If you have already downloaded the JAMB Biology syllabus, you know the problem with it. It is a list. Five sections, dozens of topic headings, and a right-hand column of “candidates should be able to” statements written in the flat language of a government document. Nothing in it tells you which topics carry the most questions, which ones are quietly worth skipping until the last week, or what an examiner is actually looking for when the syllabus says “relate the structure of the kidneys to the excretory and osmo-regulatory functions.”
I wrote this to fill those gaps. Every topic in the official syllabus is here, in the official order, with the detail JAMB expects you to have, the question styles that keep coming back, and the mistakes I see cost candidates marks year after year.
Read it once from top to bottom to see the shape of the subject. Then come back to it topic by topic while you study. Where I am giving you my own judgment rather than the syllabus, I say so.
Quick answers
What is the JAMB Biology syllabus? It is the official document from the Joint Admissions and Matriculation Board that lists every topic UTME Biology questions may be drawn from, along with the specific skills candidates are expected to demonstrate on each topic. Questions outside it are not set.
How many sections does it have? Five: (A) Variety of Organisms, (B) Form and Functions, (C) Ecology, (D) Heredity and Variations, and (E) Evolution.
How many Biology questions will I answer? Use of English is compulsory for every candidate and carries 60 multiple-choice questions, while each of the other three subjects carries 40. So Biology is 40 questions.
How long is the exam? You answer 180 multiple-choice questions across four subjects in a total of two hours, which works out to roughly 40 seconds per question if you spread the time evenly.
Is the Biology syllabus different every year? No. It has been stable for years. Check the official copy on jamb.gov.ng before you start studying anyway, because the version circulating on WhatsApp is often an old scan.
Which section carries the most questions? Section B, Form and Functions. It is the longest section by a wide margin and past papers reflect that.
How to actually read the syllabus (most candidates get this wrong)
Open the official syllabus and you will see two columns. The left column has topics, contents and notes. The right column, headed “Objectives”, begins with “Candidates should be able to…” and then lists numbered skills.
Almost everyone reads the left column and ignores the right one. I would do it the other way round, because the right column is where the questions come from.
Look at the difference. Under Nutrition, the left column says “The mammalian tooth (structures, types and functions).” That tells you a topic exists. The right column says candidates should be able to “compare the dental formulae of man, sheep and dog.” That tells you a question is coming that requires you to know three dental formulae well enough to tell them apart under time pressure.
Another one. Left column: “Transport.” Right column: “compare specific functions of the hepatic portal vein, the pulmonary vein and artery, aorta, the renal artery and vein.” Five named vessels. If you only know that the heart pumps blood, you will lose that mark.
The method I use follows from that:
- Take each objective statement in the right column as a mini-syllabus of its own.
- Notice the verb. Identify and state mean recall. Compare, differentiate and relate mean you need two or more things held side by side. Deduce, analyse and apply mean a scenario or a set of data is coming and you will have to reason from it.
- Notice the named examples. When the syllabus names an organism, a gland, a vessel or a disease, that name is fair game in a question stem or an option. Amoeba, Euglena, Paramecium, Spirogyra, Rhizopus, Hydra, Taenia, Dryopteris, Cycad, Loranthus, sundew, bladderwort. All of those appear by name. Learn them by name.
The verbs matter more than they look. Roughly a third of the objectives in the Biology syllabus use apply, deduce, analyse or determine. In my experience those are the questions that separate a 60 from an 85, and they are the ones you cannot cram the night before.
The 2027 UTME: format, timing and what it means for Biology
The UTME is a computer-based test. You sit at a terminal, questions appear one at a time, and you navigate with the mouse or the keyboard. All four subjects are multiple choice, with Use of English compulsory and three others chosen to match your intended course.
Four consequences for Biology candidates:
Forty questions, four options each. No essays, no short answers, no practical paper. Everything JAMB wants to test about the structure of a nephron has to fit into a stem and four options.
No negative marking. Answer every question. A blank is worth zero and a guess is worth a one in four chance. There is no version of this exam where leaving a question unanswered is the right move.
Diagrams appear as images on screen. JAMB draws on standard textbook diagrams: the mammalian heart, the nephron, the eye, the ear, a longitudinal section of a flower, the internal structure of a leaf, a food web. You will be shown a labelled diagram with letters and asked which label performs a named function. Practise reading diagrams with the labels covered.
The clock is shared. Two hours for all four papers together. If you spend fifty minutes on Biology because you enjoy it, you have stolen that time from Chemistry or Mathematics. Give Biology twenty-five to thirty minutes and move on.
Registration usually opens in January or February and the exam usually runs in April, but JAMB announces the exact dates each year and they shift. Confirm on jamb.gov.ng rather than trusting a screenshot.
Section A: Variety of Organisms
This section is about what living things are, how they are grouped, and how they are built to survive where they live. It is the most memorisation-heavy part of the syllabus and, for that reason, the cheapest marks in the paper. When I have seen candidates lose marks here, it has been to carelessness rather than difficulty.
A1. Living organisms
What the syllabus lists: characteristics of living things; cell structure and the functions of cell components; and levels of organisation, from the single cell up through tissue, organ, system and organism.
What you must be able to do: distinguish living from non-living things; identify the structures of plant and animal cells; explain what each cell component does; compare plant and animal cells; and place the five levels of organisation in the correct sequence.
Characteristics of living things
The standard seven are movement, respiration, nutrition, growth, excretion, reproduction, irritability (response to stimuli), and in many textbooks an eighth, adaptation or death. The usual mnemonic in Nigerian classrooms is MR NIGER D: Movement, Respiration, Nutrition, Irritability, Growth, Excretion, Reproduction, Death.
The subtlety worth holding on to is that some non-living things show one of these. A car moves and consumes fuel. A crystal grows. A flame consumes oxygen and produces carbon dioxide and heat. The distinguishing point is that living things show all of them, and that growth in living things happens from within (intussusception) rather than by addition on the outside (accretion). That word pair, intussusception versus accretion, shows up in options.
Cell structure and function
You need both cells and both lists.
| Component | Function | Found in |
|---|---|---|
| Cell wall (cellulose) | Rigid support and protection; freely permeable | Plant only |
| Cell membrane | Selectively permeable boundary; controls what enters and leaves | Both |
| Nucleus | Contains chromosomes; controls cell activities and inheritance | Both |
| Cytoplasm | Site of many reactions; holds the organelles | Both |
| Mitochondrion | Aerobic respiration; produces ATP | Both |
| Chloroplast | Contains chlorophyll; site of photosynthesis | Plant only |
| Ribosome | Protein synthesis | Both |
| Endoplasmic reticulum | Transport within the cell; rough ER carries ribosomes | Both |
| Golgi body | Packaging and secretion of cell products | Both |
| Lysosome | Contains digestive enzymes; breaks down worn-out parts | Mainly animal |
| Large central vacuole | Stores cell sap; maintains turgidity | Plant (animal vacuoles are small and many) |
| Centriole | Spindle formation during cell division | Animal only |
The comparison question usually comes down to four differences: cell wall, chloroplast, vacuole size, and centrioles. Know those four cold and you can answer any phrasing of it.
Frequent trap: candidates say plant cells have no cell membrane because they have a cell wall. Plant cells have both. The wall lies outside the membrane.
Levels of organisation
Cell → tissue → organ → system → organism. The syllabus gives its own examples and those are the ones to memorise, because they turn up as options:
- Cell level: Euglena, Paramecium, Amoeba, Chlamydomonas. One cell carries out all life functions.
- Tissue level: Hydra, epithelial tissue. Cells of the same type working together.
- Organ level: onion bulb, leaf, heart. Different tissues forming a structure with a job.
- System level: digestive, reproductive, excretory. Organs working together.
- Organism level: the whole individual.
Note the wrinkle in the official document. It lists Chlamydomonas at the organism level and Euglena and Paramecium at the cell level, even though all three are unicellular. In JAMB’s framing, a unicellular organism is simultaneously a cell and a complete organism. If a question asks which level Chlamydomonas represents, go with the syllabus.
Advantage of higher organisation: division of labour, specialisation of cells, greater efficiency, larger body size. Disadvantage: loss of independence, so damage to one organ can kill the whole organism.
A2. Classification and evolution among the five kingdoms
What the syllabus lists: Monera, Protista, Fungi, Plantae and Animalia, with named examples for each; the four plant divisions; plants grouped by life cycle length; and the invertebrate and vertebrate groups.
What you must be able to do: analyse the external features of the listed organisms; use those features to show increasing structural complexity; trace their life histories; explain the transition from life in water to life on land; and trace the evolution of the listed plants.
That fourth objective is the one candidates underestimate. Knowing the groups is only half of it. You also have to explain why the sequence runs in the order it does.
The five kingdoms at a glance
| Kingdom | Cell type | Wall | Nutrition | Syllabus examples |
|---|---|---|---|---|
| Monera | Prokaryotic, no true nucleus | Present (not cellulose) | Autotrophic or heterotrophic | Bacteria, blue-green algae |
| Protista | Eukaryotic, unicellular | Absent or present | Both | Amoeba, Euglena, Paramecium |
| Fungi | Eukaryotic, mostly multicellular | Chitin | Saprophytic or parasitic | Mushroom, Rhizopus |
| Plantae | Eukaryotic, multicellular | Cellulose | Autotrophic | Spirogyra, mosses, ferns, seed plants |
| Animalia | Eukaryotic, multicellular | None | Heterotrophic | Hydra to mammals |
Euglena comes up a lot. It has chlorophyll and photosynthesises like a plant, but it also has a flexible pellicle instead of a cell wall, a flagellum for movement, an eyespot, and a contractile vacuole, and it can feed heterotrophically in darkness. That mixture is why it sits in Protista. Expect a question phrased as “which organism has both plant and animal characteristics.”
The plant kingdom, in evolutionary order
This is the sequence JAMB wants, and each step solves a specific problem of leaving water:
- Thallophyta (Spirogyra). A filament of identical cells. No true roots, stems or leaves. Body is a thallus. Lives in water. Reproduces by conjugation and fragmentation.
- Bryophyta (mosses and liverworts; Brachymenium, Marchantia). First land plants. Have rhizoids rather than roots and no vascular tissue, so they stay small and stay damp. Gametophyte generation dominant. Still need a film of water for the sperm to swim to the egg.
- Pteridophyta (ferns; Dryopteris). First plants with true vascular tissue, so xylem and phloem, and therefore true roots, stems and leaves. Sporophyte generation dominant. Reproduce by spores on the underside of fronds in sori. Still water-dependent for fertilisation.
- Spermatophyta (seed plants). Reproduce by seeds, so they no longer need external water for fertilisation. Split into:
- Gymnosperms (cycads, conifers). Naked seeds, borne in cones, not enclosed in an ovary. Needle-like leaves.
- Angiosperms (flowering plants). Seeds enclosed in a fruit; true flowers. Divided into monocots (maize: one cotyledon, parallel venation, fibrous roots, floral parts in threes, scattered vascular bundles) and dicots (water leaf: two cotyledons, net venation, tap root, floral parts in fours or fives, vascular bundles in a ring).
The pattern to say out loud until it sticks: thallus → rhizoids → vascular tissue → seeds → enclosed seeds and flowers. Each step reduces dependence on water.
Plants classified by life span
- Annuals: complete the life cycle in one season, then die. Maize, rice, cowpea, tomato.
- Biennials: take two seasons, storing food in the first and flowering in the second. Carrot, cabbage, onion.
- Perennials: live for many years and flower repeatedly. Mango, oil palm, cocoa, cashew.
Note that the official syllabus contains a typing error here, asking candidates to “classify plants into animals, biennials and perennials.” It means annuals. Do not let it confuse you.
The invertebrates, in order of advancement
| Phylum | Symmetry | Key features | Syllabus example |
|---|---|---|---|
| Coelenterata | Radial | Two body layers, single opening, tentacles with stinging cells | Hydra |
| Platyhelminthes | Bilateral | Flattened, no body cavity, hooks and suckers if parasitic | Taenia (tapeworm) |
| Nematoda | Bilateral | Cylindrical, unsegmented, pointed at both ends | Roundworm, Ascaris |
| Annelida | Bilateral | Segmented body, chaetae, closed blood system | Earthworm |
| Arthropoda | Bilateral | Jointed appendages, chitinous exoskeleton, moulting | Mosquito, cockroach, housefly, bee, butterfly |
| Mollusca | Bilateral | Soft unsegmented body, muscular foot, calcareous shell | Snail |
Arthropoda is the largest phylum in the animal kingdom, and the insects in it are named individually in the syllabus because JAMB wants their economic importance.
Economic importance of the named insects. Honeybee: pollination, honey, beeswax. Butterfly and moth: pollination, silk from the silkworm moth; larvae are crop pests. Mosquito: vector of malaria, yellow fever, filariasis, dengue. Housefly: mechanical vector of cholera, typhoid, dysentery. Cockroach: contaminates food, carries pathogens. When a question asks for the beneficial insect, it is nearly always the bee or the silkworm.
The vertebrates
- Pisces. Cartilaginous (shark, ray: cartilage skeleton, placoid scales, five gill slits with no operculum, no swim bladder) and bony (tilapia: bony skeleton, cycloid or ctenoid scales, operculum covering the gills, swim bladder for buoyancy).
- Amphibia. Toads and frogs. Moist skin without scales, gills as larvae and lungs as adults, external fertilisation, eggs laid in water.
- Reptilia. Lizards, snakes, turtles. Dry scaly skin, internal fertilisation, shelled eggs laid on land, cold-blooded.
- Aves. Feathers, beaks without teeth, forelimbs modified as wings, hollow bones, warm-blooded, hard-shelled eggs.
- Mammalia. Hair, mammary glands, external ears, diaphragm, four-chambered heart, warm-blooded, mostly viviparous, heterodont teeth.
The advancement trend runs: aquatic to terrestrial, external to internal fertilisation, unprotected eggs to shelled eggs to internal development, cold-blooded to warm-blooded. Every one of those transitions has been a question.
