231/2 BIOLOGY Paper 2

(THEORY)
2 hours
Name……………………………………………..Index No…………………………/………..
Candidate’s Signature…………………Date……………………………………….…………..

KIMJOGA JOINT EXAM

POST MOCK – February 2022
KENYA CERTIFICATE OF SECONDARY EDUCATION (K.C.S.E)
Instructions to candidates
(a) Write your name and index number in the spaces provided above.
(b) Sign and write the date of examination in the spaces provided above.
(c) This paper consists of two sections; A and B.
(d) Answer all questions in section A in the spaces provided.
(e) In section B answer question 6 (compulsory) and either question 7 or 8 in the spaces
provided after question 8.
(f) This paper consists of 8 printed pages.
(g) Candidates should check the question paper to ascertain that all pages are printed as
indicated and no questions are missing.
(h) Candidates should answer all the questions in English.

For Examiner’s Use Only

Section Question Maximum Candidate’s score
score
A 1 8
2 8
3 8
4 8
5 8
B 6 20
20

Total Score 80

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 SECTION A (40 MARKS)
Answer all questions in this section in the spaces provided.
1. A few blood cells of animal A were introduced into animal B. After a minute reaction
was noted. The blood from animal B was drawn and blood cells filtered out together with
large plasma protein to leave an almost colourless liquid.
(a) (i) Name this colourless liquid (1 mark)
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(ii) A part from the water content, what else does it contain that is significant for this
experiment? (1 mark)
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(b) Blood was drawn from other three animals C, D and E and placed in test tubes. Two
drops of the colourless liquid indicated above were added to each of the three test tubes
and the results were as follows relatively after centrifuge.
B C D E

(i) What is the most likely aim of this experiment? (1mark)

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(ii) What is the name of the particular branch of biology? (1 mark)

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 (iii) Make deduction from the results shown concerning the relative closeness of A to
each of the other three. (1 mark)
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(c) State three evolutionary characteristics that adapt man to his environment. (3 marks)
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2. A person met a lion as he walked along a forest path. His adrenal glands secreted
adrenaline to prepare him to run away.
What was the effect of adrenaline on his?
(a) Circulatory system (5 marks)
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(b) Respiratory system (3 marks)
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 A homozygous plant with rough stem was crossed with another with smooth stem. The
gene for controlling rough stem is dominant over that controlling smooth stem.
(a) Using letter R to represent the gene for rough stem and r to represent the gene for smooth
stem,
(i) Work out the genotype of the F1 generation. (3 marks)
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(ii) State the phenotype of the F1 generation. (1 mark)
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(b) If one of the F1 offspring was crossed with a parent with dominant genes,
(i) Work out the genotypic ratio of the offspring. (1 mark)

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(ii) State the phenotype of the offspring in (b) (i) above (1 mark)
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 (iii) State two causes of mutation (2 marks)
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In an experiment, a group of students set up four glass jars as shown in the
diagram below. Jars A, B and C were maintained at 250C for 7 days, while jar D
was maintained at 00C for the same period of time

A B C D

Bean
seeds Dry cotton
Wet cotton Wet Cotton
0 0
Wet 25 C Wool 25 c
Cotton
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wool C 0c
25o25 wool
25o25
C c 0oC 00c
Wool

(a) What was this set up supposed to investigate? (1 mark)

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(b) Why was pyrogallic acid included in the glass jar A? (1 mark)
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(c) Explain why glass jars C and D were included in this experiment? (3 marks)
C
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D
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(d) What results would you expect in glass jars A and B at the end of the experiment?
(2 marks)
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State one artificial way of breaking seed dormancy (1 mark)

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3. The diagram below represents some stages in mitosis.

