Trajectories and models of individual growth

Abstract

It has long been recognized that the patterns of growth play an important role in the evolution of age trajectories of fertility and mortality (Williams, 1957). Life history studies would benefit from a better understanding of strategies and mechanisms of growth, but still no comparative research on individual growth strategies has been conducted.Growth patterns and methods have been shaped by evolution and a great variety of them are observed. Two distinct patterns -determinate and indeterminate growth -are of a special interest for these studies since they present qualitatively different outcomes of evolution. We attempt to draw together studies covering growth in plant and animal species across a wide range of phyla focusing primarily on the noted qualitative features. We also review mathematical descriptions of growth, namely empirical growth curves and growth models, and discuss the directions of future research.1 Email: karkach@demogr.mpg.de http://www.demographic-research.org 347Karkach: Trajectories and models of individual growth IntroductionThe ontogenetic growth of an individual is intuitively understood to be an increase in the size of the whole organism or parts of it with age. But the very "natural" notion of growth is, in fact, very difficult to define. Living organisms are complex systems, consisting of parts that often grow at different rates and displaying different patterns. Some parts of the body may grow faster than others, some may stop growing at a certain stage while others continue to grow, and organs may grow "on demand" during regeneration. The cells of an organ may divide continuously throughout an organism's life, replacing aging cells and producing cell turn-over in the tissues; still the body size may remain constant. Growth is coordinated by a program of ontogenetic development that allows for variability in the development rates and sizes in order to adapt to environmental conditions. Size and growth rates are subject to evolutionary optimization and constraints. On the one hand, larger size usually leads to greater mating success, greater fertility, lower vulnerability to environmental hazards, and thus lower mortality. On the other, growth needs resources, and trades-off with other traits.Studies on growth and maintenance shed light on the problem of senescence. Most organisms experience cell turn-over in most tissues. Some organisms (e.g. hydra) apparently escape senescence due to a quick turn-over of cells (Martínez, 1998).Growth and body size are strongly related to other traits and fitness. Research on extant species showed a strong statistical relationship between body mass and a remarkable variety of biological features (Smith, 1996). Measures of growthGrowth as an increment in size can be measured in many different ways, each having advantages and drawbacks. An increase in mass or volume often can be measured easily, but may be only indirectly related to growth as increase in biomass. Organisms may change in content of water or fat, in mass and volume, but this i...

Preliminary observations on the bone histology of the Middle Triassic pseudosuchian archosaurBatrachotomus kupferzellensisreveal fast growth with laminar fibrolamellar bone tissue

“…The reason why some pseudosuchians grow faster than others, however, remains unclear. Possible triggers for fast growth in Batrachotomus might be in response to environmental parameters (Botha-Brink and Smith, 2011;Botha-Brink et al, 2016), respiration and metabolic rates (Cubo et al, 2012;Seymour et al, 2004), large body size , a possible earlier onset of sexual maturity (Karkach, 2006), or an erect stance combined with an active predatory life style (Benton, 1984;Seymour et al, 2004). For instance, in an unstable environment, fast growth and earlier maturity may have been favorable , which is in agreement with the supposed habitat of Batrachotomus.…”

“…Understanding aspects of growth provides crucial data for the reconstruction of life history strategies in long-extinct clades, because the pattern of growth is impacted by ontogenetic development, metabolism, and external environmental factors (Karkach, 2006). Two divergent tissue types are found in extant tetrapods, reflecting two main growth patterns: lamellar-zonal bone (LZB) and fibrolamellar bone tissue type (FLB).…”

Dissecting the Phenotypic Components of Crop Plant Growth and Drought Responses Based on High-Throughput Image Analysis

“…The complexity of plant growth has been long recognized (Gompertz, 1825;Blackman, 1919;Erickson, 1976;Hunt, 1982;Karkach, 2006). Many mechanistic growth models have been established to model the laws of plant growth (Karkach, 2006;Thornley and France, 2007;Paine et al, 2012), which aim to provide the simplest description that accurately captures the growth dynamics of individuals.…”

Senescence or selective disappearance? Age trajectories of body mass in wild and captive populations of a small-bodied primate

“…We employ long-term body mass (BM) data from one captive and two wild populations (10-18 years covering 7-16 cohorts) of the grey mouse lemur (Microcebus murinus) to characterize variation in body condition. In mammals, including M. murinus [31], body growth typically ceases around the age of sexual maturity [32] (six to eight months in M. murinus [31,33]). Thereafter, BM fluctuates in response to imbalances in energy acquisition and expenditure, cyclic seasonal changes [21,34,35] or senescent muscle loss [36].…”