tailieunhanh - From Individuals to Ecosystems 4th Edition - Chapter 1

Introduction We have chosen to start this book with chapters about organisms, then to consider the ways in which they interact with each other, and lastly to consider the properties of the communities that they form. One could call this a ‘constructive’ approach. We could though, quite sensibly | Introduction We have chosen to start this book with chapters about organisms then to consider the ways in which they interact with each other and lastly to consider the properties of the communities that they form. One could call this a constructive approach. We could though quite sensibly have treated the subject the other way round - starting with a discussion of the complex communities of both natural and manmade habitats proceeding to dcconstruct them at ever finer scales and ending with chapters on the characteristics of the individual organisms - a more analytical approach. Neither is correct . Our approach avoids having to describe community patterns before discussing the populations that comprise them. But when we start with individual organisms we have to accept that many of the environmental forces acting on them especially the species with which they coexist will only be dealt with fully later in the book. This first section covers individual organisms and populations composed of just a single species. We consider initially the sorts of correspondences that we can detect between organisms and the environments in which they live. It would be facile to start with the view that every organism is in some way ideally fitted to live where it does. Rather we emphasize in Chapter 1 that organisms frequently are as they are and live where they do because of the constraints imposed by their evolutionary history. All species are absent from almost everywhere and we consider next in Chapter 2 the ways in which environmental conditions vary from place to place and from time to time and how these put limits on the distribution of particular species. Then in Chapter 3 we look at the resources that different types of organisms consume and the nature of their interactions with these resources. The particular species present in a community and their abundance give that community much of its ecological interest. Abundance and distribution variation in abundance from place