Date of Award

2002

Document Type

Master Thesis

Degree Name

Masters of Science (Research)

Department

Mathematics and Computing

First Advisor

Mr. Paul Rothwell

Abstract

This thesis presents a mathematical analysis and computational simulation which is used to investigate the evolution of cell colonies. The evolutionary transition from unicellular to cell colony form is a prerequesite for multicellular life as it exists abundantly on earth. This transition has occured numerous times independently so that we expect a high selective advantage to be associated with it. The photosynthetic green algae order Volvocaceae is an appropriate set of model organisms for the study of the evolution of cell colonies since it comprises living unicellular organisms, cell colonies, and multicellular organisms of different shapes, sizes and levels of complexity.

Though there is an increasing understanding of the evolutionary heritage of the colonial Volvocaceae, the phenotypical properties which led to their evolution are only vaguely understood. To gain an insight into these, a mixed mathematical and computational approach was employed. Based on the hypothesis that, with certain restrictions, fitness can be measured by speed of growth, a mathematical growth model for Volvocaceae was constructed and analysed with the aim of explaining the emergence of colonies in Volvocaceae. Three growth-influencing properties which depend on the colonial form were identified: (a) colony size, (b) cell temperature and (c) speed of movement. The analysis showed that the effect of the cell temperature on growth was negligible while the other two effects had considerable influence. The analytical approach was too limited for further analysis of some dynamical properties and so a computer simulation was required. A simulation environment dedicated to the modeling of cells and small organisms was therefore developed: the Cell Simulation Library (CSL). Using CSL, a Volvocaceae simulation was constructed which was used to test the different effects of colonial form on the growth rate with given environmental settings. Under certain circumstances, large cell colonies can significantly outgrow smaller colonies and unicellular organisms because of their higher movement velocity.

Finally, a series of artificial evolution experiments were conducted which showed that such cell colonies spontaneously evolve under beneficial circumstances.

Access Level

info:eu-repo/semantics/openAccess

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