A3. Structural, functional and behavioural adaptations
What the syllabus lists: adaptive colouration and its functions; behavioural adaptations in social animals; structural adaptations.
What you must be able to do: describe how structure, function and behaviour fit an organism to its environment; categorise countershading and warning colouration; differentiate the castes in social insects; account for basking, territorial behaviour, hibernation and aestivation; and explain adaptations for obtaining food, defence, securing mates, temperature regulation and water conservation.
Adaptive colouration
- Camouflage (cryptic colouration): the organism blends in. The stick insect and the praying mantis are the syllabus examples.
- Countershading: dark above, light below. Fish, toads and snakes are named explicitly. It works because a fish seen from above blends with the dark water below, and seen from below blends with the bright sky.
- Warning (aposematic) colouration: bright colours advertising that the organism is poisonous or distasteful. The syllabus names mushrooms.
- Mimicry: a harmless species resembles a harmful one.
Social insects and their castes
Termites: the queen (large abdomen, lays eggs), the king (fertilises the queen), workers (sterile, build the mound, forage, feed the young), soldiers (large heads and mandibles, defend the colony). Honeybees: queen (single fertile female, lays eggs), drones (males, fertilise the queen), workers (sterile females, collect nectar, build combs, feed larvae, guard the hive).
Two facts that show up in options: the queen termite is the largest member of the colony, and worker bees are sterile females, not males.
Behavioural adaptations
- Basking: lizards spread themselves on warm surfaces in the morning to raise body temperature, because reptiles are ectothermic and cannot generate enough heat internally.
- Territorial behaviour: an animal defends an area to secure food, nesting space and mates. The male Agama lizard’s head-bobbing display is the local example.
- Hibernation: a period of dormancy through cold conditions, with metabolic rate lowered.
- Aestivation: a period of dormancy through hot, dry conditions. The African lungfish aestivating in dried mud is the classic example.
Structural adaptations by function
Obtaining food. Birds’ beaks and legs are the standard question. A hawk has a hooked beak and taloned feet for tearing flesh; a duck has a broad flattened beak and webbed feet for filtering and swimming; a woodpecker has a chisel beak and clinging feet; a sunbird has a long slender beak for nectar. Insect mouthparts: the mosquito has piercing and sucking mouthparts, the butterfly and moth have a long coiled proboscis for siphoning nectar, the housefly has sponging mouthparts, the cockroach and grasshopper have biting and chewing mouthparts.
Protection and defence. Stick insect and praying mantis by camouflage, the toad by its poison glands and its ability to inflate, the tortoise by its shell, the porcupine by its quills.
Securing mates. The red head of the male Agama lizard in the breeding season, and the display of feathers by male birds.
Regulating body temperature. Sweat glands and skin capillaries in mammals, feathers in birds trapping insulating air, hair in mammals doing the same, panting in dogs.
Conserving water. Spines instead of leaves in cactus, thick waxy cuticle, sunken stomata, scales on reptiles, and in mammals a long loop of Henle producing concentrated urine.
Section B: Form and Functions
This is the largest section in the syllabus and it carries the most questions. If your revision time is limited, I would weight it here. Nine topics, running from the internal anatomy of a plant through to hormonal control and homeostasis.
B1. Internal structure of a flowering plant and a mammal
What you must be able to do: identify transverse sections of root, stem and leaf; relate the structure of each to its function; identify the supporting tissues; describe how those tissues are distributed; examine the arrangement of mammalian internal organs; and describe the appearance and position of the digestive, reproductive and excretory organs.
Reading a transverse section
You will be shown a drawing and asked to identify it or to name a labelled tissue. The distinguishing features:
Root (dicot). Vascular bundles arranged in a central star-shaped core. Xylem forms the arms of the star, phloem sits between the arms. No pith in a young dicot root. Endodermis with a Casparian strip surrounds the stele. Root hairs on the epidermis, no cuticle, no stomata.
Stem (dicot). Vascular bundles arranged in a ring, each with xylem to the inside and phloem to the outside, separated by cambium. Pith in the centre, cortex outside the ring. Epidermis with a cuticle.
Monocot stem. Vascular bundles scattered throughout the ground tissue rather than arranged in a ring, and no cambium, which is why monocots do not show true secondary thickening.
Leaf. Upper epidermis with a thick cuticle, then palisade mesophyll (tall, tightly packed, most chloroplasts, main site of photosynthesis), then spongy mesophyll (rounded, loose, air spaces for gaseous exchange), then lower epidermis with most of the stomata. Vascular bundle in the midrib with xylem above phloem.
One relationship to fix in memory: xylem sits above phloem in a leaf midrib, inside phloem in a stem, and alternating with phloem in a root.
Supporting tissues in plants
- Collenchyma: living cells with cellulose thickened at the corners. Flexible support in young stems and leaf stalks.
- Sclerenchyma: dead cells with uniformly lignified walls. Rigid support and strength.
- Xylem: dead, lignified vessels and tracheids. Conducts water and mineral salts upward, and provides mechanical support.
- Phloem fibres: lignified fibres associated with phloem tissue, giving support.
- Parenchyma: thin-walled living packing tissue. Support comes from turgidity rather than thickening.
Distribution: collenchyma is concentrated just under the epidermis of young stems and in petioles; sclerenchyma appears in caps over vascular bundles and in the pericycle; xylem is central in roots and inner in stems.
The mammalian body plan
Learn the positions, because a labelled diagram question is common. Thoracic cavity above the diaphragm holds the lungs and the heart, the heart sitting slightly to the left between the lungs. Below the diaphragm: liver on the right, stomach on the left, spleen behind the stomach, pancreas in the loop of the duodenum, kidneys at the back of the abdominal cavity against the dorsal wall, the right kidney slightly lower than the left because the liver occupies space above it. Bladder in the pelvic cavity.
B2. Nutrition
The largest topic in the largest section. Twenty-one separate objectives are listed for it.
Modes of nutrition
Autotrophic: the organism makes its own organic food from simple inorganic substances. Two kinds: photosynthesis, using light energy, and chemosynthesis, using energy from oxidising inorganic chemicals. Green plants photosynthesise; nitrifying bacteria such as Nitrosomonas and Nitrobacter, and sulphur bacteria, chemosynthesise.
Heterotrophic: the organism depends on ready-made organic food. The syllabus names four types:
- Holozoic: taking in solid food and digesting it internally. Sheep and man are the named examples. Subdivided into herbivores, carnivores and omnivores.
- Parasitic: feeding on a living host and harming it. Roundworm and tapeworm are the animal examples; Loranthus, the mistletoe found on Nigerian trees, is the plant example. Loranthus is a partial parasite, because it has chlorophyll and photosynthesises but draws water and minerals from its host through haustoria.
- Saprophytic: feeding on dead organic matter by secreting enzymes onto it and absorbing the products. Rhizopus and mushroom.
- Carnivorous plants: sundew and bladderwort. These photosynthesise normally but trap insects to supplement their nitrogen supply, because they grow in nitrogen-poor swampy soil. The question is almost always about which nutrient they are after, and the answer is nitrogen, not energy.
Photosynthesis
The equation: six molecules of carbon dioxide plus six of water, in the presence of light and chlorophyll, give one molecule of glucose and six of oxygen.
Light reaction. Takes place in the grana of the chloroplast. Requires light. Chlorophyll absorbs light energy, which splits water into hydrogen and oxygen. This is photolysis. Oxygen is released as a by-product and hydrogen is picked up by NADP. ATP is generated. This is the stage that produces the oxygen you breathe.
Dark reaction (Calvin cycle). Takes place in the stroma. Does not require light directly, but does require the ATP and hydrogen made in the light reaction. Carbon dioxide is fixed and reduced to form carbohydrate.
Learn the pairings as a table, because the questions test exactly this split:
| Light reaction | Dark reaction | |
|---|---|---|
| Site | Grana | Stroma |
| Light needed | Yes | No (needs light-reaction products) |
| Key event | Photolysis of water | Fixation and reduction of carbon dioxide |
| Products | ATP, reduced NADP, oxygen | Glucose |
Experiments you must recognise. Testing a leaf for starch: boil the leaf in water to kill it and break the cell walls, boil in ethanol to remove chlorophyll (using a water bath, because ethanol is flammable), soften in warm water, then add iodine solution. Blue-black means starch is present. To show light is necessary, partly cover a leaf with black paper and test after several hours; only the exposed part turns blue-black. To show carbon dioxide is necessary, enclose a leaf in a flask with sodium hydroxide, which absorbs carbon dioxide. To show chlorophyll is necessary, use a variegated leaf; only the green parts give a positive test.
Mineral requirements
Macronutrients, needed in large amounts: nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, and in most lists carbon, hydrogen and oxygen.
Micronutrients (trace elements), needed in small amounts: iron, zinc, copper, manganese, boron, molybdenum, chlorine.
Deficiency symptoms the syllabus names specifically:
- Nitrogen: stunted growth and chlorosis, the yellowing of older leaves, because nitrogen is needed for chlorophyll and protein.
- Phosphorus: poor root development, stunted growth, leaves turning dark green or purplish, delayed maturity.
- Potassium: yellowing and scorching at leaf margins, weak stems, premature leaf fall.
Classes of food
| Class | Elements | Sources | Function | Deficiency |
|---|---|---|---|---|
| Carbohydrates | C, H, O | Yam, rice, cassava, maize, bread | Energy | Marasmus, weakness |
| Proteins | C, H, O, N (± S, P) | Beans, meat, fish, eggs, milk | Growth and repair | Kwashiorkor, marasmus |
| Fats and oils | C, H, O | Palm oil, groundnut, butter | Energy store, insulation, protection of organs | Weight loss, poor insulation |
| Vitamins | Various | Fruits, vegetables, liver | Regulate body processes | Specific deficiency diseases |
| Mineral salts | Various | Salt, milk, vegetables, liver | Bones, teeth, blood, enzymes | Anaemia, rickets, goitre |
| Water | H, O | Drinks, food | Solvent, transport, temperature regulation | Dehydration |
| Roughage | None | Vegetables, unrefined cereals | Adds bulk, prevents constipation | Constipation |
Vitamin deficiencies to memorise. Vitamin A: night blindness and xerophthalmia. Vitamin B1 (thiamine): beriberi. Vitamin B3 (niacin): pellagra. Vitamin B12: pernicious anaemia. Vitamin C (ascorbic acid): scurvy. Vitamin D: rickets in children, osteomalacia in adults. Vitamin K: delayed blood clotting.
Mineral deficiencies. Iron: anaemia. Calcium and phosphorus: rickets and poor teeth. Iodine: goitre. Sodium: muscle cramps.
A balanced diet contains all the classes in the right proportions for the individual’s age, sex, occupation, state of health and climate. Those five factors are examinable as a list.
Food tests
| Food substance | Test | Positive result |
|---|---|---|
| Starch | Add iodine solution | Blue-black |
| Reducing sugar | Add Benedict’s solution and boil | Brick-red precipitate |
| Non-reducing sugar | Boil with dilute acid, neutralise, then Benedict’s | Brick-red precipitate |
| Protein | Add sodium hydroxide then a few drops of copper sulphate (Biuret) | Violet or purple |
| Protein | Millon’s reagent and heat | Brick-red precipitate |
| Oil or fat | Rub on paper | Translucent spot that does not dry |
| Oil or fat | Shake with ethanol, pour into water | Milky white emulsion |
A recurring question gives you a result and asks what the food is. Learn the table in both directions, from result to substance as well as from substance to result.
The mammalian tooth and dentition
Structure. Crown above the gum, neck at the gum line, root embedded in the jaw. Enamel is the hardest substance in the body and covers the crown. Dentine lies beneath it and forms the bulk. The pulp cavity in the centre holds blood vessels and nerves. Cement fixes the root in its socket, and the periodontal fibres anchor it.
Types and functions. Incisors: chisel-shaped, for cutting and biting. Canines: pointed, for tearing and piercing. Premolars: with cusps, for crushing and grinding. Molars: broad with several cusps, for grinding and chewing.
Dental formulae. Written as one half of the upper jaw over one half of the lower, then doubled.
- Man: I 2/2, C 1/1, PM 2/2, M 3/3 = 32 teeth. Omnivorous, so no tooth type is exaggerated.
- Sheep: I 0/3, C 0/1, PM 3/3, M 3/3 = 32 teeth. Note the missing upper incisors and canines, replaced by a horny pad the sheep bites against, and the diastema, a gap that lets the tongue move grass around. Herbivore.
- Dog: I 3/3, C 1/1, PM 4/4, M 2/3 = 42 teeth. Large canines and carnassial teeth for shearing flesh. Carnivore.
The numbers matter less than what they tell you. Absent upper incisors mean a grazing herbivore. Large canines and carnassials mean a carnivore.
The alimentary canal and its accessory organs
The route: mouth → oesophagus → stomach → duodenum → ileum → colon → rectum → anus.
Mouth. Mechanical breakdown by teeth. Salivary glands secrete saliva containing ptyalin (salivary amylase), which acts on cooked starch in an alkaline medium to give maltose. Saliva also lubricates.
Stomach. Gastric glands secrete gastric juice: hydrochloric acid, which kills bacteria and provides the acid medium; pepsin, which converts proteins to peptides; and rennin in young mammals, which curdles milk protein. Churning mixes the food into chyme.
Duodenum. Two secretions arrive. Bile from the liver, stored in the gall bladder, contains no enzymes but emulsifies fats, breaking large globules into small droplets, and neutralises the acid chyme. Pancreatic juice from the pancreas contains amylase (starch to maltose), trypsin (proteins to peptides) and lipase (fats to fatty acids and glycerol).
Ileum. Intestinal juice completes digestion: maltase (maltose to glucose), sucrase, lactase, peptidase (peptides to amino acids), lipase. Absorption happens here, through villi.
