JAMB Biology 2010

30 reviewed questions with answers and explanations.

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Question 2

Which of the following characterizes a mature plant cell?

  1. the cytoplasm fills up the entire cell space
  2. the nucleus is pushed to the centre of the cell
  3. the cell wall is made up of cellulose
  4. the nucleus is small and irregular in shape
Answer and explanation

C: the cell wall is made up of cellulose

A typical plant cell has a cell wall containing cellulose. In many mature cells, a large central vacuole occupies much of the volume and displaces the cytoplasm and nucleus toward the edge.

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Question 4

The dominant phase in the life cycle of a typical fern is the

  1. gametophyte
  2. prothallus
  3. sporophyte
  4. antheridium
Answer and explanation

C: sporophyte

The familiar leafy fern is the diploid sporophyte, the larger and longer-lived generation. The gametophyte is usually a small prothallus, which bears the sexual reproductive organs.

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Question 8

In the historical five-kingdom classification, which listed group consists of cells without membrane-bound nuclei?

  1. algae
  2. monera
  3. fungi
  4. viruses
Answer and explanation

B: monera

The historical group Monera consists of prokaryotic organisms, whose cells lack a membrane-bound nucleus. Modern classification separates these organisms into Bacteria and Archaea.

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Question 11

Which statement is true of a transverse section of a typical dicot stem?

  1. the epidermis is completely encircled by the cortex
  2. the xylem is more interiorly located than the phloem
  3. the cambium lies between the cortex and the vascular bundles
  4. the vascular bundles are randomly scattered within the cortex
Answer and explanation

B: the xylem is more interiorly located than the phloem

In a typical dicot stem vascular bundle, xylem lies toward the centre and phloem toward the outside. Cambium is between them, and the bundles form a ring inside the outer tissues.

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Question 16

When a food sample is warmed with Benedict’s solution, an orange to brick-red precipitate forms. This indicates the presence of

  1. reducing sugar
  2. fatty acid
  3. sucrose
  4. amino acid
Answer and explanation

A: reducing sugar

A reducing sugar can reduce copper ions in warmed Benedict’s reagent, forming an orange to brick-red copper(I) oxide precipitate. The colour depends on the amount present and the test conditions.

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Question 17

Which listed structure pumps blood into the mammalian systemic circulation?

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

D: left ventricle

The left ventricle ejects blood into the aorta, supplying the systemic circuit. The right ventricle supplies the pulmonary circuit, so the two sides of the heart serve different circulatory pathways.

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Question 18

The blood circuit supplying body tissues, as distinct from the pulmonary gas-exchange circuit, is

  1. the pulmonary artery
  2. systemic circulation
  3. the lymphatic system
  4. pulmonary circulation
Answer and explanation

B: systemic circulation

Systemic circulation supplies tissues through the aorta and its branches and returns blood to the right side of the heart. The pulmonary circuit carries blood between the heart and the lungs for gas exchange.

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Question 19

Yeast carries out alcoholic fermentation to convert simple sugar to carbon dioxide and

  1. alcohol
  2. acid
  3. oxygen
  4. water
Answer and explanation

A: alcohol

During alcoholic fermentation, yeast produces ethanol and carbon dioxide from the products of glycolysis. Regeneration of NAD+ permits glycolysis to continue when oxygen is unavailable.

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Question 20

The sheet of muscle that separates the thoracic and the abdominal cavities is the

  1. diaphragm
  2. intercostal muscle
  3. pleural membrane
  4. pericardium
Answer and explanation

A: diaphragm

The diaphragm is a sheet of skeletal muscle separating the thoracic and abdominal cavities. Its contraction increases thoracic volume and contributes to inhalation.

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Question 21

The oily substance that lubricates mammalian hair is secreted by the

  1. sweat glands
  2. sebaceous glands
  3. fatty cells
  4. granular layer
Answer and explanation

B: sebaceous glands

Sebaceous glands release sebum, an oily secretion that lubricates skin and hair. Sweat glands principally produce a watery secretion and are not the main source of this oil.

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Question 22

The outer layer of the kidney where the Bowman's capsules are found is the

  1. cortex
  2. pelvis
  3. medulla
  4. pyramid
Answer and explanation

A: cortex

Renal corpuscles, including Bowman’s capsules and their glomeruli, lie in the kidney cortex. The medulla contains renal pyramids, while the pelvis collects urine toward the ureter.

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Question 24

In the male reproductive system of a mammal, sperm is stored in the

  1. vas deferens
  2. urethra
  3. epididymis
  4. seminiferous tubules
Answer and explanation

C: epididymis

Sperm mature and are stored in the epididymis after leaving the testis. During ejaculation they travel into the vas deferens and onward through the reproductive tract.

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Question 26

Which part of the human gut normally has strongly acidic contents because it secretes hydrochloric acid?

  1. stomach
  2. duodenum
  3. ileum
  4. colon
Answer and explanation

A: stomach

The stomach normally has a strongly acidic lumen because gastric glands secrete hydrochloric acid. Acid helps activate pepsin and supports protein digestion before intestinal neutralisation.

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Question 27

I. Stomata → Spirogyra. II. Alveoli → earthworm. III. Malpighian tubule → mammal. IV. Contractile vacuole → protozoans. Which pairing is correct?

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

D: IV

Contractile vacuoles occur in many freshwater protozoans and remove excess water. Spirogyra has no stomata, earthworms do not have alveoli, and mammals do not use Malpighian tubules.

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Question 30

The barrier between maternal and foetal blood is the

  1. placenta
  2. liver
  3. umbilical cord
  4. uterine wall
Answer and explanation

A: placenta

Maternal and fetal blood are normally separated by placental tissues while gases, nutrients and wastes pass across the exchange barrier. The placenta is an exchange organ, not a completely impermeable wall.

