In which of the following does external fertilization take place?

Analyze the question: We need the animal in which fertilization happens outside the female's body, with sperm and eggs meeting in the external environment, usually water.

Concept:

• External fertilization: The female releases eggs and the male releases sperm into water, and they fuse there. It is common in fish and amphibians (frogs and toads), which need moist or aquatic conditions.
• Internal fertilization: Sperm is deposited inside the female's body, and fertilization happens there. It is found in reptiles, birds, mammals and insects.

Step-by-step solution:

• A. Toad: A toad is an amphibian. The male clasps the female (amplexus) and sheds sperm over the eggs as she lays them in water. This is external fertilization.
• B. Lizard: A lizard is a reptile. Fertilization is internal, and it then lays shelled eggs on land.
• C. Bird: Fertilization is internal, and the shell forms afterward around the fertilized egg.
• D. Cockroach: A cockroach is an insect. The male transfers sperm to the female, so fertilization is internal.

Answer: The toad, which is option A.

Tip: Remember "fish and amphibians = water = external." Reptiles, birds, mammals and insects fertilize internally. In JAMB, if you see a toad, frog or fish among the options, it is usually the answer to an external fertilization question.