Introduction
Do organisms undergo a long and gradual processes of evolution, or do they exist for long periods of stasis – minimal change – and abruptly evolve into a different form? These two questions surround the debate of whether evolution occurs by phyletic gradualism, or by punctuated equilibrium, respectively. This paper will present both hypotheses and reasons for their prevalence, then it will argue one hypothesis with current research on the topic, finishing with suggestions for further research and direction.
Hypotheses
The hypothesis of gradual change is termed Phyletic Gradualism, and it describes evolution to happen as a slow and gradual process, whereby a large ancestral population transforms into a distinct descendent (Eldredge …show more content…
21224). The researchers then conducted a study where they analyzed marine plankton fossils through multiple layers of ocean rock, and across a wide range of area. This method was used to analyze the successive evolved species of plankton throughout time (layers of rock), and to analyze if this evolution was common across the species in distant regions of the ocean floor (Hull & Norris, 2009, p. 21225). What was previously understood through analysis of the bedrock was that the species of plankton G. plesiotumida transformed directly into G. tumida over a period of ~300,000 years (Hull & Norris, 2009, p. 21225). After deeper analysis of morphology, the researchers found that G. plesiotumida did not entirely contribute to the evolution of G. tumida, but had a subpopulation that changed into an alternative form, one distinct from both G. plesiotumida and G. tumida (Hull & Norris, 2009, p. 21225). Remarkably, the alternative form was indeed the precursor to G. tumida, and had abruptly evolved over ~44,000 years into G. tumida (Hull & Norris, 2009, p. 21226). To add to the findings, Hull and Norris (2009) found that “stratigraphic analysis from other sites has shown that G. plesiotumida persists after the evolution of G.tumida”, suggesting that the parent species coexisted with its two descendants rather than being cut …show more content…
715). Zeh et al. (2009) discuss in their paper that under physiological stress an organism’s epigenetic mechanisms for suppressing a disruptive form of genetic change, known as Transposable Elements (TE), becomes altered and results in TE activation (p. 715). Precisely, “Mobilized TEs rapidly restructure the genome and alter gene expression patterns by inserting into promoters and enhancers, and by causing chromosomal breakage, exon shuffling, sequence expansion, gene duplication, ectopic recombination, novel gene formation and expansion and re-wiring of genetic regulatory networks”, which can ultimately result in “rapid morphological change and speciation (Zeh et al., 2009, p. 715). This sort of mechanism becomes unleashed when there is significant stress to an organism, such as major climate change, and therefore responds rapidly (Zeh et al., 2009, 715). Zeh et al. (2009) further point out that genetic evidence from extant mammals shows evidence for intense TE activity during the massive extinction that occurred 65 Mya, leading to the expansion of mammals (p. 721). These rapid adjustments made by the organism’s genetic code to adapt to the environment can begin to show a genetic basis for punctuated equilibrium evolution. Thus, further research can be done in the field to better understand how the environment influences the epigenetics of an