2025 JUPEB Biology B

2025 JUPEB Biology B

BIO 001 – BIO 004: EXAMINATION QUESTIONS — Paper 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]

©
(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]

© 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]

© 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]

© 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]

© 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]

© 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]

©
(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]

©
(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:

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 © — 3 hydrogen bonds

The strands run antiparallel to each other and are twisted into a double helix (Watson and Crick model).

Functions of DNA:

  1. Stores genetic information — carries hereditary information from parent to offspring
  2. Protein synthesis — provides the template (via mRNA) for the production of proteins
  3. Replication — can copy itself during cell division to ensure each daughter cell receives a complete set of genetic information
  4. Mutation and variation — changes in DNA sequence lead to genetic variation and evolution
  5. Gene expression — controls all cellular activities by directing enzyme and protein production

(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

©(i) FOUR Functions of Protein [2 Marks]

  1. Structural — e.g. keratin in hair and nails, collagen in connective tissue
  2. Enzymatic — proteins act as biological catalysts (enzymes) to speed up chemical reactions
  3. Transport — e.g. haemoglobin transports oxygen in the blood
  4. Defensive — antibodies (immunoglobulins) are proteins that fight pathogens

©(ii) TWO Approaches to Ecological Studies [1 Mark]

  1. Field study — direct observation and collection of data in the natural environment
  2. Laboratory/Experimental study — controlled experiments conducted under regulated conditions to study ecological relationships

Question 2

(a) SIX Characteristics of an Enzyme [3 Marks]

  1. Enzymes are biological catalysts — they speed up chemical reactions without being consumed
  2. Enzymes are protein in nature — made of amino acids
  3. Enzymes are specific — each enzyme acts on a particular substrate (lock and key principle)
  4. Enzymes are reusable — they are not permanently altered after a reaction
  5. Enzymes are sensitive to temperature — they have an optimum temperature; excess heat denatures them
  6. Enzymes are sensitive to pH — each enzyme has an optimum pH range for maximum activity

(b) Graph Questions [4 Marks]

(i) Adamu (180 cm, 70 kg) → falls in Band B (Satisfactory/Normal)
Ifeoma (150 cm, 70 kg) → falls in Band D (Fat)

(ii) At 150 cm, Band B upper limit ≈ 55 kg; Ifeoma weighs 70 kg
Weight to lose = 70 − 55 = approximately 15 kg

(iii) For a person of average height (~170 cm), the FAT band corresponds to approximately 85 – 100 kg

© THREE Biological Impacts of Climate Change [3 Marks]

  1. Loss of biodiversity — rising temperatures and habitat destruction cause extinction of plant and animal species
  2. Disruption of breeding and migration patterns — animals and birds alter their seasonal behaviours due to changing climates
  3. 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]

  1. Attachment (Adsorption) — the virus attaches to specific receptor sites on the host cell surface
  2. Penetration (Injection) — the virus injects its nucleic acid (DNA or RNA) into the host cell
  3. Biosynthesis (Replication) — the viral nucleic acid hijacks the host cell’s machinery to produce viral components (proteins and nucleic acids)
  4. Maturation (Assembly) — new viral particles are assembled from the synthesized components
  5. Lysis (Release) — the host cell bursts (lyses), releasing hundreds of new virions to infect other cells

(b) FOUR Factors Affecting Effectiveness of Antimicrobial Agents [2 Marks]

  1. Concentration of the agent — higher concentrations are generally more effective
  2. Temperature — higher temperatures usually increase antimicrobial activity
  3. pH of the environment — extreme pH can enhance or reduce the agent’s effectiveness
  4. Nature/type of microorganism — some microbes are inherently resistant (e.g. spore-forming bacteria are harder to kill)

©(i) The Microbial Growth Curve [3 Marks]

Log        |          ___________
Number     |        /             \
of cells   |       /               \
           |      /                 \___
           |_____/
           |_________________________________
                Lag  Log  Stationary  Death
                          (Time)
  • 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 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]