(a) Name the stages represented by the diagrams labelled A, B and C. (3 marks)
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(b) State the significance of mitosis to an organism. (3 marks)
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(c) State the advantages of sexual reproduction to the survival of a species. (2 marks)
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SECTION B (40 MARKS)

Answer question 6 (compulsory) and either question 7 or 8 in the spaces provided after
question 8.
6 An experiment was carried out to investigate the nutritional value of two dry powder
animal feeds X and Y over a period of six months. Twenty 5 months old castrated goats
were used. The goats were divided into two equal groups A and B.
The animals in group A were fed on feed X throughout the experiment while those of
group B were fed on feed Y.
The feeds were supplemented with dry hay and water. The average body weight of each
group of goats and the weight of the dry powder feeds were determined and recorded
each month. The faeces produced by each group was dried and weighed and the average
dry faecal output per month was also recorded. The results are as shown below:
GROUP A GROUP B
Months since Average Average Average Average Average Average
commencemen total weight monthly total weight monthly
t of the weight of total dry weight of total dry
experiment of goats feed faecal of goats feed faecal
(Kg) (Kg) output (kg) (kg) output
(Kg) (kg)
0 20.4 26.7 10.5 20.5 35.4 16.5
1 22.5 27.5 10.7 19.4 34.3 17.7
2 24.5 25.8 10.3 19.0 35.2 17.2
3 26.3 18.5 8.8 18.5 36.1 17.5
4 28.0 16.6 7.2 17.1 36.0 16.9
5 29.4 16.3 6.0 16.3 35.8 16.8
6 29.5 16.1 5.6 15.6 35.5 16.6

(a) (i) What is the relationship between the amount of feed and the faecal output? (1 mark)
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(ii) Work out the average increase in weight for the animals in group A during:
The first for months (2 marks)
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 The last two months (2 marks)
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(iii) Account for the average increase in weight for the goats in group A during:
The first four months. (1 mark)
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The last two months. (2 marks)
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(iv) Which of the two feeds is more nutritious? (1 mark)
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Give reasons for your answer. (3 marks)
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(b) State four uses of digested food in the bodies of animals (4 marks)
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(c) State four uses of water in the bodies of animals. (4 marks)
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7 (a) Describe how the digestion of a protein is achieved in the following portions of
alimentary canal
(i) Stomach (4 marks)
(ii) Duodenum (4 marks)
(c) (b) (i) Describe the process of absorption at the root hair to the xylem of the root.
(8 marks)
(ii) Describe how temperature and light intensity affect the rate of transpiration.
(4 marks)

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8 (a) Name the three types of skeletons found in multicellular animals. (3 marks)
(b) Describe how the cervical, lumbar and sacral vertebrae are suited to their functions.
(17 marks)
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231/2 BIOLOGY Paper 2

Marking scheme
Kimjoga Feb. 2022
Section A
1. (a) (i) serum ; 1mk
(ii) Antibodies 1mk
(b) (i) test for antibody – antigen reaction; 1mk
(ii) Serology 1mk
(iii) D is closely related to A followed by E and finally C; or vice versa 1mk
(c) Bipedal gait / upright / erect posture;
Fore limbs used for manipulation; Opposable thumbs;
Use of speech to communicate;
Non-opposable toe in foot for stability on the ground;
High intellectual capacity (important for moral judgement or
rationalize);
1st 3 pts 3mks
2. (a) heart beat increased / cardiac output increased / pulse increased; blood
vessels to the brain and skeletal muscles dilate; and hence more blood to the
tissue / body; to deliver more oxygen and glucose / nutrients; and remove
metabolic waste products; Acc. CO2
5mks
(b) Intercostal muscles and diaphragm muscles contract and relax faster
(maximally); to increase ventilation / breathing rate / rate of respiration; so as to
supply more oxygen and remove excess CO2;
3mks
3. (a) (i) parental phenotype rough stem smooth stem
P. genotype RR X rr ;
Gametes
r rr
R R

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 Rr Rr Rr Rr ;
3mks
(iii) (ii) ALL have rough stem; 1mk

