Chapter 18: Cambrian Explosion and Extinction

geological time scale

The ________ is divided into eons, eras, periods, epochs, and stages.

Cambrian Explosion

543 million years ago to 495 million years ago

Phanerozoic Eon

543 million years ago to the present day

Fossil

any trace of an organism that lived in the past

Fossil record

the complete collection of fossils located in my institutions around the world

The 5 categories of fossils include

Unaltered remains, permineralized fossils, natural casts and molds, compression and suppression, and trace fossils

Unaltered Remains

forms in environments where decomposition, weathering, and scavenging by animals do not occur

Permineralized Fossils

form when structures are buried in sediments and dissolved minerals such as silica, calcium carbonate, or iron circulate through the enclosing deposits and precipitate in cavities such as bone marrow cavities and canals once occupied by blood vessels or nerves

Natural cast and molds

form when remains (bones and shells) decay but leave impressions in the surrounding sediment

Compression and Impression fossils

are formed when water or wind-born sediment buries organic matter, the weight of the sediment on top of the organic matter can push the material into the sediment below, creating an impression

Trace Fossils

the preserved remains or traces of animals, plants, and other organisms

Cambrian Explosion

(543-495 MYA) almost all of the animal phyla known today originated in the early Cambrian and most of the major vertebrate classes too

Ediacaran Fauna

are soft-bodied organisms (Sponges, jellyfish, comb jellies), small organisms with asymmetrical or radial symmetry

Burgess shale fauna

dated at 505 mya, contains large, complex, and bilaterally symmetrical forms (arthropods, segmented worms, several chordates, at least 2 species of jawless vertebrates resembling extant hagfish and lampreys)

Extinction

is the ultimate fate of all species

Mass extinction

a large-scale, sudden extinction event that is geographically and taxonomically widespread

The Big 5

5 prominent mass extinction events throughout the Phanerozoic eon

Terminal Ordovician

440 mya

Late Devonian

365 mya

End Permian

250 Mya

End Triassic

215 mya

Cretaceous-Tertiary (K-T)

65 mya

Background extinction

extinction that occurred at a normal rate

Mass extinctions are

global, involve a wide range of organisms (marine and terrestrial), occur rapidly, and result from extraordinary sudden temperature changes in the environment

Background extinctions are

a result of poor adaptations, environmental changes, and or competition

K-T

high impact extinction is also known as Cretaceous-Paleogene (K-Pg) extinction

Impact hypothesis

a large asteroid hit the surface of the earth