Adaptations of the ileum for absorption: it is very long; it is folded and lined with millions of villi and microvilli, giving an enormous surface area; the villus wall is one cell thick; each villus has a dense network of blood capillaries for glucose and amino acids and a lacteal for fatty acids and glycerol; and it has a rich blood supply that maintains the concentration gradient.
Colon. Absorption of water and mineral salts. Bacterial action. Faeces formed and stored in the rectum.
End products. Carbohydrates give glucose. Proteins give amino acids. Fats give fatty acids and glycerol. Learn the three as a set.
General characteristics of enzymes. They are proteins; they act as catalysts and are not used up; they are specific in action; they work fastest at an optimum temperature, around 37 degrees Celsius in mammals; they are denatured by high temperature; each has an optimum pH; they can be inhibited; and they work in very small amounts.
Nutrition processes in order: ingestion, digestion, absorption, assimilation, egestion. Note that egestion is the removal of undigested material and is not excretion, since faeces were never part of the body’s metabolism. That distinction is a favourite trap.
B3. Transport
What you must be able to do: connect increasing size and complexity with the need for a transport system; identify what is transported and in what form; describe the circulatory system; compare the functions of named blood vessels; identify the plant vascular system; state the composition and functions of blood and lymph; describe diffusion, osmosis, plasmolysis and turgidity; and compare transport mechanisms in animals and plants.
Why a transport system is needed
A small organism like Amoeba has a large surface-area-to-volume ratio, so diffusion alone moves substances fast enough across its whole body. As an organism gets bigger, volume grows faster than surface area, the ratio falls, and the distance from the surface to the innermost cells becomes too great for diffusion. A transport system solves this. That reasoning is the answer to “why do large organisms need a transport system,” and JAMB phrases it as a surface-area-to-volume question.
Materials transported and their forms
Water and dissolved mineral salts move up the xylem. Manufactured food travels in the phloem, mainly as sucrose. In mammals, glucose, amino acids, hormones and salts travel dissolved in plasma; oxygen travels combined with haemoglobin as oxyhaemoglobin; carbon dioxide travels mostly as hydrogencarbonate in plasma; urea travels dissolved in plasma from liver to kidney.
Blood
Plasma is about 90 per cent water and carries dissolved food, hormones, excretory products, salts, plasma proteins including fibrinogen, and heat.
Red blood cells (erythrocytes) are biconcave, have no nucleus when mature, contain haemoglobin, are made in the red bone marrow, live about 120 days and are destroyed in the liver and spleen. The biconcave shape increases surface area for gas exchange, and the missing nucleus makes room for more haemoglobin. Both of those points are asked.
White blood cells (leucocytes) are larger, nucleated and fewer. Phagocytes engulf bacteria; lymphocytes produce antibodies.
Platelets (thrombocytes) are cell fragments involved in clotting. Clotting sequence to know: damaged platelets release thrombokinase, which with calcium ions converts prothrombin to thrombin, which converts soluble fibrinogen into insoluble fibrin threads that trap red cells and form the clot.
Functions of blood: transport of oxygen, carbon dioxide, digested food, excretory products and hormones; defence against disease; clotting; and distribution of heat, which regulates body temperature.
Lymph is tissue fluid that has drained into lymph vessels. It resembles plasma but has less protein, no red blood cells, and many lymphocytes. It returns fluid and protein to the blood, absorbs fats from the ileum through the lacteals, and filters pathogens in the lymph nodes.
The heart and named vessels
The mammalian heart has four chambers. Deoxygenated blood from the body enters the right atrium through the vena cava, passes to the right ventricle, and leaves by the pulmonary artery to the lungs. Oxygenated blood returns by the pulmonary vein to the left atrium, passes to the left ventricle, and leaves by the aorta to the body. Valves prevent backflow: tricuspid on the right, bicuspid or mitral on the left, and semilunar valves at the base of the arteries.
The left ventricle has a much thicker wall than the right, because it pumps blood to the whole body while the right pumps only to the lungs. That is one of the most frequently asked single facts in this topic.
The named vessels in the syllabus:
| Vessel | From | To | Carries |
|---|---|---|---|
| Pulmonary artery | Right ventricle | Lungs | Deoxygenated blood |
| Pulmonary vein | Lungs | Left atrium | Oxygenated blood |
| Aorta | Left ventricle | Body | Oxygenated blood at high pressure |
| Hepatic portal vein | Small intestine | Liver | Blood richest in digested food |
| Renal artery | Aorta | Kidney | Blood with the most urea |
| Renal vein | Kidney | Vena cava | Blood with the least urea |
Two exceptions worth stating plainly: the pulmonary artery is the only artery carrying deoxygenated blood, and the pulmonary vein is the only vein carrying oxygenated blood. And the hepatic portal vein is unusual because it starts in capillaries and ends in capillaries rather than running from a capillary bed to the heart.
Artery versus vein. Arteries have thick muscular elastic walls, a narrow lumen, no valves along their length, and carry blood away from the heart at high pressure in pulses. Veins have thinner walls, a wide lumen, valves along their length, and carry blood towards the heart at low pressure without pulsing. Capillaries are one cell thick, which is what allows exchange.
Open versus closed circulation. In an open system, as in insects and other arthropods, blood leaves the vessels and bathes the tissues directly in a haemocoel; pressure is low and the blood is not confined. In a closed system, as in earthworms and vertebrates, blood stays inside vessels throughout, which allows higher pressure and faster delivery.
Transport in plants
Xylem conducts water and dissolved minerals upwards only. Its cells are dead, lignified, and lack cross-walls, so they form continuous tubes. Phloem conducts manufactured food both up and down, and its sieve tubes are living, with sieve plates and companion cells.
The mechanisms JAMB names:
- Root pressure: a push from the roots caused by the active uptake of water into the root, enough to move water some distance up a short stem.
- Transpiration pull: the main mechanism. Water evaporating from the leaves creates tension that pulls the continuous water column up the xylem, held together by cohesion between water molecules and adhesion to the xylem walls.
- Capillarity: the rise of water in narrow tubes.
- Active transport: movement of mineral ions against a concentration gradient, requiring energy from respiration.
Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration until evenly distributed. It needs no energy and no membrane.
Osmosis is the movement of water molecules from a dilute solution to a concentrated solution through a semi-permeable membrane. Its correct definition mentions the membrane and specifies water; options that leave out either are wrong.
Turgidity happens when a plant cell in a dilute (hypotonic) solution takes in water, the vacuole swells, and the protoplasm presses against the cell wall. The cell becomes firm. Turgor is what holds up herbaceous plants and opens stomata.
Plasmolysis happens when a cell is placed in a concentrated (hypertonic) solution, loses water, and the protoplasm shrinks away from the cell wall. A plasmolysed plant wilts. Putting it back into distilled water reverses the process, which is deplasmolysis. An animal cell in a hypotonic solution has no wall to resist the pressure, so it bursts, which is haemolysis in a red cell.
B4. Respiration
What you must be able to do: explain the significance of respiration; outline glycolysis and the Krebs cycle with reference to ATP; deduce the products of respiration from experimental set-ups; describe the named respiratory organs and surfaces and which organisms have them; describe how stomata open and close; examine the role of oxygen; explain the effect of insufficient oxygen in muscles; use yeast and sugar to demonstrate fermentation; and state the economic importance of yeast.
Respiration versus breathing
Respiration is the chemical breakdown of food in cells to release energy. Breathing is the mechanical movement of air in and out. Candidates who use the words interchangeably lose marks on a definition question.
Characteristics of a respiratory surface
Thin, usually one cell thick; moist, so gases dissolve; large in surface area; permeable to gases; and well supplied with blood or close to the transport system. These five apply to gills, lungs, the skin of a toad and the spongy mesophyll alike.
Named respiratory organs and where they occur:
| Surface or organ | Organism |
|---|---|
| Body surface (general) | Amoeba, Paramecium, earthworm, toad (partly) |
| Gills | Fish, tadpole, prawn |
| Tracheae and spiracles | Insects: cockroach, grasshopper |
| Lungs | Mammals, birds, reptiles, adult amphibians |
| Stomata | Leaves |
| Lenticels | Woody stems |
Aerobic respiration
Glucose plus oxygen gives carbon dioxide, water and energy. About 2,900 kilojoules, or roughly 38 molecules of ATP, from one glucose molecule.
Glycolysis takes place in the cytoplasm, does not require oxygen, and breaks one glucose molecule into two molecules of pyruvic acid with a net gain of 2 ATP.
Krebs cycle takes place in the mitochondrial matrix, requires oxygen, and completely oxidises pyruvic acid to carbon dioxide and water while generating hydrogen carriers. The electron transport chain on the cristae then produces most of the ATP.
The site question is a near-certainty: glycolysis in the cytoplasm, Krebs cycle in the mitochondrion.
Anaerobic respiration
In the absence of oxygen, glucose is only partly broken down, so much less energy is released, about 2 ATP.
In yeast and some bacteria: glucose gives ethanol plus carbon dioxide plus energy. This is fermentation.
In muscle: glucose gives lactic acid plus energy. Lactic acid accumulating in muscle during hard exercise causes fatigue and cramp, and the body then owes an oxygen debt, which is repaid by continued deep breathing after exercise so that the lactic acid can be oxidised. Both the term and the mechanism are examinable.
Economic importance of yeast: brewing beer and wine; baking, where the carbon dioxide raises the dough; production of ethanol; a source of vitamin B and single-cell protein; and use in the pharmaceutical industry.
The stomata
Each stoma is a pore bounded by two guard cells. Guard cells differ from other epidermal cells in two ways that matter: they contain chloroplasts and their inner walls are thicker than their outer walls.
Opening. In light, guard cells photosynthesise and accumulate solutes, potassium ions move in, the osmotic pressure rises, water enters by osmosis from neighbouring cells, and the guard cells become turgid. Because the inner wall is thick and inelastic while the outer wall stretches, the cells curve apart and the pore opens.
Closing. In darkness, or in drought when abscisic acid is released, solutes leave, water follows, the guard cells become flaccid, the walls straighten and the pore closes.
Experiments to recognise
Limewater turning milky shows carbon dioxide is produced. Cobalt chloride paper turning from blue to pink shows water vapour. A thermometer or thermos flask showing a temperature rise in germinating seeds shows heat is released. A control of boiled, killed seeds is what makes each of those set-ups valid, and questions frequently ask why the control is needed.
B5. Excretion
What you must be able to do: define excretion and state its significance; relate each excretory structure to its function; relate kidney structure to excretion and osmoregulation; identify the functions and products of the lungs and skin; and deduce the economic importance of plant excretory products.
Excretion is the removal of metabolic waste products from the body. The key word is metabolic. Waste that resulted from a chemical reaction in the body counts. Undigested food does not, because it was never absorbed or metabolised.
Excretory structures and their organisms
| Structure | Organism | Excretes |
|---|---|---|
| Contractile vacuole | Amoeba, Paramecium | Excess water, some nitrogenous waste |
| Flame cell | Flatworms such as Planaria, Taenia | Water, nitrogenous waste |
| Nephridium | Earthworm | Urea, water, salts |
| Malpighian tubule | Insects | Uric acid (dry, conserving water) |
| Kidney | Vertebrates | Urea, water, salts |
| Stomata and lenticels | Plants | Oxygen, carbon dioxide, water vapour |
Note the logic behind the insect case. Insects excrete uric acid, which is almost insoluble and is passed out nearly dry with the faeces. That is a water conservation adaptation for terrestrial life. Freshwater organisms have the opposite problem, taking in water constantly by osmosis, which is why Amoeba needs a contractile vacuole to pump it back out.
The kidney and the nephron
The kidney has an outer cortex, an inner medulla, and a pelvis leading to the ureter. Its functional unit is the nephron, of which there are about a million per kidney.
Trace the path: blood arrives by the renal artery, which branches into an afferent arteriole that feeds the glomerulus, a knot of capillaries inside the cup-shaped Bowman’s capsule in the cortex. The afferent arteriole is wider than the efferent arteriole leaving it, which raises the pressure inside the glomerulus and drives ultrafiltration. Water, glucose, amino acids, salts and urea pass into the capsule. Blood cells and plasma proteins are too large and stay behind.
The filtrate then passes through the proximal convoluted tubule, where selective reabsorption returns all the glucose, most of the amino acids, salts and much of the water to the blood by active transport and osmosis. Next the loop of Henle, which concentrates salts in the medulla and makes it possible to produce urine more concentrated than blood. Then the distal convoluted tubule and the collecting duct, where the final adjustment of water happens under the control of antidiuretic hormone.
Osmoregulation. When the body is short of water, the pituitary releases more ADH, the collecting duct becomes more permeable, more water is reabsorbed, and the urine is small in volume and concentrated. When there is excess water, less ADH is released and the urine is copious and dilute. That inverse relationship is asked in both directions, so learn it as a pair.
Composition of urine: water, urea, uric acid, creatinine, and salts. Glucose in urine is abnormal and suggests diabetes mellitus. Protein in urine is abnormal and suggests damage to the glomerulus.
Lungs and skin
The lungs excrete carbon dioxide and water vapour. The skin excretes water, salts and small amounts of urea in sweat, and also regulates temperature and acts as a sense organ and a barrier. Note the double role: sweating is both excretion and thermoregulation, and a question may ask you to name the organ that does both.
Excretory products of plants and their uses
Plants have no specialised excretory organs. Most waste is stored in leaves and bark that are later shed, or diffused out. The syllabus asks for economic importance:
- Latex from the rubber tree: rubber.
- Resins from pines: varnish, adhesives.
- Gums from acacia: adhesives, food and pharmaceutical industries.
- Tannins: tanning leather, ink.
- Alkaloids: quinine, morphine, caffeine, nicotine, used in medicine.
- Mucilage: thickeners.
- Oxygen: a by-product of photosynthesis used by all aerobes.
