Paper type: option A
BIO 001: GENERAL BIOLOGY
1. (a) Briefly state ONE function each of the cell organelles listed below:
- i. Nucleus
- ii. Plasma membrane
- iii. Mitochondria
- iv. Ribosome
- v. Golgi apparatus
- vi. Rough Endoplasmic Reticulum [3 Marks]
(b) Itemize THREE differences between DNA and RNA. [3 Marks]
(c)
- i. List FOUR characteristics of enzymes. [2 Marks]
- ii. List FOUR evidences of evolution. [2 Marks]
2. (a)
- i. Define ecological succession. [1 Mark]
- ii. Define food chain. [1 Mark]
(b) State TWO reasons for the choice of garden pea plant by Gregor Mendel for his experiment in genetics. [2 Marks]
(c) In an investigation into breathing rates, a university student had this number of per minutes recorded when exercising at different levels. The procedure was repeated three times and the results are shown in the table below.
| Exercise | 1st Trial | 2nd Trial | 3rd Trial | Average |
|---|---|---|---|---|
| Bending sideways | 13 | 12 | 14 | 13 |
| Walking | 23 | 25 | 24 | 24 |
| Jogging | 30 | 32 | 34 | 32 |
| Running | 55 | 51 | 53 | 53 |
- i. Calculate the percentage change in the average breathing rates when running compared with bending sideways. [3 Marks]
- ii. What is the relationship between the level of exercise and breathing rates? [1 Mark]
- iii. With ONE example each, state FOUR different forms in which cell exists. [2 Marks]
BIO 002: MICROBIOLOGY
3. (a) Describe the process that leads to the production of human antibodies. [5 Marks]
(b) Explain the following microbial interactions with given examples:
- i. Mutualism
- ii. Amensalism
- iii. Proto-cooperation [3 Marks]
(c) The oil immersion objective lens of a light microscope was used to observe bacterial cells of 10μm. Calculate:
- i. the total magnification of the image [2 Marks]
- ii. the image size
4. (a) Define the following terms:
- i. Viroids
- ii. Prions
- iii. Virions
- iv. Capsomeres [2 Marks]
(b) Highlight and state the functions of the dyes and chemicals used in the Gram Staining procedure. [4 Marks]
(c)
- i. Describe the steps of binary fission in bacteria. [3 Marks]
- ii. State the function of any TWO enzymes used in genetic engineering. [1 Mark]
BIO 003: BOTANY
5. (a) Distinguish the following pair of terms:
- i. Parasites and Saprophytes
- ii. Species and Genus
- iii. Nomenclature and Classification
- iv. Fruits and Seeds [4 Marks]
(b) In a tabular form, differentiate between pteridophytes and bryophytes. [4 Marks]
(c)
- i. Define cross pollination. [1 Mark]
- ii. What is vegetative propagation? [1 Mark]
6. (a) Tabulate FOUR differences between monocotyledous and dicotyledous plants. [4 Marks]
(b) Define the following terms:
- i. Parthenocarpy
- ii. Fertilization
- iii. True fruits
- iv. Dehiscent fruits
- v. Anemophilous flowers
- vi. Entomophilous flowers [6 Marks]
BIO 004: ZOOLOGY
7. (a) State FIVE classes of the Phylum Echinodermata with one example each. [5 Marks]
(b) Highlight the steps involved in the process of blood clotting. [5 Marks]
8. (a) State FIVE functions of the mammalian liver. [5 Marks]
(b) Explain briefly how the skeleton is important to humans with specific examples. [5 Marks]
Solutions
BIO 001: GENERAL BIOLOGY
Question 1
(a) Functions of Cell Organelles:
| Organelle | Function |
|---|---|
| Nucleus | Controls all cell activities and contains genetic material (DNA) |
| Plasma membrane | Regulates movement of substances in and out of the cell (selective permeability) |
| Mitochondria | Site of aerobic respiration; produces energy (ATP) for the cell |
| Ribosome | Site of protein synthesis |
| Golgi apparatus | Packages, modifies and secretes proteins and lipids out of the cell |
| Rough Endoplasmic Reticulum | Transports proteins synthesized by ribosomes; involved in protein processing |
| (b) THREE Differences between DNA and RNA: | |
| Feature | DNA |
| --- | --- |
| Sugar | Deoxyribose |
| Bases | Adenine, Thymine, Guanine, Cytosine |
| Strands | Double-stranded |
| (c) | |
| i. FOUR Characteristics of Enzymes: |
- They are biological catalysts — they speed up chemical reactions without being consumed
- They are specific — each enzyme acts on a particular substrate (lock and key model)
- They are sensitive to temperature and pH — each enzyme has an optimum temperature and pH
- They are reusable — they are not permanently altered after a reaction
ii. FOUR Evidences of Evolution: - Fossil records — preserved remains show gradual changes in organisms over time
- Comparative anatomy — homologous structures (e.g. human arm and whale flipper) suggest common ancestry
- Comparative embryology — embryos of different vertebrates look similar at early stages
- Biochemical evidence — similar DNA and proteins across species suggest evolutionary relationships
Question 2
(a)
i. Ecological Succession:
Ecological succession is the gradual and sequential process by which communities of organisms change and develop over time in a given area, eventually leading to a stable climax community.
