JAMB Biology 2000

27 reviewed questions with answers and explanations.

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Question 2

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In the pupa shown, the part labelled II is the

  1. silk thread
  2. thorax
  3. fore wing
  4. anchor

Question 3

Which features are typically associated with monocots?

  1. Fibrous root system, branched network of veins and one seed leaf
  2. Fibrous root system, two seed leaves and floral parts in threes
  3. One seed leaf, petals in threes or groups of threes and parallel venation of leaves
  4. One seed leaf, net-veined leaves and petals in three or multiples of three
Answer and explanation

C: One seed leaf, petals in threes or groups of threes and parallel venation of leaves

Typical monocots have one cotyledon, parallel leaf veins and floral parts arranged in threes or multiples of three. These characteristics are useful together when comparing monocots with typical eudicots.

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Question 4

The set of fins that controls steering, balancing and change of direction and pitch in fish is

  1. dorsal and anal
  2. pectoral and pelvic
  3. caudal and dorsal
  4. anal and pelvic
Answer and explanation

B: pectoral and pelvic

The paired pectoral and pelvic fins help a fish manoeuvre and maintain its orientation. They can affect steering, balance and pitching, while the caudal fin is particularly important in propulsion.

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Question 6

A true coelom is absent in which animal group?

  1. mollusca
  2. reptilia
  3. arthropoda
  4. Cnidaria (coelenterates)
Answer and explanation

D: Cnidaria (coelenterates)

Cnidarians have a digestive cavity but no true coelom lined by mesoderm. A digestive cavity is not a coelom. Molluscs and arthropods have a reduced coelom, while reptiles have a well-developed body cavity.

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Question 9

In which part of the human body does the secretion of the growth hormone occur?

  1. head region
  2. waist region
  3. neck region
  4. gonads
Answer and explanation

A: head region

Growth hormone is secreted by the anterior pituitary, located at the base of the brain in the head. It influences growth and metabolism, often through effects mediated by other tissues.

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Question 16

The scapula and the ischium are part of the

  1. pectoral girdle
  2. pelvic girdle
  3. appendicular skeleton
  4. hind limb
Answer and explanation

C: appendicular skeleton

The scapula belongs to the pectoral girdle and the ischium to the pelvic girdle. Both girdles are components of the appendicular skeleton, which includes the limbs and their attachments.

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Question 18

Short-sightedness can be corrected by lenses which are

  1. convex
  2. biconvex
  3. plano-convex
  4. concave
Answer and explanation

D: concave

A concave lens diverges incoming light. This reduces the excessive convergence associated with myopia, helping distant objects focus on the retina rather than in front of it.

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Question 19

Which pair of structures is located in the inner ear?

  1. eardrum and Eustachian tube
  2. cochlea and semi-circular canals
  3. oval window and ossicles
  4. pinna and cochlea
Answer and explanation

B: cochlea and semi-circular canals

The cochlea and semicircular canals are both in the inner ear. The cochlea is involved in hearing, while the semicircular canals contribute to sensing head rotation and maintaining balance.

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Question 20

For net growth in an organism’s body material, the rate of

  1. food storage must be low
  2. catabolism must exceed that of anabolism
  3. anabolism must exceed that of catabolism
  4. food storage must be high
Answer and explanation

C: anabolism must exceed that of catabolism

Anabolism builds complex substances, whereas catabolism breaks them down. Net accumulation of body material requires synthesis to exceed breakdown over the growth period.

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Question 21

In a Biuret test, a food sample turns violet after dilute NaOH and drops of 1% CuSO₄ are added with mixing. This indicates the presence of

  1. protein
  2. carbohydrates
  3. fats
  4. reducing sugar
Answer and explanation

A: protein

A violet Biuret reaction indicates peptide bonds, which occur in proteins. Copper ions in alkaline solution form a coloured complex with those bonds.

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Question 22

For equal 100 kg masses of the ordinary foods listed, which would usually yield the most energy on complete oxidation?

  1. meat
  2. butter
  3. sugar
  4. biscuits
Answer and explanation

B: butter

Butter is predominantly fat, which releases more energy per gram on oxidation than carbohydrate or protein. For equal masses of ordinary forms of these foods, butter therefore usually supplies the most energy.

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Question 23

The chamber of the mammalian heart with the thickest wall is the

  1. right ventricle
  2. left auricle
  3. right auricle
  4. left ventricle
Answer and explanation

D: left ventricle

The left ventricle pumps blood through the systemic circulation and must generate higher pressure than the right ventricle. Its muscular wall is consequently the thickest heart chamber wall.

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Question 24

Serum differs from blood plasma because it

  1. contains blood cell and fibrinogen
  2. contains soluble food and mineral salts
  3. lacks the blood protein fibrinogen
  4. lacks blood cells and albumin
Answer and explanation

C: lacks the blood protein fibrinogen

Serum is the liquid remaining after blood has clotted. Fibrinogen is converted into fibrin during clot formation, so serum lacks the fibrinogen present in plasma.

