NAKURU DISTRICT SEC. SCHOOLS K.C.S.E TRIAL EXAMINATIONS2015
Kenya Certificate of Secondary Education (K.C.S.E)
MARKING SCHEME
BIOLOGY PAPER
2
(1 mark)
1(a)
(b)
(c)
(d)
(e)
2(a)
(b)
Emulsification ;
Bile juice;
(i) sodium taurocholate ;
(ii) sodium glycocholate ;
Bile is produced in the liver ;
Surface area of digestion would be reduced hence the rate of digestion ;
- Absorption process would be reduced ;
(2 x 1)
(1 mark)
(1mark)
(1 mark)
(1 mark)
(2 marks)
Sickle cell anaemia ;
(i) Advantage – individual having this condition rarely suffer from malaria
(ii) disadvantage – suffocation due to insufficient supply of oxygen to the (respiring) body
tissues ;
Parental phenotypes
Person A
Person B
Parental Genotype
HbA HbA X
HbS HbS
;
Gametes
HbA
HbA
HbS
HbS;
fusion
F 1 Generation
HbAHbS
HbAHbS
Phenotypes; All have sickle cell traits,
Genotypes; All are HbAHbS;
3(a)
(b)
(c)
(d)
(e)
HbAHbS
HbAHbS
Pathway followed by a nerve impulse that gives rise to a reflex action
1- motor neurone
2 – relay neurone/intermediate neurone
The arrows point towards neurone 1 from 2 and 3
Grey matter
Impulse reaching the dendrite end of relay neurone causes the synaptic vesicles to release a
acetylcholine/transmitter substance; into the synaptic cleft, the acetylcholine/transmitter
chemical diffuses across the cleft; and causes the depolarization of the neurone
4(a)
(2 marks)
(1 mark)
(1 mark)
(3 marks)
(4 marks)
Guinea
fowls
Vultures
Termites
Grasshoppers
Leopard
Grass
(1 mark)
Gazelles
1
: Award a mark for every
trophic level
(b)
(c)
(d)
5(a)
(b)
(c)
(d)
(e)
Grass
Grass
Grass
Vultures
Grasshoppers
Termites
Guinea fowls;
Guineas Fowls;
A- Photosynthesis ;
B – Respiration
Provision of food to plants organisms when convert light energy into chemical energy to
make their own food which is later consumed by animals ;
A – chloroplast ;
B – Mitochondrion ;
Glycolysis ;
Kreb’s cycle;
This is the point when the rate of photosynthesis is equal to the rate respiration ;
6(a)(i) 3.00 p.m or 1500 – pH
(ii) 3.00 p.m of 1500 – dissolved oxygen
(b)(i)
pH increased between 06.00 to 09.00; because of increased rate of photosynthesis ; in
aquatic plants, which consumed more carbon(IV) oxide gas dissolved in water;
(ii) pH decreased between 2100 to 2400; of carbon (IV) oxide which was being produced; by the
respiring; water plants, but was not being used for photosynthesis;
(c)
Increasing light intensity increases the rate of photolysis/photosynthesis hence increased
production of oxygen gas while decreasing light intensity decreases the rate of photolysis;
hence reduce production of oxygen gas;
Acc. Photosynthesis instead of photolysis
(d)
Have dissected/branched leaves which provide a large surface area of light absorption and
gaseous exchange;
Leaves have chlorophyll which is very sensitive to light;
(e)
Some nitrate fertilizer would get into the river water; thus causing rapid growth of many
water plants;
Many water plants, photosynthesize food under high light intensity using a lot of carbon (IV)
oxide gas thus raising pH value; and produce a lot of Oxygen, increasing the concentration
of oxygen;
The very many water plants also respire rapidly under low light intensity thus producing
large volume of carbon (IV) oxide gas which greatly lowers the pH of water ;
7 (a)
15 marks
Roots extensively developed/roots superficial; to provide large surface area for water
absorption;
Rej. Fibrous roots
Roots grow deep/long roots; to reach water table/source deep in the ground; Acc.
Fleshy stem/tissues/leaves
Succulent/possession of water storage tissues; to store water/to survive drought
Possession of waxy/thick cuticle; to reduce transpiration;
Hairy leaves; sunken stomata; reduce leaf size/spines/scales/thorns/leaves modified
to needle like/reduced number of stomata;
Xerophytes
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2
 Rolled leaves/folding leaves’ shedding leaves; reversed stomatal rhythm;
 Short life cycle/quick growth after rains; to make use of the available water quickly;
Rej. Flowering alone
Rej. Long/short roots alone
(b)
8
Hydrophytes
20 marks
 Aerenchyma tissue/air spaces intercellular spaces;/long fibrous roots; for
buoyancy/to float on water;
 Poorly developed support tissues/sclerechyma;
 Upper epidermis leaves have more stomata than lower Epidermis; for gaseous
exchange/increased rate of transpiration;
 poorly developed conducting tissues/xylem and phloem; plants obtain water by
diffusion;
Acc. Stomata on upper surface only Total 8 Max 7
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The process of mitosis occurs in cells its important in cell multiplication; for growth;
and asexual reproduction; in some species
Its occurs in one nuclear division/divisional process;
It is divided into five phases; A diplopid mother/parent cell; enters into interphase;
during interphase the cell exhibits a very high rate of respiration; to produce large
amounts of energy; for the process; genetic material replicates; to maintain
chromosomal number in daughter cells.
New organelles are synthesized (for the cells);
The cell then enters prophase; during this phase centrioles migrate; to opposite poles;
and form spindle fibres; the nuclear membrane dissolves/break down; to free the
chromosomes into the cytoplasm; the chromosomes shorten and thicken; to prevent
brewage during separation; Each chromosome is seen to have chromatids/sister
chromatids;
The cell enters metaphase; during metaphase chromosomes are free in the
cytoplasm; and the spindles attach to the centromeres(of chromosome);
Chromosomes align themselves at the equator of the spindle/cell;
The cell then enters anaphase; during anaphase spindles shorten/contract; sister
chromatides separate; at the centromere; and migrate to oppose poles;
The spindles then disappear; the cell membrane begins to constrict; in animals; while
in plants; a wall plate/cell wall is deposited;
The cell then enterstelophase;
During telophase chromatids reach opposite poles; and a nuclear membrane forms
around each set;
They cytoplasm divides into two; to form two; diploid; daughter cells;
The Chromosomes become less distinct;
𝟑𝟔 𝒙 𝟏
Total marks =
= 18 maximum marks
𝟐
NB: Marking stops at a point where a student does not follow the sequence
3