B6. Support and movement
What you must be able to do: determine the need for support and movement; identify plant supporting tissues and their distribution; relate plant responses to light, water, gravity and touch; identify regions of growth and the role of auxins; relate chitin, cartilage and bone to support; relate skeleton structure to support, locomotion and respiration; differentiate types of joints; and apply skeletal functions to the animal’s wellbeing.
Movements in plants
Tropic movements are growth movements of a fixed plant part in response to a directional stimulus, and the direction of the response depends on the direction of the stimulus.
- Phototropism: response to light. Shoots are positively phototropic, roots negatively so.
- Geotropism: response to gravity. Roots positively geotropic, shoots negatively so.
- Hydrotropism: response to water. Roots positively hydrotropic.
- Thigmotropism (haptotropism): response to touch, as in tendrils coiling round a support.
- Chemotropism: response to chemicals, as in the pollen tube growing towards the ovule.
Tactic movements are movements of a whole free-moving organism towards or away from a stimulus. Euglena swimming towards light is positive phototaxis; a sperm swimming towards a chemical from the egg is chemotaxis.
Nastic movements are non-directional. The response is the same whatever direction the stimulus comes from. The closing of Mimosa pudica leaves when touched, the opening of a flower in the morning, the closing at night.
Sleep movements (nyctinasty) are the daily folding of leaves at night, as in Mimosa and many legumes.
The distinction that trips candidates: tropism is directional and involves growth; taxis involves locomotion of the whole organism; nasty is non-directional. If the organism moves from place to place, it is a taxis, not a tropism.
Auxins are produced at the shoot and root tips. In a shoot lit from one side, auxin migrates to the shaded side, where it stimulates greater cell elongation, so that side grows faster and the shoot bends towards the light. Auxins also cause apical dominance, promote root formation in cuttings, and prevent premature fruit drop. Interestingly, the concentration that promotes growth in shoots inhibits it in roots, which is why roots bend the opposite way.
Supporting tissues in animals
- Chitin: the exoskeleton of arthropods. Light, strong, waterproof, but must be shed periodically for growth (ecdysis).
- Cartilage: flexible, found at the ends of bones, in the pinna, nose, trachea and intervertebral discs; the entire skeleton in cartilaginous fish.
- Bone: rigid, mineralised with calcium phosphate and calcium carbonate, forms the endoskeleton of most vertebrates.
Exoskeleton versus endoskeleton. An exoskeleton is outside the body, protects well and prevents water loss, but limits growth and becomes heavy at large size. An endoskeleton is inside, grows with the animal, allows large body size and greater mobility, but gives less protection to the surface.
The mammalian skeleton
Three divisions: axial (skull, vertebral column, ribs, sternum), appendicular (limb bones and girdles), and the girdles themselves (pectoral and pelvic).
Vertebrae to distinguish: the atlas is the first cervical vertebra, has no centrum and articulates with the skull, allowing nodding. The axis is the second, has an odontoid process, and allows the head to rotate. Cervical vertebrae have vertebrarterial canals. Thoracic vertebrae have long neural spines and facets for ribs. Lumbar vertebrae are large with strong transverse processes for muscle attachment.
Functions of the skeleton: support and shape; protection of organs, the skull for the brain and the rib cage for the heart and lungs; locomotion, by providing attachment for muscles and acting as levers; respiration, since rib and sternum movement ventilates the lungs; production of blood cells in the red bone marrow; and storage of calcium and phosphorus.
Types of joints. Immovable (fixed or fibrous), as in the sutures of the skull. Slightly movable (cartilaginous), as between vertebrae. Freely movable (synovial), which subdivide into: ball-and-socket at the shoulder and hip, allowing movement in all directions; hinge at the elbow, knee and finger, allowing movement in one plane; pivot between atlas and axis, allowing rotation; and gliding between the carpals and tarsals.
Muscles work in antagonistic pairs. The biceps contracts to flex the arm while the triceps relaxes; the triceps contracts to extend it while the biceps relaxes. Muscles pull, they never push, which is why they must come in pairs. Tendons attach muscle to bone, ligaments attach bone to bone.
B7. Reproduction
What you must be able to do: differentiate asexual and sexual reproduction; apply natural vegetative propagation in crop production; apply grafting, budding and layering; relate flower parts to their functions; state the advantages of cross-pollination; deduce placentation types and fruit types; differentiate male and female reproductive organs; describe fertilisation; relate the mother’s health and drug use to embryo development; and explain in vitro fertilisation and birth control.
Asexual reproduction
One parent, no gametes, no fertilisation, offspring genetically identical to the parent.
- Binary fission: Amoeba, Paramecium, bacteria. The nucleus divides, then the cytoplasm.
- Budding: yeast, Hydra. An outgrowth forms and detaches.
- Spore formation: Rhizopus, mushroom, ferns.
- Regeneration: Planaria, starfish.
- Natural vegetative propagation: by stem tubers (Irish potato), root tubers (sweet potato, cassava), bulbs (onion), corms (cocoyam), rhizomes (ginger, canna), runners or stolons (sweet potato, grass), suckers (banana, plantain, pineapple), and bulbils.
Artificial vegetative propagation: cutting (a piece of stem is planted, as in cassava and sugarcane), layering (a branch is bent to the ground and covered with soil until it roots, then separated), marcotting or air layering (roots induced on an aerial branch), grafting (a scion from one plant is joined to the stock of another, used in mango, citrus and cocoa), and budding (a bud with a patch of bark is inserted into the stock, used in citrus and rubber).
Advantages: offspring mature quickly, desirable characteristics are preserved exactly, plants that produce no viable seeds can still be propagated, and no pollinating agent is needed. Disadvantages: no variation, so the whole crop is equally vulnerable to one disease; overcrowding; and diseases pass from parent to offspring.
The flower
Calyx (sepals): protects the bud. Corolla (petals): attracts insects in insect-pollinated flowers. Androecium (stamens): each stamen has an anther producing pollen grains and a filament. Gynoecium or pistil (carpels): each carpel has a stigma to receive pollen, a style, and an ovary containing ovules.
Essential parts are the stamens and carpels. Sepals and petals are non-essential. A flower with both stamens and carpels is bisexual or hermaphrodite; one with only one is unisexual.
Pollination
Transfer of pollen from anther to stigma. Self-pollination is transfer within the same flower or the same plant; cross-pollination is transfer to a different plant of the same species.
| Insect-pollinated | Wind-pollinated | |
|---|---|---|
| Petals | Large, brightly coloured, scented | Small, dull or absent, no scent |
| Nectar | Present | Absent |
| Pollen | Small amount, sticky or spiky, heavy | Large amount, smooth, light, dry |
| Anthers | Inside the flower, firmly attached | Hanging outside, loosely attached, versatile |
| Stigma | Small, sticky, inside | Large, feathery, protruding |
Advantages of cross-pollination: it produces variation, which improves the chances of adaptation and evolution; offspring are usually more vigorous and better able to resist disease; and seed yield is often higher. Its disadvantage is dependence on an external agent, so pollination may fail.
Devices that favour cross-pollination: unisexual flowers, dichogamy (anthers and stigma maturing at different times, whether protandry or protogyny), heterostyly (styles and stamens of different lengths), and self-sterility.
Fertilisation in flowering plants
A pollen grain lands on a compatible stigma, absorbs nutrients and germinates. The pollen tube grows down the style, guided chemotropically, and enters the ovule through the micropyle. The tube nucleus degenerates. The generative nucleus divides into two male gametes. One fuses with the egg cell to form the diploid zygote; the other fuses with the two polar nuclei to form the triploid endosperm nucleus. This is double fertilisation, and it happens only in flowering plants.
After fertilisation: the ovule becomes the seed, the integuments become the testa, the ovary becomes the fruit, the ovary wall becomes the pericarp, and the zygote becomes the embryo. Petals, sepals, stamens and style usually wither.
Placentation is the arrangement of ovules within the ovary: marginal (cowpea and other legumes), axile (orange, tomato), parietal (pawpaw), basal (sunflower), free-central, and apical.
Fruits. Simple fruits come from one ovary of one flower, and are either fleshy (drupe such as mango and coconut; berry such as tomato and pawpaw; pome such as apple) or dry. Dry fruits are dehiscent, splitting to release seeds (legume or pod, capsule, follicle), or indehiscent (achene, caryopsis in maize, nut, samara). Aggregate fruits come from several ovaries of one flower, as in soursop and strawberry. Multiple or composite fruits come from the ovaries of several flowers in an inflorescence, as in pineapple and breadfruit.
Reproduction in mammals
Male: two testes in the scrotum, held outside the body because sperm production needs a temperature slightly below body temperature; epididymis for storage and maturation; vas deferens; seminal vesicle, prostate gland and Cowper’s gland, which add the seminal fluid; urethra; penis. Testes produce sperm and testosterone.
Female: two ovaries producing ova and the hormones oestrogen and progesterone; oviducts or Fallopian tubes, where fertilisation happens; uterus, where implantation and development happen; cervix; vagina.
The menstrual cycle runs about 28 days. Menstruation on days 1 to 5, follicle development and repair of the uterine lining under FSH and oestrogen to about day 13, ovulation around day 14 under LH, then the corpus luteum secretes progesterone to maintain the thickened lining. If fertilisation does not occur, the corpus luteum degenerates, progesterone falls, and the lining is shed. Ovulation around day 14 is the single most-asked fact in this topic.
Fertilisation takes place in the oviduct. One sperm penetrates the ovum, the membranes fuse, and the two haploid nuclei combine to form a diploid zygote. The zygote divides repeatedly to form a ball of cells that implants in the uterine wall. The placenta develops and allows exchange of oxygen, food and antibodies from mother to foetus, and carbon dioxide and urea from foetus to mother, while keeping the two blood supplies separate. The umbilical cord connects foetus to placenta, and the amniotic fluid cushions the foetus.
The mother’s health and the embryo. Poor maternal nutrition causes low birth weight and impaired development. Alcohol crosses the placenta and causes foetal alcohol syndrome. Smoking reduces oxygen supply. Some drugs cross the placenta and cause deformities, thalidomide being the historical example. Infections such as rubella, HIV and syphilis can be transmitted. That is why self-medication in pregnancy is dangerous.
Modern methods of regulating reproduction. In vitro fertilisation, in which the ovum is fertilised outside the body and the embryo transferred to the uterus, used in cases of blocked oviducts. Birth control methods include natural methods such as the rhythm and withdrawal methods, barrier methods such as condoms and diaphragms, chemical methods such as spermicides, hormonal methods such as the pill and implants, the intrauterine device, and surgical methods such as vasectomy and tubal ligation.
B8. Growth
What you must be able to do: apply the conditions necessary for germination to plant growth, and differentiate epigeal from hypogeal germination.
Growth is an irreversible increase in the size, dry weight and complexity of an organism resulting from cell division, cell enlargement and cell differentiation. The three phases are important, because a question may ask which phase happens at which region.
Aspects of growth: cell division at the meristems, cell enlargement just behind them, and cell differentiation, where cells become specialised.
Regions of growth in plants: apical meristems at the tips of roots and shoots for growth in length, lateral meristems (cambium) for growth in girth, and intercalary meristems at the nodes of grasses.
The growth curve is S-shaped or sigmoid: a lag phase of slow initial growth, an exponential phase of rapid growth, a decelerating phase, and a plateau where growth stops. In insects with an exoskeleton, growth is stepwise rather than smooth, because increases in size only happen at each moult.
Conditions necessary for germination: water, oxygen, a suitable temperature, and a viable seed. Some seeds also need light and all need enzymes. Light is not required by most seeds during germination, which is a common trap, since photosynthesis only starts after the seedling emerges.
Epigeal germination: the hypocotyl elongates and pushes the cotyledons above the soil, where they become green and photosynthesise briefly. Cowpea, groundnut, castor oil.
Epigeal versus hypogeal: in hypogeal germination the epicotyl elongates instead, and the cotyledons stay below the soil. Maize, rice, broad bean.
The mnemonic that works: hypo means below, and in hypogeal germination the cotyledons stay below.
Viability is the ability of a seed to germinate. Dormancy is a resting period during which a viable seed will not germinate even in favourable conditions, caused by an impermeable seed coat, immature embryo or the presence of inhibitors.
B9. Coordination and control
What you must be able to do: apply knowledge of the central nervous system to coordination; illustrate reflex actions; differentiate reflex, voluntary and conditioned reflex actions; relate the sense organs to their functions; apply that knowledge to detecting and correcting defects; state the location of the endocrine glands; relate each hormone to its function; examine the effects of phytohormones; and relate hormones to homeostasis.
The nervous system
Central nervous system: brain and spinal cord. The brain has three main regions. The cerebrum is the largest, controls intelligence, memory, reasoning and voluntary action, and receives sensations. The cerebellum controls balance, posture and the coordination of muscular movement. The medulla oblongata controls involuntary activities such as heartbeat, breathing, swallowing and peristalsis. The hypothalamus controls body temperature, thirst, hunger and the pituitary.
Peripheral nervous system: cranial and spinal nerves, plus the autonomic system, itself divided into the sympathetic (which prepares the body for action, raising heart rate and dilating pupils) and parasympathetic (which restores the resting state) divisions. They are antagonistic.
The neurone. Cell body, dendrites receiving impulses, and an axon carrying impulses away, often insulated by a myelin sheath which speeds conduction. Sensory neurones carry impulses from receptors to the CNS, motor neurones from the CNS to effectors, and relay or intermediate neurones connect the two within the CNS.
Transmission of impulses. An impulse travels along the axon as a wave of electrical depolarisation. At a synapse, the gap between two neurones, the impulse cannot jump. Instead the arriving impulse triggers the release of a chemical transmitter, acetylcholine, which diffuses across the gap and starts a new impulse in the next neurone. The transmitter is then broken down by an enzyme. Because transmitter is released on one side only, the synapse makes transmission one-way, and that is what a question about the function of a synapse is testing.
The reflex arc: stimulus → receptor → sensory neurone → relay neurone in the spinal cord → motor neurone → effector → response. The response is rapid, automatic, and does not involve the brain in a spinal reflex.
