6Name :………………………………………………………… ADM No :…………….................

231/2

BIOLOGY

Paper 2

March 2014

Time: 2 Hours

MOKASA JOINT EVALUATION EXAMINATIONS

Kenya Certificate of Secondary Education

231/2 BIOLOGY Paper 2

March 2014

Time: 2 Hours

Instructions To Candidates

Write your name and index number in the spaces provided above.

Answer all questions in section A in the spaces provided

In section B, answer question 6 (compulsory) and either question 7 or 8 in the space provided after question 8.

For examiners use only

Section Question Maximum Score Candidate’s Score

A 1 8
2 8
3 8
4 8
5 8
B 6 20
7 or 8 20
Total 80

This paper consists of 8 printed pages

Candidates should check the question paper to ensure that all pages are printed as indicated and no

questions are missing

SECTION A (40 MARKS) Answer all the questions in this section.

1. Examine the diagram below carefully and use it to answer the questions that follow.

(a) Name the parts X, Y and Z. (3 marks)

X: Sap vacuole;

Y: Tonoplast;

Z: Chloroplast;

(b) State the main substance which make-up the part labeled W. (1 mark)

Cellulose;

(c) Name the process through which mineral salts move into the structure labeled X. (1 mark)

Active transport; /Diffusion;

(d) Explain what happens to a red blood cell when placed in distilled water. (3 marks)

The cell sap is hypertonic to the distilled water; Water molecules move into the cell by osmosis;
making the cell to swell and eventually burst;

2. (a) What is meant by natural selection? (4 marks)

Organisms with suitable variations in a population survives in a competition for resources; those with

unsuitable variations die out; Through the process suitable genes are passed on to offspring’s; while

unsuitable genes are eliminated from the population;

(b) State four sources of evidences that support the theory of organic evolution. (4 marks)

Fossil records/ Paleontology;

Comparative anatomy;
Comparative embryology;
Geographical distribution;
Cell biology;
Serology;
3. The diagram below shows a set up that was used to demonstrate a certain physiological process.

The glucose solution was boiled and oil added on top of it. The glucose solution was then allowed to
cool before adding yeast suspension.

(a) Identify the physiological process that was being investigated using the above set up. (1 mark)

Fermentation / Alcoholic fermentation / Anaerobic respiration;

(b) Why was glucose boiled during the experiment? (1 mark)

Drive off dissolved oxygen/air; from the glucose solution.

(c) What was the importance of cooling the glucose before adding the yeast suspension? (1 mark)

To avoid denaturing the enzymes in yeast cell / destroy zymase enzymes;

(d) What observation would be made in test tube at the end of the experiment? (1 mark)

Calcium hydroxide forms a white precipitate;

(e) How would the observation made in (d) above be affected if oil was not added on top of the yeast
suspension during the experiment? (1 mark)

Calcium hydroxide remains colourless;

(f) In another investigation, a bird was found to use 10 litres of oxygen to give a respiratory quotient of
0.7 during period of flight. Name the type of food that was being respired by the bird and determine
the amount of carbon (IV) oxide produced during the same flight.

Type of food :- Lipid / fat or Oil; (1 mark)

Volume of carbon (IV) oxide produced. (2 marks)

R.Q = Volumeof CO2 produced; 0.7 = CO2 = 7 litres;

Volume of O2 used 10

4. Pure breed of red cows and pure breed of white bulls were crossed to give F1 calves which had a
mixture of red and white coat known as roan. The F1 were selfed.
(a) Using letter R to represent gene for red colour and W to represent gene for white colour work out
the phenotypic ratio of F2. (4 marks)

Parental Genotype RW R W;

R W R W
Gametes X ;

Fertilization

F2 genotypes
RR RW RW W W;

Phenotypic ratio 1 Red : 2 Roan : 1 White;

Rej. 1 : 2 : 1 only

(b) Work out the genotypic ratio of a cross between F1 offspring and white bull. (3mks)

Parental genotypes RW W W;

R W W W
Gametes X ;

F1 Genotype RW RW WW WW
 Genotype RW : WW

Ratio 1RW : 1WW; Rej. Ratio only.

