Title:
Quantifiying morphology - from non-living to living systems

Abstract:
The diversity of shapes and sizes displayed by modern life is striking. Morphology has therefore been used for centuries now to recognize and classify organisms. However, in the early stages of life evolution, and more particularly before the apparition of multicellularity, the morphologies of individual organisms were simpler. Besides, several abiotic systems are able to create morphologies similar to unicellular life, such as silica-witherite biomorphs.

What is the actual range of morphologies which can be produced in these abiotic systems and what is the influence of environmental conditions on these morphologies? I present first some results of my work on silica-witherite biomorphs. The diversity of biomorph shapes is integrated to a morphogenetic model, and the effect of environment on the growth is assessed by scanning a wide range of conditions of pH and concentrations.

The problem is then to know whether life, not as individual organisms but as a system, displays morphological characteristics which distinguish it from abiotic systems. I present in a second part the results of a study in which I compared quantitatively the morphology of populations from specific biological (microbial communities) and abiotic (silica-witherite biomorphs, interstitial spaces) systems. Differences are found between microbial populations and abiotic populations, and the discrimination between the systems is improved when looking at more parameters and/or more populations.

However, the emergence of the morphological characteristics of life on Early Earth and the actual mechanisms controlling them are not well understood yet. I present in a third part my research project in ELSI. Diverse natural microbial communities will be compared in parallel to numeric simulations in order to understand the effect of several environmental and ecological parameters on population morphometry. Silica-witherite biomorphs and other abiotic systems will be grown experimentally under various conditions in order to assess which parameters can generate morphologic complexity at the scale of populations. This research project has the general goal to better understand life as a morphological system and has important implications for ecology, paleontology and astrobiology.