Which of the following is an evolutionary trend commonly observed in organisms?

Step 1: Analyze the question The question asks which option describes a trend commonly seen in evolution. We need the statement that fits how populations change over long periods.

Step 2: Explain the concept Evolution is the gradual change in the characteristics of populations over generations. The main drivers are:

• Mutation and genetic recombination, which create new variation
• Natural selection, which favours traits that improve survival and reproduction
• Gene flow and genetic drift, which spread or change variation in a population

Over time, living things generally show adaptation to their environments, and populations tend to build up variation that gives them material to adapt to new conditions.

Step 3: Evaluate each option

• A. Decreased complexity over time: Not a general trend. Many lineages became more complex, though some (such as parasites) simplified. It is not the common pattern.
• B. Increased dependence on external resources: Not an evolutionary trend. Organisms evolve to use resources more efficiently, and some become more self-sufficient.
• C. Increased genetic diversity within populations: Mutation, recombination, and gene flow keep adding variation. This variation is the raw material for natural selection, so it fits as a commonly observed trend.
• D. Decreased adaptation to the environment: This is the opposite of what natural selection produces. Selection improves adaptation.

Step 4: Answer The best answer is C. Increased genetic diversity within populations.

Step 5: Exam tip In evolution questions, eliminate options that describe organisms becoming less adapted or less fit, since these contradict natural selection. Remember the chain: variation → selection → adaptation. Genetic diversity is the starting point of that chain.