WAEC Biology 2020 past questions

Checked by the Skolra question team · Last updated 15 October 2026

Ten questions from the 2020 WAEC Biology paper, with answers and explanations. We hold 58 questions from this paper, and the Skolra app has all of them.

WAEC Biology 2020 questions and answers

1. 1.

   An example of a trace element is

   1. A
      Oxygen
   2. B
      Carbon
   3. C
      Iron
      Correct
   4. D
      Nitrogen
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   Answer: C

   Iron (Fe) is a trace element — a mineral required by living organisms in very small (trace) amounts but essential for normal physiological function. Iron is a component of haemoglobin (for oxygen transport) and cytochrome enzymes (for cellular respiration). Other trace elements include iodine, zinc, copper, manganese, and fluorine. Carbon, oxygen, and nitrogen are bulk elements (macronutrients) required in large amounts as they form the backbone of organic molecules such as proteins, fats, carbohydrates, and nucleic acids.
2. 2.

   The respiratory organ of a cockroach

   1. A
      lungs
   2. B
      book lungs
   3. C
      gills
   4. D
      tracheae and tracheoles
      Correct
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   Answer: D

   The cockroach, like all insects, breathes through a system of tracheae and tracheoles. Air enters the body through small openings called spiracles on the sides of the thorax and abdomen, then passes through branching tracheae (larger tubes) into finer tracheoles that deliver oxygen directly to individual cells. This system bypasses the blood for gas transport. Book lungs are the respiratory organs of arachnids (spiders and scorpions), gills are for aquatic animals, and lungs are for vertebrates such as mammals and birds.
3. 3.

   Which of the following substances is not a conservable natural resource?

   1. A
      Solar energy
      Correct
   2. B
      Forest timber
   3. C
      Soil minerals
   4. D
      Wildlife
   Show answerHide answer

   Answer: A

   Solar energy is not a conservable natural resource because it is inexhaustible and renewable — the sun continuously emits energy and humans cannot deplete it through use. Conservable resources are those that can be reduced, damaged, or exhausted by human activities and therefore require protection. Forest timber, wildlife, and soil minerals are all finite resources that can be depleted or degraded, making them targets of conservation efforts.
4. 4.

   Oxygen comes out of the stomata during photosynthesis through the process known as

   1. A
      diffusion
      Correct
   2. B
      transpiration
   3. C
      active transport
   4. D
      osmosis
   Show answerHide answer

   Answer: A

   Diffusion is the process by which oxygen produced during the light-dependent reactions of photosynthesis moves out of the leaf through the stomata. Oxygen builds up to a higher concentration inside the leaf's air spaces (mesophyll) than outside, so it moves passively down this concentration gradient through the stomatal pores. This is a passive process requiring no energy expenditure. Transpiration refers to water vapour loss; osmosis involves water movement across membranes; and active transport moves substances against concentration gradients using energy.
5. 5.What happens when the ciliary muscles of the eye contract? The
   1. A
      retina moves forward to focus on distant objects
   2. B
      suspensory ligaments tighten and the lens becomes flattened for distant vision
   3. C
      pupil dilates to allow more light in
   4. D
      suspensory ligaments become slack and the lens becomes rounder for near vision
      Correct
   Show answerHide answer

   Answer: D

   When the ciliary muscles contract, the ciliary body moves inward (towards the lens), causing the suspensory ligaments to slacken. Without the tension from the suspensory ligaments, the elastic lens springs back to its rounder, more convex shape, increasing its refractive power. This adjustment — called accommodation — allows the eye to focus on near objects. Conversely, when the ciliary muscles relax, the suspensory ligaments pull tight, flattening the lens for distance vision.
6. 6.Which of the following statements best explains the reason why termites swarm at night?
   1. A
      They swarm at night to avoid competition with ants
   2. B
      Their wings only develop in darkness
   3. C
      They are negatively phototactic and swarm at night to avoid desiccation from sunlight
      Correct
   4. D
      They can only reproduce in the absence of light
   Show answerHide answer

   Answer: C

   Termites are negatively phototactic, meaning they are repelled by light. Swarming at night allows them to avoid the desiccating (drying) effects of direct sunlight, which would dehydrate their soft, thin exoskeletons. Nighttime also reduces predation pressure from visually hunting birds and other daytime predators. This behaviour is an adaptation that improves the survival rate of reproductive termites (alates) during their mating flights.
7. 7.

   The part of the central nervous system that controls unconscious actions in humans is the

   1. A
      medulla oblongata
      Correct
   2. B
      cerebrum
   3. C
      hypothalamus
   4. D
      thalamus
   Show answerHide answer

   Answer: A

   The medulla oblongata is the part of the brainstem that controls vital autonomic (unconscious) actions such as breathing, heart rate, blood pressure, swallowing, coughing, and vomiting. These are essential life-sustaining functions that occur without conscious control. The cerebrum controls conscious thought, voluntary movement, and higher cognitive functions. The hypothalamus regulates homeostasis (temperature, hunger, thirst), and the thalamus relays sensory signals to the cerebrum.
8. 8.

   In an experiment, mould and yeast cells were transferred into an environment with low oxygen concentration. After a few days, the mould dies while the yeast cells did not. Which of the following statements best explains the following observation.

   1. A
      Yeast can respire anaerobically, while mould is an obligate aerobe that cannot survive without oxygen
      Correct
   2. B
      Mould cells are smaller and therefore use up oxygen faster
   3. C
      Mould has no cell wall and is destroyed by low oxygen pressure
   4. D
      Yeast produces more carbon dioxide than mould, which helps it survive
   Show answerHide answer

   Answer: A

   Yeast is a facultative anaerobe — it can respire both aerobically (using oxygen) and anaerobically (without oxygen) through the process of fermentation, producing ethanol and carbon dioxide. This flexibility allows yeast to survive in low-oxygen environments. Mould, however, is an obligate aerobe that requires oxygen for cellular respiration to produce ATP. Without adequate oxygen, mould cannot generate sufficient energy for growth and survival, leading to its death. This difference in metabolic flexibility explains the experimental observation.
9. 9.

   A child that can receive blood donation from anybody belongs to the blood group

   1. A
      A
   2. B
      B
   3. C
      O
   4. D
      AB
      Correct
   Show answerHide answer

   Answer: D

   Blood group AB is the universal recipient because individuals with this blood group have both A and B antigens on their red blood cells and produce neither anti-A nor anti-B antibodies in their plasma. This means they can receive blood from donors of any ABO blood group (A, B, AB, or O) without a major agglutination reaction. Blood group O is the universal donor because O-negative blood has no A, B, or Rh antigens.
10. 10.

    Use the list of insects below to answer the question below;

    I.Cotton stainer II.Honeybee III.Termite IV.Weevil

    Which of the insects destroys grains?

    1. A
       II and III
    2. B
       IV only
       Correct
    3. C
       I and III
    4. D
       I only
    Show answerHide answer

    Answer: B

    The weevil (IV) is the insect that destroys stored grains. Weevils (family Curculionidae) bore into grains such as rice, wheat, and maize, laying eggs inside the grain; the larvae feed on the grain from within, causing severe post-harvest losses. The cotton stainer (I) damages cotton bolls. The honeybee (II) is a pollinator and honey producer. The termite (III) primarily destroys wood and cellulose-based materials. Only the weevil is specifically known as a grain pest.

The questions come from past JAMB, WAEC and NECO papers. We use software to help write the answer options and explanations, and every answer is checked twice before it goes on the site. How we check

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