04:43
Life Goes On: Vertebrates: Marine and Terrestrial
Marine biologists informally classify marine animals into two large groups: invertebrates and vertebrates. Vertebrates have backbones, while invertebrates do not. There are far more invertebrates than vertebrates in the ocean, but the vertebrates-wh...
02:53
Survivors: Long-Term Survivors
Despite the challenges of long-term survival on Earth, some phyla-including sponges, jellyfish, arthropods and mollusks-have endured for hundreds of millions of years, even in the most extreme environments.
01:06
Survivors: Early Invertebrates
The first animals on Earth were invertebrates-animals without backbones-and they diversified rapidly in the geologic period known as the Cambrian.