ------------------------------------------------------------------------------1

to facilitate exchange by simple diffusion -----------------------------------------------------------------1

(iii) (1) * left ventricle ---------------------------------------------------------------------------------------------1

(2) * right atrium / auricle -----------------------------------------------------------------------------------1

(iv) (1) white blood cell -------------------------------------------------------------------------------------------1

their amoeboid shape enables them ----------------------------------------------------------------1

to squeeze through the capillary wall -------------------------------------------------------------1

(2) for body defence / to kill germs -----------------------------------------------------------------------1

(v) (1) * lymph -----------------------------------------------------------------------------------------------------1

(2) contraction of surrounding muscles -----------------------------------------------------------------1

presence of valves --------------------------------------------------------------------------------------1

Total : 13 Marks

2. (a) (i)&(ii) Many candidates, in writing about the thickness of the blood vessels, wrote "cell walls"

instead of "the wall of the vessels".

(iv) Many candidates wrongly thought that white blood cells are so small that they can actually

diffuse through the walls of the capillaries. They failed to realize that white blood cells can

utilize amoeboid movement to actually squeeze through the walls of the blood vessels.



2. (b) (i) (1) * geotropism / geotropic response -------------------------------------------------------------------1

(2) the force of gravity ---------------------------------------------------------------------------------------1

results in a higher concentration of auxin / hormone on the lower side of the root ------1

since a high concentration of auxin / hormone retards growth of the root -----------------1

upper part of the root grows faster / lower side of the root grows slower ------------------1

(ii) (1) the root bends upwards / towards the source of water instead of downwards -----------1

because the effect of water ----------------------------------------------------------------------------1

is greater than that of gravity --------------------------------------------------------------------------1

(2) root grows towards sources of water to

ensure enough supply of water for growth --------------------------------------------------------1

Total : 9 Marks

2. (b) (i) The term "geotropism" was often wrongly spelt as "geotroprism" or "geotrophism".

(ii) Many candidates stated incorrectly that auxin can inhibit the growth of roots without giving

the relative concentration. Many failed to provide a proper explanation of geotropism on a

hormonal basis. This weakness was also mentioned in last years’ report and this should be

brought to the notice of students by teachers. Quite a number of candidates did not know

the meaning of "significance" with respect to the growth response of a seedling.



2. (c) (i) white flower -------------------------------------------------------------------------------------------------------1

this trait appears in the offspring but not in parents in cross II --------------------------------------1

[also accept : about of the offspring in cross II produce white flowers ]

(ii) (1) Ff -------------------------------------------------------------------------------------------------------------1

(2) FF and Ff --------------------------------------------------------------------------------------------1 or 0

N.B. No marks to be awarded for answers using other symbols.

(iii) (1) a pair of genes which controls a certain character / different forms of a gene ------------1

(2) appearance / expression of a character ------------------------------------------------------------1

(3) an individual which results from crossing two

individuals (homozygous) which are genetically unlike -----------------------------------------1

(iv) 2N -------------------------------------------------------------------------------------------------------------------1

Total : 8 Marks

2. (c) (ii) Despite the stipulation given in the question requiring the use of the symbols F and f in

listing the genotypes, some candidates used different symbols to represent the dominant

and recessive alleles. Many ignored the instruction to "list" and so put down detailed genetic

crossings instead of just giving the genotypes as required.

(iii) Very few candidates were able to give a simple explanation of basic genetic terms. Many

confused alleles with chromosomes; in fact, alleles are alternative forms of a gene. Others

wrongly considered hybrids as resulting from the crossing of two different species.



3. (a) (i) C - * spongy mesophyll / cells / layer ----------------------------------------------------------------------1

D - * guard cell ---------------------------------------------------------------------------------------------------1

(ii) cells are closely packed ---------------------------------------------------------------------------------------1

possessing a large number of chloroplasts ---------------------------------------------------------------1

(iii) for rapid diffusion of gases to facilitate photosynthesis ------------------------------------------------1

(iv) (1) air in the intercellular aces expands on heating --------------------------------------------------1

and passes out through the stomata ----------------------------------------------------------------1

(2) stomata occur on only one surface of the leaf ----------------------------------------------------1

(v) A (cuticle) there is no danger of desiccation 1+1

cell D(guard cell) gaseous diffusion occurs all over the plant

surfaces where there is no cuticle

1+1

[accept other suitable answers]

Total : 12 Marks

3. (a) (i) Many candidates could not distinguish clearly a stoma from the guard cells surrounding it.

Some misspell "guard cells" as "gaurd cells".

