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Experimental Evolution

Gestel, J. van (2009) Experimental Evolution. Bachelor's Thesis, Biology.

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Abstract

Evolution is considered as the most fundamental process in biology, connecting all life by what is called the common ancestor. Since Darwin proposed the idea of evolutionary adaptation by natural selection, many theoretical and comparative studies have been performed to elucidate the underlying processes. But in the last decades experimental evolution allowed us to study the evolutionary dynamics as they happen, by directly monitoring microorganisms that propagate in an experimental environment. Here, we aim to comprehend the insights that these studies gave in the process of evolutionary adaptation by natural selection. The longest-running microbial evolution experiment was started in 1988, at which twelve populations were founded by the same strain of Escherichia coli. In this, and other evolution experiments, adaptive radiation was observed in both spatially and temporally heterogeneous environments. The most fundamental process in maintaining diversity was shown to be frequency-dependent selection. In addition, the long-term experiment showed a remarkable parallelism in phenotypic changes that were observed in the twelve independently evolving populations, which is a hallmark for adaptive evolution. These parallelisms were affecting two different levels of gene regulation, namely global regulatory networks and local regulons. Especially two highly interconnected networks – genes that regulate DNA topology and the stringent response – have been demonstrated to be involved in the phenotypic and genetic adaptation. The dynamics of this evolutionary adaptation could quite readily, although not completely, be explained by the observed beneficial mutations that were substituted, in which the roles of natural selection and clonal interference seem to be the most dominant. These dynamics, together with the discovery of many epistatic interactions, demonstrated that the adaptive landscape was quite rugged. In general, experimental evolution has provided one of the most straightforward evidences for adaptive evolution by natural selection.

Item Type: Thesis (Bachelor's Thesis)
Degree programme: Biology
Thesis type: Bachelor's Thesis
Language: English
Date Deposited: 15 Feb 2018 07:28
Last Modified: 15 Feb 2018 07:28
URI: http://fse.studenttheses.ub.rug.nl/id/eprint/8567

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