2020 JUPEB Biology

2020 JUPEB Biology

BIO 001: GENERAL BIOLOGY

Question 1

(a) State one (1) function of the following cell organelles:

i. Nucleus ii. Plasma membrane iii. Ribosome iv. Chloroplast v. Ribosomal Endoplasmic Reticulum vi. Golgi apparatus vii. Mitochondria viii. Cell wall ix. Lysosome x. Vacuoles. [5 marks]

(b) Mention three (3) similarities between a prokaryotic and a eukaryotic cell. [3 marks]

© Mention two (2) differences between a prokaryotic and a eukaryotic cell. [2 marks]

Question 2

A breed of dog has genes for hair colour and leg length. Allele ‘A’ is dominant and gives brown hair. Allele ‘a’ is recessive and gives black hair. Allele ‘L’ is dominant and gives long legs, and allele ‘l’ is recessive and gives short legs.

(a) Present in tabular form the various types of genotypes and phenotypes that the dogs may have. [5 marks]

(b) Construct a genetic table to show the offspring a breeder would expect between two dogs that are heterozygous for both genes, using a Punnett square. [4 marks]

© State the phenotypic ratio of the cross. [1 mark]

BIO 002: BOTANY

Question 3

(a) What is conservation? [2 marks]

(b) Differentiate between in-situ and ex-situ conservation. [2 marks]

© Outline the merits and demerits of each of in-situ and ex-situ conservation. [6 marks]

Question 4

(a) With the aid of a labelled diagram alone, show the general sexual life cycle of fungi. [5 marks]

(b) Outline the general characteristics of Basidiomycetes. [5 marks]

BIO 003: MICROBIOLOGY

Question 5

(a) Name three (3) major constituents of plant tissues decomposed by fungi. [3 marks]

(b) Write two (2) importance of fungi to the soil. [2 marks]

© List five (5) general characteristics of fungi. [5 marks]

Question 6

(a) In tabular form, name six (6) microorganisms causing infectious diseases in animals, indicating the diseases caused and their common sources. [6 marks]

(b) Briefly describe yeast reproduction. [4 marks]

BIO 004: ZOOLOGY

Question 7

(a) Define the term: tissue. [1 mark]

(b) State the four (4) main types of tissue found in animals. [2 marks]

© Write short notes on each of the various types of epithelial tissues, indicating their structures, locations, and functions. [7 marks]

Question 8

(a) Describe sexual reproduction in Hydra. [6 marks]

(b) Briefly describe nutrition in Hydra. [4 marks]

ANSWERS

BIO 001: GENERAL BIOLOGY

Question 1(a) — Functions of Cell Organelles

| Organelle | Function |

|—|---|

| Nucleus | Controls all cellular activities; houses the genetic material (DNA) and directs growth, metabolism, and reproduction |

| Plasma membrane | Regulates the passage of substances into and out of the cell; maintains cell integrity and mediates communication with the environment |

| Ribosome | Site of protein synthesis; translates mRNA into polypeptide chains |

| Chloroplast | Carries out photosynthesis; converts light energy into chemical energy (glucose) using carbon dioxide and water |

| Rough Endoplasmic Reticulum | Synthesises and transports proteins destined for secretion, membrane insertion, or delivery to other organelles |

| Golgi apparatus | Modifies, sorts, and packages proteins and lipids received from the ER for secretion or intracellular delivery |

| Mitochondria | Site of aerobic cellular respiration; produces ATP, the cell’s primary energy currency |

| Cell wall | Provides structural rigidity, mechanical support, and protection to plant, fungal, and bacterial cells |

| Lysosome | Contains hydrolytic enzymes that digest worn-out organelles, cellular debris, and engulfed foreign particles |

| Vacuoles | Store water, nutrients, and metabolic waste; in plant cells they maintain turgor pressure and cell shape |

Question 1(b) — Three Similarities Between Prokaryotic and Eukaryotic Cells

  1. Both are bounded by a plasma membrane that acts as a selective barrier controlling what enters and leaves the cell.

  2. Both contain cytoplasm in which metabolic reactions take place.

  3. Both possess ribosomes as the site of protein synthesis (though they differ in size — 70S in prokaryotes, 80S in eukaryotes).

