Paper type B
BIO 001: GENERAL BIOLOGY
1. (a) Describe the structure and function of Deoxyribonucleic acid (DNA) as a vital biological molecule in living organisms. [5 Marks]
(b) Outline in a tabular form FOUR differences between DNA and RNA. [2 Marks]
(c) (i) State FOUR functions of Protein. [2 Marks]
(ii) Mention TWO approaches to ecological studies. [1 Mark]
2. (a) State SIX characteristics of an Enzyme. [3 Marks]
(b) Doctors and insurance companies use graphs to decide if a person has suitable weight for their height. The graph below is an example.
Adamu and Ifeoma both weigh 70kg. Adamu's height is 180cm. Ifeoma's height is 150cm.
i. Use the graph to decide which of the bands, A – E, Adamu and Ifeoma belongs?
ii. How much weight would Ifeoma have to lose to place her in Band B?
iii. A third person, Lekan is adjudged FAT, determine his weight range? [4 Marks]
(c) State THREE biological impact of Climate change. [3 Marks]
BIO 002: MICROBIOLOGY
3. (a) Describe the stages or steps of the lytic cycle in Viruses. [3 Marks]
(b) Outline FOUR factors that can affect the effectiveness of an antimicrobial agent in controlling the activities of microorganisms. [2 Marks]
(c) The growth of bacteria in a closed system can be represented in a curve.
i. Draw and label the curve. [3 Marks]
ii. Describe the metabolic activities going on in any TWO phases of the microbial growth curve. [2 Marks]
4. (a) Make a large labelled diagram of a prokaryotic cell. [4 Marks]
(b) Describe the term Adaptive Immunity. [3 Marks]
(c) Highlight THREE roles of microbes in the nitrogen cycle stating their names and functions. [3 Marks]
BIO 003: BOTANY
5. (a) State FOUR characteristics of the Division Pteridophyta. [2 Marks]
(b) i. State FOUR adaptive features of insect pollinated flowers. [4 Marks]
ii. Highlight TWO differences between insect and wind pollinated flowers. [2 Marks]
(c) State how each of the following characteristics help the xylem to perform its functions of transport of water.
i. Possession of Lignified walls.
ii. Possession of dead cells. [2 Marks]
6. (a) i. Draw and label the transverse section of a dicotyledonous stem. [4 Marks]
ii. State the ONE advantage and ONE disadvantage each for In-situ and Ex-situ conservation. [2 Marks]
(b) State FOUR modifications of leaves and the roles they perform. [2 Marks]
(c) State FOUR factors that affect the rate of Photosynthesis. [2 Marks]
BIO 004: ZOOLOGY
7. (a) i. Define a sense organ. [1 Mark]
ii. Make a large labelled diagram of the cross section of the human eye. [4 Marks]
(b) Name TWO major components of the mammalian blood. [1 Mark]
(c) i. Describe the structure of a reflex arc. [2 Marks]
ii. State TWO parasitic adaptations of Taenia solium. [2 Marks]
8. (a) State the function of the following parts of the human alimentary canal:
i. Teeth
ii. Tongue
iii. Saliva
iv. Stomach [4 Marks]
(b) State the functions of the following parts of the human reproductive system:
i. Epididymis
ii. Seminiferous tubules
iii. Fimbriae
iv. Oviduct [2 Marks]
(c) i. Define hormone. [1 Mark]
ii. State THREE differences between hormonal coordination and nervous coordination. [3 Marks]
SOLUTIONS
BIO 001: GENERAL BIOLOGY
Question 1(a): Structure and Function of DNA [5 Marks]
Structure of DNA:
DNA (Deoxyribonucleic acid) is a double-stranded helical molecule made up of nucleotides. Each nucleotide consists of:
- A deoxyribose sugar (5-carbon)
- A phosphate group
- A nitrogenous base (Adenine, Thymine, Guanine, or Cytosine)
The two strands are held together by hydrogen bonds between complementary base pairs:
- Adenine (A) pairs with Thymine (T) — 2 hydrogen bonds
- Guanine (G) pairs with Cytosine (C) — 3 hydrogen bonds
The strands run antiparallel to each other and are twisted into a double helix (Watson and Crick model).
