Life: Biological Principles and the Science of Zoology
The Uses of Principles
We gain knowledge of the animal world not in a passive or haphazard manner but by actively applying important guiding principles to our investigations. Just as the exploration of outer space is both guided and limited by available technologies, exploration of the animal world depends critically on our questions, methods, and principles. The body of knowledge that we call zoology makes sense only when the principles that we use to construct it are clear.
The principles of modern zoology have a long history and many sources. Some principles derive from the laws of physics and chemistry, which all living systems obey. Others derive from the scientific method, which tells us that our hypotheses regarding the animal world are useless unless they guide us to gather data that potentially can refute them. Many important principles derive from previous studies of the living world, of which animals are one part. Principles of heredity, variation, and organic evolution guide the study of life from the simplest unicellular forms to the most complex animals, fungi, and plants. Because all of life shares a common evolutionary origin, principles learned from the study of one group often may be applied to other groups as well. By tracing the origins of our operating principles, we see that zoologists are not an island unto themselves but form an integrated part of the scientific community.
We begin our study of zoology not by focusing narrowly within the animal world, but by searching broadly for our most basic principles and their diverse sources. These principles simultaneously guide our studies of animals and integrate those studies into the broader context of human knowledge.
Zoology, the scientific study of animal life, builds on centuries of human inquiry into the animal world. The mythologies of nearly every human culture document attempts to solve the mysteries of animal life and its origin. Zoologists now confront these same mysteries with the most advanced methods and technologies developed throughout all branches of science. We start by documenting the diversity of animal life and organizing it in a systematic way. This complex and exciting process builds on the contributions of thousands of zoologists working in all dimensions of the biosphere (Figure 1-1). We strive through this work to understand how animal diversity originated and how animals perform the basic processes of life that permit them to thrive in many diverse environments.
This section introduces the fundamental properties of animal life, the methodological principles on which their study is based, and two important theories that guide our research: (1) the theory of evolution, which is the central organizing principle of biology, and (2) the chromosomal theory of inheritance, which guides our study of heredity and variation in animals. These theories unify our knowledge of the animal world.