The theory of evolution can be defined as

Step 1: Analyze the question You are asked to pick the best general definition of the theory of evolution.

Step 2: Explain the concept The theory of evolution says that living organisms change gradually over many generations. These changes happen through natural processes such as natural selection, mutation, genetic variation, and genetic drift. Over long periods, this leads to new species and the diversity of life we see today. Charles Darwin and Alfred Russel Wallace proposed natural selection as the main mechanism.

Step 3: Evaluate each option

• A. All species were created in their current form. This describes special creation (fixity of species), which is the opposite of evolution. ❌
• B. Organisms strive to improve themselves over generations. This is close to Lamarck's idea of use and disuse and the inheritance of acquired characteristics. It is not the modern theory, because evolution has no "striving" or goal. ❌
• C. Species change over time through natural processes. This matches the theory. It covers change over generations and natural mechanisms such as natural selection. ✅
• D. Evolution occurs through sudden and dramatic changes. This resembles saltation or catastrophism. Evolution is generally a gradual process, so this is not the general definition. ❌

Step 4: Answer

Step 5: Exam tip Remember the keywords for evolution: change over time + natural processes. Watch for these traps:

• "Created as they are" means special creation.
• "Striving" or "need" means Lamarckism.
• "Sudden" means saltation or catastrophism.