NYATIKE SUB-COUNTY JOINT EVALUATION EXAM
BIOLOGY PAPER TWO
JULY /AUGUST 2014
MARKING SCHEME
Incomplete dominance rj co-dominance
a) RR ;WW ;
b) Paretnal genotype
RW
Hametes
R
F2
RR
W
RW
x
x
Rw ;
R
RW
W
WW
Henotypic ration 1RR : 2 RW : 1 WW
Phenotypic ratio ! red : 2 ink : 1 white;
c) ¼ = 480
( 2/4 = 2/4 x 480 x 4/1 )
= 960 pink flowers;
2 (a) (i) Xylem vessel;
(ii) - Lignified ; to prevent collapsing;
 Long and narrow lumen; to facilitate capillarity;
 Made of dead cells; to ensure
 Passage of water;
(b) Water moves from the soil into root hair’s by Osmosis;
The concentration of the cell sap of the root hair is higher than surrounding soil. Water moves into the cell sap
by osmosis and it is diluted making it less.
Concentrated than neighbouring/Cortex cells; water move into neghbouring cells/cortex by osmosis into
L /Xylem veselse;
c) Transpirations; pull;
- Root pressure;
- Cohesion & adhesion forces.
3 (a) (i) A and B
Rate of reaction increases with increase in substrate concentration; more active sites of enzymes are available
; for a large number of substrates;
(ii) B and C
Rate of reaction remains constant; all active sites are occupied;
b) Raising the concentration of enzymes;
(c) PH
Temperature
Inhibiotrs/cor factors;
4. A – Nitrogen fixation;
D – Absorption;
(b) Nitrite/nitrite/NO2(c) Denitrifyig bacteria/denitrifieres
(d) (i) Leguminous plants; acc. Legumes
(ii) Root nodules; rej root or nodules alone
(e) Killing /reduction of decomposers
Killing/reducing of nitrogen fixing bacteria/ microorganisms
Destruction of leguminous plants
5 (a) (i) A – remain straight /show little or no growth;
B – Grows straight upwards;
C- Will grow /bend toward light;
(ii) Light carses lateral migration of anxious from the lit side tot the darker side. When they cause more/rapid
cell division/elongation; resulting ingrowth curvature towards light;
(b) Tip would bend towards light
(c) all the seedlings will grow upwards;
6 (i) photosynthesis;
Respiration;
C (i) rate of Co2 consumption increases from 6 hrs to 12 hrs due to increase in light intensity;
The rate remain higher between 12 & 14 hrs which is the period of optimum light intensity. The rate
decreases btw 16-24 hrs due to decrease inlight intensity;
(ii) rate of CO2 released decrease from 6 hrs to 12 hrs . some were used ip for photosynthesis; from 14 to 20 hrs
the rate of Co2 increased due to decrease in the rate of photosynthesis; rate remained constant from 20hrs since
photosynthesis is no t taking place.no use of CO2;
D Point at which rate of photosynthesis equals rate of respiration/amount of carbon (IV) oxide used is same as Co2
released;
d) 7.8 ± 0.2 18.0 ± 0.2
e)
Increased the temperature increases rate of CO2 consumption upto optimum point further increase reduce rate
Co2 consumption as enzymes are de activied;
7. Pollen grains a stick in the stigama surface; that surface of stigma produces a chemical substance ; which
stimulates the pollen grain to produce a pollen tube/germinate. The pollen tube grows down ( into the tissue of the
syle) from where it derives nutrient; the generative nucleus divides to give rise to two male nuclei and the embryo
sac contains eight nuclei, 2 synegads, ovum two polar nuclei,three antipodal cels, when pollen tube reaches the
micropile the vegetative nucleus/pollen tube nucleus in the pollen tube disintegrates and make nucleus fuses with
the egg cell and form the zygote.
The other male nucleus fuss with the two polar nucei to form a tripod nucleus.
The process involves double fertilization.
b)
Intergument changes into seed coat/testa
Zygote into embryo
Ovary wall into pericarp
Ovary into fruit
Ovule into sedd
Tribloid nucleues into endosperm
Style dries up/fall of leaving a scar/corolla dries up (falls off) stamen dry up ( rej degeration disinergrates)
8. (a) Accommodation is the ability of the eye to focus both far and near objects;
For accommodation of a distant object ciway Muscles realx; creating a tension on suspensory ligametns
/suspensory ligments contract; the lens become flattened otr less conveys; minimizing the refractive power of
lens; bringing light rays from afar object to focus on the retina;
For a accommodation of a neat object aliany muscles contracts relaxing lesion on suspensory
ligametns/sensory ligaments spherical in shape; this increase the refractive power of lens; that brings light
rays from a near object to focus on the retina;
(b)
funnel shaped pinna collects sound waves; and directs them to the auditory meatus/ear drum;
Ear drum vibrates and transforms sound wave into vibrations; the vibrations core transmitted to the ear
ossiclis where they are amplified and transmitted to the oral window. Vibrations front eh oral windo.
Vibrations from the oral window creates pressure waves on the fluid/perlymph in cochlea; movement of fluid
in cochlea causes sensory hairs to be stimulated /torched; generating an impulse; the impulse is transmitted to
the brains via auditory nerve for interpretation on pitch. intensity and direction of sound;