The early Earth's atmosphere was primarily composed of gases like carbon dioxide, nitrogen, and ammonia. Oxygen was not a significant component and only became abundant later due to the photosynthetic activity of organisms.
List I | List II | ||
---|---|---|---|
A | Mesozoic Era | I | Lower invertebrates |
B | Proterozoic Era | II | Fish & Amphibia |
C | Cenozoic Era | III | Birds & Reptiles |
D | Paleozoic Era | IV | Mammals |