THE UNITED REPUBLIC OF TANZANIA
CERTIFICATE OF SECONDARY EDUCATION EXAMINATION
BIOLOGY 1
033/1
TIME: 3 HOURS YEAR:2026
INSTRUCTIONS
1. This paper consists of Sections A, B and C with a total of 11 questions.
2. Answer ALL questions in Sections A and B.
3. Answer TWO questions from Section C.
4. All working and explanations should be clearly shown where necessary.
5. Write your answers in the spaces provided in your answer booklet.
6. Draw well-labelled diagrams where required.
SECTION A: OBJECTIVE QUESTIONS
16 MARKS
1. Choose the correct answer from the alternatives A, B, C and D.
(i) Which characteristic distinguishes living organisms from non-living things?
A. They occupy space
B. They have mass
C. They respire
D. They have a fixed shape
(ii) Which cell organelle controls most activities of a cell?
A. Ribosome
B. Nucleus
C. Vacuole
D. Mitochondrion
(iii) Which blood vessel carries blood away from the heart?
A. Vein
B. Capillary
C. Artery
D. Venule
(iv) The movement of water molecules through a selectively permeable membrane is called:
A. Diffusion
B. Osmosis
C. Active transport
D. Transpiration
(v) Which structure is mainly responsible for gaseous exchange in the lungs?
A. Trachea
B. Bronchus
C. Alveolus
D. Diaphragm
(vi) Which organ removes urea from the blood?
A. Heart
B. Kidney
C. Lung
D. Pancreas
(vii) Which hormone is mainly responsible for lowering blood glucose concentration?
A. Adrenaline
B. Insulin
C. Thyroxine
D. Oestrogen
(viii) A cross between two heterozygous tall pea plants can produce:
A. Only tall plants
B. Only short plants
C. Tall and short plants
D. Only heterozygous plants
(ix) Which process produces two genetically identical daughter cells?
A. Meiosis
B. Fertilisation
C. Mitosis
D. Mutation
(x) Which of the following is an example of a sexually transmitted infection?
A. Malaria
B. Tuberculosis
C. Gonorrhoea
D. Cholera
2. Match the items in List A with the correct responses in List B.
LIST A
(i) Mitochondrion
(ii) Chlorophyll
(iii) Platelets
(iv) Nephron
(v) Synapse
(vi) Ovary
LIST B
A. Site of impulse transmission between neurons
B. Produces female gametes
C. Responsible for blood clotting
D. Site of aerobic respiration
E. Functional unit of the kidney
F. Absorbs light energy during photosynthesis
G. Produces digestive enzymes
H. Carries oxygen in blood
SECTION B: SHORT ANSWER QUESTIONS
54 MARKS
3. (a) Define Biology.
(b) State four branches of Biology and give one area studied under each branch.
(c) Explain three importance of studying Biology in everyday life.
4. A student investigated the effect of temperature on the activity of an enzyme. The following observations were obtained:
Temperature (°C): 10, 20, 30, 40, 50, 60
Enzyme activity: 2, 5, 9, 14, 7, 1
(a) Identify the independent variable.
(b) Identify the dependent variable.
(c) At what temperature was enzyme activity highest?
(d) Describe the trend shown by the results.
(e) Explain why enzyme activity decreased at very high temperature.
(f) State two factors, apart from temperature, that can affect enzyme activity.
5. (a) Distinguish between diffusion and active transport.
(b) Give three differences between arteries and veins.
(c) Explain two adaptations of red blood cells for transporting oxygen.
6. A farmer grows maize continuously on the same piece of land. After several years, the maize yield decreases.
(a) Give two possible biological reasons for the decrease.
(b) Explain three methods the farmer can use to maintain soil fertility.
(c) State two environmental problems that may result from excessive use of chemical fertilisers.
7. (a) What is gaseous exchange?
(b) Explain how gaseous exchange takes place in the alveoli.
(c) State four adaptations of alveoli for efficient gaseous exchange.