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Question 25

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In the fruit section, the part labelled II is the

  1. mesocarp
  2. pericarp
  3. endocarp
  4. epicarp

Question 26

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The fruit represented is naturally adapted for dispersal by

  1. animals
  2. water
  3. wind
  4. birds

Question 27

A dry, air-containing soil sample has bulk volume q cm³. Water initially occupies p cm³. After mixing, allowing trapped air to escape without loss of water or soil, the total mixture volume is r cm³. Which relation follows?

  1. r=p+q
  2. r>p+q
  3. q=r-p
  4. r<p+q
Answer and explanation

D: r<p+q

The initial soil volume includes air-filled pore spaces. When water enters those spaces and air escapes, the final mixture occupies less than the sum of the separately measured water and soil volumes.

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Question 28

Compared with an early pioneer stage, ecological succession often leads to which change in diversity?

  1. an increase in species diversity
  2. a decrease in species diversity
  3. an unstable community
  4. the dispersal of species
Answer and explanation

A: an increase in species diversity

As succession proceeds, new species can establish and additional habitats and interactions develop. This often increases species diversity compared with an early pioneer stage, although the pattern is not universal.

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Question 30

I: high birth and immigration rates. II: low birth and high immigration rates. III: low mortality and emigration rates. IV: high mortality and emigration rates. Which combination most consistently favours rapid population increase?

  1. II and III
  2. I and III
  3. I and IV
  4. I and II
Answer and explanation

B: I and III

High births and immigration add individuals, while low mortality and emigration minimise losses. Combining I and III therefore most consistently favours rapid population increase.

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Question 31

A graph plots plant growth against increasing soil essential-element concentration. The curve begins low in region I, rises steeply through II, reaches a broad maximum plateau in III, then declines toward zero in IV at the highest concentrations. Which region corresponds to toxic excess?

  1. IV
  2. III
  3. II
  4. I
Answer and explanation

A: IV

Region IV has the highest element concentrations and declining growth. This is the excess range, where an otherwise essential nutrient can inhibit growth through toxicity.

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Question 32

A graph plots plant growth against increasing soil essential-element concentration. The curve begins low in region I, rises steeply through II, reaches a broad maximum plateau in III, then declines toward zero in IV at the highest concentrations. Which region corresponds to optimal growth?

  1. IV
  2. III
  3. II
  4. I
Answer and explanation

B: III

The maximum-growth plateau is region III. Within that range, the essential element is sufficient for growth without the high-concentration inhibition seen farther to the right.

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Question 35

Which adaptation helps support some tall tropical forest trees with shallow root systems?

  1. Few stomata
  2. Thick bark
  3. Buttress roots
  4. Reduced leaves
Answer and explanation

C: Buttress roots

Buttress roots spread outward from the base of some tall tropical forest trees. They enlarge the supporting base and help stabilise the tree, especially where much of the root system is shallow.

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Question 39

Which set lists major climatic factors influencing the distribution of vegetation zones?

  1. temperature, light, rain and humidity
  2. light, humidity, air and mist
  3. temperature, light, air and humidity
  4. humidity, snow, frost and dew
Answer and explanation

A: temperature, light, rain and humidity

Temperature and water availability strongly influence broad vegetation patterns. Light and humidity also affect plant growth and water balance, so the first set includes major climatic controls.

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Question 41

The pollutants that contribute to the depletion of the ozone layer in the atmosphere are

  1. radioactive materials
  2. oxides of sulphur
  3. oxides of carbon
  4. chlorofluorocarbons
Answer and explanation

D: chlorofluorocarbons

Chlorofluorocarbons can reach the stratosphere, where ultraviolet light releases chlorine that catalyses ozone destruction. This reduces the protective stratospheric ozone layer.

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Question 44

Older fossil-bearing rocks, compared with more recent ones, are more likely to contain

  1. animals rather than plant remains
  2. invertebrates rather than birds
  3. flowering plants rather than mosses
  4. reptiles rather than fishes
Answer and explanation

B: invertebrates rather than birds

Invertebrate lineages existed long before birds evolved. Older fossil-bearing deposits can therefore preserve invertebrates from periods before birds appeared, although preservation varies among environments.

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Question 45

In a breeding group of male Agama agama, the male with the most conspicuous head colour is typically the

  1. dominant
  2. youngest
  3. oldest
  4. largest
Answer and explanation

A: dominant

Dominant breeding males of Agama agama typically display conspicuous head and body colours. Colour can also vary with physiological and environmental conditions, so it is a social signal rather than an exact measure of age or size.

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Question 46

Which pair gives a water-borne disease followed by a usually sex-linked inherited disorder?

  1. taeniasis and malaria
  2. cholera and gonorrhoea
  3. typhoid and syphilis
  4. dracunculiasis and haemophilia
Answer and explanation

D: dracunculiasis and haemophilia

Dracunculiasis can be acquired by drinking water containing infected copepods. Haemophilia A and B are usually inherited in an X-linked pattern, which differs from sexual transmission of an infection.

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Question 47

The mutation theory of organic evolution was propounded by

  1. Gregor Mendel
  2. Hugo de Vries
  3. Jean Lamarck
  4. Charles Darwin
Answer and explanation

B: Hugo de Vries

Hugo de Vries developed the historical mutation theory, presenting it in Die Mutationstheorie. He emphasised sudden heritable changes as a source of new forms, distinct from Darwin’s emphasis on natural selection.

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