231/2
BIOLOGY
PAPER 2
(THEORY)
MARCH/APRIL- 2015
TIME 2 HOURS.
CHEPALUNGU SUB- COUNTY JOINT EVALUATION TEST-2015
Kenya certificate of Secondary Education(KCSE)
MARKING SCHEME
1.
(a)
(i)
(air bubble) potometer.
(ii)
The rate of transpiration.
(iii)
-The leafy shoot should be from a herbaceous plant.
-Cut off the last few centimeters of the stalk under water.
-All the air in the capillary tubule should be expelled.
-Jelly should be applied around the stem and around the rubber bungo
-The end of the capillary tubing should rest in beaker of water.
Any 2 x 1mk
(iv)
-Temperature
-Humidity
-Wind
-Atmospheric pressure
Light intensity.
Any 2 x 1mk
(b)
-To ensure that donors blood and that of the recipient are compatible.
-To ascertain that blood being transfused is freee from pathogens e.g. HIV/AIDS.
2.
(a)
(b)
Incomplete dominance /partial dominance ;
Parental phenotype Red flowered x white flowered
Parental genotype RR x ; WW
(1mk)
(1mk)
(2mks)
(2mks)
(1mk)
Gametes
(c)
(d)
F2 genotype
1Red : 2Pink : 1White ;
(1mk)
Parental phenotype : Pink x white
Parental genotype RW x WW
R
×
(2mks)
WW
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231/2 Biology
Marking Scheme
R
W
W
W
RW
RW
W
WW
WW
Genotypic ratio 2RW : 2WW;
Phenotypic ratio 2Pink : 2White;
3.
4.
5.
(a)
Villi rej Villus
(1mk)
(b)
A – epithellum
C – Lacteal
(1mk)
(c)
C – is responsible for absorption of fats
(1mk)
(d)
They secrete mucus to lubricate food and form a protective layer to prevent the gut wall
from being digested.
(1mk)
(e)
(i)
(ii)
(f)
Goitre
(1mk)
(a)
Q – Scrotum
R – Urethra
(1mk)
(1mk)
(b)
It is long to increase surface area / space for storage of sperms.
(1mk)
(c)
Meosis
(1mk)
(d)
(i)
-Refer to the attachment of the blastosyst to the wall of the uterus by the villi(1mk)
(ii)
-Is the process by which Ovum is released from a mature graaffian follicle into the
funnel of the fallopian tube
(1mk)
-Pepsin
-Trypsin.
(1mk)
(1mk)
(e)
-Production of hormones oestrogen and progesterone which help in sustaining pregnancy.
-Site for exchange of material e.g. water , mineral hormone , antibodies and nitrogenous
waste products between the foetal and maternal circulation systems.
(2mks)
(i)
-Refer to the massive growth of water plants due to accumulation of nutrients such as
Nitrates , Phosphates and Sulphates.
(1mk)
(ii)
-Depletion of oxygen concentration in water.
-Reduced light penetration in water .
-Causes blockage of water ways.
Any 2 x 1mk
(iii)
-Sulphur(iv) oxide
-Carbon (iv) oxide
© 2015 Tigania West Sub – County Academic Committee
(2mks)
(1mk)
(1mk)
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231/2 Biology
Marking Scheme
(iv)
6.
-CFC cause depletion of the ozone layer which consequently allows the penetration of
harmful u.v radiations from the sun which causes skin cancer.
(3mks)
(a)
(b)
(i)
The blood sugar level increased as a result of the glucose being absorbed in the
ileum by diffusion and / or active transport.
(2mks)
(ii)
The blood sugar level dropped as a result of conversion of glucose to glycogen and
fats by insult. There was also an increased rate of respiration which reduced the
blood sugar level.
(2mks)
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231/2 Biology
Marking Scheme
7.
(c)
90mg/100ml of blood.
(d)
Person B has a defect in the pancreas. Not enough insulin was produced to control the
blood sugar level.
(2mk)
(e)
By administration of insulin
(f)
Excess amino acids are broken down to form carbohydrates and amino group (NH2);
The amino group combines with hydrogen ion to form ammonia (NH3);. The ammonia
combine with carbon (iv) oxide The ammonia combine with carbon (iv) oxide ; to form
urea; . The process is called deamination;
(a)
(i)
Stomata are located on the upper side of the leaves for quick loss of excess water
and efficient gaseous exchange.
(ii)
They have large airfilled tissue (aerenchyma) which cause buoyancy to plants and
assist in gaseous exchange.
Flowers are raised above the water to allow pollination.
Have poorly developed roots to reduce absorption of water.
Have leaves with sensitive chloroplast that photosynthesize under low light
intensity.
Leaves are deeply dissected into threadlike straws to increase surface area for
maximum absorption of light.
(Any 4 x 1mk )
(4mks)
(iii)
(iv)
(v)
(vi)
8.
(1mk)
(1mk)
(b)
When pollen grains land on the stigma ;the stigma produces a sticky substances which
makes the pollen grains to adhere onto it; The sticky substances also stimulates the pollen
grains to germinate ; sending out a pollen tube down the stigma and style; The pollen tube
secrets an enzyme that dissolve tissues as it grows into the stigma, style to the ovary; the
cells also provide nourishment to the pollen tube.
The tube nucleus occupies a position at the tip of the pollen tube with the generative
nucleus behind;
The generative nucleus divides by mitosis to form two male gametes nuclei;
When the pollen tube reaches an ovule ; it enters the ovule through the microphyle; and
penetrates the wall of the embryo sac.;
The tip of the pollen tube ruptures and the tube nucleus dissintergrates ; the male gamete
nucleus enters the embryo sac; one of male nuclei fuse with the functional which develop
into an embryo ; the other male gamete nucleus fuses with primary polar nuclei; to form a
triploid primary endosperm nucleus ; which develop into endosperm;
18 max
(16mks)
(a)
During inhalation external intercostals muscle contract while internal intercostals muscles
relax; This pulls the ribs upwards and outward; diaphragm muscle contract hence flatten;
This movement increases the volume and pressure decrease inside it; Atmospheric
pressure being highest forces air into the lungs; and the lungs inflate;
(6mks)
(b)
-They contain haemoglobin; that has high affinity for oxygen;
-They lack nuclei; leaving room for more haemoglobin to be packed in the cell to enable
them take more oxygen.
-They are biconcave; in shape to increase their surface area for absorption of oxygen.
-Have a thin plasma membrane which allows rapid diffusion of gases.
-They are small and numerous; thus increasing the surface area for absorption of oxygen.
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231/2 Biology
Marking Scheme
-They are able to change their shape hence are capable of squeezing through the narrow
capillaries to reach all the body parts.
Any 3 x 2mks
(6mks)
(c)
-Antibodies which are antitoxins; neutralize the toxins; (antigens) produced by pathogenic
micro – organisms.
Some antibodies such as agglutinins; cause clumping; together of micro- organism .
This stops the micro organisms from multiplying and they eventually die.
-Some antibodies e.g. lysins; destroy micro- organisms by destroying their cell
membranes; or walls.
-Others such as opsonins; adhere to the outer surface ; of micro - organisms thus
making it easier for phagocytes to ingest them.
4 x2mks
(8mks)
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231/2 Biology
Marking Scheme