(iv) Many candidates could not explain the bubbles on the leaf when it was placed in hot water

and wrongly attributed this to the influx of water - presumably driving air out of the leaf.

(v) Many candidates could not explain why in an aquatic leaf, the cuticle, guard cells and

palisade layer may be absent. They were not aware that aquatic plants respire by general

diffusion of respiratory gases all over the plant leaf surface and therefore do not require

stomata. They wrongly thought that if the guard cells and stomata are present, the aquatic

leaf will die of suffocation as the water may enter. Many incorrectly thought that in an

aquatic plant, the palisade cells are absent because there is no need for photosynthesis.



3. (b) (i) species A --------------------------------------------------------------------------------------------------------1+

because less water is lost by evaporation / water content in faeces is smaller -----------------1

showing that species A has a better ability to

conserve water / less likely to become dehydrated ----------------------------------------------------1

(ii) oxidation of food / respiration --------------------------------------------------------------------------------1

(iii) breathing ----------------------------------------------------------------------------------------------------------1

sweating -----------------------------------------------------------------------------------------------------------1

(iv) * large intestine / * colon --------------------------------------------------------------------------------------1

(v) group B would die off first -----------------------------------------------------------------------------------1+

because both groups of rats gained similar amount of metabolic water --------------------------1

but group B has a poorer ability to conserve water / loses more water ---------------------------1

Total : 10 Marks

3. (b) (ii) Many candidates inappropriately considered reabsorption of water by the kidneys as a type

of metabolic activity for gaining water.

(iii) Many candidates wrongly considered urine formation to be water loss by evaporation.

(v) Few candidates realized that, as shown from the table in this questions, both groups of rats

gained a similar amount of metabolic water.



3. (c) (i)

11

10

9

8

7

6

5

4

3

2

1

056|

60

61|

65

66|

70

71|

75

76|

80

81|

85

86|

90

91|

95

96|

10058 63 68 73 78 83 88 93 89

H eart bes t per m inute

m id-po ints

Num

ber

of s

tude

nts

correct choice of axes------------------------------------------------------------------------------------------1

correct labels------------------------------------------------------------------------------------------------------1

correct plotting of all data--------------------------------------------------------------------------------------2

(5 data correct 1 mark only)

(ii) continuous variation ------------------------------------------------------------------------------------------1+

characteristics show gradation from one extreme to the other --------------------------------------1

OR variation shows e normal distribution

(iii) (1) height / weight / I.Q. / skin colour (any ONE) -----------------------------------------------------1

(2) eye colour / tongue-rolling ability / characteristics of ear lobe (any ONE) -----------------1

Total : 8 Marks

3. (c) (i) Most candidates could plot the histogram correctly although some drew bar charts instead.

(ii) Many could not distinguish clearly between continuous and discontinuous variation.



4 (a) (i) photosynthesis absorption of light by chlorophyll -------------------------------------------------------1

(ii) chemical energy / food substances / starch --------------------------------------------------------------1

(iii) predation / feeding ----------------------------------------------------------------------------------------------1

(iv) (1) Pyramid of biomass : ------------------------------------------------------------------------------2 or 0

(2) energy is lost at each trophic level ------------------------------------------------------------------1

due to respiration / exertion / death -----------------------------------------------------------------1

(v) decomposers / saprophytes / bacteria / fungi ------------------------------------------------------------1

for recycling of materials --------------------------------------------------------------------------------------1

(vi) they do not compete for the same resources ------------------------------------------------------------1

[accept other suitable answers]

Total : 11 Marks

4. (a) (iv) Many candidates drew a pyramid of numbers instead of pyramid of biomass. Some even

drew an inverted pyramid with the first trophic level, the trees, having a much smaller

biomass.

(v) Many candidates wrongly thought that energy can be recycled by decomposers.

(vi) Very few candidates were aware that the caterpillar and bee population do not compete for

the same resources on the same tree.



4. (b) (i) A - * nucleus ------------------------------------------------------------------------------------------------------1

B - * cytoplasm --------------------------------------------------------------------------------------------------1

(ii) (1) root hair / long cellular extension --------------------------------------------------------------------1

(2) increases surface area ---------------------------------------------------------------------------------1

for absorption of water and mineral salts ----------------------------------------------------------1

(iii) (1) hollow cell / no cell content ----------------------------------------------------------------------------1

reduces resistance to flow -----------------------------------------------------------------------------1

(2) thick cell wall ----------------------------------------------------------------------------------------------1

offers great physical strength for support ----------------------------------------------------------1

(iv) cell type II in region X, and cell type III in region Z ----------------------------------------------1 or 0

Total : 10 Marks

4. (b) (iii) Many candidates failed to give proper explanations "with reference to the diagrams only"

and gave features which were not found in the diagrams. Many did not know that the thick

cell walls of plant cells provide mechanical support. Many also considered the turgidity of

cells (which was a feature not clearly seen in the diagrams) to be a means of support.