(d) Give two differences between aerobic and anaerobic respiration.
8. A person accidentally touches a very hot metal object and immediately withdraws the hand.
(a) Name the type of response involved.
(b) Identify the receptor involved.
(c) State the pathway followed by the nerve impulse.
(d) Explain the role of the spinal cord in this response.
(e) State two advantages of reflex actions.
SECTION C: ESSAY QUESTIONS
30 MARKS
Answer TWO questions only.
9. Nutrition is essential for growth, repair and maintenance of the body.
(a) Define a balanced diet.
(b) Describe the functions of:
(i) carbohydrates
(ii) proteins
(iii) fats and oils
(iv) vitamins
(v) mineral salts
(vi) water
(c) Explain four problems that may result from poor nutrition.
10. Reproduction ensures continuity of life.
(a) Distinguish between sexual and asexual reproduction.
(b) Describe the process of fertilisation in humans.
(c) Explain the importance of the following structures in the female reproductive system:
(i) ovary
(ii) oviduct
(iii) uterus
(iv) cervix
(v) vagina
(d) State three ways of preventing unwanted pregnancy.
11. Genetics explains how characteristics are transmitted from parents to offspring.
A tall pea plant with genotype Tt is crossed with another tall pea plant with genotype Tt.
(a) State the meaning of:
(i) gene
(ii) allele
(iii) genotype
(iv) phenotype
(b) Construct a genetic cross showing the possible genotypes of the offspring.
(c) State the phenotypic ratio obtained.
(d) Calculate the probability of obtaining a short plant.
(e) Explain the difference between inherited variation and environmental variation.
(f) Give two examples of inherited characteristics in humans.
CSEE BIOLOGY 033/1
THEORY — MARKING SCHEME
TOTAL: 100 MARKS
SECTION A: OBJECTIVE QUESTIONS
16 MARKS
1. Multiple Choice — 10 marks
Each correct answer = 1 mark.
(i) C — Respire
(ii) B — Nucleus
(iii) C — Artery
(iv) B — Osmosis
(v) C — Alveolus
(vi) B — Kidney
(vii) B — Insulin
(viii) C — Tall and short plants
(ix) C — Mitosis
(x) C — Gonorrhoea
2. Matching Items — 6 marks
Each correct answer = 1 mark.
(i) D — Site of aerobic respiration
(ii) F — Absorbs light energy during photosynthesis
(iii) C — Responsible for blood clotting
(iv) E — Functional unit of the kidney
(v) A — Site of impulse transmission between neurons
(vi) B — Produces female gametes
SECTION B: SHORT ANSWER QUESTIONS
54 MARKS
3. INTRODUCTION TO BIOLOGY — 9 MARKS
(a) Biology is the scientific study of living organisms and their interactions with one another and their environment. — 1 mark
(b) Any four:
(i) Botany — study of plants. — 1 mark
(ii) Zoology — study of animals. — 1 mark
(iii) Microbiology — study of microorganisms. — 1 mark
(iv) Ecology — study of organisms and their environment. — 1 mark
(c) Any three:
(i) Helps in treatment and prevention of diseases. — 1 mark
(ii) Improves agricultural production. — 1 mark
(iii) Helps in conservation of the environment. — 1 mark
(iv) Provides knowledge about nutrition and health. — 1 mark
(v) Helps in understanding human reproduction. — 1 mark
Maximum = 9 marks
4. ENZYMES AND EXPERIMENTAL SKILLS — 9 MARKS
(a) Independent variable:
Temperature. — 1 mark
(b) Dependent variable:
Enzyme activity. — 1 mark
(c) Highest enzyme activity:
40°C. — 1 mark
(d) Trend:
Enzyme activity increases as temperature rises from 10°C to 40°C, then decreases as temperature increases above 40°C. — 2 marks
(e) At very high temperature:
High temperature denatures the enzyme, changing the shape of its active site and reducing enzyme activity. — 2 marks
(f) Any two:
(i) pH
(ii) Substrate concentration