Functions of DNA:
- Stores genetic information — carries hereditary information from parent to offspring
- Protein synthesis — provides the template (via mRNA) for the production of proteins
- Replication — can copy itself during cell division to ensure each daughter cell receives a complete set of genetic information
- Mutation and variation — changes in DNA sequence lead to genetic variation and evolution
- Gene expression — controls all cellular activities by directing enzyme and protein production
Question 1(b): FOUR Differences Between DNA and RNA [2 Marks]
| Feature | DNA | RNA |
|---|---|---|
| Sugar | Deoxyribose | Ribose |
| Strands | Double-stranded | Single-stranded |
| Bases | Adenine, Thymine, Guanine, Cytosine | Adenine, Uracil, Guanine, Cytosine |
| Location | Mainly in nucleus | Nucleus and cytoplasm |
Question 1(c)(i): FOUR Functions of Protein [2 Marks]
- Structural function — e.g. keratin in hair and nails, collagen in connective tissue
- Enzymatic function — proteins act as biological catalysts (enzymes) to speed up chemical reactions
- Transport function — e.g. haemoglobin transports oxygen in the blood
- Defensive function — antibodies (immunoglobulins) are proteins that fight pathogens
Question 1(c)(ii): TWO Approaches to Ecological Studies [1 Mark]
- Field study — direct observation and collection of data in the natural environment
- Laboratory/Experimental study — controlled experiments conducted under regulated conditions to study ecological relationships
Question 2(a): SIX Characteristics of an Enzyme [3 Marks]
- Enzymes are biological catalysts — they speed up chemical reactions without being consumed
- Enzymes are protein in nature — made of amino acids
- Enzymes are specific — each enzyme acts on a particular substrate (lock and key principle)
- Enzymes are reusable — they are not permanently altered after a reaction
- Enzymes are sensitive to temperature — they have an optimum temperature; excess heat denatures them
- Enzymes are sensitive to pH — each enzyme has an optimum pH range for maximum activity
Question 2(b): Graph Questions [4 Marks]
Using the BMI/weight-height chart described:
i. Bands for Adamu and Ifeoma (both 70 kg):
- Adamu (180 cm, 70 kg) → falls in Band B (Satisfactory/Normal)
- Ifeoma (150 cm, 70 kg) → falls in Band D (Fat)
ii. Weight Ifeoma must lose to reach Band B:
- At 150 cm, Band B upper limit is approximately 55 kg
- Ifeoma weighs 70 kg
- Weight to lose = 70 − 55 = approximately 15 kg
iii. Lekan's weight range if adjudged FAT at average height:
- Band D (FAT) on the chart corresponds to a body weight range of approximately 100 – 115 kg (depending on height)
- For a person of average height (~170 cm), the FAT range is approximately 85 – 100 kg
Question 2(c): THREE Biological Impacts of Climate Change [3 Marks]
- Loss of biodiversity — rising temperatures and habitat destruction cause extinction of plant and animal species
- Disruption of breeding and migration patterns — animals and birds alter their seasonal behaviors due to changing climates
- Spread of diseases — warmer temperatures expand the habitat range of disease vectors like mosquitoes, increasing diseases like malaria
BIO 002: MICROBIOLOGY
Question 3(a): Stages of the Lytic Cycle in Viruses [3 Marks]
- Attachment (Adsorption) — the virus attaches to specific receptor sites on the host cell surface
- Penetration (Injection) — the virus injects its nucleic acid (DNA or RNA) into the host cell
- Biosynthesis (Replication) — the viral nucleic acid hijacks the host cell's machinery to produce viral components (proteins and nucleic acids)
- Maturation (Assembly) — new viral particles are assembled from the synthesized components
- Lysis (Release) — the host cell bursts (lyses), releasing hundreds of new virions to infect other cells
Question 3(b): FOUR Factors Affecting Effectiveness of Antimicrobial Agents [2 Marks]
- Concentration of the agent — higher concentrations are generally more effective
- Temperature — higher temperatures usually increase antimicrobial activity
- pH of the environment — extreme pH can enhance or reduce the agent's effectiveness
- Nature/type of microorganism — some microbes are inherently resistant (e.g. spore-forming bacteria are harder to kill)
Question 3(c): Bacterial Growth Curve [3 Marks + 2 Marks]
i. The Microbial Growth Curve (described):
The curve has four distinct phases plotted as log number of cells vs. time:
Log | ___________
Number | / \
of cells | / \
| / \___
|_____/
|_________________________________
Lag Log Stationary Death
(Time)
Phases:
- Lag phase — adaptation period, no significant growth
- Log (Exponential) phase — rapid cell division
- Stationary phase — birth rate equals death rate
- Death (Decline) phase — death rate exceeds birth rate
ii. Metabolic Activities in ANY TWO Phases [2 Marks]:
Lag Phase:
- Cells are metabolically very active
- Synthesizing enzymes, proteins, and RNA
- Adapting to the new environment
- No cell division yet
Log (Exponential) Phase:
- Cells divide rapidly at a constant rate
- Maximum rate of nutrient consumption and metabolism
- Maximum production of waste products
- Cells are most sensitive to antibiotics at this stage
Question 4(a): Labelled Diagram of a Prokaryotic Cell [4 Marks]
Key structures to draw and label:
Pili Flagellum
| |
______|_________|______
| Capsule |
| ___________________ |
| | Cell wall | |
| | _________________ | |
| || Cell membrane || |
| || ___________ || |
| || |Nucleoid | || | ← (circular DNA)
| || |_(DNA)____| || |
| || Ribosome • || |
| || Plasmid ○ || |
| ||_______________ || |
| |_________________| | |
|_______________________|
Labelled structures:
- Capsule — outermost protective layer
- Cell wall — gives shape and protection (peptidoglycan)
- Cell membrane — controls entry/exit of substances
- Nucleoid region — contains circular DNA (no nuclear membrane)
- Ribosomes (70S) — site of protein synthesis
- Plasmid — small circular extrachromosomal DNA
- Flagellum — used for locomotion
- Pili (Fimbriae) — attachment to surfaces
Question 4(b): Adaptive Immunity [3 Marks]
Adaptive (Acquired) Immunity is the specific defense mechanism of the body that develops in response to exposure to a particular antigen (pathogen or foreign substance).