ii. Food Chain:
A food chain is a linear sequence showing the transfer of energy and nutrients from one organism to another, beginning with a producer and ending with a top consumer. Example: Grass → Grasshopper → Frog → Snake → Eagle
(b) TWO Reasons Mendel Chose Garden Pea Plant (Pisum sativum):
- It has clearly contrasting characteristics (e.g. tall vs. dwarf, round vs. wrinkled seeds) that are easy to observe and record
- It has a short generation time and produces many offspring, making statistical analysis reliable
(c)
i. Percentage Change in Breathing Rate (Running vs. Bending sideways):
- Average for Running = 53 breaths/min
- Average for Bending sideways = 13 breaths/min
$$\text{Percentage change} = \frac{53 - 13}{13} \times 100 = \frac{40}{13} \times 100 = \textbf{307.7\%}$$
-
The breathing rate increased by approximately 307.7% when running compared to bending sideways.
ii. Relationship between Level of Exercise and Breathing Rates:
There is a direct/positive relationship — as the level of exercise increases, the breathing rate also increases. This is because more intense exercise demands more oxygen and produces more CO₂, stimulating faster breathing.
iii. FOUR Forms in Which a Cell Exists (with examples):
- Unicellular — the organism consists of a single cell e.g. Amoeba
- Colonial — cells live together but each is independent e.g. Volvox
- Filamentous — cells arranged in thread-like chains e.g. Spirogyra
- Multicellular — many cells organized into tissues and organs e.g. Human beings
BIO 002: MICROBIOLOGY
Question 3
(a) Process Leading to Production of Human Antibodies (Humoral Immune Response):
- An antigen (foreign substance, e.g. a bacterium) enters the body
- Macrophages engulf and process the antigen, then present it on their surface — these are called Antigen Presenting Cells (APCs)
- Helper T-cells recognize the presented antigen and become activated
- Activated Helper T-cells release lymphokines/cytokines that stimulate B-lymphocytes
- B-lymphocytes proliferate and differentiate into plasma cells and memory B-cells
- Plasma cells produce large quantities of specific antibodies (immunoglobulins)
- Antibodies bind to the specific antigen, neutralizing or marking it for destruction
- Memory B-cells remain in the body for a faster response upon future exposure to the same antigen
(b) Microbial Interactions:
i. Mutualism:
A relationship where both organisms benefit from each other.
Example: Rhizobium bacteria live in the root nodules of leguminous plants. The bacteria fix atmospheric nitrogen for the plant, while the plant provides carbohydrates and shelter for the bacteria.
ii. Amensalism:
A relationship where one organism is harmed or inhibited while the other is unaffected.
Example: Penicillium mold produces penicillin which kills or inhibits nearby bacteria, while the mold itself is unaffected.
iii. Proto-cooperation:
A relationship where both organisms benefit from each other but the association is not obligatory (not essential for survival).
Example: Certain birds pick ticks off the backs of cattle. The birds get food; the cattle are relieved of parasites, but both can survive without each other.
(c) Microscope Calculations:
Given:
- Actual size of bacterial cell = 10 μm
- Oil immersion objective lens = ×100
- Eyepiece lens (standard) = ×10
**i. Total Magnification:**
$$\text{Total magnification} = \text{Eyepiece} \times \text{Objective} = 10 \times 100 = \textbf{×1000}$$
**ii. Image Size:**
$$\text{Image size} = \text{Actual size} \times \text{Magnification} = 10\,\mu m \times 1000 = \textbf{10,000\,\mu m} = \textbf{10\,mm}$$
Question 4
(a) Definitions:
i. Viroids:
Viroids are the smallest known infectious agents consisting of a short, single-stranded, circular RNA molecule with no protein coat. They infect plants only. Example: Potato spindle tuber viroid.