         Pili    Flagellum
          |         |
    ______|_________|______
   |   Capsule             |
   |  ___________________  |
   | |   Cell wall       | |
   | | _________________ | |
   | || Cell membrane   || |
   | ||  ___________    || |
   | ||  | Nucleoid |   || |   <- circular DNA
   | ||  |_ (DNA)___|   || |
   | ||    Ribosome •   || |
   | ||   Plasmid  o    || |
   | ||_______________  || |
   | |_________________| | |
   |_______________________|
Structure Description
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

(b) Adaptive Immunity [3 Marks]

Adaptive (Acquired) Immunity is the specific defence mechanism of the body that develops in response to exposure to a particular antigen (pathogen or foreign substance).

Key features:

  • Specific — directed against a particular pathogen
  • Has memory — upon re-exposure, the immune response is faster and stronger
  • Involves lymphocytes:
    • B-lymphocytes → produce antibodies (Humoral immunity)
    • T-lymphocytes → directly attack infected cells (Cell-mediated immunity)
  • Can be natural (from infection) or artificial (from vaccination)

© 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]

  1. They are vascular plants — possess xylem and phloem for transport
  2. They reproduce by spores, not seeds or flowers
  3. They show alternation of generations — sporophyte is the dominant generation
  4. They have true roots, stems, and leaves (fronds)

(b)(i) FOUR Adaptive Features of Insect-Pollinated Flowers [4 Marks]

  1. Brightly coloured petals — to attract insects visually
  2. Production of nectar and scent — to lure insects as a food reward
  3. Large, sticky, or spiky pollen grains — to adhere easily to insect bodies
  4. Large, feathery or sticky stigma — positioned to receive pollen from visiting insects

(b)(ii) TWO Differences Between Insect and Wind Pollinated Flowers [2 Marks]

Feature Insect-Pollinated Wind-Pollinated
Petals Large, brightly coloured Small, dull, or absent
Pollen Heavy, sticky, produced in small quantities Light, smooth, produced in large quantities

© 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]

         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

(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

(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

© FOUR Factors Affecting Rate of Photosynthesis [2 Marks]

  1. Light intensity — higher light intensity increases the rate up to a saturation point
  2. Carbon dioxide concentration — more CO₂ increases the rate of the Calvin cycle
  3. Temperature — enzymes work optimally within a certain temperature range
  4. 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 specialised 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.

(a)(ii) Cross Section of the Human Eye [4 Marks]

              Cornea (front transparent layer)
                  |
         Aqueous humour (fluid in front chamber)
                  |
              Iris (coloured 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)

Additional labels: Sclera, Choroid, Ciliary body/muscle, Suspensory ligaments

(b) TWO Major Components of Mammalian Blood [1 Mark]

  1. Plasma — the liquid component (~55%) carrying nutrients, hormones, and waste products
  2. Formed elements (Blood cells) — Red blood cells (erythrocytes), White blood cells (leukocytes), and Platelets (thrombocytes)

©(i) Structure of a Reflex Arc [2 Marks]

A reflex arc consists of five components in sequence:

Receptor → Sensory (afferent) neuron → Relay (interneuron) → Motor (efferent) neuron → Effector

  • Receptor — detects the stimulus (e.g. pain receptor in skin)
  • Sensory neuron — carries impulse from receptor to spinal cord
  • Relay neuron — found in the spinal cord; connects sensory and motor neurons
  • Motor neuron — carries impulse from spinal cord to effector
  • Effector — muscle or gland that produces the response

©(ii) TWO Parasitic Adaptations of Taenia solium [2 Marks]

  1. Presence of hooks and suckers (scolex) — used to attach firmly to the intestinal wall of the host, preventing expulsion
  2. 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 flavours
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

(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 fertilisation

©(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.

©(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 Short-lived, immediate
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