Three types of action to distinguish:
| Reflex action | Voluntary action | Conditioned reflex | |
|---|---|---|---|
| Control | Spinal cord | Cerebrum | Cerebrum, then automatic |
| Speed | Very fast | Slower | Fast |
| Learned? | Inborn | Deliberate | Learned by repeated association |
| Examples | Knee jerk, blinking, withdrawing hand from heat, sneezing, pupil contraction | Writing, talking, walking deliberately | Salivating at the sight of food, riding a bicycle, swimming |
Pavlov’s dogs are the standard illustration of the conditioned reflex.
The sense organs
Skin contains receptors for touch, pressure, pain, heat and cold.
Nose: olfactory receptors detect chemicals in the air. Smell and taste are linked, so food seems tasteless when you have a cold.
Tongue: taste buds detect four basic tastes, sweet, sour, salty and bitter, with the substance needing to be dissolved first.
Eye. Light passes through the cornea, which does most of the refraction, then the pupil, whose size the iris controls, then the lens, which is adjusted by the ciliary muscles and suspensory ligaments for accommodation. The image forms on the retina, inverted and smaller than the object. Rods in the retina work in dim light and detect black and white; cones need bright light and detect colour. The fovea or yellow spot has the highest concentration of cones and gives the sharpest vision; the blind spot is where the optic nerve leaves and has no receptors.
Accommodation. To see a near object, the ciliary muscles contract, the suspensory ligaments slacken, and the lens becomes more convex. To see a distant object, the ciliary muscles relax, the ligaments tighten, and the lens flattens. The direction of this is worth learning carefully, because the two are commonly swapped in options.
Eye defects and corrections:
| Defect | Cause | Correction |
|---|---|---|
| Short sight (myopia) | Eyeball too long or lens too convex; image forms in front of retina | Concave (diverging) lens |
| Long sight (hypermetropia) | Eyeball too short or lens too flat; image forms behind retina | Convex (converging) lens |
| Astigmatism | Uneven curvature of cornea or lens | Cylindrical lens |
| Presbyopia | Lens loses elasticity with age | Convex or bifocal lens |
| Cataract | Lens becomes cloudy | Surgery |
| Colour blindness | Defective cones, inherited and sex-linked | No correction |
Ear. The outer ear is the pinna, which collects sound, and the auditory canal. The middle ear holds the ear drum and the three ossicles, malleus, incus and stapes, which amplify vibrations, plus the Eustachian tube, which equalises pressure on both sides of the ear drum. The inner ear holds the cochlea, which converts vibrations into nerve impulses and is responsible for hearing, and the three semicircular canals, which are responsible for balance and are set at right angles to one another. Hearing in the cochlea, balance in the semicircular canals. That split is the whole question.
Hormones in animals
A hormone is a chemical messenger produced by an endocrine gland, secreted directly into the blood, and carried to a target organ where it produces an effect in small amounts.
| Gland | Location | Hormone | Effect | Malfunction |
|---|---|---|---|---|
| Pituitary | Base of the brain | Growth hormone | Growth of bones and muscle | Too little: dwarfism. Too much: gigantism, acromegaly in adults |
| Pituitary | ADH (vasopressin) | Water reabsorption in kidney | Too little: diabetes insipidus | |
| Pituitary | FSH, LH, prolactin, oxytocin, TSH, ACTH | Reproduction, milk, control of other glands | ||
| Thyroid | Neck | Thyroxine (needs iodine) | Controls metabolic rate; growth and development | Too little: goitre, cretinism in children, myxoedema in adults. Too much: exophthalmic goitre |
| Parathyroid | Behind thyroid | Parathormone | Controls blood calcium and phosphate | Too little: muscle spasm (tetany) |
| Adrenal | Above kidneys | Adrenaline (medulla) | Fight-or-flight: raises heart rate, blood glucose, breathing rate | |
| Adrenal | Cortisol and aldosterone (cortex) | Glucose metabolism; salt and water balance | Addison’s disease | |
| Pancreas | Loop of duodenum | Insulin (islets of Langerhans) | Lowers blood glucose | Too little: diabetes mellitus |
| Pancreas | Glucagon | Raises blood glucose | ||
| Ovary | Abdomen | Oestrogen, progesterone | Female secondary characteristics, menstrual cycle, pregnancy | |
| Testis | Scrotum | Testosterone | Male secondary characteristics, sperm production |
The pituitary is called the master gland because its hormones control other endocrine glands. The pancreas is worth noting twice, because it is both an endocrine gland (insulin and glucagon into the blood) and an exocrine gland (pancreatic juice through a duct).
Nervous versus hormonal coordination. Nervous: transmission by electrical impulse along nerves, very fast, short-lived, precise target. Hormonal: transmission by chemicals in the blood, slower, longer-lasting, wider effect. Both are asked as a comparison.
Plant hormones
- Auxins: cell elongation, tropisms, apical dominance, root formation in cuttings, prevention of premature fruit fall. Synthetic auxins in high concentration act as selective weedkillers.
- Gibberellins: stem elongation and bolting, breaking seed dormancy, promoting germination and flowering.
- Cytokinins: promote cell division, delay leaf ageing, used in tissue culture.
- Ethylene (ethene): a gas that ripens fruit and promotes leaf abscission. One ripe fruit will ripen the others in the same basket.
- Abscisic acid: inhibits growth, maintains dormancy, closes stomata under water stress.
Homeostasis
Homeostasis is the maintenance of a constant internal environment despite changes outside. It works by negative feedback: a deviation from the norm triggers a response that reverses it.
Temperature regulation. When body temperature rises, the skin arterioles dilate so more blood flows near the surface and loses heat, sweat glands secrete more sweat which evaporates and takes latent heat away, and hairs lie flat. When temperature falls, arterioles constrict, sweating stops, hairs stand erect to trap insulating air, and shivering generates heat by muscle contraction. The hypothalamus is the control centre.
Blood glucose regulation. After a meal, blood glucose rises, the pancreas releases insulin, and the liver converts glucose to glycogen while cells take up more glucose, so the level falls. During fasting, glucose falls, the pancreas releases glucagon, and the liver converts glycogen back to glucose. Adrenaline also raises blood glucose. Failure of insulin production causes diabetes mellitus, with glucose appearing in the urine.
Salt and water regulation is described under the kidney above, controlled by ADH and aldosterone.
Section C: Ecology
Ecology is the study of the relationship between organisms and their environment. It is the section where questions most often come with a scenario, a diagram of a food web, or a set of data to interpret. Learn the vocabulary precisely. In my experience most of the marks here turn on using the right term.
Terms to fix first. Habitat is the place where an organism lives. Niche is the role it plays there, including what it eats, when it is active and where it breeds. Population is all the individuals of one species in an area. Community is all the populations of different species in an area. Ecosystem is the community plus the non-living environment. Biosphere is the whole part of the earth where life exists.
C1. Factors affecting the distribution of organisms
Abiotic (non-living) factors: temperature, rainfall, relative humidity, wind speed and direction, light, altitude, salinity, turbidity, pH, pressure, and edaphic (soil) factors such as texture, mineral content and water-holding capacity.
Biotic (living) factors: competition, predation, parasitism, mutualism, and above all human activity, including farming, deforestation, urbanisation, pollution, bush burning and overgrazing.
Instruments and what they measure. JAMB names three explicitly and adds more in practice:
| Instrument | Measures |
|---|---|
| Secchi disc | Turbidity or water transparency |
| Thermometer | Temperature |
| Rain gauge | Rainfall |
| Hygrometer | Relative humidity |
| Anemometer | Wind speed |
| Wind vane | Wind direction |
| pH meter or universal indicator | Acidity or alkalinity |
| Hydrometer | Salinity or density of water |
| Photometer or light meter | Light intensity |
| Quadrat | Population density of sedentary organisms |
| Sweep net, pooter, pitfall trap | Collecting small animals |
Learn the Secchi disc separately. It is the least familiar instrument on the list and the one candidates most often miss.
C2. Symbiotic interactions, energy flow and nutrient cycling
Associations between organisms:
- Mutualism (symbiosis): both benefit. Rhizobium in the root nodules of legumes; lichen, an association of a fungus and an alga; cellulose-digesting bacteria in the rumen of a cow.
- Commensalism: one benefits, the other is unaffected. Epiphytes such as orchids growing on tree branches for light; the remora attached to a shark; the sea anemone on a hermit crab’s shell.
- Parasitism: one benefits, the other is harmed. Tapeworm in the human gut; Loranthus on a tree; Plasmodium in a human.
- Amensalism: one is harmed, the other is unaffected. Penicillium producing penicillin that kills nearby bacteria; the allelopathic effect of the shade of a large tree on herbs beneath it.
- Predation: one organism kills and eats another. Hawk and chick, lion and antelope.
- Competition: two organisms need the same limited resource. Intraspecific competition is within one species and is more intense, because the needs are identical. Interspecific competition is between different species.
- Saprophytism: feeding on dead organic matter. Mushroom, Rhizopus, bacteria of decay.
- Cooperation: members of a species working together, as in a termite colony or a pack hunt.
Food chains and food webs. A food chain is a linear sequence showing the transfer of energy from one organism to the next, with the arrow pointing in the direction of energy flow, that is, from the eaten to the eater. A food web is several interconnected food chains in a habitat, and it is a more realistic picture because most organisms have more than one food source.
Trophic levels. First: producers, the green plants. Second: primary consumers, the herbivores. Third: secondary consumers, the primary carnivores. Fourth: tertiary consumers. Decomposers act at every level. A typical savanna chain: grass → grasshopper → lizard → hawk.
Energy flow. Energy enters as sunlight, is fixed by producers, and passes along the chain. Only about 10 per cent of the energy at one trophic level is passed to the next; the rest is lost as heat in respiration, in undigested material, and in excretion. This is why food chains rarely have more than four or five links and why there are always fewer top carnivores than producers.
Ecological pyramids. A pyramid of numbers plots the number of organisms at each level, and can be inverted when one large producer such as a tree supports many insects. A pyramid of biomass plots dry mass, and is usually upright. A pyramid of energy is always upright, because energy is always lost at each transfer. That “always” is examinable.
The carbon cycle. Carbon dioxide is removed from the atmosphere by photosynthesis and returned by respiration in plants and animals, by decay through decomposers, by combustion of fossil fuels and wood, and by volcanic activity. The oceans act as a store. Burning fossil fuels and deforestation raise atmospheric carbon dioxide, which contributes to the greenhouse effect and global warming, with consequences including melting ice, rising sea levels, and shifts in rainfall.
The water cycle. Evaporation from water bodies and transpiration from plants together give evapotranspiration; water vapour condenses to form clouds; precipitation returns water as rain; some runs off into rivers, some infiltrates to become groundwater. The water cycle affects every other nutrient cycle, because nutrients move in solution.
The nitrogen cycle. Nitrogen makes up about 78 per cent of the atmosphere but cannot be used directly by plants. Learn the four processes and the organisms:
- Nitrogen fixation: atmospheric nitrogen converted to nitrogen compounds. By Rhizobium in the root nodules of legumes, by free-living Azotobacter and Clostridium in the soil, by blue-green algae, and physically by lightning.
- Ammonification: decomposers break down dead organisms, urine and faeces into ammonia.
- Nitrification: Nitrosomonas converts ammonia into nitrites; Nitrobacter converts nitrites into nitrates, the form plants absorb.
- Denitrification: Pseudomonas denitrificans and other denitrifying bacteria convert nitrates back into free nitrogen, returning it to the atmosphere.
The bacteria names are worth memorising in pairs. Nitroso- makes nitrite, Nitro-bacter makes nitrate. Alphabetical order matches the sequence.
C3. Natural habitats
Aquatic habitats.
- Freshwater (pond, stream, lake): low salt concentration, so organisms constantly gain water by osmosis and must remove it. Organisms include water lily, Spirogyra, tilapia, tadpoles, water snails, mosquito larvae.
- Marine (sea, ocean): high and stable salinity, so organisms lose water and must conserve it. Deepest, largest, most stable habitat. Organisms include seaweed, sharks, whales, corals.
- Estuarine and mangrove swamp: salinity fluctuates with the tide, so organisms must be euryhaline. Mangrove plants such as Rhizophora have breathing roots (pneumatophores) for oxygen in waterlogged mud, stilt roots for support in soft mud, and viviparous germination in which the seed germinates while still on the parent. Periwinkles, crabs, mudskippers.
- Seashore: the intertidal zone. Organisms face wave action, alternate exposure and submersion, and must attach firmly or burrow.
Terrestrial and arboreal habitats. Tree-tops support epiphytes, birds, monkeys and insects, with adaptations for climbing such as prehensile tails, curved claws and clinging feet. Abandoned farmland or a savanna field supports grasses, shrubs, grasshoppers, lizards, rodents and snakes. Burrows and holes support rodents, snakes and earthworms, offering shelter from heat and predators.
Adaptations to look for. Aquatic: streamlined shape, fins, gills, swim bladder, waterproof feathers, webbed feet. Terrestrial: waterproof skin or cuticle, lungs, internal fertilisation, limbs for support. Arboreal: grasping limbs, tails, hooks, light body.
