Great Transformations

- If all of time were condensed into an hour, animals appeared in the last 10 min and humans in the last 1/100th of a second.

- 200 MYA mammals appeared.

- Bones like those in the ear of a whale have been found on the skeleton of a wolf-like mammal. Could be part of the missing link between terrestrial and marine mammals. Ancient whales had pelvis and legs (Basilosaurus, 40 MYA). More transitional whales (species between ancient and modern) are now known. Shows nostrils migrating backward to form blowhole

- Oceans recede so marine fossils can sometimes be found quite far inland.

- Fish bend spine left to right when swimming.

- Mammals bend spine same way when swimming or when running on land (e.g., whale, otter, seal, dog). Suggests marine mammals evolved from land mammals.

- Most land animals are tetrapods which suggests a strong connection.

- Fossils suggest that limbs developed then animals moved onto land rather than moving onto land and then developing limbs. Limbs may have been an advantage for a benthic lifestyle.

- Bone structure of the fin of a fish is strikingly similar to that of the limb of land animals. i.e., the structure was already present - it just needed tinkering.

- The Cambrian explosion occurred 570 MYA with many animals appearing on land which show the same body plan. The problem is that the ideas are based on just a few fossils.

- Single genes that are able to control the development of an entire body segment have been discovered. Genes could be switched from one species to another. e.g., eye gene in mouse can induce formation of compound eye in fruit fly. This indicates that the genes are very old. Also, that evolution works with packets of information rather than starting from scratch with each animal or group of animals

- Skeletons of similar organisms show small differences due largely to differences in lifestyle.