Enterobacter is a genus of common Gram-negative, facultatively anaerobic, rod-shaped, non-spore-forming bacteria of the family Enterobacteriaceae.nterobacter is a genus of common Gram-negative, facultatively anaerobic, rod-shaped, non-spore-forming bacteria of the family Enterobacteriaceae.
Trilobite fossil from the Cambrian Period. Photo Credit: Archbob. The first period in the Paleozoic Era is known as the Cambrian Period. Many of the ancestors of the species that have evolved into what we know today first came into existence during the Cambrian Explosion in the early Cambrian Period.
An era of geologic time, from the end of the Precambrian to the beginning of the Mesozoic. The word Paleozoic is from Greek and means old life. Permian (286 - 248 million years ago) The final period of the Paleozoic era.It is named after the province of Perm, Russia, where rocks of this age were first studied.ver time, life forms change. Their fossil record allows geologists to date and compare rocks across geological time. For example, dinosaur fossils are only found during the Mesozoic era some 245 to 65 million years ago. The following table shows the geologic time scale.