Additional Contributor Is Willard D. Hartman.

A unique account of the biology, ecology and evolution of choanoflagellates - the closest, known, living, unicellular relatives of animals.

Recently, new genes and their proteins that revealed striking new insights into the early evolution of multicellular animals have been identified and characterized from members of the lowest metazoan phylum, the porifera (sponges). The unexpected result was that the sequences obtained from sponge displayed high similarity to those found in higher metazoa; in consequence, it was concluded that during the transition from protozoa to metazoa the major structural and regulatory proteins evolved only once. The data gathered are now powerful arguments to establish monophyly of metazoa; in addition, new insights on the evolutionary diversification of metazoa were obtained.

Tackling one of the most difficult and delicate of the evolutionary questions, this challenging book summarizes the more recent results in phylogenetics and developmental biology that address the evolution of key innovations in metazoans. Divided into three sections, the first considers the phylogenetic issues involving this area of the tree of lif

General Editor: Peter Calow, Department of Zoology, University of Sheffield, England The main aim of this series will be to illustrate and to explain the way organisms 'make a living' in nature. At the heart of this - their functional biology - is the way organisms acquire and then make use of resources in metabolism, movement, growth, reproduction, and so on. These processes will form the fundamental framework of all the books in the series. Each book will concentrate on a particular taxon (species, family, class or even phylum) and will bring together information on the form, physiology, ecology and evolutionary biology of the group. The aim will be not only to describe how organisms work, but also to consider why they have come to work in that way. By concentrating on taxa which are well known, it is hoped that the series will not only illustrate the success of selection, but also show the constraints imposed upon it by the physiological, morpho logical and developmentallimhations of the groups. Another important feature of the series will be its organismic orientation. Each book will emphasise the importance of functional integration in the day-to-day lives and the evolution of organisms. This is crucial since, though it may be true that organisms can be considered as collections of gene-determined traits, they neverthe less interact with their environment as integrated wholes and it is in this context that individual traits have been subjected to natural selection and have evolved.