2019 JUPEB Biology

2019 JUPEB Biology

BIO 001: GENERAL BIOLOGY

Question 1

Two parents with normal skin and hair colouring had six (6) children, of whom three (3) were albino. Albino people have no colouring in their skin or hair, due to having an inactive form of the enzyme tyrosinase. Tyrosinase is essential for the formation of the brown pigment melanin.

(a) The normal allele of the tyrosinase gene is ‘A’ and the allele that produces faulty tyrosinase is ‘a’. State the genotype of the parents and their albino children. [5 marks]

(b) Albinism is a relatively frequent condition in humans, but one (1) of these albino children had a very unusual phenotype. While most of her hair was white, the hair of her eyebrows developed some brown colouring, as did the hair on her hands and lower legs. Genetic analysis suggested that a mutation had occurred in the faulty tyrosinase allele. Suggest why it is likely that this mutation occurred in the child with brown-coloured eyebrows rather than in the testes and ovaries of the parent. [2 marks]

© A man with normal vision married a lady with normal vision. Incidentally, their first son is colour blind. Use a genetic diagram to show the possibility of this man being the rightful father of the colour-blind child. [2 marks]

(d) What was the genotype of the man and his wife? [1 mark]

Question 2

As the team leader of an environmental study team, you have been commissioned to conduct a field study to determine the population density and population size of a given species in a habitat.

(a) Design a pro-forma that would guide your team to success. [5 marks]

(b) Mention any four (4) materials that would be required. [4 marks]

© If the population size of grasshoppers is 700 in a sample plot of 100 m², what is the population density of grasshoppers in the plot? [1 mark]

BIO 002: BOTANY

Question 3

(a) Using six (6) points each, describe the following:

i. Biological control [3 marks]

ii. Chemical control [3 marks]

(b) Enumerate four (4) impacts of climate change on plants. [4 marks]

Question 4

(a) Outline eight (8) general characteristics of ferns. [4 marks]

(b) With the aid of a diagram only, describe the life cycle of Selaginella. [6 marks]

BIO 003: MICROBIOLOGY

Question 5

(a) State the following characteristics of the Archaea:

i. Mesophiles ii. Halophiles iii. Acidophiles iv. Alkaliphiles v. Thermophiles [5 marks]

(b) Highlight five (5) biotechnological or beneficial uses of microorganisms. [5 marks]

Question 6

(a) List two (2) media used for the growth of microorganisms in the laboratory. [2 marks]

(b) Briefly write on the structures that prokaryotes use for attachment. [3 marks]

© With illustration, describe the events in each stage of a microbial growth curve of a batch culture. [5 marks]

BIO 004: INTRODUCTORY ZOOLOGY

Question 7

(a) Describe the life cycle of Plasmodium in man. [8 marks]

(b) Mention four (4) economic importances of Plasmodium. [2 marks]

Question 8

(a) List ten (10) characteristics of the Class Reptilia. [5 marks]

(b) Itemise five (5) adaptations of animals in transition from water to land. [5 marks]

ANSWERS

BIO 001: GENERAL BIOLOGY

Question 1(a) — Genotypes of Parents and Albino Children

Albinism is an autosomal recessive condition. For two parents with normal pigmentation to produce albino offspring, both parents must be heterozygous carriers of the recessive allele.

  • Parents: Both are Aa (heterozygous normal)

  • Albino children: All are aa (homozygous recessive)

Supporting Punnett Square (Aa × Aa):

| | A | a |

|—|---|—|

| A | AA | Aa |

| a | Aa | aa |

Ratio: 1 AA : 2 Aa : 1 aa → 3 normal pigmentation : 1 albino. Having three albino children out of six is consistent with this 1-in-4 probability.