Question 1© — Two Differences Between Prokaryotic and Eukaryotic Cells

| Feature | Prokaryotic Cell | Eukaryotic Cell |

|—|---|—|

| Nucleus | No true membrane-bound nucleus; DNA lies free in a nucleoid region | Possesses a well-defined membrane-bound nucleus housing chromosomal DNA |

| Membrane-bound organelles | Absent — no mitochondria, ER, Golgi apparatus, etc. | Present — contains various specialised membrane-bound organelles |

Question 2(a) — Genotypes and Phenotypes of Dogs

| Genotype | Phenotype |

|—|---|

| AALL, AALl, AaLL, AaLl | Brown hair, Long legs |

| AAll, Aall | Brown hair, Short legs |

| aaLL, aaLl | Black hair, Long legs |

| aall | Black hair, Short legs |

Question 2(b) — Punnett Square (AaLl × AaLl)

Gametes produced by each parent: AL, Al, aL, al

| | AL | Al | aL | al |

|—|---|—|---|—|

| AL | AALL | AALl | AaLL | AaLl |

| Al | AALl | AAll | AaLl | Aall |

| aL | AaLL | AaLl | aaLL | aaLl |

| al | AaLl | Aall | aaLl | aall |

Question 2© — Phenotypic Ratio

9 : 3 : 3 : 1

  • 9 Brown hair, Long legs

  • 3 Brown hair, Short legs

  • 3 Black hair, Long legs

  • 1 Black hair, Short legs

BIO 002: BOTANY

Question 3(a) — Conservation

Conservation is the planned management, sustainable use, and protection of natural resources, biodiversity, and ecosystems to prevent their depletion, degradation, or extinction, and to ensure their continued availability for present and future generations.

Question 3(b) — In-situ vs Ex-situ Conservation

| | In-situ Conservation | Ex-situ Conservation |

|—|---|—|

| Definition | The protection and management of species within their natural habitats | The protection of species outside their natural habitats in controlled environments |

| Examples | National Parks, Game Reserves, Biosphere Reserves | Zoos, Botanical gardens, Seed banks, Aquaria |

Question 3© — Merits and Demerits

In-situ Conservation

Merits:

  • Allows species to continue evolving naturally within their ecological relationships and food webs.

  • Protects the entire ecosystem, not just individual species, preserving interdependencies.

  • Generally more cost-effective for large populations over wide areas.

Demerits:

  • Species remain vulnerable to natural disasters, disease outbreaks, and poaching within the protected area.

  • Difficult to control all threats (habitat loss, climate change, invasive species) operating at landscape scale.

Ex-situ Conservation

Merits:

  • Provides controlled security, veterinary care, and breeding programmes for critically endangered species.

  • Essential for species already extinct in the wild, enabling eventual reintroduction.

Demerits:

  • Species may lose natural behaviours, ecological adaptations, and genetic diversity over generations in captivity.

  • Establishment and maintenance of facilities (zoos, gene banks) are extremely expensive.