(b) P. Genotypes Rr X RR
Gametes R
R
R r R

RR RR Rr Rr
2 RR : 2Rr; 1mk

(ii) All have rough stem; 1mk

(iii) Chemicals e.g. mustard gas, cyclamate, acridine orange
Radiation (e.g. X-rays, UV, gamma, Beta, radioactive emitions
2mks
4.
a) – Conditions necessary for the germination of seeds/to show that water
Oxygen and warmth are needed for germination; 1mk
b) –To absorb all oxygen from the jar 1mk
c) C- To show that water is needed for germination of seeds
D- To show that warmth is needed for germination 2mks
d) Jar A- Seeds would not germinate
Jar B- Seeds would have germinated 2mks
e) i) Scarification i.e scratching / pricking to make impermeable seed coat
permeable;
ii) Vernalisation- Cold treatment e.g some species of wheat-Burning; 2mks

5. (a) A -Metaphase;
B -Anaphase; Acc. Early anaphase
C -Telophase; Acc. late anaphase 3mks
(b) Retention / maintenance of a constant chromosome number;
It gives rise to new cells / growth;
For binary / multiple fission / asexual reproduction; 2mks

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(c) -improves quality of the species due to gene recombination during meiosis and
fertilization;
-individuals show variation from parents that often lead to hybrid vigour and high
adaptability to environmental conditions.
-Variations provide the basis for evolutionary changes. OWTTE

Section B

6 (a) (i) the more the feed the more the faecal output or vice versa; 1mk

(ii) First 4 months 2.1+2.0+1.8+1.7; = 1.9 kg; or 28.0 – 20.4 = 1.9 kg

4 4

2mks
The last two months
1.4+0.1; = 0.75 (per month or 29.4-28.0 29.5-29.4 or
2 2
29.5 -28.0 = 0.75 2mks
2
(iii) Active / rapid growth hence increase in weight; 1mk

Slow growth; reached maturity; 2mks

(iv) X; Group A gained more weight; on less food; while group least weight on
more food; 3mks
b) Protection since they act as shock absorbers;
Repair of worn tissues;
Growth and development;
Energy production; 4mks
(c) As solvent;
As medium of transport;
Hydrolysis of food;
Maintenance / regulation of temperature / coolant; 4mks
Total 20 marks

7 (a) (i) arrival of food in the stomach stimulates its glands to release/ secrete
gastrin; the hormone stimulates glandular cells to produce gastric juice
constituting of hydrochloric acid, enzymes and mucus; the enzymes are released
in inactive form as pepsinogen and prorennin which are converted into active
form as pepsin and rennin by HCl; to digest proteins into peptides and
polypeptides; 4mks OWTTE

(iii) Arrival of food in the duodenum stimulates its walls to produce hormones
secretin and cholecystokinin into blood stream; the

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 hormones stimulate the liver to release bile and the
pancreas to release pancreatic juice; bile contains salts that
neutralize acidic chyme to provide alkaline medium for action of
trypsin; trypsin breaks down proteins into peptides and amino
acids;
4mks

(c) (i) Absorption of water.

The soil particles are surrounded by film of water where the root hair cells act as
semi-permeable membrane; The cell sap of the root hair is more concentrated than
soil water; and because this difference in concentration water is drawn into root
hair by osmosis; As a result of this cell sap becomes more dilute compared to
adjacent cells of the cortex; therefore water moves into these cells by osmosis (either
from vacuole to vacuole, cytoplasm to cytoplasm or across cell wall). The process
continues from one cortical cell to the next along osmotic gradient until the cells of
endodermis are reached; Because of the presence of casparian strip in the
endodermis; further movement of water into the root xylem is controlled by active
transport; 6mks
Uptake of mineral salts
The root hair cells have cell sap that is highly concentrated than soil solution;
Therefore ions are drawn / taken up into the root hairs against concentration
gradient the process called active transport;
2mks

