Give the most important cause of success of insects.

Explanation

**Step-by-Step Text Solution:**

1. **Introduction to Insect Success**: Insects are one of the most successful groups of animals on Earth, with a vast number of species and a significant presence in various ecosystems.

2. **Species Richness**: Insects account for approximately 80% of all known species on the planet, showcasing their incredible diversity and adaptability.

3. **Key Factor for Success - Exoskeleton**: The most important cause of the success of insects is their exoskeleton, which is primarily made of chitin. This structure provides several advantages.

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