Fossils Are the Preserved Remains

Fossils are the preserved remains or traces of those remains from animals, plants and other organisms from. The fossil record and their placement in geological strata (rock formations containing fossils) is known as the fossil record. The science of paleontology is the study of fossils across geological time -- how they were formed, what the evolutionary relationships were between the different fossils, and most importantly the relationship between organisms across time. Fossils vary in size, of course, based on the organism -- from microscopic to gigantic.

Soft tissue is not normally preserved, so it is the bones or marks left behind (footprints or feces) that are typically found. In general, fossils are formed by the replacement of the empty spaces or parts of the organism with minerals or molds. There are several types of this: permineralization fills cavities with minerals from groundwater; authigenic mineralization forms mineral casts around the organism, or expression that compresses material and changes the carbon to rock over time (Pojeta and Springer, 2005).

The theory of evolution was developed out of the work of 19th century botanist and explorer, Charles Darwin and his book On the Origin of Species. Essentially, it is a scientific theory that postulates that organisms change over time based on pressures from the environment that cause genetic mutations within the organism. Over time, these changes are more adapted to a specific environment, more of that organism live longer and reproduce more, thus causing those traits to become even more entrenched in the population.

Life then, is part of a gigantic tree in which primitive organisms, over millions and millions of years, evolved into higher beings due to the product of two opposing forces: variation in traits (common or rare) and natural selection (which traits aid survival) (Understanding Evolution). Classic Darwinian evolution holds that species gradually change over time based on environmental pressures. However, that does not explain the manner in which the fossil record shows leaps in between species. Punctuated evolution (equilibrium), a theory from Stephen J.

Gould and others, holds that rather than gradually, evolution gets a "kick start" with certain external or environmental changes (drastic weather, etc.). Instead of gradually over thousands of generations, then, it happens quickly (in genetic terms) over hundreds of generations. This theory, developed with Niles Eldedge proposes that evolution is not gradual, but really the combination of long period of species stability, puntuated by dramtic instances of genetic mutation and species change.

When evolution occures, it is localized in rare and rapid events that are proven by the fossil record, as well as a thorough study of natural history (Gould and Eldredge, 1972). There are, however, gaps in the fossil record that remain controversial both in the scientific and philsophical communities. The religious right believes that the world is relatively young and the fossil record is only a few thousand years old, just pre-Noah flood. Gaps in the fossil record tend to suggest abrupt transitions in species.

There are, however, several reasons for gaps/abrupt transitions in the fossil record that are scientific in nature: Logistical -- there is clear bias in the record because many species are underpresented or have not yet been found. Not all organisms preserve the same, and many simply were never preserved. Not all bones survive well, some are scavanaged- indeed it is rare to find fossils at all.

Statistical -- When only a few species are found of an organism it is hard to decide just how representative they are of the species in total. It takes quite a number of fossils to make a picture of the species over time. Climatological -- Depending on the extinction event, the animal's death, etc. conditions may or may not have been appropriate for preservation. The climnate has changed many, many times; often resulting in a lack of fossils rather than a dearth (O'Neill, 2010).

Logic - Because we do not have a.