Question 1(b) — Why the Mutation Occurred in the Child, Not the Parent

The localised pattern of brown colouring (confined to the eyebrows, hands, and lower legs) is characteristic of a somatic mutation — one that arose in a specific cell lineage during the embryonic development of the child, not in the germline of the parent. Two key reasons support this:

  1. If the mutation had occurred in the germline (testes/ovaries) of the parent, it would have been present in the fertilised egg and therefore inherited by every cell of the child’s body through mitosis. The child would then have uniform normal pigmentation throughout, not patchy brown colouring restricted to certain regions.

  2. Because the brown colouring is localised, it means the back-mutation (restoration of a functional tyrosinase allele) happened in only one or a few somatic cells at a particular stage of development. All descendants of that cell lineage could produce melanin, while the rest of the body retained the original aa genotype and remained albino. This mosaic pattern is a hallmark of somatic, not germline, mutation.

Question 1© — Genetic Diagram: Colour Blindness (X-linked Recessive)

Key:

  • X^N = dominant allele for normal vision

  • X^n = recessive allele for colour blindness

  • Y = male sex chromosome

For the couple to have a colour-blind son (X^n Y), the mother must be a carrier (X^N X^n), since the son receives his X chromosome from the mother and his Y from the father. The father himself has normal vision (X^N Y).

Punnett Square (X^N Y × X^N X^n):

| | X^N (Mother) | X^n (Mother) |

|—|---|—|

| X^N (Father) | X^N X^N (Normal daughter) | X^N X^n (Carrier daughter) |

| Y (Father) | X^N Y (Normal son) | X^n Y (Colour-blind son) |

This demonstrates that the man can indeed be the biological father; there is a 25% probability per child (or 50% probability among sons) of this couple producing a colour-blind son. The father’s genetic contribution is entirely consistent with the child’s phenotype.

Question 1(d) — Genotypes of the Man and His Wife

  • Man (father): X^N Y (normal vision, hemizygous)

  • Wife (mother): X^N X^n (normal vision, heterozygous carrier)

Question 2(a) — Field Study Pro-Forma

POPULATION ECOLOGY FIELD STUDY PRO-FORMA

| Section | Details |

|—|---|

| Study title | Population density and size estimation of (target species) |

| Date and time | __________ |

| Study site / habitat | __________ (GPS coordinates if available) |

| Team members | __________ |

| Target species | __________ |

| Sampling method | Quadrat / Mark-recapture / Transect (circle as appropriate) |

| Quadrat/plot size (m²) | __________ |

| Number of quadrats/samples | __________ |

| Total count per quadrat | Quadrat 1: ___ Quadrat 2: ___ Quadrat 3: ___ … |

| Total individuals counted | __________ |

| Total area sampled (m²) | __________ |

| Calculated population density | __________ individuals/m² |

| Estimated total population size | Density × total habitat area = __________ |

| Environmental observations | Weather, vegetation cover, disturbances |

| Remarks / anomalies | __________ |

| Supervisor’s signature | __________ |

Question 2(b) — Four Materials Required

  1. Quadrat frames (wire or string squares of known area, e.g., 1 m² or 0.5 m²) for demarcating sample plots

  2. Metre rule / measuring tape for measuring plot dimensions and spacing between quadrats

  3. Tally counters and data recording sheets / pro-formas for counting and recording individuals

  4. GPS device or compass and map for locating, marking, and navigating between study plots within the habitat

Question 2© — Population Density of Grasshoppers

Population Density=Total Number of IndividualsTotal Area Sampled=700100 m2=7 grasshoppers/m2\text{Population Density} = \frac{\text{Total Number of Individuals}}{\text{Total Area Sampled}} = \frac{700}{100 \text{ m}^2} = \textbf{7 grasshoppers/m}^2

BIO 002: BOTANY

Question 3(a)(i) — Biological Control (Six Points)

  1. Biological control is the deliberate use of living organisms — natural enemies such as predators, parasitoids, or pathogens — to reduce the population of a pest to below economically or ecologically harmful levels.

  2. It is an environmentally friendly strategy that does not introduce synthetic chemicals into the ecosystem.

  3. It can be highly specific; a well-chosen control agent targets only the pest species with minimal harm to non-target organisms.

