Step 1: Understanding Rivet Popper Hypothesis.
The Rivet Popper Hypothesis compares the loss of species in an ecosystem to rivets in an airplane. Each rivet represents a species, and their loss weakens the ecosystem. It highlights the importance of biodiversity.
Step 2: Analyzing the options.
(1) Biodiversity: Correct. The Rivet Popper Hypothesis emphasizes the role of biodiversity in maintaining the integrity of ecosystems.
(2) sex-ratio: Incorrect. The hypothesis does not address the significance of sex-ratio.
(3) natality: Incorrect. The hypothesis does not focus on natality.
(4) age distribution ratio: Incorrect. The hypothesis deals with species loss and not age distribution.
Step 3: Conclusion.
The correct answer is (1) Biodiversity, as the Rivet Popper Hypothesis focuses on the loss of species and its impact on ecosystems.