No one can ever have secure knowledge about the gods and creatures, and should anyone hit by chance upon the right thing, he will not know it for sure; that is why everything that we believe to be true is "opinion". XENOPHANES around 500 B.C. (According to ROD 1988, p.85) The goal of phylogenetic systematics (cladistics) is to discover the kinship relations between all organisms on earth and to translate the order we perceive in Nature into an equivalent man-made system. Although the goal is easily formulated, the path is thorny, and the results achieved continue to be imperfect. This is the fate of any science that bases its propositions on the interpretation of histor ical evidence. The diversity found in the millions of species originated as a result of the continuous splitting of biopopulations through time. Combined with this was the emergence of hierarchically linked des cent communities of species. We call the process of origin of descent communities phylogenesis. We do not know, however, the exact course of phylogenesis - we can only formulate hypotheses. The historical evidence at hand consists of the feature patterns of extant species and of extinct species with their combination of original and derived traits which are the result of evolution.

The system of multicellular animals presented here is an alternative to the traditional classification system. In a new approach to the phylogenetic order, this book strives for an objective systematization of the metazoa, seeking a new path in the field of academic research and teaching.

Volume III

Among the most important innovations in the history of life is the transition from single-celled organisms to more complex, multicellular organisms. Multicellularity has evolved repeatedly across the tree of life, resulting in the evolution of new kinds of organisms that collectively constitute a significant portion of Earth’s biodiversity and have transformed the biosphere. This volume examines the origins and subsequent evolution of multicellularity, reviewing the types of multicellular groups that exist, their evolutionary relationships, the processes that led to their evolution, and the conceptual frameworks in which their evolution is understood. This important volume is intended to serve as a jumping-off point, stimulating further research by summarizing the topics that students and researchers of the evolution of multicellularity should be familiar with, and highlighting future research directions for the field.

Looks at cells as life's building blocks, focusing on animal cells, showing how animal and plant cells differ, and examining the various types of cells at work in animal bodies.