  4. Once established, biological control agents can be self-sustaining, providing long-term suppression without repeated application.

  5. It reduces the risk of pesticide resistance developing in pest populations.

  6. Examples include the introduction of the ladybird beetle (Rodolia cardinalis) to control cottony cushion scale insects, and the use of Bacillus thuringiensis (Bt) toxin to control caterpillar pests.

Question 3(a)(ii) — Chemical Control (Six Points)

  1. Chemical control involves the application of synthetic or naturally derived chemical substances — pesticides, herbicides, fungicides, or insecticides — to kill, repel, or inhibit the growth of pest organisms.

  2. It provides rapid knockdown of large pest populations and is effective in emergency or severe infestation situations.

  3. Chemical pesticides are available in various formulations (sprays, dusts, granules, fumigants) allowing versatile application methods.

  4. They are generally easy to apply over large areas using mechanised equipment such as sprayers or aerial application.

  5. Major disadvantages include the development of pesticide resistance in target pest populations through repeated exposure and natural selection.

  6. Chemical residues can persist in soil, water, and food chains, causing harm to non-target organisms including beneficial insects, wildlife, and humans — a significant environmental and public health concern.

Question 3(b) — Four Impacts of Climate Change on Plants

  1. Phenological disruption: Rising temperatures alter the timing of key plant life-cycle events (bud burst, flowering, seed set, leaf senescence), creating mismatches with pollinators and seed-dispersers that co-evolved with the plant.

  2. Water stress and drought: Increased temperatures raise evapotranspiration rates; coupled with altered and unpredictable rainfall patterns, this leads to soil moisture deficits, wilting, reduced growth, and in severe cases, plant death.

  3. Range shifts: Plants adapted to specific temperature and moisture regimes are being forced to migrate polewards or to higher altitudes as their original habitat becomes climatically unsuitable; species unable to migrate fast enough face local extinction.

  4. Reduced agricultural productivity: Elevated temperatures interfere with pollination, fertilisation, and grain-filling processes in crop plants; heat stress during critical growth periods can drastically reduce yields, threatening food security.

Question 4(a) — Eight General Characteristics of Ferns

  1. Ferns are vascular plants possessing well-developed xylem and phloem for water, mineral, and food conduction.

  2. The dominant generation in the life cycle is the diploid sporophyte; the gametophyte is small, independent, and short-lived.

  3. They reproduce asexually by means of spores produced in sporangia.

  4. The vegetative body typically consists of an underground horizontal stem called a rhizome from which roots and leaves arise.

  5. The leaves (foliage organs) of ferns are called fronds, which are often large and pinnately divided.

  6. Young fronds exhibit circinate vernation — they are tightly coiled (like a crozier or fiddlehead) as they emerge and unroll progressively from the tip.

  7. Sporangia are grouped into clusters called sori (singular: sorus), typically found on the undersurface of fertile fronds, often protected by a flap of tissue called the indusium.

  8. Fertilisation requires the presence of a film of water, through which the flagellated antherozoids (male gametes) swim to reach the archegonium (female sex organ) on the prothallus (gametophyte).

Question 4(b) — Life Cycle of Selaginella (Diagram)

(A fully labelled diagram is required in the examination. The key stages are represented below:)


SPOROPHYTE (2n) — dominant generation

|

Bears two types of sporangia on sporophylls:

| |

MEGASPORANGIUM MICROSPORANGIUM

(produces megaspores) (produces microspores)

| |

MEGASPORE (n) MICROSPORE (n)

(large, few per (small, many per

sporangium, female) sporangium, male)

| |

FEMALE GAMETOPHYTE MALE GAMETOPHYTE

(megaprothallus) (microprothallus)

Bears archegonia Bears antheridia

| |

OVUM (n) ANTHEROZOIDS (n)

\ /

\ FERTILISATION /

\ (requires water)

|

ZYGOTE (2n)

|

EMBRYO develops within

megaspore wall / female

gametophyte tissue

|

Young SPOROPHYTE (2n)

|

Mature SPOROPHYTE

(returns to top of cycle)

Key features of Selaginella’s life cycle:

  • Selaginella is heterosporous — it produces two morphologically and functionally distinct types of spores (megaspores and microspores), a significant advance over homosporous ferns.