(c) Comment on the gene(s) controlling the colour of coats in cattle mentioned above. (1mk)

Gene for red colour coat and white colour coat are codominant/ have equal dominance;

acc. Incomplete dominance

5. You are provided with photographs of animals. Study the photographs and the dichotomous key
below to enable you identify the taxonomic group to which each animal belongs.

KEY
1. a) Jointed legs present ………………………………………………………………go to 2
b) Jointed legs absent………………………………………………………………..go to 7
2. a) Three pairs of legs ………………………………………………………………..go to 3
b) More than 3 pairs of legs………………………………………………………….go to 5
3. a) Wings present …………………………………………………………………….go to 4
b) Wings absent………………………………………………………………………Anoplura
4. a) One pair of wings…………………………………………………………………Diptera
b) Two pairs of wings……………………………………………………………Hymenoptera
5. a) Four pairs of legs ………………………………………………………………… Arachnida
b) More than ten pairs of legs ………………………………………………………. go to 6
6. a) One pair of legs in each body segment…………………………………………… Chilopoda
b) Two pairs of legs in each body segment ………………………………………… Diplopoda
7. a) Body partially enclosed in a shell………………………………………………… Mollusca
b) Body surface has spiny projection…………………………………………….Echinodermata
a) Using the key, identify the following organisms to their taxonomic groups. In each case, give the
sequence of steps which you followed in identifying them. (4 marks)
Animal Identity Steps followed
A Arachnida
B Hymenoptera
D Chilopoda
E Anoplura

b) i) Using observable features only, state the class to which the animal labeled A and B on the
photographs above belong (2 marks)
A- Arachnida;
B- Insecta;
State two observable features on B, that enabled you to arrive at that answer in (b (i) above.(2mks)
i) Has three pairs of legs;
ii) Has three body parts;
SECTION B (40 MARKS) Answer question six (6) in the spaces provided (compulsory). Choose
either question 7 or 8 and answer in the space provided after question 8.

6. During an ecological study of a lake, a group of students recorded the following observations.

(i) Planktonic crustaceans feed on planktonic algae;

(ii) Small fish feed on planktonic crustaceans, worms and insect larvae;

(iii) Worms feed on insect larvae;

(iv) A bird species feeds on small fish, planktonic crustaceans, worms and large fish;

(v) Insect larvae feed on planktonic algae;

(vi) Large fish feed on small fish.

(a) From this record of observations, construct a food web. (4 marks)

Bird species Large fish;

Worms Small fish;

Insect larvae Planktonic crustaceans;

Planktoni algae;

(b) From the food web, isolate and write down a food chain that ends with:-

(i) Bird species as a secondary consumer. (1 mark)

Planktonic algae Planktonic crustaceans Bird species;

(ii) Large fish as a tertiary consumer. (1 mark)

Planktonic algae Planktonic crustaceans Small fish Large fish;

Planktonic algae Insect larvae Small fish Large fish;

(c) The biomass of the producers in the lake was found to be greater than that of primary consumers.
Explain this observation. (2 marks)
Energy is lost as it passes from the producers up the trophic levels; Producers require greater
biomass to compensate for the energy losses in order to support consumers depending on it;

(d) Using the food web, identify three pairs of organisms that compete for food in the lake and for
each case, name the food being competed for. (6 marks)
Bird species and small fish; compete for planktonic crustaceans;
Bird species and small fish; compete for worms;
Bird species and large fish; compete for small fish;
Small fish and worms; compete for insect larvae;
Planktonic crustaceans and insect larvae; compete for planktonic algae;
(e) (i) State three ways by which human beings may interfere with this lake ecosystem. (3 marks)

Pollution of water;
Overfishing;
Introduction of new fish species into the lake;
Biological control of mosquitoes;
(i) Explain how each of the ways stated in (e) (i) above may affect life in the lake. (3 marks)

