| 1. | Aerobic as it release more energy |
| 2. | Anaerobic as it releases more energy |
| 3. | Aerobic as it is more complex |
| 4. | Anaerobic as early atmosphere contained no free from of oxygen |
| 1. | Devonian period | - | Age of fishes |
| 2. | Carboniferous period | - | Age of amphibians |
| 3. | Ordovician period | - | Age of invertebrates |
| 4. | Cretaceous period | - | Age of reptiles |