Sexually reproducing organisms use DNA copying mechanisms to maintain species stability. During reproduction, the DNA is copied using chemical reactions and passed to offspring. Although copying is not 100% accurate and small variations arise, the consistency of DNA copying ensures that body design features are preserved, maintaining stable populations suited to their ecological niche.
The examiner expects two key points: (1) DNA copying ensures inheritance of body design features, and (2) the consistency (not perfection) of this copying maintains population stability. Avoid writing only about variation — the question focuses on stability. The phrase "consistency of DNA copying" directly from the chapter is important to include.
Source: Chapter 7, Section 7.1 and 7.1.1