ii. Prions:
Prions are infectious, misfolded protein particles that contain no nucleic acid (DNA or RNA). They cause fatal neurodegenerative diseases. Example: Prions cause Creutzfeldt-Jakob disease (CJD) and BSE ("mad cow disease") in cattle.
iii. Virions:
A virion is a complete, fully assembled, extracellular virus particle that is capable of infecting a host cell. It consists of a nucleic acid core surrounded by a protein coat (capsid).
iv. Capsomeres:
Capsomeres are the individual protein subunits that assemble together to form the capsid (protein coat) of a virus. Many capsomeres join to form the complete capsid structure surrounding the viral nucleic acid.
(b) Dyes and Chemicals in Gram Staining:
| Dye/Chemical | Function |
|---|---|
| Crystal violet (primary stain) | Stains all bacterial cells purple/violet initially |
| Gram's iodine (mordant) | Forms a complex with crystal violet to fix the stain inside the cell wall |
| Acetone/Alcohol (decolorizer) | Washes out the crystal violet-iodine complex from Gram-negative cells (thin peptidoglycan); Gram-positive cells retain the stain |
| Safranin (counterstain) | Stains decolorized Gram-negative cells pink/red, making them visible |
| Result: Gram-positive bacteria appear purple/violet; Gram-negative bacteria appear pink/red | |
| (c) | |
| i. Steps of Binary Fission in Bacteria: |
- The bacterial cell grows to its maximum size
- The circular DNA replicates — the chromosome duplicates, forming two identical DNA molecules
- Each DNA molecule moves to opposite ends of the cell
- The cell elongates and the plasma membrane grows inward at the center, forming a septum (cross wall)
- The cell wall and membrane completely divide, producing two identical daughter cells
- The two daughter cells separate and each grows into a full-sized bacterium
ii. Functions of TWO Enzymes Used in Genetic Engineering: - Restriction endonucleases (Restriction enzymes): Cut DNA at specific recognition sequences, producing fragments of DNA that can be inserted into vectors. They act as "molecular scissors."
- DNA ligase: Joins (seals) the cut ends of DNA fragments together, linking the insert DNA to the vector DNA to form recombinant DNA. It acts as "molecular glue."
BIO 003: BOTANY
Question 5
(a) Distinguishing Pairs of Terms:
i. Parasites vs. Saprophytes:
| Parasites | Saprophytes |
|---|---|
| Obtain nutrients from a living host | Obtain nutrients from dead/decaying organic matter |
| Harm the host organism | Do not harm any organism |
| Example: Cuscuta (dodder plant) | Example: Rhizopus (bread mould) |
| ii. Species vs. Genus: | |
| Species | Genus |
| --- | --- |
| A group of organisms that can interbreed and produce fertile offspring | A group of closely related species sharing common characteristics |
| Lowest taxonomic rank in classification | Rank above species |
| Example: sapiens (in Homo sapiens) | Example: Homo |
| iii. Nomenclature vs. Classification: | |
| Nomenclature | Classification |
| --- | --- |
| The system of assigning scientific names to organisms | The grouping of organisms into categories based on shared characteristics |
| Governed by binomial nomenclature (Linnaeus) | Based on evolutionary relationships and similarities |
| Example: Naming man Homo sapiens | Example: Placing man in Kingdom Animalia, Phylum Chordata, etc. |
| iv. Fruits vs. Seeds: | |
| Fruits | Seeds |
| --- | --- |
| Developed from the ovary wall (pericarp) after fertilization | Developed from the ovule after fertilization |
| May be fleshy or dry | Contains the embryo and stored food |
| Encloses and protects the seed | Gives rise to a new plant upon germination |
| Example: Mango, tomato | Example: Bean, maize grain |
| (b) Differences Between Pteridophytes and Bryophytes: | |
| Feature | Pteridophytes |
| --- | --- |
| Vascular tissue | Present (xylem and phloem) |
| Dominant generation | Sporophyte |
| Roots | True roots present |
| Habitat | Mostly terrestrial |
| Examples | Ferns, horsetails |
| (c) | |
| i. Cross Pollination: | |
| Cross pollination is the transfer of pollen grains from the anther of a flower on one plant to the stigma of a flower on a different plant of the same species, usually aided by wind, insects, water or animals. | |
| ii. Vegetative Propagation: | |
| Vegetative propagation is a form of asexual reproduction in plants whereby new plants are produced from vegetative parts of the parent plant such as stems, roots, leaves or buds, without the involvement of seeds or spores. Examples include budding, grafting, runners, corms and bulbs. |
