This book is written for ecologists and protozoologists. Ecologists who
study environments and biotic communities in which protozoa are im-
ponant should find this book especially useful. During the last decade
it has become clear that protozoa play important roles in natural eco-
systems, but few ecologists have a feeling for the functional properties
and the diversity of these organisms. Protozoa pose or exemplify many
general problems of population and community ecology, and of evo-
lutionary biology. In most respects the general ecological propenies of
protozoa are not fundamentally different from those of larger organisms;
yet, due to their small size, short generation times, and ubiquitous oc-
currence they often present ecological phenomena in a new and dif-
ferent light. To this should be added that protozoa are well-suited for
experimental work. Despite these advantages, the study of protozoa has
played a relatively modest role in the development of ecology and ev-
olutionary biology, primarily, I believe, because most ecologists are
unfamiliar with these organisms. I hope this book will attract more
attention to these favorable characteristics of protozoa. I also hope
that this book may make protozoologists aware of new aspects of their
pet organisms. For a long time (that is, until the fun- damental
distinction between prokaryotic and eukaryotic cells was rec- ognized)
protozoa were believed to represent the simplest form of life. They were
therefore extensively used for the experimental study of basic questions
of cell biology.