(iii) Enzyme concentration
(iv) Presence of inhibitors
(v) Presence of activators
2 × 1 = 2 marks
Total = 9 marks
5. TRANSPORT IN LIVING ORGANISMS — 9 MARKS
(a) Diffusion and active transport:
Diffusion:
Movement of particles from a region of higher concentration to a region of lower concentration. — 1 mark
Active transport:
Movement of substances from a region of lower concentration to a region of higher concentration using energy. — 1 mark
(b) Differences between arteries and veins:
(i) Arteries carry blood away from the heart, while veins carry blood towards the heart. — 1 mark
(ii) Arteries have thick muscular walls, while veins have thinner walls. — 1 mark
(iii) Arteries generally have no valves, while veins contain valves. — 1 mark
(c) Adaptations of red blood cells:
(i) They contain haemoglobin which combines with oxygen. — 1 mark
(ii) They have a biconcave shape, providing a large surface area for gas exchange. — 1 mark
(iii) They lack a nucleus, providing more space for haemoglobin. — 1 mark
Maximum = 9 marks
6. SOIL FERTILITY AND AGRICULTURE — 9 MARKS
(a) Possible reasons:
(i) Depletion of mineral nutrients from the soil. — 1 mark
(ii) Continuous cultivation of the same crop removes particular nutrients. — 1 mark
(b) Methods of maintaining soil fertility:
(i) Crop rotation — different crops are grown in successive seasons to maintain soil nutrients. — 1 mark
(ii) Application of organic manure/compost — adds nutrients and improves soil structure. — 1 mark
(iii) Planting leguminous crops — nitrogen-fixing bacteria increase available nitrogen. — 1 mark
(iv) Appropriate use of fertilisers. — 1 mark
Any three = 3 marks
(c) Environmental problems:
(i) Water pollution through fertiliser runoff. — 1 mark
(ii) Eutrophication of water bodies. — 1 mark
(iii) Soil degradation/acidification. — 1 mark
(iv) Harm to aquatic organisms. — 1 mark
Any two = 2 marks
Total = 7 marks
NOTE: To maintain the intended 9-mark allocation, award up to 4 marks in (b) and up to 3 marks in (c), where justified by the student's answers.
7. GASEOUS EXCHANGE AND RESPIRATION — 9 MARKS
(a) Gaseous exchange:
The process by which oxygen enters an organism and carbon dioxide leaves the organism. — 1 mark
(b) Gaseous exchange in alveoli:
Oxygen diffuses from the air in the alveoli into the blood because its concentration is higher in the alveoli. Carbon dioxide diffuses from the blood into the alveoli because its concentration is higher in the blood. — 2 marks
(c) Adaptations of alveoli:
(i) Large number of alveoli provides a large surface area. — 1 mark
(ii) Walls are very thin, approximately one cell thick. — 1 mark
(iii) They have a rich blood supply. — 1 mark
(iv) Moist surface allows gases to dissolve. — 1 mark
Any four = 4 marks
(d) Differences:
(i) Aerobic respiration requires oxygen, whereas anaerobic respiration occurs without oxygen. — 1 mark
(ii) Aerobic respiration releases more energy, whereas anaerobic respiration releases less energy. — 1 mark
Total = 9 marks
8. COORDINATION AND REFLEX ACTION — 9 MARKS
(a) Type of response:
Reflex action. — 1 mark
(b) Receptor:
Pain/temperature receptors in the skin. — 1 mark
(c) Pathway:
Receptor → sensory neurone → relay neurone in spinal cord → motor neurone → effector. — 3 marks
(d) Role of spinal cord:
It receives the sensory impulse and coordinates a rapid response by transmitting impulses through the appropriate neurones to the muscles. — 2 marks
(e) Advantages:
(i) Produces a rapid response. — 1 mark
(ii) Protects the body from injury/danger. — 1 mark
Total = 9 marks
SECTION C: ESSAY QUESTIONS
30 MARKS
Candidates answer TWO questions.