  • Both gametophytes are endosporic — they develop entirely within the spore wall, never becoming free-living.

  • The life cycle represents a transition toward the seed habit seen in higher plants, as the megaspore is retained within the megasporangium during fertilisation in some species.

BIO 003: MICROBIOLOGY

Question 5(a) — Characteristics of Archaea Groups

| Group | Characteristics |

|—|---|

| Mesophiles | Thrive at moderate temperatures, typically between 20°C and 45°C; these are the most common archaea and include many found in ordinary soil and aquatic environments |

| Halophiles | Require extremely high salt concentrations (2–5 M NaCl) for growth; found in hypersaline environments such as the Dead Sea, Great Salt Lake, and solar salterns; their enzymes and membranes are adapted to function in conditions that would denature ordinary proteins |

| Acidophiles | Grow optimally at very low pH values (pH 1–5); inhabit acidic environments such as volcanic hot springs, acid mine drainage, and hydrothermal vents; their cell membranes and proteins are structurally resistant to acid denaturation |

| Alkaliphiles | Thrive at high pH values (pH 9–11 or above); found in soda lakes, alkaline soils, and carbonate-rich environments; they maintain a near-neutral internal pH using ion-transport mechanisms despite the external alkalinity |

| Thermophiles | Grow optimally at elevated temperatures above 45°C; extreme thermophiles (hyperthermophiles) thrive above 80°C in hydrothermal vents and geysers; their enzymes (e.g., Taq polymerase) are heat-stable and have important biotechnological applications |

Question 5(b) — Five Biotechnological or Beneficial Uses of Microorganisms

  1. Food production: Microorganisms are used in the fermentation of beverages (beer, wine), dairy products (yoghurt, cheese), bread, and traditional fermented foods. Yeast (Saccharomyces cerevisiae) ferments sugars to produce ethanol and carbon dioxide for baking and brewing.

  2. Antibiotic production: Many antibiotics are derived from microorganisms — Penicillium notatum produces penicillin, and Streptomyces species produce streptomycin, erythromycin, and tetracycline — revolutionising the treatment of bacterial infections.

  3. Production of industrial enzymes and biochemicals: Microorganisms are used as bioreactors to produce enzymes (amylases, proteases, lipases), organic acids (citric acid, lactic acid), vitamins, and amino acids used in food processing, detergent manufacturing, and pharmaceuticals.

  4. Bioremediation: Certain bacteria and fungi can degrade or detoxify environmental pollutants such as petroleum hydrocarbons, heavy metals, and pesticides, making them valuable for cleaning up oil spills and contaminated soil and water.

  5. Genetic engineering and vaccine production: Microorganisms serve as hosts for recombinant DNA technology; Escherichia coli and yeast are used to produce human insulin, growth hormone, interferons, and recombinant vaccines (e.g., Hepatitis B vaccine) on an industrial scale.

Question 6(a) — Two Media Used for Microbial Growth in the Laboratory

  1. Nutrient agar — a solid general-purpose medium suitable for the routine cultivation of a wide range of non-fastidious bacteria

  2. Nutrient broth — a liquid (aqueous) general-purpose medium used for culturing bacteria in suspension and for bulk growth

(Other acceptable examples: Blood agar, MacConkey agar, Sabouraud dextrose agar for fungi, Mannitol salt agar)

Question 6(b) — Structures Used by Prokaryotes for Attachment

Prokaryotes employ several surface structures to adhere to host cells, other surfaces, or each other:

  1. Fimbriae: Short, numerous, hair-like protein appendages distributed over the entire cell surface. They enable bacteria to adhere to epithelial surfaces, substrates, and other bacterial cells. They are important virulence factors in pathogenic bacteria (e.g., E. coli fimbriae facilitate colonisation of the urinary tract).