4. (c) (i) A- * pancreas ----------------------------------------------------------------------------------------------------1

B - * caecum / large intestine --------------------------------------------------------------------------------1

(ii) A and C ------------------------------------------------------------------------------------------------------1 or 0

(iii) - bile secreted by the liver causes emulsification of fat )

- by reducing surface tension of fat )

- to increase surface area for the enzymatic action )

- enzyme from pancreas ) any FIVE -------------1,1,1,1,1

- breaks down fat into absorbable forms )

- pancreatic juice / bile neutralizes acid from stomach )

- to provide an alkaline medium for enzyme to work )

(iv) mix the extract with starch solution for some time ------------------------------------------------------1

test for disappearance of starch with iodine

solution / test for presence of reducing sugar with

Benedict’s / Fehling’s solution -------------------------------------------------------------------------------1

Total : 10 Marks

4. (c) (i) Many candidates misspell "pancreas" as "pancrease".

(iii) Many candidates failed to mention the neutralizing effect of bile in fat digestion. Others

wrongly thought that bile contains fat-digesting enzymes. Still others wrongly identified the

caecum as the colon or appendix. A common misconception was that bile is produced in the

gall-bladder. In fact, the gall-bladder is a temporary depot for bile which is produced by the

liver.



5. (a) (i) (1) air



5. (b) (i) possession of a backbone / vertebral column -----------------------------------------------------------1

(ii) * mammal ---------------------------------------------------------------------------------------------------------1

C (bat) and D (whale) ------------------------------------------------------------------------------------1 or 0

(iii) (1) A - * skin ----------------------------------------------------------------------------------------------------1

(2) B - * gills ----------------------------------------------------------------------------------------------------1

(iv) no buoyancy of water to support its body weight -------------------------------------------------------1

therefore rib cage / lungs cannot expand -----------------------------------------------------------------1

(v) (1) sudden / drastic change of an organism -----------------------------------------------------------1

from a larval / young stage to an adult stage -----------------------------------------------------1

(2) egg larva pupa adult -------------------------------------------------------------------2 or 0

Total : 11 Marks

5. (b) (i) Many candidates could not distinguish between "vertebrate" and "vertebrae".

(ii) Many candidates wrongly classified the penguin as a mammal .

(iii) Some candidates did not read the question carefully and failed to limit their answers to the

respiratory structures of the animals mentioned in the question.

(iv) Most candidates could not relate the respiration of an aquatic mammal (e.g. whale) to the

buoyancy of water. This indicates that candidates are generally weak in applying basic

biological principles to new situations. Quite a number wrongly thought that the whale uses

gills for breathing under water.

(v) Most candidates could not point out clearly that metamorphosis is a sudden, drastic change

in the form or structure of an animal. Many did not know the meaning of the term "word

diagram".



5. (c) (i) X - * bone ---------------------------------------------------------------------------------------------------------1

Y - * tendon -------------------------------------------------------------------------------------------------------1

(ii) Q and R -----------------------------------------------------------------------------------------------------2 or 0

Q only -1 mark

R only -1 mark

No other alternatives

(iii) P and S ---------------------------------------------------------------------------------------------------1 or 0 +

both are extensors / extend / straighten the joint -------------------------------------------------------1

Q and R ---------------------------------------------------------------------------------------------------1 or 0 +

both are flexors / flex / bend the joint ----------------------------------------------------------------------1

(iv) In the model : movement in one plane only --------------------------------------------------------------1

In actual case : movement in three planes ---------------------------------------------------------------1

Total : 10 Marks

5. (c) (i) Most candidates mixed up "tendons" with "ligaments" and also confused "flexors" with

"extensors".

(ii) Many candidates did not know that when muscles contract they become fatter and shorter.

(iii) Many candidates could not clearly distinguish the flexors from the extensors. Quite a

number wrongly considered "categories" to be antagonistic pairs of muscles.

In general candidates appear to have little problem in recalling basic biological facts and

principles. They are however quite weak in providing clear and concise explanations of

basic biological terms and processes. Their ability to present data in a graphical form has

improved but they are still weak in applying their biological knowledge to daily life or new

situations.


Documents

1989 Biology Paper I Marking Scheme