Each question = 15 marks.
9. NUTRITION — 15 MARKS
(a) Balanced diet:
A diet containing all essential nutrients in the correct proportions according to the body's requirements. — 2 marks
(b) Functions:
(i) Carbohydrates:
Provide energy for body activities. — 1 mark
(ii) Proteins:
Required for growth and repair of body tissues. — 1 mark
(iii) Fats and oils:
Provide concentrated energy and help in insulation and protection of organs. — 1 mark
(iv) Vitamins:
Needed in small amounts for normal body functions and prevention of deficiency diseases. — 1 mark
(v) Mineral salts:
Required for body processes such as formation of bones, blood and proper functioning of nerves. — 1 mark
(vi) Water:
Acts as a solvent, transports substances and helps regulate body temperature. — 1 mark
(c) Problems of poor nutrition:
Any four:
(i) Malnutrition. — 1 mark
(ii) Obesity. — 1 mark
(iii) Anaemia. — 1 mark
(iv) Stunted growth. — 1 mark
(v) Kwashiorkor. — 1 mark
(vi) Marasmus. — 1 mark
(vii) Weak immunity. — 1 mark
Maximum = 7 marks
Total = 15 marks
10. REPRODUCTION — 15 MARKS
(a) Differences:
Sexual reproduction:
Involves fusion of male and female gametes. — 1 mark
Asexual reproduction:
Involves reproduction without fusion of gametes and usually involves one parent. — 1 mark
(b) Fertilisation:
A sperm cell fuses with an ovum, normally in the oviduct, forming a zygote. The zygote undergoes repeated mitotic divisions and develops into an embryo. — 3 marks
(c) Functions of female reproductive structures:
(i) Ovary:
Produces ova and female reproductive hormones. — 1 mark
(ii) Oviduct:
Receives the ovum and is the usual site of fertilisation; transports the ovum/zygote towards the uterus. — 2 marks
(iii) Uterus:
Site where the embryo implants and develops. — 1 mark
(iv) Cervix:
Controls the opening between the uterus and vagina and helps retain the foetus during pregnancy. — 1 mark
(v) Vagina:
Receives sperm during sexual intercourse and serves as the birth canal. — 1 mark
(d) Any three methods:
(i) Abstinence. — 1 mark
(ii) Condoms. — 1 mark
(iii) Hormonal contraceptives. — 1 mark
(iv) Intrauterine devices. — 1 mark
(v) Other medically recognised contraceptive methods. — 1 mark
Maximum = 3 marks
Total = 15 marks
11. GENETICS — 15 MARKS
(a) Definitions:
(i) Gene:
A unit of heredity responsible for a particular characteristic. — 1 mark
(ii) Allele:
An alternative form of a gene. — 1 mark
(iii) Genotype:
The genetic constitution of an organism. — 1 mark
(iv) Phenotype:
The observable characteristics of an organism. — 1 mark
(b) Genetic cross:
Parents:
Tt × Tt
Gametes:
T, t × T, t
Punnett square:
T t
----------------
T | TT | Tt |
----------------
t | Tt | tt |
----------------
Offspring:
TT, Tt, Tt, tt — 4 marks
(c) Phenotypic ratio:
3 tall : 1 short. — 1 mark
(d) Probability of obtaining a short plant:
1/4 or 25%. — 1 mark
(e) Variation:
Inherited variation:
Differences caused by genetic differences passed from parents to offspring. — 1 mark
Environmental variation:
Differences caused mainly by environmental conditions rather than inherited genetic differences. — 1 mark
(f) Examples of inherited characteristics:
Any two:
(i) Blood group
(ii) Eye colour
(iii) Natural hair characteristics
(iv) Ability to roll the tongue
(v) Certain inherited disorders
2 × 1 = 2 marks
Total = 15 marks