Key features:
- It is specific — directed against a particular pathogen
- It has memory — upon re-exposure, the immune response is faster and stronger
- It involves lymphocytes:
- B-lymphocytes → produce antibodies (Humoral immunity)
- T-lymphocytes → directly attack infected cells (Cell-mediated immunity)
- It can be natural (from infection) or artificial (from vaccination)
Question 4(c): THREE Roles of Microbes in the Nitrogen Cycle [3 Marks]
| Microbe | Role | Function |
|---|---|---|
| Rhizobium (bacteria) | Nitrogen fixation | Converts atmospheric N₂ into ammonia (NH₃) in root nodules of legumes |
| Nitrosomonas (bacteria) | Nitrification (Step 1) | Converts ammonia to nitrites (NO₂⁻) |
| Pseudomonas (bacteria) | Denitrification | Converts nitrates back to atmospheric nitrogen N₂ |
BIO 003: BOTANY
Question 5(a): FOUR Characteristics of Division Pteridophyta [2 Marks]
- They are vascular plants — possess xylem and phloem for transport
- They reproduce by spores, not seeds or flowers
- They show alternation of generations — sporophyte is the dominant generation
- They have true roots, stems, and leaves (fronds)
Question 5(b)(i): FOUR Adaptive Features of Insect-Pollinated Flowers [4 Marks]
- Brightly colored petals — to attract insects visually
- Production of nectar and scent — to lure insects as a food reward
- Large, sticky, or spiky pollen grains — to adhere easily to insect bodies
- Large, feathery or sticky stigma — positioned to receive pollen from visiting insects
Question 5(b)(ii): TWO Differences Between Insect and Wind Pollinated Flowers [2 Marks]
| Feature | Insect-Pollinated | Wind-Pollinated |
|---|---|---|
| Petals | Large, brightly colored | Small, dull, or absent |
| Pollen | Heavy, sticky, few | Light, smooth, produced in large quantities |
Question 5(c): How Xylem Characteristics Aid Water Transport [2 Marks]
i. Possession of Lignified Walls:
- Lignin strengthens the xylem walls, preventing them from collapsing under the tension/negative pressure created during water transport (transpiration pull). This maintains an open continuous column for water movement.
ii. Possession of Dead Cells:
- Dead xylem cells have no cell contents (cytoplasm/organelles), leaving a hollow lumen. This provides an unobstructed continuous tube for water to flow freely from roots to leaves.
