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Biology subjects

S, S. I.

Publications and source records attributed to S, S. I..

3 recordsLinked to original sources

Modeling Montbeillards height data of a human male

Growth is a dynamic activity of simultaneous biological processes happening at multiple time-scales varying from orders of fractions of a second to several years. Rather than modeling growth with differential equations, this multiple time-scale dynamics is modeled using a simpler algebraic approach that involves continued fraction of the linear time scale. This algebraic approach offers models that are infinitely differentiable like an exponential function but also robust and superposable like linear equations. Thus, unique insights into growth dynamics can be obtained without much need of a calculus background. Growth of bacterial colonies, yeast cultures, Drosophila population, mean individual attributes of Helianthus and rats have already been modeled using this approach. In this work, we extend the modeling procedure to individual human growth using Montbeillards height measurements of his son starting from birth upto almost 18 years of age. Good fits are obtained on the data and growth rates are estimated directly from the model. Thus, this methodology provides generic, flexible, simpler and more interpretable growth models.

developmental biology↗

A biological growth curve is a sum of two distinct S-curves

A growing population consists of successive generations of individuals interacting with each other and their environment. At every instant, these interactions can lead to either promotion or restriction of the population growth. Thus, within a growing population, differences arise over time due to both extrinsic and intrinsic factors such as resource utilization, competition, age distribution etc. These differences can lead to divergence within the population growth. The sum of these differences is manifested as the net population growth. In this work, we propose that these differences that arise over time within a growing population can be represented as two distinct S-curves. The sum of these two S-curves results in the growth curve of a population. These differences also arise in the growth curves of a populations attributes such as height or weight. We demonstrate this by applying the a- m biological growth model on (i) the population growth curves of Drosophila and yeast and (ii) the growth curves of the mean height of a population of sunflower plants and the mean body weight of male white rats. Finally, we also discuss the results using a coordinate system with the two distinct S-curves as the axes.

ecology↗

A Biological Growth Model using Continued Fraction of Straight Lines

S-shaped curves are ubiquitous in biology especially when it comes to growth of a population or even an individual. Growth models such as the classical Verhulst-Pearl logistic growth equation and its extensions effectively model such S-shaped growth curves. Most of these models are parametrised by three or more parameters. In this work, continued fraction of straight lines has been applied to model S-shaped curves of biological growth through the use of only two parameters a and m. Here, m is the maximum growth rate and a is the parameter restricting the growth rate. The parameters a and m help to better interpret the data when compared to the logistic growth model since m represents factors promoting growth while a represents the constraints on growth. This model is effective for modeling both population as well as individual growth, especially around the phase of rapid growth.

ecology↗