Question 6
(a) FOUR Differences Between Monocotyledonous and Dicotyledonous Plants:
| Feature | Monocotyledonous Plants | Dicotyledonous Plants |
|---|---|---|
| Cotyledons (seed leaves) | One cotyledon | Two cotyledons |
| Leaf venation | Parallel venation | Network/reticulate venation |
| Floral parts | In multiples of 3 | In multiples of 4 or 5 |
| Root system | Fibrous root system | Tap root system |
| (b) Definitions: | ||
| i. Parthenocarpy: | ||
| Parthenocarpy is the development of fruit from the ovary without fertilization, resulting in seedless fruits. Example: Seedless bananas and seedless grapes. | ||
| ii. Fertilization: | ||
| Fertilization is the fusion of the male gamete (from the pollen tube) with the female gamete (egg cell) in the ovule to form a diploid zygote, which later develops into a seed. | ||
| iii. True Fruits: | ||
| True fruits are fruits that develop solely from the fertilized ovary of a flower. Example: Mango, tomato, orange. | ||
| iv. Dehiscent Fruits: | ||
| Dehiscent fruits are dry fruits that split open at maturity along definite lines to release their seeds. Example: Pea pods, cotton bolls, castor. | ||
| v. Anemophilous Flowers: | ||
| Anemophilous flowers are flowers that are pollinated by wind. They are typically small, dull-colored, lack nectar and scent, have feathery stigmas and produce large quantities of light, smooth pollen. Example: Maize, grasses, wheat. | ||
| vi. Entomophilous Flowers: | ||
| Entomophilous flowers are flowers pollinated by insects. They are usually brightly colored, fragrant, and produce nectar to attract insects. Pollen is sticky or spiny to attach to insects. Example: Sunflower, hibiscus, rose. |
BIO 004: ZOOLOGY
Question 7
(a) FIVE Classes of Phylum Echinodermata with Examples:
| Class | Example |
|---|---|
| Asteroidea | Starfish (Asterias) |
| Echinoidea | Sea urchin (Echinus) |
| Holothuroidea | Sea cucumber (Holothuria) |
| Ophiuroidea | Brittle star (Ophiura) |
| Crinoidea | Sea lily / Feather star (Antedon) |
| (b) Steps Involved in Blood Clotting: |
- When a blood vessel is injured, platelets (thrombocytes) are attracted to the site of injury and aggregate to form a temporary platelet plug
- Damaged tissues and platelets release thromboplastin (tissue factor/clotting factor III)
- Thromboplastin, in the presence of calcium ions (Ca²⁺) and vitamin K, converts the plasma protein prothrombin into active thrombin (enzyme)
- Thrombin converts soluble plasma protein fibrinogen into insoluble fibrin threads
- Fibrin threads form a mesh/network that traps red blood cells and platelets, forming a blood clot (thrombus)
- The clot hardens and dries to form a scab, preventing further blood loss and entry of pathogens
- Eventually the clot is dissolved by plasmin once the vessel is repaired (fibrinolysis)
Question 8
(a) FIVE Functions of the Mammalian Liver:
- Deamination — removes the amino group from excess amino acids, converting them to urea which is excreted by the kidneys
- Glycogen storage — converts excess glucose to glycogen for storage (glycogenesis) and reconverts glycogen to glucose when blood sugar is low (glycogenolysis)
- Bile production — produces bile salts that emulsify fats in the small intestine, aiding fat digestion
- Detoxification — breaks down and neutralizes harmful substances such as alcohol, drugs and toxins in the blood
- Heat production — the liver is highly metabolically active and generates a large amount of heat, helping to maintain body temperature.
- Support — the skeleton provides a rigid framework that supports the body and maintains its shape. Example: The vertebral column supports the head and trunk.
- Protection of vital organs — bones protect delicate internal organs from injury. Example: The skull protects the brain; the ribcage protects the heart and lungs.
- Movement — bones act as levers on which muscles pull to produce movement at joints. Example: The femur and tibia work with muscles to allow walking and running.
- Blood cell production (Haemopoiesis) — red bone marrow in certain bones produces red blood cells, white blood cells and platelets. Example: The sternum and femur contain red bone marrow.
- Mineral storage — the skeleton stores important minerals such as calcium and phosphorus, releasing them into the blood when needed for metabolic processes. Example: Calcium stored in the femur is released to maintain blood calcium levels.