Question 4(a) — General Sexual Life Cycle of Fungi (Labelled Diagram)

(A complete labelled diagram is required in the examination. The key stages to illustrate are as follows:)


Haploid mycelium (+) Haploid mycelium (−)

| |

└──────── Plasmogamy ──────────┘

|

Dikaryotic mycelium (n + n)

|

Karyogamy

|

Diploid zygote (2n)

|

Meiosis

|

Haploid spores (n)

/ \

Germinate Germinate

| |

(+) mycelium (−) mycelium

Key stages:

  • Plasmogamy — fusion of cytoplasm of two compatible haploid mycelia

  • Karyogamy — fusion of the two nuclei to form a diploid (2n) nucleus

  • Meiosis — reduction division producing haploid (n) spores

  • Spore dispersal and germination — spores germinate into new haploid mycelia, restarting the cycle

Question 4(b) — General Characteristics of Basidiomycetes

  1. They are commonly known as club fungi; examples include mushrooms, toadstools, puffballs, and bracket fungi.

  2. They produce sexual spores called basidiospores, borne externally on club-shaped structures called basidia.

  3. The basidia are typically grouped on or within a fruiting body called the basidiocarp (e.g., the mushroom cap).

  4. Their vegetative body consists of septate hyphae that form a well-developed mycelium; the dominant stage in the life cycle is the dikaryotic (n + n) mycelium.

  5. They play critical ecological roles as decomposers of wood (especially lignin) and as mycorrhizal partners with the roots of higher plants; some species are serious plant pathogens (rusts and smuts).

BIO 003: MICROBIOLOGY

Question 5(a) — Major Constituents of Plant Tissues Decomposed by Fungi

  1. Cellulose — the main structural polysaccharide of plant cell walls

  2. Lignin — the complex aromatic polymer that gives wood its rigidity

  3. Hemicellulose — the branched polysaccharide matrix surrounding cellulose fibres in the cell wall

Question 5(b) — Importance of Fungi to the Soil

  1. Nutrient cycling: Fungi decompose complex organic matter (leaf litter, dead wood), releasing essential mineral nutrients such as nitrogen, phosphorus, and potassium back into the soil for plant uptake.

  2. Soil structure improvement: Fungal hyphae physically bind soil particles into aggregates, enhancing soil aeration, porosity, and water retention capacity, which supports plant root growth.

Question 5© — Five General Characteristics of Fungi

  1. They are eukaryotic organisms with membrane-bound nuclei.

  2. They are heterotrophic, obtaining nutrition by absorption — either as saprotrophs (decomposing dead matter) or as parasites.

  3. Their cell walls are composed of chitin, a nitrogen-containing polysaccharide.

  4. They reproduce by means of spores, produced both sexually and asexually.

  5. They lack chlorophyll and are therefore incapable of photosynthesis.

Question 6(a) — Microorganisms Causing Infectious Diseases in Animals

| Microorganism | Type | Disease Caused | Common Source |

|—|---|—|---|

| Mycobacterium tuberculosis | Bacterium | Tuberculosis | Airborne droplets from infected individuals |

| Plasmodium falciparum | Protozoan | Malaria | Bite of infected female Anopheles mosquito |

| Rabies virus | Virus | Rabies | Bite or saliva of infected animals (dogs, bats) |

| Trypanosoma brucei | Protozoan | Trypanosomiasis (sleeping sickness) | Bite of infected tsetse fly |

| Salmonella typhi | Bacterium | Typhoid fever | Contaminated food and water |

| Influenza virus | Virus | Influenza (flu) | Airborne droplets; contact with infected animals or persons |

Question 6(b) — Yeast Reproduction

Yeast reproduces both asexually and sexually.

Asexual reproduction (Budding): Under favourable conditions, a small outgrowth (bud) develops on the parent cell wall. The nucleus divides mitotically; one daughter nucleus migrates into the bud. The bud enlarges and eventually separates to become an independent cell. Under rapid growth, buds may remain attached, forming chains called pseudohyphae.

Sexual reproduction: Under unfavourable conditions (nutrient limitation), two haploid yeast cells of opposite mating types (a and α) fuse — first by plasmogamy (cytoplasmic fusion), then karyogamy (nuclear fusion) — to form a diploid zygote. The diploid cell undergoes meiosis, producing four haploid ascospores enclosed within an ascus. When conditions improve, ascospores are released and germinate into new haploid cells.

