Colorado Technical university| Sci210-1104B-11| Phase 2 – Individual Project| | Deanna Filkins| 11/27/2011| | Phyletic gradualism is the theory that one species changes to another by combining the better genetic features of the species and these genetics mutate and result in an entirely different species. This change is slow and gradual and most often occurs in small populations. The species changes a little at a time over a certain period until it no longer has any traits of its ancestors. Thus, it becomes a new species. There are gaps in the fossil record which have raised many questions to the validity of this theory.
One example believed to be a result of phyletic gradualism is the foraminiferans. This tiny marine species remained the same from 10 million to 6 million years ago. They then began a gradual change which lasted approximately 600,000 years. At this point they were a totally different species from their ancestors. (Dictionary, 2009) Another example is found in rocks that dated at approximately 370 million years old, only sea creatures are found.
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However, in 1998, scientists found a fossilized fin that had 8 digits and the appearance was similar to the fingers on a human hand. This fossilized fin was determined to be 370 million years old. The Biologos Foundation, 2011). There is no doubt the fin was that of a sea creature, but the fossil is strong evidence of a gradually changing form. These examples are few and far between. There is very little evidence which supports phyletic gradualism due to no intermediate species being found in the fossil record. Punctuated equilibrium is a theory that evolution is characterized by long periods of stability in the characteristics of an organism and short periods of rapid change during which new forms appear, especially from small subpopulations of the ancestral form in restricted parts of its geographic ange. (Merrium-Webster, 1978). Tribolites, ancient arthropods, lived on this planet for over 300 million years. During this time, they took many forms—size ranged from less than a centimeter to two feet long. Due to the abundance of these creatures, scientists have a complete fossil record. In 1933, a German Jewish scientist, Rudolf Kaufman, noted that the evolution of tribolites was slow for long periods of time—then changed dramatically and quickly. This major change was punctuated. Punctuated equilibrium predicts the sudden appearance of new species in the fossil record.
Changes occur in small regions and populations; therefore, there is little probability of finding intermediate species. Presumably, major environmental changes in predation pressure, food supply and climate caused rapid periods of change. Likely, triggers for rapid evolution were severe droughts, major volcanic eruptions and the beginning and ending of the ice ages. Fossils are the best evidence of life history that we have today. They include such things as shells, seeds, skeletons, DNA and traces of organisms from long ago.
The fossil record reveals evidence of when life began, what kinds of organisms existed and the length of their existence. It provides information about how organisms evolved. Scientists can even determine what type of climate was in an area and how it changed. Due to many natural factors; such as decay—many organisms have not been preserved. The result is an incomplete fossil record. We will never know the complete record of most organisms that have existed on this planet. Over time, organisms have notably changed.
http://www. merriam-webster. com/dictionary/punctuated%20equilibrium
http://www. biology-online. org/dictionary/Phyletic_gradualism
http://biologos. org/questions/fossil-record Lienhard