C4. Nigerian biomes
Learn these as a north-to-south sequence, because rainfall decreases as you move north and the vegetation changes with it.
| Biome | Location | Rainfall and features | Vegetation |
|---|---|---|---|
| Mangrove and freshwater swamp | Niger Delta, coastal Rivers, Bayelsa, Delta | Very high rainfall; waterlogged, saline | Mangrove with stilt and breathing roots, raffia palm |
| Tropical rainforest | Ondo, Edo, Cross River, Ogun, Osun | Over 1,500 mm; hot and humid all year | Tall trees in three layers, buttress roots, lianas, epiphytes; evergreen |
| Guinea savanna | Middle belt, Kwara, Niger, Benue, Plateau | 1,000 to 1,500 mm; distinct dry season | Tall grasses with scattered fire-resistant trees |
| Sudan savanna | Kano, Katsina, Sokoto, Zamfara | 500 to 1,000 mm; long dry season | Short grasses, thorny scattered trees, baobab, acacia |
| Sahel savanna | Extreme north: Borno, Yobe | Under 500 mm | Sparse short grass, date palm, thorny shrubs; desert encroachment |
| Montane forest and grassland | Jos, Obudu and Mambilla plateaus | High altitude, cooler temperatures | Grassland with patches of forest in valleys |
Rainforest adaptations to name: buttress roots for support in shallow soil, drip tips on leaves to shed heavy rain, epiphytes reaching for light, lianas climbing to the canopy, and layering into emergent, canopy and undergrowth. Savanna adaptations: deep tap roots reaching groundwater, thick fire-resistant bark, reduced or thorny leaves, and grasses with underground rhizomes that survive burning.
C5. The ecology of populations
Population density is the number of organisms per unit area or volume. Divide the number of organisms by the area. If 400 grasshoppers are counted in 50 square metres, the density is 8 per square metre. Expect a calculation like this.
Factors that increase population: natality (birth rate) and immigration. Factors that decrease population: mortality (death rate) and emigration. Population change equals births plus immigration minus deaths minus emigration.
Why human population is rising rapidly: better medical care and vaccination lowering the death rate, improved food production and nutrition, better sanitation and water supply, control of epidemics, and early marriage with high fertility in some societies. Consequences of overcrowding: food shortage, unemployment, pressure on housing and land, rapid spread of disease, pollution, deforestation, and increased crime.
Factors that limit population size. Biotic: food supply, predation, disease, parasitism, competition, reproductive ability. Abiotic: temperature, light, rainfall, space, pH, topography, pressure. These often interact. Drought reduces water, which reduces plant growth, which reduces food, which increases competition and disease.
Niche differentiation reduces competition by allowing species with similar requirements to use resources in slightly different ways, feeding at different times, in different parts of a tree or on different sizes of prey. Note the syllabus’s own wording says it reduces intraspecific competition; in most textbook treatments it is interspecific competition that niche differentiation relieves.
Ecological succession is the orderly, gradual replacement of one community by another in the same area until a stable climax community is reached.
- Primary succession starts on bare ground never previously occupied, such as bare rock, a new sand dune or a lava flow. The pioneer organisms are lichens, which break down rock into soil. Then mosses, then herbs and grasses, then shrubs, then trees.
- Secondary succession starts where a community previously existed but was destroyed, as on abandoned farmland or after a fire. It is faster because soil is already present.
- Hydrosere is succession beginning in water; xerosere is succession beginning in a dry place.
Characteristics of a climax community: stable, self-sustaining, greatest diversity of species, and in balance with the climate.
C6. Soil
Soil types.
| Sandy | Clayey | Loamy | |
|---|---|---|---|
| Particle size | Largest (0.02 to 2 mm) | Smallest (below 0.002 mm) | Mixed |
| Air spaces | Large | Very small | Moderate |
| Drainage | Very rapid | Very poor, waterlogs | Good |
| Water retention | Poor | Excessive | Good |
| Capillarity | Low | High | Moderate |
| Humus content | Low | Moderate | High |
| Mineral content | Poor, leaches easily | Rich but often unavailable | Rich |
| Best for farming? | No | No | Yes |
Loamy soil is the best agricultural soil because it combines good drainage with good water retention, holds nutrients, is well aerated and easy to work. That sentence is the answer to a question that appears very frequently.
Components of soil, by approximate volume: mineral matter about 45 per cent, water about 25 per cent, air about 25 per cent, organic matter about 5 per cent. Plus the soil organisms: bacteria, fungi, earthworms, termites, millipedes, rodents, and plant roots.
Humus is decayed organic matter. It improves soil structure, increases water-holding capacity, supplies nutrients as it decomposes, provides food for soil organisms, and darkens the soil so it absorbs heat.
Experiments. To find the water content, weigh a sample, dry it in an oven at 100 degrees Celsius to constant weight, weigh again, and the difference is the water. To find the humus content, heat the dried sample strongly until the organic matter burns off; the further loss in weight is the humus. To show air, add soil to water and watch for bubbles. To compare porosity, pour equal volumes of water through equal volumes of each soil in filter funnels and measure the volume collected in a fixed time; sandy soil gives the largest volume fastest.
Loss of soil fertility is caused by leaching, erosion of the topsoil, continuous cropping with one variety, monocropping, overgrazing, bush burning, compaction, and loss of organic matter.
Maintaining and renewing fertility: crop rotation, especially including a legume; mixed cropping and polyculture; adding organic manure and compost; applying inorganic fertilisers; mulching; cover cropping; shifting cultivation and bush fallowing; contour ridging and terracing on slopes; strip cropping; and planting windbreaks.
C7. Humans and the environment
Diseases
The syllabus wants the causative organism, the vector or mode of transmission, and the control for each named disease.
| Disease | Cause | Transmission or vector | Control |
|---|---|---|---|
| Malaria | Plasmodium (protozoan) | Bite of female Anopheles mosquito | Insecticide-treated nets, clear stagnant water, antimalarials, insecticides |
| Cholera | Vibrio cholerae (bacterium) | Contaminated water and food | Safe water, sanitation, vaccination, oral rehydration |
| Typhoid fever | Salmonella typhi | Contaminated food and water; houseflies | Sanitation, safe water, vaccination |
| Tuberculosis | Mycobacterium tuberculosis | Airborne droplets | BCG vaccination, isolation, treatment, ventilation |
| Poliomyelitis | Poliovirus | Contaminated water and food; droplets | Oral polio vaccine, sanitation |
| Meningitis | Neisseria meningitidis | Airborne droplets, worse in the dry, dusty harmattan | Vaccination, avoiding crowding |
| Onchocerciasis (river blindness) | Onchocerca volvulus (worm) | Bite of blackfly, Simulium, which breeds in fast-flowing rivers | Ivermectin, control of blackfly breeding sites |
| Schistosomiasis (bilharzia) | Schistosoma (fluke) | Water snails as intermediate host; larvae penetrate skin in infected water | Snail control, avoid urinating in water, safe water supply |
| Dracunculiasis (guinea worm) | Dracunculus medinensis | Drinking water containing infected Cyclops | Filtering drinking water, safe boreholes |
| Gonorrhoea | Neisseria gonorrhoeae | Sexual contact | Abstinence, faithfulness, condoms, prompt treatment |
| Syphilis | Treponema pallidum | Sexual contact; mother to foetus | As above |
| AIDS | HIV (virus) | Sexual contact, infected blood, sharing sharp objects, mother to child | Abstinence, screened blood, sterile instruments, antiretroviral therapy |
Inoculation and vaccination. A vaccine introduces a weakened, killed or modified pathogen, or its antigen, into the body. The immune system responds by producing antibodies and memory cells, so that a later encounter with the real pathogen produces a rapid, strong response. This is active acquired immunity. Passive immunity is receiving ready-made antibodies, as a baby does through the placenta and breast milk, and it is immediate but temporary.
Drug abuse
Drug abuse is the use of a drug for a purpose other than that for which it is medically intended, or in excessive quantity, or without prescription. Drug addiction is a state of physical or psychological dependence in which the user cannot function normally without the drug and suffers withdrawal symptoms when deprived of it.
Commonly abused drugs: alcohol, tobacco and nicotine, cannabis (Indian hemp, marijuana), cocaine, heroin, amphetamines, barbiturates, tramadol, codeine-containing cough syrups, and caffeine.
Effects on health: liver damage (cirrhosis) from alcohol; lung cancer, emphysema and heart disease from smoking; mental disturbance, hallucination and psychosis; addiction and withdrawal; damage to the kidneys and brain; accidents and violent behaviour; transmission of HIV and hepatitis through shared needles; loss of appetite and malnutrition; and among students, poor academic performance and dropping out.
Prevention: public health education, counselling, avoiding negative peer influence, strict enforcement of drug laws by agencies such as the NDLEA, control of the sale of prescription drugs, rehabilitation of addicts, and parental supervision.
Pollution
Air pollution. Sources: vehicle exhaust, industrial smoke, burning refuse, gas flaring, generators. Pollutants: carbon monoxide, sulphur dioxide, nitrogen oxides, particulates, chlorofluorocarbons. Effects: respiratory disease, acid rain, global warming, depletion of the ozone layer. Control: catalytic converters, unleaded fuel, filters and scrubbers on chimneys, alternative energy, laws.
Water pollution. Sources: sewage, industrial effluent, oil spillage, agricultural run-off carrying fertilisers and pesticides. Effects: death of aquatic organisms, waterborne disease, eutrophication, in which excess nutrients cause algal blooms that die, decompose and deplete dissolved oxygen, killing fish. Control: treating effluent before discharge, controlling fertiliser use, preventing spillage, laws.
Soil pollution. Sources: pesticides, non-biodegradable plastics, dumping of refuse, industrial waste. Effects: loss of fertility, death of soil organisms, accumulation of toxins in food chains through biomagnification. Control: recycling, proper waste disposal, biodegradable materials, biological pest control.
Noise pollution from generators, traffic, industry and loudspeakers causes deafness, hypertension and loss of concentration.
Sanitation and sewage. Sewage should be treated in sedimentation tanks, then by bacterial digestion, before the effluent is discharged. Solid waste should be sorted and either recycled, composted, incinerated in controlled conditions, or landfilled properly. Personal hygiene, safe water, food hygiene and proper drainage break the routes by which most communicable diseases spread.
Conservation and the agencies
Conservation is the wise use, management and protection of natural resources so that they are available to future generations. Renewable resources such as forests, water, wildlife and soil can be replaced; non-renewable resources such as crude oil, coal and minerals cannot.
Methods: afforestation and reforestation; controlled logging and grazing; establishment of game reserves and national parks; laws against poaching and against fishing with chemicals or small-mesh nets; erosion control; crop rotation; recycling; and public education.
Benefits: maintains biodiversity and the gene pool; prevents extinction; prevents desertification, especially in the north; maintains the water table; provides for research, education, recreation and tourism; and secures resources for future generations.
Agencies to know:
- International health: World Health Organization (WHO), United Nations International Children’s Emergency Fund (UNICEF), International Red Cross Society (IRCS).
- International conservation: World Wide Fund for Nature (WWF), International Union for Conservation of Nature (IUCN), United Nations Environment Programme (UNEP).
- Nigerian: Nigerian Conservation Foundation (NCF), Federal Ministry of Environment, Federal Ministry of Health, Nigeria National Parks Service, NESREA, NDLEA for drugs, NAFDAC for food and drugs.
Nigerian national parks and reserves: Kainji Lake National Park in Niger and Kwara, the oldest; Gashaka-Gumti in Taraba and Adamawa, the largest; Cross River National Park; Old Oyo National Park; Chad Basin National Park; Okomu National Park in Edo. Yankari in Bauchi is the best known game reserve. Their importance: protecting wildlife from extinction, conserving vegetation, research and education, tourism and revenue, and preserving the gene pool.
Section D: Heredity and Variations
Small section, high yield. The genetics questions are among the few in JAMB Biology that reward reasoning rather than recall, which is why I think you can get them right without having memorised much, provided you know how to set out a cross.
D1. Variation in populations
Variation is the difference between individuals of the same species.
Continuous variation shows a gradual range with no clear-cut categories, and a graph of it gives a normal, bell-shaped curve. Height, weight, skin colour, milk yield, intelligence. It is controlled by many genes together and is strongly affected by the environment.
Discontinuous variation falls into clear-cut categories with no intermediates. Blood group, ability to roll the tongue, ability to taste PTC, sex, fingerprint pattern, presence or absence of attached earlobes. It is controlled by one or a few genes and is little affected by the environment.
Morphological variations: size (height and weight), colour of skin, eye, hair, coat, scales and feathers, and fingerprint patterns.
Fingerprints come in four main patterns: arch, loop, whorl, and composite or compound. No two people, not even identical twins, have identical fingerprints, and the pattern does not change through life. That is why fingerprints are used in criminal investigation, national identity systems, banking and immigration.
Physiological variations: the ability to roll the tongue, the ability to taste phenylthiocarbamide (PTC), and blood group.
Blood groups. The ABO system has four groups: A, B, AB and O.
| Group | Antigen on red cells | Antibody in plasma | Can donate to | Can receive from |
|---|---|---|---|---|
| A | A | anti-B | A, AB | A, O |
| B | B | anti-A | B, AB | B, O |
| AB | A and B | none | AB | all (universal recipient) |
| O | none | anti-A and anti-B | all (universal donor) | O |
Group O is the universal donor because its cells carry no antigens for the recipient’s antibodies to attack. Group AB is the universal recipient because its plasma has no antibodies to attack the donor’s cells. Candidates reverse these constantly.
The rhesus factor. People who carry the rhesus antigen are Rh positive; those who do not are Rh negative. The danger arises when an Rh negative mother carries an Rh positive foetus. During the first birth, foetal blood may enter the mother’s circulation and she produces anti-Rh antibodies. In a later pregnancy with another Rh positive foetus, those antibodies cross the placenta and destroy the foetal red cells, causing haemolytic disease of the newborn (erythroblastosis foetalis). The first child is normally unaffected, and that detail is often the point of the question.
Applications of discontinuous variation.
- Blood transfusion: matching donor and recipient to avoid agglutination.
- Determination of paternity: blood groups can exclude a man as the father but cannot by themselves prove that he is. Two group O parents cannot have a group AB child, for instance.
- Crime detection: fingerprints, blood groups and DNA profiling from blood, hair or semen at a scene.
- Marriage counselling: genotype testing for sickle cell and rhesus compatibility.
D2. Heredity
Heredity is the transmission of characteristics from parents to offspring. Genetics is the study of it.
