To answer the question of how long ago invertebrates became common on Earth, we need to refer to the geologic time scale provided.
The table contains various eras, periods, and key events that happened throughout Earth's history. The key events column provides significant evolutionary milestones associated with each era.
From the geologic time scale:
- The "Paleozoic" era is highlighted with key events, and specifically mentioned is that "Invertebrates become common."
To determine the exact time frame, let's break it down:
- The Paleozoic era includes periods like the Permian, Carboniferous, Devonian, Silurian, Ordovician, and Cambrian.
- According to historical records and geological findings, invertebrates are known to have become common during the early periods of the Paleozoic era.
Given the options provided:
1. 1.6 million years ago
2. 132 million years ago
3. 410 million years ago
4. 520 million years ago
We need to select the most accurate one. The Paleozoic era spans from approximately 541 million years ago to 252 million years ago. Within this era, the Cambrian explosion, which significantly increased the diversity of invertebrates, occurred about 541 to 485 million years ago.
Given these periods, the most accurate and closest approximation to when invertebrates became common is:
410 million years ago
Therefore, the correct answer is:
410 million years ago
