1.2Basic Characteristics of Organisms
Listed below are the basic characteristics of organisms.
- Cells are enclosed by a cell membrane to separate the internal environment from the external environment (membrane structure).
- Organisms produce virtually identical offspring by proliferation (self-replication).
- Offspring produced by proliferation inherit characteristics of the original organism (heredity).
- In multicellular organisms, their unique bodies are produced through repeated division of a single cell (morphogenesis).
- Free energy produced by degradation of substances assimilated by the cell from the external environment is used for growth and these substances are converted to produce own body (metabolism).
- Internal environment is maintained in a stable and constant condition while the cell appropriately perceives and responds to environmental changes (homeostasis and environmental response).
Considering these characteristics, one may be amazed by the mystery of living things. Moreover, nature is highly ordered because an organism can respond to external stimuli and stress appropriately and effectively, resulting in its own favor. Ancient and modern scholars coined the term teleonomy to describe this phenomenon in which the biological phenomenon is greatly different from the inanimate one. The concept of vitalism has been proposed since the era of Greek biologists to explain teleonomy and the special properties inherent in life, which are not present in inorganic substances. Even now, many people might believe in vitalism to some extent. However, as per modern biological science, all biological phenomena can be explained by a causal relationship of substances governed bt physical/chemical laws (reductionism). Molecular and signal transduction networks (see Chapter 14) are the mechanisms supporting teleonomy, with organic evolution (see Chapter 24) having led to the development of these networks into sophisticated systems. We hope our readers will gain a sense of understanding of teleonomy after reading this book.
Contemporary biology has used microscopic analysis of biological components to describe the properties of the aforementioned macroscopic characteristics of organisms with the help of material science. The two major driving forces of contemporary biology are as follows: (1) continuing elucidation of microscopic structures of organisms using a range of microscopic techniques, which are being developed, (see Appendix) and (2) description of the arrangement of biomolecules comprising these structures and mechanisms underlying molecular associations. Elucidating gene structure through this process and in turn decoding all the genes (the genome) of an organism have given rise to the concept that an organism can be composed of numerous genetic interactions.
In the first part of this book, we begin by observing the macroscopic characteristics of living things. In the second part, we introduce a microscopic perspective, beginning with the substances comprising organisms, and explain how we can use this microscopic perspective to understand the macroscopic properties of organisms.