BIO 004: ZOOLOGY

Question 7(a) — Definition of Tissue

A tissue is a group of structurally similar cells that are derived from the same origin and work together to perform a specific function within an organism.

Question 7(b) — Four Main Types of Animal Tissue

  1. Epithelial tissue

  2. Connective tissue

  3. Muscle tissue

  4. Nervous tissue

Question 7© — Types of Epithelial Tissue

| Type | Structure | Location | Function |

|—|---|—|---|

| Simple squamous epithelium | Single layer of flat, scale-like cells with a central nucleus | Walls of alveoli, lining of blood and lymph capillaries, Bowman’s capsule | Filtration, diffusion, and osmosis across thin surfaces |

| Simple cuboidal epithelium | Single layer of cube-shaped cells, approximately equal in height and width | Kidney tubules, thyroid follicles, small gland ducts | Secretion and absorption |

| Simple columnar epithelium | Single layer of tall, column-like cells, often with a basally located nucleus | Lining of the stomach, small and large intestines | Absorption of nutrients; mucus secretion |

| Ciliated epithelium | Columnar cells bearing hair-like cilia on their free surface; often contains goblet cells | Lining of the trachea, bronchi, uterine tubes, and nasal passages | Propulsion of mucus, dust particles, or ova across the epithelial surface |

| Stratified squamous epithelium | Multiple layers of cells; outermost layers are flat and squamous | Epidermis of skin, lining of oral cavity, oesophagus, and vagina | Protection against abrasion, dehydration, and microbial invasion |

| Pseudostratified epithelium | Single layer of cells of varying heights giving a falsely layered appearance; all cells contact the basement membrane | Lining of the trachea and upper respiratory tract | Secretion and movement of mucus via cilia |

Question 8(a) — Sexual Reproduction in Hydra

Hydra normally reproduces asexually by budding, but switches to sexual reproduction under unfavourable environmental conditions such as cold temperatures, overcrowding, or food scarcity.

Sexual reproduction proceeds as follows:

  1. Gonad formation: The ectoderm of the body wall gives rise to temporary gonads. Testes develop as cone-shaped protuberances in the upper region of the body, while ovaries develop as rounded swellings near the base.

  2. Gamete production: The testes produce numerous flagellated spermatozoa by meiosis. Each ovary typically produces a single large egg (ovum) by meiosis, which remains attached to the body wall.

  3. Fertilisation: Ripe spermatozoa are released into the surrounding water and swim to a receptive ovum on the same or another individual. Fertilisation is usually cross-fertilisation (the testes mature before the ovaries in the same individual — a condition called protandry — minimising self-fertilisation). Fusion of sperm and egg forms a diploid zygote.

  4. Embryo protection: The zygote secretes a tough, chitinous shell around itself, forming a resistant embryo (cyst or dormant embryo) that can withstand harsh conditions.

  5. Resumption of development: When favourable conditions return, the shell ruptures and the embryo develops into a new young Hydra.

Question 8(b) — Nutrition in Hydra

Hydra is a carnivorous animal that feeds on small aquatic invertebrates such as Daphnia (water fleas), small crustaceans, and mosquito larvae. Nutrition involves the following steps:

  1. Capture: The tentacles, which bear specialised stinging cells called cnidoblasts (containing the organelles nematocysts), discharge on contact with prey. Nematocysts either inject paralysing toxins, entangle, or adhere to the prey, immobilising it.

  2. Ingestion: The paralysed prey is manoeuvred by the tentacles through the mouth into the gastrovascular cavity (enteron).

  3. Extracellular digestion: Gland cells lining the gastrovascular cavity secrete digestive enzymes that begin breaking down the prey into smaller fragments within the cavity.

  4. Intracellular digestion: Nutritive-muscular cells engulf the partially digested particles by phagocytosis; digestion is completed inside food vacuoles within these cells.

  5. Egestion: Undigested waste material is expelled back out through the mouth (Hydra has no separate anus).

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