Read the passage carefully and give the answers to the next five questions:

Does the number of species in a community really matter to the functioning of the ecosystem? This is a question for which ecologists have not been able to give a definitive answer. For many decades, ecologists believed that communities with more species generally tend to be more stable than those with less species. According to the International Union for Conservation of Nature and Natural Resources (IUCN) (2004), the total number of plant and animal species described so far is more than 1.5 million.

In ’rivet popper hypothesis’ the ‘rivet’ signifies:

The correct answer/option is Species.

Step-by-Step Explanation:

1. Understanding the Rivet Popper Hypothesis:
The "Rivet Popper Hypothesis" is an analogy proposed by Stanford ecologist Paul Ehrlich to explain the significance of species diversity to the stability and functioning of an ecosystem.

2. The Airplane Analogy:
In this hypothesis, Ehrlich compares an ecosystem to an airplane and the species within the ecosystem to the rivets holding the parts of the airplane together.
Specifically:
• The airplane represents the entire ecosystem.
• The rivets holding the plane together represent the individual species in the ecosystem.
• The passengers popping (removing) rivets out of the plane represent humans causing the extinction of species.

3. Logical Deduction:
If passengers start popping rivets (causing species extinction) from the plane, it may not initially affect flight safety (ecosystem functioning). However, as more and more rivets are removed, the plane becomes dangerously weak. Furthermore, removing a rivet from a critical part like the wing (representing a key species) is far more dangerous than removing one from a seat inside. Therefore, in this analogy, the "rivet" directly signifies a species.