BIOLOGY 2006 PNEB (PUNTLAND NATIONAL EXAMINATION BOARD)

1. Name .............................................................School .......................................…………………
Roll Number........................………………….
Puntland State of Somalia
Ministry of Education
Puntand National Examination Board
Form IV Biology Examination
July 2006
2½ hours
PLUS 10 MINUTES before the exam for reading through the paper
TOTAL TIME 2 hours 40 minutes
INSTRUCTIONS TO CANDIDATES
This paper consists of 19 PRINTED pages.
Count them now. Inform the invigilator if there are any missing.
This paper consists of two parts:
Section A: 10 marks
Section B: 90 marks
TOTAL 100 marks
• Answer ALL questions.
• All answers must be written on this paper in the spaces provided
immediately after each question. ONLY WRITE ON THIS EXAM PAPER.
• ALL WORKING SHOULD BE CLEARLY SHOWN IN THE SPACE AFTER THE
QUESTION.
• Rough work can be done on page 2. This will not be marked
• NO extra paper is allowed.
• NO CALCULATORS are allowed.
• If you make a mistake cross out the incorrect answer clearly and write your
correct answer.

2. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
USE THIS PAPER FOR ROUGH WORK, IT WILL NOT BE MARKED.
2

3. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
Sections:- A B
Question
Num
ber:-
1 2 3 4 5 6 7 8
Possible
Marks:-
10 12 10 15 12 10 20 11
Actual
marks:-
Section A Multiple Choice Questions (10 marks)
Instructions: For each question in this section, circle the correct answer. If you change your
mind, cross out the answer you have wrongly chosen and clearly circle the correct answer.
If the examiner thinks you have marked two answers you will not receive a mark for that
question.
For each question there is only one correct answer. Each question is worth one mark.
1. All of the following diseases are caused by bacteria, except
A AIDS B tuberculosis (TB)
C syphilis D gonorrhoea?
2. A gene can be defined as:
A a small circular piece of DNA found in bacteria.
B an enzyme that joins DNA sections.
C the bonding of DNA fragments from a donor cell to the plastids.
D a section of DNA coding for a specific protein.
3. Which of the following are NOT true cells
A eukaryotic cells B bacteria
C viruses D prokaryotic cells?
4. Where are pollen grains produced
A stigma B carpel
C ovary D anther?
3

4. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
5. If a diploid tomato cell with 24 chromosomes undergoes meiosis, how many chromosomes
will each of the gametes have produced.
A 6 B 12
C 24 D 48?
6. Implantation of blastocyst normally takes place in the:
A Epithelium of the uterus B Ovary
C Fallopian tube D Uterine wall
7. Transpiration from the leaves of a plant is greatest on days that are
A cold and still B cold and windy
C warm and windy D warm and still
8. The elbow joint is an example of a
A ball and socket joint B peg and socket joint
C hinge joint D sliding joint
9. Which of the following animals belongs to the phylum annelida?
A Centipede B Roundworm
C Flatworm D Earthworm
10. A flower appears in two forms, red and white. The allele for red is dominant.
If two heterozygous red flowers are crossed and the resulting seeds are grown the
flowers will be:
4

5. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
A all red B about 75% red and 25% white
C about 50% red and 50% white D all white
Section B
Structured Questions
Instruction: Answer all the questions below as fully as possible. You must write all the
answers in the spaces provided on the paper. The marks awarded for each section are
shown.
Question 2
Enzymes control metabolic reactions in the body and the rate (speed) at which they occur.
(a) What name is given to metabolic reactions that synthesise (make) new molecules?
..........................................................................................................................................(1)
(b) Does building new molecules take or give energy overall?
..........................................................................................................................................(1)
(c) Enzymes are termed biological catalysts. What does the term catalyst mean?
..........................................................................................................................................
........................................................................................................................................ (2)
(d) The following diagram shows how an enzyme reacts. Complete it to give the missing
names of the shapes (2)
5

6. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
(e) Explain what is meant by the lock and key theory to describe how an enzyme works
.........................................................................................................................................
.........................................................................................................................................
..........................................................................................................................................(2)
(f) Name the reactions which are catalysed the following enzymes:-
[i] Amylase .............................................................……..........................................(1)
[ii] Lipase ..............………........................................................................................(1)
(g) Where in the human body are these two found?
[i] Amylase ..............................................................................................................
[ii] Lipase ...............................................................................................................(2)
6
Enzyme substrate Enzyme-substrate complex enzyme products
+ +→→

7. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
Total 12 marks
Question 3.
Give reasons for each of the following: (3)
(a) A constant body temperature of 37o
C is maintained in mammals
...................................................................................................................................................
...................................................................................................................................................
..................................................................................................................................................
..............................................................................................................................…................
(b) Low blood sugar level is harmful to the body (4)
..................................................................................................................................................
7

8. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
..................................................................................................................................................
..................................................................................................................................................
...........................................................................................................….....................................
(c) State the main three differences between the composition of maternal blood entering the
placenta and the maternal blood leaving the placenta. (3)
..................................................................................................................................................
..................................................................................................................................................
..................................................................................................................................................
Total 10 Marks
Question 4
Study the food web below and answer the questions.
lion
cheetah
fox
guinea fowl
grasshopper rat rabbit
8

9. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
grass
(a) Construct the longest food chain from the food web
..................................................................................................................................................
(b) Name the organisms found in the third trophic level
......................................................................................................................................... (1)
(c) If an outbreak of disease destroys 55% of the guinea fowl population
[i] what would happen to the population of cheetah?
......................................................................................................................................... (1)
[ii] Explain your answer to part [i]
.............................................................................................................................................
......................................................................................................................................... (2)
(d) In a study done by a group of students to estimate the density and total population
of water -melon seedlings in a field, the following information was obtained:-
Water-melon count in five rows = 6, 7, 9, 11 and 12. (5 rows occupy 1 m2
)
Size of the field = width 20 meters, length 50 meters
Calculate the approximate density and total population of water-melon seedlings in the field
Density =
9

10. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
Area of a field =
Total population =
Don’t forget to put the units in each case
(6)
(e) Explain the difference between pyramid of numbers and pyramid of biomass? (2)
pyramid of numbers
.............................................................................................................................................
pyramid of biomass
.............................................................................................................................................
(f) The table below shows a pyramid of energy
Tertiary consumers, e.g. top carnivores 1.8 kJ m-2
yr-1
Secondary consumers, e.g. carnivores 200 kJ m-2
yr-1
Primary consumers, e.g. herbivores 2400 kJ m-2
yr-1
Producers 144000 kJ m-2
yr-1
Energy is expressed as kJ m-2
yr-1
. What does this mean? (2)
.............................................................................................................................................
Total 15 marks.
Question 5
The diagram shows the structure of an amino acid molecule:-
10

11. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
(a) What does the R represent?
.......................................................................................................................…....……(1)
(b) What name is given to a compound formed when more than 3, but less than 50 amino
acids join together?
.......................................................................................................................…....……(1)
(c) What name is given to a compound formed when more than 50 amino acids join together?
.......................................................................................................................…....……(1)
(d) Draw a diagram to show 2 amino acids joining together by water loss (condensation.)
Your diagram should give the name of the link (bond) formed between the acids (3)
11

12. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
(e) The diagram shows a nucleotide
[i] What name is given to any sugar containing 5 carbon atoms?
.......................................................................................................................…....……(1)
[ii] Give two types of compound which contain nucleotides.
.......................................................................................................................…....……(2)
[ii] There are 5 possible bases in a nucleotide. Name any one.
.......................................................................................................................…....……(1)
(f) Most lipids (fats, oils or waxes) are made from compounds called triglycerides.
Triglycerides are made from glycerol and fatty acids.
[i] What name is given to the bond that joins a fatty acid to glycerol?
12
Phosphate
Base
Sugar

13. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
.......................................................................................................................…....……(1)
[ii] What type of reaction breaks up lipids into fatty acids and glycerol?
.......................................................................................................................…....……(1)
Total 12 marks
Question 6
(a) Explain the following terms:
(i) Excretion : ………………………………………………………………..……….… (1)
(ii) Secretion: ........................................................................................................(1)
.......................................................................................................................…....……(1)
(b) The following diagram shows a human nephron.
13

14. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
A distal convoluted tubule B glomerulus C Bowman’s capsule
D efferent arteriole E Loop of Henlé
(i) In which organ of the body are nephrons to be found?
.......................................................................................................................…....……(1)
(ii) Name either the artery or the vein that serves this organ.
.......................................................................................................................…....……(1)
(d) The following table shows the concentration of some substances in the blood plasma,
the liquid passing from the Bowman’s capsule and the urine.
Substance % in blood
plasma
% in liquid passing from
Bowman’s capsule
% in
urine
chloride ions 0.4 0.4 0.6
glucose 0.1 0.1 0
protein 7.0 0 0
sodium ions 0.3 0.3 0.35
urea 0.03 0.03 2.0
water 90-93 90-93 95
Use the diagram and the information in the table to explain as fully as you can what takes
place in:
(i) Bowman’s capsule (C) (3)
14

15. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
.......................................................................................................................……………....……
.......................................................................................................................……………....……
.......................................................................................................................……………....……
(ii) The convoluted part of the tubule immediately beneath Bowman’s capsule (A). (3)
.......................................................................................................................……………....……
.......................................................................................................................……………....……
.......................................................................................................................……………....……
Total 10 marks
Question 7
The following question is about respiration.
(a) What are the properties of a respiratory surface?
.......................................................................................................................……………....……
15

16. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
.......................................................................................................................……………....……
.......................................................................................................................……………....……
.......................................................................................................................……………....……
.....................................................................................................................................…..(6)
(b) For each of the following animals name the structures that are the site for gaseous
exchange.
Fish: ……………………………………………………………………………….(1)
Mammals: ……………………………………………………………………………….(1)
Insects: ……………………………………………………………………………….(1)
Amoeba: ……………………………………………………………………………….(1)
Crocodile: …………………………………………….………………………………….(1)
16

17. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
(c) Name the process by which a 6 carbon sugar is converted to pyruvic acid
......................................................................................................................................... (1)
(d) Aerobic respiration can be summed up by the following biochemical equation:-
C6H12O6 + 6O2 → 6CO2 + 6H2O + 2880 kJ
[i] Which part of the equation shows energy release and what units is it measured in?
......…………………………………………………………………………………………….…(2)
[ii] Does the process take place in a single step or many steps (multi-step)?
......…………………………………………………………………………………..…………..(1)
(e) ATP is found as an energy carrier in all cells and releases energy by the following
equation:-
.
ATP → ADP + P + Energy
[i] What are the names of the molecules ATP and ADP ?
......…………………………………………………………………………………..…………..(1)
......…………………………………………………………………………………..…………..(1)
[ii] Does the process take place in a single step or multi-steps (many steps)?
17

18. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
......…………………………………………………………………………………..…………..(1)
(f) The energy released is used to transmit nervous impulses. Name 2 other uses of the
released energy.
......…………………………………………………………………………………..…………..(1)
......…………………………………………………………………………………..…………..(1)
Total 20 marks
Question 8
The following question is about photosynthesis.
(a) Photosynthesis takes place in 2 stages, the light dependent stage and the light
independent stage. In which part of the chloroplasts does each take place?
Light Dependant Stage……….…………………………………………………………………(1)
Light Independant Stage....……………………………………………………..………..….…(1)
(b) During the light dependent stage water is split by light.
[i] What name is given to this process? …………………..……….……..………..….…(1)
[ii] Complete the given equation for this process
H2O → H+
+ ½O2 + 2 (2)
(c) During the light independent stage carbon dioxide is converted to carbohydrate with ATP.
18

19. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
What other important biochemical is used in this process?
.....………………………………………………………….………………………………..……...(1)
(d) Apart from glucose name 3 other useful final products of photosynthesis.
.....………………………………………………………….…………….……………………..……...
.....………………………………………………………….…………….……………………..……...
......…………………………………………………………………………………………..…….(3)
(e) The rate (speed) at that photosynthesis takes place depends on the quality and quantity
of light. Name 2 other factors that change the rate.
.....………………………………………………………….………………………………..……...(1)
.....………………………………………………………….………………………………..……...(1)
Total 11 marks
19

20. Puntland National Examination Board Secondary School Form Four Examination
Puntland Certificate of Education Biology Examination July 2006
20