Which of the following theories was NOT considered by Darwin in his evolutionary theory?

1. Analyze the question You are asked which idea Darwin did NOT include in his theory of evolution by natural selection.

2. Explain the concept Darwin's theory of natural selection rests on these ideas:

• Variation: individuals in a population differ from one another.
• Overproduction and competition: organisms produce more offspring than can survive, so they compete for limited resources such as food, water and space.
• Survival of the fittest: individuals with favourable variations survive and reproduce.
• Inheritance: the favourable traits are passed on to offspring.

Use and disuse is not Darwin's idea. It belongs to Jean-Baptiste Lamarck, who said that organs used often become better developed, while organs not used waste away. Lamarck also said these acquired characteristics are inherited. Think of the giraffe stretching its neck, which Lamarck said made the neck longer, and the offspring then inherited it.

3. Solution, option by option

• A. Variation: used by Darwin. ✔
• B. Survival of the fittest: used by Darwin. ✔
• C. Use and disuse: Lamarck's theory, not Darwin's. ✘
• D. Competition (struggle for existence): used by Darwin. ✔

4. Answer The correct option is C. use and disuse.

(Note: Darwin did accept use and disuse as a minor supporting idea in later editions of On the Origin of Species. But it is not part of his main theory, and in JAMB it is credited to Lamarck.)

5. Exam tip Remember: Lamarck = Use and disuse + inheritance of acquired characters. Darwin = Variation + Competition + Natural selection. If you see "use and disuse" or "acquired characteristics", think Lamarck.