  2. Pili (singular: pilus): Longer and fewer than fimbriae; they are hollow, tubular protein appendages. The sex pilus (conjugation pilus) connects two bacterial cells during conjugation to facilitate the transfer of genetic material. Some pili also mediate attachment to host tissues.

  3. Glycocalyx / Capsule: A layer of polysaccharide (or glycoprotein) secreted external to the cell wall. When organised as a discrete, tightly adherent layer it is called a capsule; when loosely associated it is a slime layer. The glycocalyx facilitates adhesion to surfaces and to other cells, enabling the formation of biofilms, and also protects the bacterium from desiccation and immune attack.

Question 6© — Stages of the Microbial Growth Curve (Batch Culture)


| ___________

| / \

Log | / \

(N) | / \

or | / \__________

CFU |____________________/

|

+-----------------------------------------------------> Time

Lag Log Stationary Death

Phase Phase Phase Phase

| Stage | Description |

|—|---|

| Lag phase | No increase in cell number; organisms are metabolically active, synthesising enzymes and other molecules needed to exploit the new medium, repairing cellular components, and adapting to the environment. Duration depends on the age of the inoculum and the difference between the old and new medium. |

| Log (Exponential) phase | Cells divide at a constant, maximum rate for the given conditions; population doubles at regular intervals (the generation time). Growth is exponential; cells are uniform, physiologically active, and most susceptible to antibiotics that target active processes. |

| Stationary phase | The rate of cell division equals the rate of cell death; net population remains constant. Growth is limited by nutrient depletion, accumulation of toxic metabolic waste products, and changes in pH. Cells may begin producing secondary metabolites (e.g., antibiotics, spores). |

| Death (Decline) phase | The rate of cell death exceeds the rate of division; population declines, typically exponentially. Caused by severe nutrient exhaustion, toxic waste accumulation, and unfavourable pH. Some cells may form endospores to survive; others undergo lysis. |

BIO 004: INTRODUCTORY ZOOLOGY

Question 7(a) — Life Cycle of Plasmodium in Man

Plasmodium (the causative agent of malaria) undergoes asexual reproduction (schizogony) in the human host and sexual reproduction (sporogony) in the female Anopheles mosquito. The stages within the human host are as follows:

1. Inoculation (Infection):

When an infected female Anopheles mosquito takes a blood meal, it injects saliva containing infective sporozoites into the human bloodstream.

2. Pre-erythrocytic (Hepatic / Liver) Stage:

Sporozoites are carried via the bloodstream to the liver, where they rapidly invade hepatocytes (liver parenchymal cells). Within the liver cells, each sporozoite undergoes exoerythrocytic schizogony — repeated nuclear division without cytokinesis — to produce a liver schizont (hepatic schizont) containing thousands of daughter cells called merozoites. This stage lasts approximately 6–16 days depending on the Plasmodium species. In P. vivax and P. ovale, some sporozoites form dormant stages called hypnozoites that persist in the liver and cause relapses months or years later.

3. Erythrocytic Stage (Blood Stage):

Merozoites are released from ruptured hepatocytes into the bloodstream, where they invade red blood cells (erythrocytes). Inside the RBC, each merozoite develops through the following sequence:

  • Ring stage (early trophozoite): The merozoite forms a ring-like appearance with a large vacuole.

  • Late trophozoite: The parasite grows, consuming haemoglobin and producing haemozoin (malarial pigment).

  • Schizont: The trophozoite undergoes erythrocytic schizogony (repeated nuclear division), producing 8–32 new merozoites (species-dependent).

  • Rupture: The RBC ruptures, releasing merozoites and toxic metabolites (including haemozoin) into the bloodstream simultaneously. This synchronised rupture causes the characteristic periodic fever and chills of malaria (P. falciparum — irregular; P. vivax/ovale — 48-hour cycle; P. malariae — 72-hour cycle).

Released merozoites infect fresh RBCs and the erythrocytic cycle repeats.

