An event in which the last members of a lineage or species die. A single species goes extinct when all members of that species die. An entire lineage goes extinct when all the species that make it up go extinct.

Simply put, biological evolution is descent with modification. This definition encompasses small-scale evolution (changes in gene frequency in a population from one generation to the next — microevolution) and large-scale evolution (the descent of different species from a common ancestor over many generations — macroevolution).

The processes by which materials of the Earth’s crust are weathered and transported from their place of origin. Rocks are worn, loosened, broken apart, or dissolved by wind, rivers, wave action, freezing and thawing, and chemical breakdown.

A member of the Phylum Echinodermata, which includes starfish, sea urchins, and crinoids. Echinoderms have radial symmetry (which is usually five-fold), and a remarkable ability to regenerate lost body parts.

At roughly 4.8-4.0 million years old, this Early Pliocene-aged formation is located in the Central Valley of California. This formation is largely made up of siltstone, silty sand, sandstone, and conglomerate containing mostly marine fossils with a few freshwater and brackish water fossils.

Results of tests and/or observations that may either help support or help refute a scientific idea. In general, raw data are considered evidence only once they have been interpreted in a way that reflects on the accuracy of a scientific idea.

A member of the Class Echinoidea from the Phylum Echinodermata. Echinoids are subdivided into two subgroups: regular echinoids, with nearly perfect pentameral (five-part) symmetry; and irregular echinoids with altered symmetry. Examples of regular echinoids are modern sea urchins and pencil urchins; irregular echinoids include the heart urchins, sea biscuits, and the sand dollars.