Elgar original reference
Environmental Systems, Dynamics and Modeling: A Primer
1. ENVIRONMENTAL SYSTEMS Our environment is a product of many different plants and animals, shaped by the past, the climate, the physical landscape and, of course, human activity. As species adapt to circumstances, they also influence their habitats and reshape the environments in which they live. Ecosystems (and our planet) are also subject to random shocks that can radically change the course of life. Indeed, the universal constant of life is change. The mass deaths that led to the extinction of the dinosaurs almost certainly contributed to mammal speciation and an increase in mammal size. Thus, if the Alvarez hypothesis is correct, and if a meteor had not hit the earth 65 million years ago at the end of the Cretaceous period, it is extremely unlikely that modern humans would exist and that you would be reading this book! One of the most important processes by which life changes over time is natural selection. This simply means that those members of a species are fortunate enough to reproduce will bequeath their genetic material to the next generation. Members of a species that by chance, or physical characteristics, or behavior are less successful at reproducing, will be less favored in the gene pool in the subsequent generation. In this manner, life evolves over time. The process of evolution involves many different paths and interactions with predators and prey, and with parasites and hosts co-evolving. For example, slower deer are more likely to be caught by, say, wolves. As a result, slower...
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