4. Gametogony (Sexual Stage Initiation):

After several erythrocytic cycles, some merozoites differentiate inside RBCs into male (microgametocytes) and female (macrogametocytes) sexual forms rather than developing into schizonts. These gametocytes circulate in the blood and are infective to the Anopheles mosquito when it takes its next blood meal — completing the human portion of the cycle and initiating sporogony in the mosquito.

Question 7(b) — Four Economic Importances of Plasmodium

  1. Loss of human productivity and labour: Malaria causes debilitating illness in working-age adults, leading to absenteeism, reduced agricultural and industrial output, and significant economic losses, particularly in endemic sub-Saharan African nations.

  2. Burden on healthcare systems: Diagnosis, treatment (antimalarial drugs), hospitalisation, vector control programmes, and insecticide-treated bed net distribution impose enormous financial costs on national health budgets and international aid organisations.

  3. Impact on child development and education: Repeated malarial infections in children cause anaemia, impaired cognitive development, school absenteeism, and increased child mortality, reducing long-term human capital formation.

  4. Stimulus for pharmaceutical and biotechnological research: The global urgency of controlling malaria has driven major investment in antimalarial drug discovery, vaccine development (e.g., the RTS,S/AS01 vaccine), and insecticide research, generating significant economic activity in the medical and biotechnology sectors.

Question 8(a) — Ten Characteristics of Class Reptilia

  1. They are ectothermic (cold-blooded); body temperature is regulated behaviourally by exploiting environmental heat sources rather than by internal metabolic heat generation.

  2. The body is covered in dry, keratinised scales or scutes that prevent desiccation and provide protection.

  3. Fertilisation is internal; males possess copulatory organs (a penis or paired hemipenes) to deposit sperm directly into the female reproductive tract.

  4. They are oviparous (egg-laying) or in some species ovoviviparous; eggs are amniotic with leathery, parchment-like shells that protect the embryo on land.

  5. Respiration is exclusively by lungs throughout the entire life cycle (no larval gill stage).

  6. Most reptiles possess a three-chambered heart (two atria and one partially divided ventricle); crocodilians are the exception, possessing a fully four-chambered heart.

  7. They possess pentadactyl limbs (five digits on each limb) adapted for terrestrial locomotion; snakes and some lizards are exceptions (limbs vestigial or absent).

  8. Digits bear claws, which assist in locomotion, digging, and prey capture.

  9. Nitrogenous waste is excreted primarily as uric acid (a paste), which conserves water — a critical adaptation for terrestrial life.

  10. Reptiles lack a middle ear cavity and external ear pinnae (with the exception of some groups such as geckos and monitor lizards that have visible external ear openings); hearing is mainly via bone conduction.

Question 8(b) — Five Adaptations of Animals in Transition from Water to Land

  1. Development of lungs for aerial respiration: Gills are efficient only in water; terrestrial animals evolved lungs (or other air-breathing organs) capable of extracting dissolved oxygen from air, which contains far more oxygen per unit volume than water.

  2. Evolution of the amniotic egg: Amphibian eggs must be laid in water to prevent desiccation. The amniotic egg (containing amnion, chorion, allantois, and yolk sac) encloses the embryo in a private aquatic environment, allowing reproduction to be completely independent of standing water.

  3. Keratinisation of the skin: Aquatic animals lose water rapidly in air by evaporation. A dry, keratinised (or scale-covered) integument greatly reduces transepidermal water loss, enabling survival in terrestrial environments.

  4. Strengthening of the skeletal system: Water provides buoyancy that partly supports an animal’s body against gravity. Terrestrial animals require a stronger, more robust skeleton — particularly stronger limb bones and a more rigid vertebral column — to support the body’s full weight in air and to transmit locomotor forces to the ground.

  5. Internal fertilisation: Aquatic animals can release gametes into water where fertilisation occurs externally. On land, water is unavailable as a medium for sperm transport; internal fertilisation ensures that sperm are delivered directly to the egg within the female’s reproductive tract, protecting gametes from desiccation.

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