Research On Regulative Mechanisms Of Animals' Size

The most obvious differences between different animals are differences in size. Why is the body of the elephant larger than that of the mice? Why do our arms grow to be the same length? Although it is clear that genes play the predominant part in determining size, it is largely unknown how they do so. Our paper concerns the basic issue of growth biology, and, from the perspective of biological systems engineering, we study the factors affecting the animals'size and the control mechanism of the body's size, try to clarify the answers how the animal genes and environmental conditions coordinate each other to control the size of animals.Firstly, we specified the factors that influent the size of animals. The size of cells in different animals of different size differs little. So, we consider the quantities of cells play a dominant role in controlling the sizes of animals. Secondly, we analyze the factors which affect the number of cells in animals. And we define the birth rate of cells in animals in unit time, through cell culture with various concentrations of culture medium, modeling of the process of cell split and proliferation and computer simulations, suppose and demonstrate the view point that it is a fixed value in the course of life. On the other hand, we also define the life-span of animals and estimation methods of it in the course of life. Lastly, basing on the above, we establish the dynamic process model of the number of the cells, with the cell quantities of the animal as the state variable, give the time-varying distribution of cell quantities and deduce the time-varying function of the mean of the cell quantities, and this function is the growth function of animals. On the basis of theoretical analysis, we work out simulators of the growth of individual animals. For a variety of cell division and programmed cell death (PCD), we investigate and analyze the growth of animals by simulation. At the same time, we compare the results of theoretical analysis and simulation tests, so as to confirm the feasibility of our theoretic model. We analyze the elements affecting the size of animals, growing-periods and balance-values of weight, discuss the environmental conditions, such as genes and nutrition that affect the birth rate and the death rate of cells and propose the preliminary models and mechanisms that the genes and environmental factors coordinate each other to control the size of individual animals. Based on the analysis, we discuss the control mechanism of animals'size, set up theoretic relations between macroscopic values of growth, such as animals'weight, and microcosmic values, e.g. cell division and cell death. We attempt to explore the effect of animals'size, animal genes and environmental conditions on the size of the animal and regulative mechanisms.