Heritable characters are controlled by genes and passed on: height, skin colour, eye colour, blood group, sickle cell trait, tongue rolling, hair type. Non-heritable (acquired) characters result from the environment and are not passed on: a scar, a broken limb, muscles built by training, a learned language, skills, and tribal marks. Lamarck believed acquired characters could be inherited; modern genetics says they cannot.
Chromosomes are thread-like structures in the nucleus, made of DNA and protein, that carry the genes. Human body cells have 46, that is 23 pairs, of which 22 pairs are autosomes and one pair are the sex chromosomes. Gametes have 23, the haploid number.
DNA is a double helix: two strands twisted round each other, each made of a sugar (deoxyribose), a phosphate and a base. The bases pair specifically, adenine with thymine and guanine with cytosine, held by hydrogen bonds. In RNA, uracil replaces thymine and the sugar is ribose and the molecule is single-stranded. A gene is a segment of DNA that codes for one protein or characteristic.
Key terms. Allele: alternative forms of a gene at the same locus. Dominant: the allele expressed in the heterozygote, written with a capital letter. Recessive: masked in the heterozygote, expressed only when homozygous. Genotype: the genetic constitution. Phenotype: the observable appearance. Homozygous: two identical alleles, such as TT or tt. Heterozygous: two different alleles, such as Tt. F1: first filial generation. F2: second.
Mendel’s laws. The law of segregation states that the two alleles of a pair separate during gamete formation so that each gamete carries only one. The law of independent assortment states that the members of different pairs of alleles assort independently of one another during gamete formation. Segregation happens at meiosis; recombination happens at fertilisation and is random.
Worked example 1: monohybrid cross
A tall pea plant homozygous for tallness (TT) is crossed with a dwarf plant (tt). Tallness is dominant.
Parents: TT × tt. Gametes: all T from one, all t from the other. F1: all Tt, so all tall.
Now cross two F1 plants: Tt × Tt. Each parent produces T and t gametes.
| T | t | |
|---|---|---|
| T | TT | Tt |
| t | Tt | tt |
F2 genotypes: 1 TT : 2 Tt : 1 tt, a ratio of 1:2:1. F2 phenotypes: 3 tall : 1 dwarf, a ratio of 3:1. The 3:1 ratio is worth knowing cold.
Worked example 2: test cross
You have a tall plant but do not know whether it is TT or Tt. Cross it with a dwarf (tt), which is always homozygous recessive. If all the offspring are tall, the unknown parent was TT. If about half are dwarf, giving a 1:1 ratio, it was Tt. A test cross is always with the homozygous recessive.
Worked example 3: incomplete dominance
In four o’clock plants, red (RR) crossed with white (rr) gives F1 pink (Rr), because neither allele is completely dominant. Crossing two pink plants gives 1 red : 2 pink : 1 white. Here the phenotypic ratio is 1:2:1, the same as the genotypic ratio, and that is what makes it distinguishable from complete dominance.
Worked example 4: dihybrid cross
Two independent pairs of characters, both parents heterozygous, gives the classic F2 phenotypic ratio of 9:3:3:1. Nine showing both dominant characters, three showing the first dominant and the second recessive, three showing the reverse, and one showing both recessives.
Sex determination
In humans, females are XX and males are XY. A female produces only X-bearing eggs. A male produces two kinds of sperm, half X and half Y. The sex of the child is therefore determined by the father’s sperm, and the theoretical chance of a boy or a girl is 50 per cent at each conception.
| X (egg) | X (egg) | |
|---|---|---|
| X (sperm) | XX girl | XX girl |
| Y (sperm) | XY boy | XY boy |
This has direct social relevance in Nigeria, where women are still sometimes blamed for the sex of their children. The biology says otherwise.
Sex-linked characters
Genes carried on the sex chromosomes, mostly on the X chromosome, which is larger than the Y. Because a male has only one X, a recessive allele on it is expressed with no second copy to mask it. That is why sex-linked recessive conditions are far more common in males.
The syllabus names haemophilia (failure of blood to clot normally), colour blindness (usually red-green), and baldness. A woman with one affected allele is a carrier: she does not show the condition but can pass it to her sons.
Sickle cell and marriage counselling
The gene for haemoglobin has a normal allele (A) and a sickle allele (S).
- AA: normal.
- AS: sickle cell trait. The person is healthy under normal conditions and is a carrier. AS individuals have some resistance to malaria, which is why the allele persists at high frequency in West Africa.
- SS: sickle cell anaemia. Red cells become sickle-shaped, block capillaries, and are destroyed rapidly, causing painful crises and anaemia.
The cross AS × AS gives 1 AA : 2 AS : 1 SS, so a one in four chance of a child with sickle cell anaemia at each pregnancy. AS × AA gives no affected children. AA × AA is entirely safe. This is exactly what genotype counselling before marriage is for, and the 25 per cent figure is asked directly.
Applications of heredity
In agriculture: cross-breeding to produce new varieties combining desirable characters such as high yield, disease resistance, drought tolerance and early maturity; artificial selection; and hybrid vigour.
Inbreeding is crossing closely related individuals. It preserves desirable characters and produces uniform, pure-breeding stock, but it concentrates harmful recessive alleles and leads to loss of vigour. Outbreeding is crossing unrelated individuals. It produces variation and hybrid vigour, but the offspring are not uniform and desirable combinations may be broken up.
In medicine: genetic counselling, screening for sickle cell and rhesus incompatibility, blood group matching, and understanding inherited disease.
D3. Biotechnology
Biotechnology is the use of living organisms or their products in industrial and other processes for the benefit of humans.
In agriculture: tissue culture for rapid propagation of disease-free plants; genetically modified crops engineered for pest resistance, herbicide tolerance, drought tolerance or improved nutrition; biofertilisers; biological pest control; artificial insemination and embryo transfer in livestock.
In medicine and pharmaceuticals: production of human insulin by inserting the human insulin gene into bacteria, which then manufacture it, replacing insulin extracted from animals; production of interferon for viral infections; human growth hormone; vaccines; monoclonal antibodies; antibiotics from fungi and bacteria; and enzymes. Gene therapy attempts to correct a defective gene by introducing a working copy.
In the food industry: fermentation to make bread, beer, wine and yoghurt; cheese-making with rennin; single-cell protein; enzymes in food processing; and local fermented foods such as ogi, garri, iru and ogiri.
In the environment: treatment of sewage by bacteria, bioremediation of oil-polluted soil, and production of biogas.
Contentious issues. Supporters of genetically modified organisms point to higher yields, reduced pesticide use, and crops fortified with nutrients. Critics raise concerns about unknown long-term health effects, transfer of genes to wild relatives, loss of biodiversity, and farmers becoming dependent on seed companies. Biosafety refers to the regulations and practices designed to manage those risks. Nigeria has a National Biosafety Management Agency for this purpose. JAMB expects you to know that the debate exists and to be able to state points on both sides, not to take a position.
Section E: Evolution
The smallest section, usually good for two or three questions, and almost entirely recall. I would not skip it, because the marks are quick.
Organic evolution is the sum total of the adaptive changes that have taken place in organisms over a long period, resulting in the diversity of forms, structures and functions we see today. The idea is that present-day organisms descended with modification from earlier, simpler ancestors.
Theories of evolution
Lamarck’s theory (1809) rests on two ideas. The law of use and disuse holds that organs used frequently develop and enlarge while those not used degenerate. The inheritance of acquired characteristics holds that changes acquired during an organism’s lifetime are passed to its offspring. Lamarck’s famous example was the giraffe: ancestral giraffes stretched their necks to reach high leaves, the necks lengthened, and the longer necks were inherited.
Lamarck’s theory is rejected today because acquired characters are not inherited. Changes to the body cells do not alter the genes in the gametes. Weismann’s experiment of cutting off the tails of mice for many generations, after which the offspring were still born with tails, is the standard refutation.
Darwin’s theory (1859), natural selection. The argument runs in steps:
- Organisms produce far more offspring than can possibly survive.
- Resources such as food and space are limited.
- This leads to a struggle for existence.
- Within any population there is natural variation.
- Individuals with variations that suit the environment are more likely to survive and reproduce. This is survival of the fittest.
- Those favourable variations are passed to the offspring.
- Over many generations, the favourable characters accumulate and a new species may emerge.
Darwin’s giraffe explanation differs from Lamarck’s: giraffes always varied in neck length, those with longer necks survived droughts better because they could reach high foliage, and they left more offspring. The neck did not lengthen through stretching; the population changed because long-necked individuals were selected.
Modern (neo-Darwinian) theory adds what Darwin did not know. The source of the variation on which selection acts is mutation, a sudden heritable change in a gene or chromosome, along with recombination during sexual reproduction. Natural selection then acts on that variation.
The organic theory in the syllabus refers to the general position that all present forms of life arose from earlier, simpler forms through gradual change.
Evidence for evolution
- Fossil records. Fossils are the preserved remains or impressions of organisms in rock, dated by their position in the strata and by radioactive dating. They show that simple organisms appear in older rocks and complex ones in younger rocks, and they provide series such as the fossil horse, from the small four-toed Eohippus to the modern single-hoofed Equus. Archaeopteryx, with feathers and wings like a bird but teeth, claws and a bony tail like a reptile, is the classic connecting link.
- Comparative anatomy. Homologous structures have the same basic structure and embryonic origin but different functions, as in the pentadactyl limb of a human arm, a whale’s flipper, a bat’s wing and a bird’s wing. They indicate a common ancestor and divergent evolution. Analogous structures have different structure and origin but the same function, as in the wing of an insect and the wing of a bird, and they indicate convergent evolution. Vestigial structures are reduced and functionless remnants of organs that were functional in ancestors: the human appendix, coccyx, ear muscles and nictitating membrane, and the splint bones of a horse.
- Comparative embryology. The early embryos of fish, amphibians, reptiles, birds and mammals look remarkably similar, with gill pouches and a tail, suggesting common ancestry.
- Comparative physiology and biochemistry. All organisms use DNA as genetic material and ATP as an energy currency. The closer two species are related, the more similar their blood proteins, their enzymes and their DNA sequences.
- Geographical distribution. Related species occur in adjoining regions, and isolated islands such as the Galapagos have distinctive species descended from mainland ancestors.
- Genetics and mutation. Observed mutation and observed selection in nature. The best-known case is industrial melanism in the peppered moth in Britain, where dark forms became common on soot-blackened trees. Resistance of insects to insecticides and of bacteria to antibiotics is natural selection happening within a human lifetime.
Evolutionary trends
In plants: from aquatic to terrestrial; from a thallus to true roots, stems and leaves; from no vascular tissue to well-developed vascular tissue; from spores to seeds; from naked seeds to seeds enclosed in fruits; from a dominant gametophyte to a dominant sporophyte; and from dependence on water for fertilisation to independence from it.
In animals: from unicellular to multicellular; from two body layers to three; from radial to bilateral symmetry; from no body cavity to a true coelom; from diffusion to specialised transport, respiratory and excretory systems; from external to internal fertilisation; from aquatic to terrestrial life; and from cold-blooded to warm-blooded.
Where the marks are: how to weight your revision
JAMB does not publish a mark allocation per section, so treat any percentage you see online with suspicion, mine included. What follows is my own estimate, worked out from the relative size of each section in the syllabus and the topics I keep seeing recur in past papers. Use it to decide where to spend your time, not as a guarantee.
| Section | Share of the syllabus | Roughly how many of the 40 questions | Priority |
|---|---|---|---|
| B: Form and Functions | Largest, nine topics | About 14 to 18 | Highest |
| C: Ecology | Seven topics | About 8 to 10 | High |
| A: Variety of Organisms | Three topics but very broad | About 6 to 8 | High |
| D: Heredity and Variations | Three topics | About 4 to 6 | Medium, but easy marks |
| E: Evolution | Two topics | About 2 to 3 | Low volume, quick marks |
How I read that table: Section B is where you can most easily lose ten marks, and Sections D and E are where you can most easily gain five for a small time investment. Candidates who run out of revision time usually sacrifice genetics and evolution. I think that is the wrong thing to cut, because both are short and self contained.
Recommended texts, and how to use them
The syllabus lists these:
- Ndu, F. O. C., Ndu, A. and Aina, J. O. (2001). Senior Secondary School Biology, Books 1 to 3. Lagos: Longman.
- Odunfa, S. A. (2001). Essentials of Biology. Ibadan: Heinemann.
- Ogunniyi, M. B., Adebisi, A. A. and Okojie, J. A. (2000). Biology for Senior Secondary Schools, Books 1 to 3. Macmillan.
- Ramalingam, S. T. (2018). Modern Biology, SS Science Series, New Edition. AFP.
- STAN (2004). Biology for Senior Secondary Schools, Revised Edition. Ibadan: Heinemann.
- Stone, R. H. and Cozens, A. B. C. (1982). Biology for West African Schools. Longman.
- Usua, E. J. (1997). Handbook of Practical Biology, 2nd Edition. University Press Limited.
- Idodo-Umeh, G. (2015). College Biology. Idodo-Umeh Publishers.
- Michael, M. C. (2018). Essential Biology for Senior Secondary Schools. TONAD Publishers.
You do not need all nine. Two is enough. The split I would recommend is Modern Biology by Ramalingam or College Biology by Idodo-Umeh as your main text, since both cover the syllabus in depth with the diagrams JAMB tends to use, and Essential Biology by Michael as a lighter second reference for topics the first one explains badly.
A word about the dates. Some of these editions are more than twenty years old. I would not worry about that for Biology at this level, because the content of the syllabus has not changed. Use a newer edition where one exists, particularly for biotechnology, where I find the older texts thin.
A study plan that works
The eight-week plan
I have assumed you can give Biology about five hours a week alongside your other three subjects.
Weeks 1 and 2: Section B, first half. Internal structure of plants and mammals, nutrition, transport. Nutrition alone deserves three sittings. Draw the alimentary canal from memory at the end of week 1 and check it against the book.
Week 3: Section B, second half. Respiration, excretion, support and movement.
