| A | B |
|---|
| evolution | the change in species over time |
| amphibians | first vertebrates to actually live on land |
| Mesozoic Era | the Age of Reptiles |
| Precambrian Time | the longest period of time in the geologic time scale |
| today's foxes | size of ancient horses |
| today's pigs | size of ancient elephants |
| ancestor bacteria | Precambrian |
| reptiles | Mesozoic |
| first apes | Cenozoic |
| trilobites and jellyfish | Precambrian |
| age of mammals | Mesozoic |
| geologic time scale | divides earth's history into 4 eras |
| purpose of geologic time scale | shows the development of life on earth |
| bacteria | dominated the Precambrian Time |
| invertebrates | animals that lack a backbone |
| vertebrates | animals that have a backbone |
| amphibians | first vertebrates to live on land |
| fish | first vertebrates |
| glaciers | covered much of the land at the end of the Paleozoic Era |
| dinosaurs | dominant life form on Earth for 150 million years |
| Cenozoic | the age we are living in now |