Pollution caused by toxic chemical substances may kill organisms in the lake;
Overfishing depletes some species of fish inceasing the numbers of another species of organism;
Newly introduced fish may clear the other species or increase competition in the lake;
Biological control of mosquitoes may lead to clearance of insect larvae which is food to other
organisms;

7. (a) Describe the digestion of a starchy meal along the human alimentary canal. (13 marks)

- Starch in food is first broken down in the mouth by action of teeth/ chewing; This increases the
surface area exposed enzyme action; saliva contains salivary amylase which breaks down some starch
to maltose; saliva has a slightly alkaline pH which is optimum for the enzyme; The food moves down
to the oespophagus and stomach; where the acidic pH, due presence of dilute Hcl, prevents further
action of salivary amylase; In the duodenum, pancreatic amylase continues digestion of starch to
maltose; Pancreatic amylase is produced in the pancrease; and enters the duodenum through pancreatic
ducts; the acidic chyme is neutralized by the sodium bicarbonate in bile/ pancreatic juice; Maltose
digestion continues in the ileum; whose walls secrete succus entericus/ intestinal juice; which contains
enzyme maltase; which breaks down maltose to glucose; (Max 13 marks)

(b) Describe the proces of urea formation. (7 marks)

-Excess amino acids / proteins; are transported to the liver; In the liver, amino acid molecule is broken
down to amino group (NH2) and carbon compound residue; The amino group (NH2) combines with a
hydrogen atom; to form ammonia; Ammonia is taken to the ornithine cycle; where it combines with
carbon (IV) oxide; to form urea;

8. (a) Describe how gaseous exchange occurs in terrestrial plants. (13 marks)

Gaseous exchange takes place in a spongy mesophyl;

During the day air diffuses into large air spaces of spongy mesophyll; through stomata; the
Carbon (IV) Oxide in the air diffuses into Photosynthetic cells; in solution form; during
photosynthesis Carbon (IV) Oxide is used while oxygen is produced and some is used in
respiration while the rest of oxygen diffuses out of the leaf; through stomata;
 During the night air diffuses into the air spaces (of spongy mesophyll); the air dissolves into film
of moisture; and the oxygen in the air diffuses into cells; and is used in respiration during which
carbon (iv) oxide is produced. The Carbon (iv) Oxide/oxygen diffuses out of the leaf; through
stomata; due to concentration/diffusion gradient;
Gaseous exchange takes place through epidermis (of young leaves and stems); epidermis of the
root carries out gaseous exchange with air in the soil; Some plants have
pneumatophores/breathing roots; (through which gaseous exchange occurs) gaseous exchange
occurs through lenticel (found in older stems); (Max = 13 mrks)

(b) Describe the process of metamorphosis in a grasshopper. (7 marks)

-An adult female lays eggs; The eggs hatch into a nymp; The nymp is an immature adult; It is
wingless; The nymp grows; undergo several moulting; and gradually develops into and adult;

8. (a) Gaseous exchange takes place in a spongy mesophyl

During the day air diffuses into large air spaces of spongy mesophyll; through stomata; the
Carbon (IV) Oxide in the air diffuses into Photosynthetic cells; in solution form; during
photosynthesis Carbon (iv) Oxide is used while oxygen is produced. Oxygen diffuses out of the
leaf; through stomata;
During the night; air diffuses into the air spaces (of spongy mesophyll), the air dissolves into film
of moisture; then oxygen diffuses into the cells; and is used in respiration during which carbon
(iv) oxide is produced, the Carbon (iv) Oxide diffuses out of the leaf; through stomata; due to
concentration/diffusion gradient;
Gaseous exchange takes place through epidermis (of young leaves and stems); epidermis of the
root carries out gaseous exchange with air in the soil; some plants have
pneumatophores/breathing roots; in which gaseous exchange occurs through lenticels; (found in
older stems) (Allow concentration gradient for O2/ CO2 only once.)