Week 4: Section B, remainder. Reproduction, growth, coordination and control. Then do a 40-question timed test on Section B only.
Week 5: Section A. Classification, the five kingdoms, plant and animal groups, adaptation. This is heavy on names, so use active recall rather than reading. Write the plant divisions in evolutionary order from a blank page every day this week.
Week 6: Section C. Ecology in full, including the cycles and the disease table. Draw the nitrogen cycle from memory.
Week 7: Sections D and E. Genetics with worked crosses, variation, biotechnology, evolution. Do at least twenty genetics problems with a pen and paper, not in your head.
Week 8: Past questions only. Five full 40-question papers under a 30-minute clock. Mark them, and for every wrong answer write one line explaining why the right answer is right. That single habit is worth more than another read of the textbook.
The four-week crash plan
If you are starting late, cut it in half but do not cut past questions.
- Week 1: Nutrition, transport, respiration, excretion. Four days, one topic each, then a test.
- Week 2: Reproduction, coordination, support and movement, growth, plus the internal structures.
- Week 3: Section A and Section C together, focusing on the tables in this guide: kingdoms, invertebrate phyla, biomes, diseases, soil types.
- Week 4: Genetics, evolution, then past questions every day.
How to revise
Most candidates revise by reading. I did too, until I noticed how little of it stayed. Reading feels productive and produces almost nothing. Three changes I would make:
Close the book and write. After each topic, write down everything you remember on a blank sheet, then open the book and fill in what you missed in a different colour. What you missed is your actual revision list.
Draw the diagrams. The nephron, the heart, the eye, the ear, a flower in longitudinal section, the internal structure of a leaf, the nitrogen and carbon cycles. Draw each one at least three times over your revision period. Diagram questions are free marks for candidates who have drawn them and guesswork for candidates who have only looked at them.
Do past questions in timed batches, not casually. Twenty questions, fifteen minutes, no book. Accuracy under time pressure is a separate skill from knowing biology, and it is the one the exam measures.
Exam technique for JAMB Biology
I would give Biology 25 to 30 minutes. Forty questions in 25 minutes is about 37 seconds each. That is enough for most Biology questions, which are recall-based, and it protects the time you need for calculation subjects.
Do the paper in two passes. First pass: answer everything you know immediately and flag anything that needs thought. Second pass: return to the flagged ones. Never let one hard question eat three minutes.
Read the stem to the end before looking at the options. JAMB writes stems that reverse meaning at the last word. “All of the following are functions of the liver EXCEPT” and “Which of the following is NOT a characteristic of…” both appear regularly, and candidates who have already decided on an answer from the first half of the sentence choose a true statement in a question asking for the false one.
Watch the absolute words. I treat options containing “always”, “never”, “all” or “only” with suspicion, because biology is full of exceptions. The exceptions to this rule of thumb are the genuine absolutes: energy pyramids are always upright, enzymes are always proteins, the pulmonary vein is the only vein carrying oxygenated blood.
Eliminate before you guess. If two options are opposites, one of them is usually the answer. If two options say the same thing in different words, neither is usually the answer, because a question can only have one correct option.
Answer every question. There is no negative marking. A flagged question you never return to should still be filled with your best guess before you leave the section.
Handle diagram questions by naming the structure first. Before you read the options, look at the diagram and say to yourself what organ it is and what the labelled part is. Then read the options. Reading the options first lets them plant an answer in your head.
Twenty practice questions
Cover the answers, work through them under time, then check. I wrote these in JAMB’s style, drawing from across the five sections.
- Which of the following is not a characteristic of living things? (A) Irritability (B) Growth by accretion (C) Excretion (D) Reproduction
- The organism that possesses both plant and animal characteristics is (A) Paramecium (B) Spirogyra (C) Euglena (D) Rhizopus
- The first plants to develop vascular tissue were the (A) Thallophyta (B) Bryophyta (C) Pteridophyta (D) Spermatophyta
- Carnivorous plants such as sundew trap insects mainly to obtain (A) energy (B) nitrogen (C) water (D) carbon
- Photolysis of water takes place in the (A) stroma (B) grana (C) cytoplasm (D) mitochondrion
- The dental formula I 0/3, C 0/1, PM 3/3, M 3/3 belongs to (A) man (B) dog (C) sheep (D) cat
- The end products of protein digestion are (A) glucose (B) amino acids (C) fatty acids and glycerol (D) maltose
- The blood vessel with the highest concentration of digested food is the (A) hepatic artery (B) hepatic portal vein (C) renal vein (D) pulmonary vein
- Glycolysis occurs in the (A) mitochondrion (B) nucleus (C) cytoplasm (D) ribosome
- Excess water is removed from Amoeba by the (A) flame cell (B) contractile vacuole (C) nephridium (D) Malpighian tubule
- Ultrafiltration in the nephron takes place in the (A) loop of Henle (B) collecting duct (C) Bowman’s capsule (D) proximal convoluted tubule
- The response of a plant shoot growing towards light is (A) positive geotropism (B) positive phototropism (C) positive phototaxis (D) photonasty
- In hypogeal germination, the structure that elongates is the (A) hypocotyl (B) epicotyl (C) radicle (D) plumule
- The part of the brain responsible for balance and coordination of movement is the (A) cerebrum (B) cerebellum (C) medulla oblongata (D) hypothalamus
- Short-sightedness is corrected using a (A) convex lens (B) concave lens (C) cylindrical lens (D) bifocal lens
- Nitrites are converted to nitrates in the soil by (A) Nitrosomonas (B) Nitrobacter (C) Rhizobium (D) Pseudomonas
- The percentage of energy transferred from one trophic level to the next is about (A) 1 per cent (B) 10 per cent (C) 50 per cent (D) 90 per cent
- A cross between two individuals with the genotype AS will produce children with sickle cell anaemia in the ratio of (A) 1 in 2 (B) 1 in 3 (C) 1 in 4 (D) none
- The wing of a bird and the wing of an insect are examples of (A) homologous structures (B) analogous structures (C) vestigial structures (D) connecting links
- The blood group known as the universal donor is (A) A (B) B (C) AB (D) O
Answers and explanations
- (B) Living things grow by intussusception, from within. Accretion, addition on the outside, is how non-living things such as crystals grow.
- (C) Euglena has chlorophyll and photosynthesises like a plant, but has a flexible pellicle rather than a cell wall, a flagellum, an eyespot and a contractile vacuole.
- (C) Ferns are the first group with true xylem and phloem, and therefore true roots, stems and leaves.
- (B) They already photosynthesise. They grow in nitrogen-poor swampy soil and use insects as a nitrogen source.
- (B) The light reaction, including photolysis, happens in the grana. The dark reaction happens in the stroma.
- (C) No upper incisors or canines, replaced by a horny pad. That pattern means a grazing herbivore.
- (B) Carbohydrates give glucose, fats give fatty acids and glycerol, proteins give amino acids.
- (B) The hepatic portal vein carries blood directly from the small intestine, where absorption happens, to the liver.
- (C) Glycolysis is the anaerobic first stage and occurs in the cytoplasm. The Krebs cycle occurs in the mitochondrion.
- (B) Freshwater protozoa constantly gain water by osmosis and pump it out with a contractile vacuole.
- (C) High pressure in the glomerulus forces small molecules into the Bowman’s capsule. Selective reabsorption then happens in the proximal convoluted tubule.
- (B) The shoot is fixed and responds by growth in the direction of the stimulus, which makes it a tropism, not a taxis.
- (B) In hypogeal germination the epicotyl elongates and the cotyledons stay below the soil. In epigeal, the hypocotyl elongates and lifts them above.
- (B) The cerebellum. The medulla controls involuntary activities such as heartbeat and breathing.
- (B) In myopia the image forms in front of the retina, so a diverging, concave lens is needed to push it back.
- (B) Nitrosomonas makes nitrite; Nitrobacter makes nitrate. Rhizobium fixes nitrogen; Pseudomonas denitrifies.
- (B) About 90 per cent is lost as heat in respiration, in undigested material and in excretion.
- (C) AS × AS gives 1 AA : 2 AS : 1 SS, so a one in four chance at each pregnancy.
- (B) Same function, different structure and embryonic origin, so analogous. Homologous structures share origin but differ in function.
- (D) Group O red cells carry neither antigen A nor antigen B, so there is nothing for the recipient’s antibodies to attack.
If you scored 15 or above, I would say your recall is in reasonable shape and your remaining work is speed. Below 10, go back to the sections where you missed questions rather than starting again from the beginning.
Common mistakes that cost marks every year
| The mistake | The correction |
|---|---|
| Confusing excretion with egestion | Faeces are undigested food that was never metabolised. Egestion is not excretion. |
| Saying plant cells have no cell membrane | They have both a wall and a membrane; the wall lies outside. |
| Reversing universal donor and recipient | O donates to all, AB receives from all. |
| Reversing accommodation | Near object: ciliary muscles contract, lens becomes more convex. |
| Swapping Nitrosomonas and Nitrobacter | Nitroso- makes nitrite. Nitrobacter makes nitrate. |
| Saying the mother determines the child’s sex | The father’s sperm carries either X or Y. |
| Calling the pulmonary artery an oxygenated vessel | It is the only artery carrying deoxygenated blood. |
| Confusing tropism with taxis | If the whole organism moves from place to place, it is a taxis. |
| Saying light is needed for germination | Most seeds germinate without light. Light is needed after emergence, for photosynthesis. |
| Defining osmosis without mentioning the membrane | Osmosis is the movement of water through a semi-permeable membrane. |
| Saying acquired characters are inherited | That is Lamarck’s rejected view. Only genetic changes are passed on. |
| Reversing epigeal and hypogeal | Hypo means below; in hypogeal the cotyledons stay below. |
Frequently asked questions
Is the JAMB Biology syllabus the same every year? It has been stable for several years. Small editorial changes are possible, so download the current copy from jamb.gov.ng before you begin rather than using a file forwarded on WhatsApp.
Where can I download the official JAMB Biology syllabus PDF? From the syllabus section of the official JAMB website, jamb.gov.ng. It is free. Any site charging you for it is selling something JAMB gives away.
How many questions come from each section? JAMB does not publish a breakdown. Judging by the size of each section and by past papers, Form and Functions carries the most, followed by Ecology, then Variety of Organisms, then Heredity and Variations, then Evolution.
Can I pass JAMB Biology using past questions alone? Past questions show you the style, the recurring topics and the pace, and I would not sit the exam without them. But JAMB rewrites and rephrases, and a candidate who has only memorised past answers is caught out by any question set from an angle they have not seen. I use past questions as a test of my reading, not a replacement for it.
Is JAMB Biology the same as the WAEC Biology syllabus? They overlap heavily, since both are built on the senior secondary curriculum. The difference is in format. WAEC has essay and practical papers that reward description and drawing; JAMB is entirely multiple choice and rewards precise recall and fast elimination. I would study the content once and practise for each format separately.
Which topics are the most difficult? The ones I hear about most are the transport system and its named blood vessels, the nephron, hormonal control, and genetics problems. Genetics is the one I would put effort into first, because the rules are few and, once you have them, they apply to every question.
How many questions will I answer in Biology? Forty. Use of English carries 60, and each of your three other subjects carries 40, for 180 questions in two hours.
Is there negative marking in JAMB? No. Nothing is deducted for a wrong answer, so answer every question, including the ones you are guessing.
Do I need to know diagrams for a multiple-choice exam? Yes. JAMB regularly displays a labelled diagram and asks you to identify a structure or state its function. Being able to draw the standard diagrams is the most reliable preparation for these.
What is the difference between the syllabus and the brochure? The syllabus lists what you will be examined on. The brochure lists courses, institutions, subject combinations and admission requirements. You need both: the brochure to confirm that your four subjects are correct for the course you want, and the syllabus to know what to study.
Which subjects do I combine with Biology? It depends on the course. For Medicine, Pharmacy, Nursing and most health sciences, the combination is English, Biology, Chemistry and Physics. For Agriculture, Biochemistry and many life sciences it is English, Biology, Chemistry and either Physics or Mathematics. Confirm your specific course in the current JAMB brochure, because requirements differ between institutions.
How long should I study Biology each day? I would take an hour of focused work, with the book closed for part of it, over three hours of reading with your phone nearby. Consistency across eight weeks matters more than the length of any single session.
Are the recommended textbooks compulsory? No. They are JAMB’s suggestions and any of them covers the syllabus. I would rather you used two texts properly than skimmed nine.
Does JAMB set questions outside the syllabus? It should not. When a question has looked unfamiliar to me, it has almost always been a syllabus topic asked from an unusual angle rather than new content. Read the stem again and look for the underlying principle.
When is the exam and when does registration open? Registration usually opens in January or February and the exam usually runs in April, but the dates are announced each year and they move. Check jamb.gov.ng rather than relying on social media.
Before you start studying: a five-minute checklist
- Download the current syllabus from jamb.gov.ng and confirm it matches the topics in this guide.
- Confirm in the JAMB brochure that Biology is required for your intended course and that your other three subjects are correct.
- Get one main textbook and one reference.
- Get past questions covering at least the last ten years.
- Buy a plain notebook for closed-book recall and a sketchpad for diagrams.
- Block out five hours a week for Biology and write the topics for each week onto a calendar.
- Take the twenty-question test above now, before you start, so you have a baseline to measure against in week eight.
Sources
- Joint Admissions and Matriculation Board, UTME Syllabus: Biology. The official document, and the basis for every topic listing in this guide.
- Joint Admissions and Matriculation Board, official announcements on exam structure and registration, published at jamb.gov.ng.
- The nine textbooks recommended within the official syllabus, listed above.
I am Jude Chinecherem, a final-year MBBS student at the University of Nigeria, Nsukka. I know what it feels like to want an education your family cannot afford. When my parents could not pay for my schooling, I had to learn how to find scholarships and work the system out on my own, with nobody to guide me. I came out the other side, and now I share everything I learned so the next student does not have to figure it out alone. This is the advice I wish someone had given me back then.