(ii) the higher the temperature the greater the evaporation of water from the
mesophyll cells and the higher the saturation of intercellular spaces with water
vapour; Also a rise in temperature lowers the relative humidity of air outside
the leaf; leading to steeper diffusion gradient of water molecules from the leaf to
the atmosphere hence increase in transpiration;
2mks
High light intensity increases the internal temperature of the leaf; thus
increasing evaporation rate in the intercellular spaces enhancing high rate of
transpiration; or high light intensity, increases the rate of photosynthesis in guard
cells leading to opening of stomata; thus more water is lost to the surrounding;
2mks

8) -Hydrostatic skeleton
-Exoskeleton
-Endoskeleton 3mks

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 (b) Cervical vertabrae
-Have Vertebraterial canals for passage of (vertebral) artery; Acc. Blood vessels for
artery
-Atlas has (broad) surfaces; for articulation with condyles of skull to permit
nodding
- Axis has odontoid process/ projection of centrum; to permit rotating / turning
movement (with atlas) / act as a pivot for atlas / skull/;
-Branched / forked/ short/ broad transverse processes, for attachment of (neck)
muscles; Has a short reduce neural spine, for attachment of (neck) muscles;
- has wide / larger neural canal; for passage of spinal cord; and has wide neural
arch for protection of spinal cord;
Acc. Zygopophysis / Prezygapophysis/ post-zygapophysis for articulation between
vertebrae;
Lumbar
-Broad/ long/ neural spine; for attachment of (powerful back) muscles; long/ large/
prominent /well development/ transverse processes; for attachment of muscles
(that maintain posture and flex the spine)
-Has metapophysis and hypapophysis / anapophysis projections provide (additional)
surfaces for muscle attachment large/ A big/ large/thick centrums; for support;
-Prezygapophysis/ post/ zygapophysis for articulation between vertebrae
(Acc. Anapophysis for hypapophyses)
Sacral Vertebrae
-Anterior vertebrae have well developed transverse process; which are fused to the
pelvis girdle; (Acc.articulate with pelvic girdle)
-Vertebrae fused, for strength / transmit weight of the stationary animal to the rest
of the body;
-Sacrum has a broad base/ short neural spine; for attachment of (back) muscle;

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8 During thunderstorm/ lightning; energy combines atmospheric nitrogen gas combines
with O2 to form oxides of nitrogen; nitrogen oxides dissolve in water to form nitric
acid and nitrous acid; Acid is deposited in the soil by rain.; Acid combines with
chemical substance to form nitrates which are absorbed by plants.;
Symbiotic bacteria/ such as Rhizobium; which are found in root nodules of
leguminous plants, fix free nitrogen to nitrates.;

Free living bacteria e.g. Clostridium/ Azotobacter fix nitrogen and also non bacteria
fixers sucnh as Nostoc algae/ Chlorella/ Anabaena fix nitrogen to ammonia;
Nitrification; this is the process of oxidising ammonium compounds or nitrites to nitrates;
Ammonia is oxidised into nitrites by nitrifying bacteria e.g. Nitrosomonas and
nitrococcus. Nitrites are converted to nitrate by ntitrifying bacteria; e.g. nitrobacter;
Absorption and assimilation
Plants absorb Nitrates that are used to form plant proteins; Animals feed on plants and
convert plant proteins into animal proteins;
Dead and decomposition
Plants and animals die and are decomposed by saprophytic bacteria/ saprophytes/ fungi;
decomposing plants/ animals/ release ammonia which is covered to nitrites by
nitrosomonas /nitrococcus bacteria;
Nitrites are converted to nitrates; by nitrobacter;
Denitrification
Nitrates in the soil can be converted to free nitrogen through denitrification by some
some denitrifying bacteria such as pseudomonas denitrificans and Thiobacillus
denitrificans.; they utilize oxygen released to carry out respiration;

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