BIOLOGY | Metamorphosis | WAEC GCE Questions And Answers

1. Meaning of Metamorphosis

Metamorphosis is the series of changes in form and structure that an organism undergoes from the egg stage to the adult stage.
It is common in insects and amphibians.

2. Types of Metamorphosis

A. Complete Metamorphosis (Holometabolous)

Organism passes through four distinct stages:
Egg → Larva → Pupa → Adult
Each stage looks very different.
Examples: Butterfly, Housefly, Mosquito, Beetle.

Features:

Larva is the feeding stage (e.g., caterpillar in butterfly).
Pupa is the resting stage where transformation occurs.
Adult is reproductive but usually not the main feeding stage.

B. Incomplete Metamorphosis (Hemimetabolous)

Organism passes through three stages:
Egg → Nymph → Adult
Nymph looks like a smaller version of the adult but without fully developed wings or reproductive organs.
Examples: Grasshopper, Cockroach, Dragonfly.

Features:

No pupa stage.
Nymph undergoes successive moulting until it becomes adult.

3. Metamorphosis in Amphibians

Example: Frog
- Egg → Tadpole → Adult frog
Tadpole has gills, tail, and swims in water.
Adult frog develops lungs, limbs, and lives on land.

4. Significance of Metamorphosis

Reduces competition for food (larva and adult feed differently).
Ensures survival and adaptation to different environments.
Helps in population control and balance in ecosystems.

5. Diagrams to Emphasize

Life cycle of a butterfly (egg → larva → pupa → adult).
Life cycle of a grasshopper (egg → nymph → adult).
Life cycle of a frog (egg → tadpole → frog).

PAST WAEC GCE QUESTIONS ON METAMORPHOSIS

Objective Questions

Which of the following organisms undergoes incomplete metamorphosis?
A. Mosquito
B. Butterfly
C. Grasshopper
D. Housefly

✅ Answer: C. Grasshopper

The resting stage in complete metamorphosis is known as:
A. Larva
B. Nymph
C. Pupa
D. Imago

✅ Answer: C. Pupa

Which feature distinguishes complete metamorphosis from incomplete metamorphosis?
A. Presence of larval stage
B. Absence of pupa stage
C. Number of moulting stages
D. Presence of wings in adult

✅ Answer: A. Presence of larval stage

Theory Questions

(WAEC GCE 2016, Biology – Paper 2)

(a) Differentiate between complete and incomplete metamorphosis.
(b) Using a named insect, describe the life cycle of an insect that undergoes complete metamorphosis.

Sample Answer:
(a) Complete metamorphosis involves four stages (egg, larva, pupa, adult) while incomplete metamorphosis involves three stages (egg, nymph, adult) and lacks a pupal stage.
(b) In a butterfly:

The egg hatches into a larva (caterpillar) which feeds actively.
The larva transforms into a pupa (chrysalis) where major changes occur.
Finally, an adult butterfly emerges, ready to reproduce.

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(WAEC GCE 2020, Biology – Paper 2)
2. Describe the life cycle of a mosquito. State its economic importance.

Sample Answer:

The mosquito undergoes complete metamorphosis:
Egg → Larva (wriggler) → Pupa (tumbler) → Adult mosquito.
Economic importance:
- Vector of malaria (Plasmodium)
- Vector of yellow fever, dengue fever.
- Causes discomfort from biting.

CLASS PRACTICE QUESTIONS

Explain why metamorphosis reduces competition for food.
List two insects each that undergo:
(a) Complete metamorphosis
(b) Incomplete metamorphosis.
Draw and label the life cycle of:
(i) Grasshopper
(ii) Butterfly.
State three advantages of complete metamorphosis to the survival of insects.

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