Person:

Strong, Liz

Variation in beak shape among Darwin’s finches has long intrigued scientists[19][5][16]. An adage in biology is “form follows function,” or in this context, the shape of the bird beak is the result of the food available to the bird. To what extent is this true? Recently, scientists from Princeton observed rapid natural selection events that caused significant changes to the beak shapes of Darwin’s finches in response to weather events that first limited food resources to large, hard seeds and then later to small, soft seeds[18]. How much of this change in beak shape is due to the mechanical properties of the available seeds? This thesis looks to develop an understanding of how beak shape alone affects the ability of a bird to crush seeds. This thesis uses an engineering analysis tool called finite element analysis (FEA) to explore these questions. This thesis provides evidence that supports the statement that “form follows function” by demonstrating that the mechanical performance of the beak is a function that depends strongly on shape. This thesis concludes that it may be possible to create models representative of the entire set of possible bird beak shapes beginning with just several experimentally verified models, and that creating and testing these models this would be a viable and efficient way to study the theoretical functional optima of beaks for crushing seeds.

Mechanical forces in the cell’s natural environment have a crucial impact on growth, differentiation and behavior. Few areas of biology can be understood without taking into account how both individual cells and cell networks sense and transduce physical stresses. However, the field is currently held back by the limitations of the available methods to apply physiologically relevant stress profiles on cells, particularly with sub-cellular resolution, in controlled in vitro experiments. Here we report a new type of active cell culture material that allows highly localized, directional, and reversible deformation of the cell growth substrate, with control at scales ranging from the entire surface to the subcellular, and response times on the order of seconds. These capabilities are not matched by any other method, and this versatile material has the potential to bridge the performance gap between the existing single cell micro-manipulation and 2D cell sheet mechanical stimulation techniques.