Question 6(a)(i): Transverse Section of a Dicotyledonous Stem [4 Marks]
Key structures to draw and label:
Epidermis (outermost layer)
↓
Cortex (parenchyma cells)
↓
[Vascular bundles arranged in a ring]
/ \
Xylem Phloem
(inner) (outer)
\ /
Cambium (between xylem & phloem)
↓
Pith (centre — parenchyma)
Labels required:
- Epidermis
- Cortex
- Endodermis
- Phloem
- Cambium
- Xylem
- Pith
- Vascular bundle
Question 6(a)(ii): Advantage and Disadvantage of In-situ and Ex-situ Conservation [2 Marks]
| In-situ Conservation | Ex-situ Conservation | |
|---|---|---|
| Advantage | Preserves organisms in their natural habitat and ecosystem interactions | Protects species from immediate extinction in a controlled environment |
| Disadvantage | Difficult to protect from poaching, disease, or natural disasters | Organisms are removed from their natural habitat and may not survive reintroduction |
Question 6(b): FOUR Modifications of Leaves and Their Roles [2 Marks]
| Modification | Role |
|---|---|
| Tendrils (e.g. pea) | Support/climbing |
| Spines/Thorns (e.g. cactus) | Protection and reduce water loss |
| Storage leaves (e.g. onion) | Store food and water |
| Reproductive leaves (e.g. Bryophyllum) | Vegetative reproduction |
Question 6(c): FOUR Factors Affecting Rate of Photosynthesis [2 Marks]
- Light intensity — higher light intensity increases the rate up to a saturation point
- Carbon dioxide concentration — more CO₂ increases the rate of the Calvin cycle
- Temperature — enzymes work optimally within a certain temperature range
- Water availability — water is a raw material for the light-dependent reactions
BIO 004: ZOOLOGY
Question 7(a)(i): Definition of a Sense Organ [1 Mark]
A sense organ is a specialized organ that contains receptor cells capable of detecting specific stimuli (such as light, sound, touch, taste, or smell) from the environment and converting them into nerve impulses sent to the brain.
Question 7(a)(ii): Labelled Diagram — Cross Section of the Human Eye [4 Marks]
Key structures to draw and label:
Cornea (front transparent layer)
↓
Aqueous humour (fluid in front chamber)
↓
Iris (colored part with pupil)
↓
Lens (focuses light)
↓
Vitreous humour (jelly in back chamber)
↓
Retina (contains rods and cones)
↓
Fovea (point of sharpest vision)
↓
Optic nerve (carries impulses to brain)
Other labels:
- Sclera (white outer coat)
- Choroid (middle pigmented layer, supplies blood)
- Ciliary body/muscle (controls lens shape)
- Suspensory ligaments
Question 7(b): TWO Major Components of Mammalian Blood [1 Mark]
- Plasma — the liquid component (~55%) carrying nutrients, hormones, waste products
- Formed elements (Blood cells) — Red blood cells (erythrocytes), White blood cells (leukocytes), and Platelets (thrombocytes)
Question 7(c)(i): Structure of a Reflex Arc [2 Marks]
A reflex arc is the neural pathway for a reflex action. It consists of:
- Receptor — detects the stimulus (e.g. pain receptor in skin)
- Sensory (afferent) neuron — carries impulse from receptor to spinal cord
- Relay (interneuron) — found in the spinal cord; connects sensory and motor neurons
- Motor (efferent) neuron — carries impulse from spinal cord to effector
- Effector — muscle or gland that produces the response
Question 7(c)(ii): TWO Parasitic Adaptations of Taenia solium (Tapeworm) [2 Marks]
- Presence of hooks and suckers (scolex) — used to attach firmly to the intestinal wall of the host, preventing expulsion
- Absence of digestive system — absorbs pre-digested nutrients directly through its body surface (tegument), suited to living in the host's intestine
Question 8(a): Functions of Parts of the Human Alimentary Canal [4 Marks]
| Part | Function |
|---|---|
| Teeth | Mechanically break down food into smaller pieces (mastication/chewing) |
| Tongue | Mixes food with saliva, helps in swallowing, and contains taste buds for detecting flavors |
| Saliva | Contains salivary amylase to begin chemical digestion of starch; moistens food to form a bolus |
| Stomach | Churns food mechanically; secretes gastric juice (HCl and pepsin) to digest proteins; kills bacteria |
Question 8(b): Functions of Parts of the Human Reproductive System [2 Marks]
| Part | Function |
|---|---|
| Epididymis | Stores sperm cells and is where sperm mature and become motile |
| Seminiferous tubules | Site of sperm production (spermatogenesis) within the testes |
| Fimbriae | Finger-like projections that sweep the ovum from the ovary into the fallopian tube |
| Oviduct (Fallopian tube) | Transports the ovum from the ovary to the uterus; site of fertilization |
Question 8(c)(i): Definition of Hormone [1 Mark]
A hormone is a chemical messenger produced by endocrine glands and secreted directly into the bloodstream to be transported to target organs where it produces a specific physiological effect.
Question 8(c)(ii): THREE Differences Between Hormonal and Nervous Coordination [3 Marks]
| Feature | Hormonal Coordination | Nervous Coordination |
|---|---|---|
| Speed | Slow — hormones travel via blood | Fast — nerve impulses travel rapidly |
| Medium of transmission | Bloodstream | Nerve fibres (neurons) |
| Duration of effect | Long-lasting effect | Short-lived, immediate effect |