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Question 31

Which listed blood component carries most oxygen by binding it to haemoglobin?

  1. lymphocytes
  2. leucocytes
  3. erythrocytes
  4. thrombocytes
Answer and explanation

C: erythrocytes

Erythrocytes contain haemoglobin, which binds and transports most blood oxygen. White blood cells primarily support defence, while platelets are chiefly involved in blood clotting.

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Question 32

Which of the following organisms is mainly found in the marine habitat?

  1. Achatina
  2. Tilapia
  3. dogfish
  4. Tortoise
Answer and explanation

C: dogfish

Dogfish are sharks that live in marine environments. The other listed organisms are principally land animals or freshwater fishes, so dogfish is the marine choice.

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Question 33

The left and right hip bones of the human pelvic girdle are joined anteriorly at the

  1. pubic symphysis
  2. ilium
  3. pubis
  4. obturator foramen
Answer and explanation

A: pubic symphysis

The left and right hip bones meet anteriorly at the pubic symphysis, a joint containing fibrocartilage. Each hip bone also joins the sacrum posteriorly.

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Question 35

Low annual rainfall, sparse vegetation, hot days and cold nights are typical of a hot

  1. tropical rainforest
  2. desert
  3. montane forest
  4. guinea savanna
Answer and explanation

B: desert

A hot desert commonly has low rainfall and sparse vegetation. Dry air and limited cloud cover can allow strong daytime heating and rapid cooling at night, producing a wide daily temperature range.

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Question 36

The activity of an organism which affects the survival of another organism in the same habitat constitutes

  1. an edaphic factor
  2. an abiotic factor
  3. a biotic factor
  4. a physiographic factor
Answer and explanation

C: a biotic factor

A biotic factor arises from living organisms, such as predation, competition or mutualism. It can affect another organism’s survival, reproduction or access to resources.

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Question 37

The average number of individuals of a species per unit area of the habitat is the

  1. population density
  2. population frequency
  3. population size
  4. population distribution
Answer and explanation

A: population density

Population density is the number of individuals per unit area or volume. Population size is the total count, while distribution describes how individuals are arranged in space.

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Question 38

Which listed mosquito or fly is a vector of yellow fever?

  1. Aedes mosquito
  2. Anopheles mosquito
  3. tsetse fly
  4. blackfly
Answer and explanation

A: Aedes mosquito

Aedes mosquitoes can transmit yellow fever virus. In the urban transmission cycle, Aedes aegypti is an important vector; the other listed insects do not identify that usual urban vector.

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Question 40

The protozoan Plasmodium falciparum is transmitted to humans by

  1. female Anopheles mosquitoes
  2. female Aedes mosquitoes
  3. female Culex mosquitoes
  4. female blackflies
Answer and explanation

A: female Anopheles mosquitoes

Female Anopheles mosquitoes transmit Plasmodium falciparum during blood feeding. Parasites develop through mosquito and human stages, with sporozoites entering the person in an infective bite.

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Question 42

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Using the plotted height distributions, which plantation has all its trees between 2 m and 4 m tall?

  1. III
  2. II
  3. I
  4. IV

Question 44

Thyroxine and adrenaline influence physiological activity that can affect

  1. blood grouping
  2. tongue rolling
  3. behavioural patterns
  4. colour variation
Answer and explanation

C: behavioural patterns

Thyroid hormones influence metabolic activity, and adrenaline contributes to rapid responses to stress. Changes in these physiological states can influence behaviour, unlike inherited blood-group identity.

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Question 46

The chromosome number of a cell before and after the process of meiosis is conventionally represented as

  1. 2n → 2n
  2. n → n
  3. n → 2n
  4. 2n → n
Answer and explanation

D: 2n → n

Meiosis reduces the chromosome-set number from diploid, 2n, to haploid, n. DNA replicates before the first division, but replication does not itself double the number of chromosome sets.

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Question 47

For a single autosomal trait with complete dominance, both parents are heterozygous (Aa). What is the probability that an offspring expresses the recessive trait?

  1. 3⁄4
  2. 1⁄2
  3. 1⁄4
  4. 1
Answer and explanation

C: 1⁄4

For Aa × Aa, each parent produces A and a gametes equally. The four equally likely combinations are AA, Aa, aA and aa, giving a recessive aa phenotype in one quarter of offspring.

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Question 48

In the usual mammalian XX/XY system, when is the zygote’s sex-chromosome combination established?

  1. at adolescence
  2. at puberty
  3. at birth
  4. at conception
Answer and explanation

D: at conception

In the usual mammalian XX/XY system, fertilisation establishes the zygote’s sex-chromosome combination. Subsequent development determines the gonads and other sex characteristics through additional genetic and hormonal processes.

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Question 49

A typical mandibulate soldier termite is distinguished by the

  1. presence of wings, possession of a small head and large thorax
  2. presence of wings, possession of a large thorax and a small head
  3. absence of wings, possession of strong mandibles and a large head
  4. absence of wings, possession of big head and the absence of mandible
Answer and explanation

C: absence of wings, possession of strong mandibles and a large head

A typical mandibulate soldier termite is wingless and has an enlarged head with strong jaws used in colony defence. Winged reproductives serve a different role, particularly during dispersal.

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Question 50

The independently evolved similarity of whale flippers and fish fins as swimming structures illustrates

  1. divergent evolution
  2. coevolution
  3. continuous variation
  4. convergent evolution
Answer and explanation

D: convergent evolution

Whales and fishes independently evolved body features suited to swimming. Their similarly functioning external swimming structures illustrate convergence, although deeper vertebrate ancestry links parts of their skeletal history.

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