Standard 8e Preknowledge
8e) Students know how to analyze fossil evidence with regard to biological diversity, episodic speciation, and mass extinction.
CALIFORNIA FRAMEWORKS SUMMARY:
Analysis of the fossil record reveals the story of major events in the history of life on earth, sometimes called macroevolution, as opposed to the small changes in genes and chromosomes that occur within a single population, or microevolution. Explosive
radiations of life following mass extinctions are marked by the four eras in the geologic time scale: the Precambrian, Paleozoic, Mesozoic, and Cenozoic. The study of biological diversity from the fossil record is generally limited to the study of the differences among species instead of the differences within a species. Biological diversity within a species is difficult to study because preserved organic material is rare as a source of DNA in fossils.
Episodes of speciation are the most dramatic after the appearance of novel characteristics, such as feathers and wings, or in the aftermath of a mass extinction that has cleared the way for new species to inhabit recently vacated adaptive zones. Extinction
is inevitable in a changing world, but examples of mass extinction from the fossil record coincide with rapid global environmental changes. During the formation of the supercontinent Pangaea during the Permian period, most marine invertebrate species disappeared with the loss of their coastal habitats. During the Cretaceous period a climatic shift to cooler temperatures because of diminished solar energy coincided with the extinction of dinosaurs.