SIAYA DISTRICT SECONDARY SCHOOLS EVALUATION EXAMINATION - 2008
Kenya certificate of Secondary Education
231/2
BIOLOGY
PAPER 2
JULY / AUGUST 2008
MARKING SCHEME
1. a)
A – ilium
B- Acetabulum
b)
Allows passage of blood vessels /and nerves to the leg.
c)
Suture / immovable /fixed joint.
d)
2. a)
b)
c)
d)
e)
f)
3. a)
b)
c)
d)
4. a)
b)
c) (i)
d)
(1mk)
(1mk)
(1mk)
(Any one 1 mark)
- The end of the cells are marked with thickened regions /intercalated disc; that form bridges
between fibres hence
transmit impulses rapidly through out the heart.
- Are myogenic: - contract and relax without nervous stimulation.
- Have more mitochondria to sustain their energy demands;
(Any 2 = 4mks)
To find out the production of the heat by germinating seeds.
(1mk)
Antiseptic killed micro-organism which could have caused decay; during which heat could be
(2mks)
Acts as a control for Y.
(1mk)
To prevent heat loss or gain.
Absence of certain wavelength of light;
Freezing of seed during winter;
Respiration
Sweep nets
- Buckets /container
- Gloves.
- Water proof marking pain + brush.
produced.
(1mk)
(2mks)
(1mk)
(½ mk each)
Method: capture – recapture
Reason: crabs are highly mobile
Wear gloves to avoid stinging by crabs.
Wear protective footwear to prevent infection.
- Direct observation.
- Examine gut contents.
- Examine droppings.
- Infer from feeding apparatus/ mouth parts.
(1mk)
(1mk)
(1mk)
(1mk)
(Any 2 points = 2mks)
i) Pupil becomes smaller
ii)Pupil widens
(1mk)
(1mk)
Fovea centralis A cc Retina
(1mk)
A condition in which light rays from a distance object are brought to focus in front of the retina while those near are
clearly focused.
(1mk)
Cones lack retinal convergence (Each one has its own Bipolar neurone which links it to optical nerve); Rods show
retinal/ convergence (several rods connected to one bipolar neurone.)
(2mks)
e (i)
(ii)
Cochlea
Vestibular apparatus.
Acc. Semi circular canals and vestibule. RJ. Vestibule alone.
(1mk)
5. a)
GUACUCA
(1mk)
b)
A (sudden) change in structure of DNA/gene /chromosome at a particular locus.
c)
(1mk)
Radiations / X-rays / gamma /befa /U-V-rays chemical e.g. mustard gas, colchicines
(Any two, 2mks)
© Siaya District Examination Council
Biology 231/2
1
d)
e)
Inversion; deletion; translocation; duplications; non disjunction;
Result in exchange of genetic material; leading to variation;
23,000  1100
x100 ; = 1990.9%;
1100
400  1300
(ii)
x100 ;= 69.23%;
1300
6. a) (i)
b)
(Any two, 2mk)
(2mk)
(2mks)
(2mks)
(i) At rest there is more blood flow through the gut because skeletal muscles have less physical (metabolic) activity
hence less glucose and oxygen required; more blood available at the gut to carry away digested food.
(2 mks)
(ii) During streneuous exercise, more energy is required in skeletal muscles, hence more glucose and more oxygen are
required by muscles; there is need for faster removal of metabolic wastes (urea, co2, H2O and heat) hence more blood
required.
(2mks)
c)
By stronger contractions; faster contractions; increased heart beat.;
d (i)
Body temperature normal; hence less blood required at the surface of the skin.
(ii)
c)
7. a)
(2mk)
(2mk)
Body temperature increases hence more blood flow to the skin /vasodilatation is necessary to take away excess heat.
(2mks)
Water; urea/uric acid/ nitrogenous waste/ creatinine/ hormones/ mineral salts/minerals
(Any 3)
Nature selects those individuals which are sufficiently adapted and allow them to survive; and reject; those that are
poorly adopted;
(3 mks)
b)
Individuals of the same species show certain variations/differences; the differences are caused by genes/mutations;
some of the variation confer an advantage to the individuals while others are disadvantages; Most organisms produce
large number of offspring’s than the parental generation, however only a few survive to adulthood and are able to
reproduce, This is due to environmental pressures; such as predation / diseases / and competition for food / and
breeding sites; this is referred to us the struggle for existence; Individuals with advantageous vanations /with
desirable variations; are well adapted for survival; they survive and reach reproductive maturity; and pass over the
favourable characteristics to their offspring; Those that do not have advantageous variations/ traits/ genes; die while
young /do not reach sexual maturity, and therefore do not pass their genes/ traits to their offsprings; and thus perish
/become eliminated; This is called survival of the fittest;
(17 mks)
8. a)
Secondary thickening in flowering plants.
Secondary thickening results into an increase in girths /width; due to the activity of the cambium. In secondary
growth new tissues are formed by vascular cambium; and cork cambium; the vascular cambium divides radially to
produce new carbrium cells between the vascular bundles. This forms a continuous cambium ring; The new cells of
the cambium differentiate to become secondary phloem on the outsides; those to the inner side differentiate to form
secondary xylem, more secondary xylem; is formed than secondary phloem; the interfascular cambium divides to
form secondary parenchyma thereby increasing the growth of medullary rays;
As a result of the increase in volume of the secondary tissue; pressure is exerted on the outer cells of the stem
resulting in rupturing of epidermal cells; In orders to replace the protective outer cover a new band of cambium cells
are formed in the cortex; The cork cambium/ phellogen differentiate into secondary cortex on the inner side; and cork
cells on the outside; cork cells are dead with thickened walls which became coated with a water proof substance
called suberin; The cork cells increase in a number and become the bark of the stem which prevents loss of water;
prevents infection from fungi and is also insulators. Bark is normally impermeable to water and respiratory gases;
periodically the cork cells form a loose mass of cells known as lenticels which makes gaseous exchange possible;
The rate of secondary growth is stem varies with seasonal changes; e.g during rainy season xylem vessels and
tracheids are formed in large number; the cells are large thin walled and with wood with light texture; In dry season
xylem and tracheids formed are few in number, are small and their wood have a dark colour. This leads to
development of two distinct layers within the secondary xylem formed in a year called annual rings; ( Allow marks
on correctly annoted diagrams.)
(14 marks)
b)
EITHER
Choose /identify a young leaf (just unfolded); use the same leaf throughout; Measure total length of the whole leaf
(accept measurements of any part of the leaf). Record; repeat at regular intervals until no more change is length
occurs / constant length. OR. Choose /identify a young leaf (just unfolded); use the same leaf throughout; Trace the
outline on a graph paper; and workout the area; Record; Repeat at regular intervals until constant area; average rate of
growth is equal to total increase in area divided by the period of time taken to achieve final area; (6 mks)
© Siaya District Examination Council
Biology 231/2
2
© Siaya District Examination Council
Biology 231/2
3