Running Head THEORIES OF EVOLUTION

Theories of Evolution

Theories of Evolution

Phyletic Gradualism and Punctuated Equilibrium

During the process of evolution of species, divergent currents of thought have proposed theories to explain the formation and perpetuation of new species, through mechanisms of speciation.

Around 1859 to 1972, phyletic gradualism was in force which is based on the theory of gradualism, proposed by Charles Darwin, defending the accumulation of small changes over several generations, so a slow event, conditioning the transfer of hereditary changes in morphological and physiological behavior of the individual.

Contrary to this current came a scientific theory formulated after 1972, by evolutionary paleontologists Stephen Jay Gould and Niles Eldredge, called punctuated equilibrium (saltationism, pontualismo balances theory or intermittent). According to this line of thought, the evolution of a species does not occur consistently, but alternating periods of little change, with sudden jumps that characterize structural changes or organic selected and adapted (Jurmain, Kilgore, Trevathan and Ciochon, 2011).

This understanding of speciation was based on questions about the discontinuity of the fossil record, the consequence of not finding evidence with respect to gradual changes. Conversely, the intermittent scan (on and off) from fossil species contained in extracts sedimentary formed along the scale geological, showed an evolutionary context in which speciation likely to occur in specific periods, which is very short by which organisms changes passed and stabilized in subsequent time (in heels). However, several challenges emerged, playing the traditional Darwinian trend, since the fossil record is inaccurate and flawed (Gould, 2007).

Fossil Record and Punctuated Equilibrium

Equilibrium predicts that many of the punctuated evolutionary changes took place in a short time, along with speciation event. In many cases, we see “bursts” of evolution in the fossil record. For example, imagine that a deeper layer of rock have the ancestral one. The next layer of rock seen ...