BIOLOGY Volume 1 - A Guide to General Biology - 2004

1. INTRODUCTION TO BIOLOGY

Biology (from the Greek bios meaning life, and logos meaning study or knowledge) is the science that studies living organisms. The Development of this science, like any other, has progressed through the successive breakdown of a complex subject of study into its constituent parts. This gave rise to the numerous branches of biology, some of which are shown in Fig. 1.1. This approach to knowledge is often referred to as "reductionist". Reductionism, carried to its logical Conclusion, focuses on studying the elementary forms of matter in both living and non-living systems. Under this approach, the laws of nature are sought by examining separate parts rather than the unified whole. The opposite approach is based on "vitalist" principles. In this view, life is regarded as a completely distinct and unique phenomenon that cannot be explained solely by the laws of chemistry and physics, since many manifestations of life are inherent only in the system as a whole. Ultimately, the primary task of biology as a science is to interpret all phenomena of the living world using scientific laws, while keeping in mind that a whole Organism possesses properties fundamentally different from The properties of its constituent parts. A neurophysiologist can describe The activity of a single neuron in terms of physicochemical processes, but The phenomenon of consciousness itself cannot be described in this way. It is quite possible that consciousness is the result of the collective activity and simultaneous electrochemical changes of millions of Neurons, yet we still have no realistic understanding of how a thought arises or what its physicochemical nature is. Nor do we know how living creatures originated and evolved. Many have attempted to answer this question. In Volume 3 (Chapters 23–27), we will explore various Perspectives on Structure/149.html">The problem of THE ORIGIN OF life, focusing primarily on biological concepts rather than theological ones. Thus, we are forced to admit that we cannot give a precise definition of what life is, nor can we say how and when it arose. All we can do is list and describe those characteristics of living matter that distinguish it from non-living matter.

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Fig. 1.1.

These primarily include:

Nutrition

Food is essential for all living creatures. It serves as a source of energy and the Materials necessary for growth and other vital processes. Living organisms utilize only Two Types of energy: sunlight and chemical bond energy. Organisms specialized for using light energy carry out Photosynthesis and contain pigments, including chlorophyll, capable of absorbing light. Such organisms include plants, Algae, and some of the simpler organisms, including Bacteria. Organisms incapable of photosynthesis must obtain chemical energy (i.e., energy stored in the chemical bonds of organic substances) from other organisms. These organisms, known as heterotrophs, include animals and Fungi. Different modes of nutrition give rise to fundamental differences among various organisms.

Respiration

All vital processes occur with the consumption of energy, the source of which is the bulk of organic substances obtained through food. During The breakdown of specific Organic compounds in The process of cellular respiration, chemical bond energy is released while simultaneously being stored in energy-rich molecules of adenosine triphosphate (ATP). This compound, found in all living Cells, is sometimes referred to as the "universal energy carrier" or "universal energy currency".

Irritability (Sensitivity)

All living creatures are capable of responding to changes in their external and internal environment, which significantly enhances their chances of survival. For example, the Blood Vessels in the Skin of mammals dilate when body Temperature rises, dissipating excess heat and thereby restoring the optimal body temperature. Similarly, a green plant sitting on a windowsill receiving light from only one direction will grow towards the light, since photosynthesis can only take place under sufficiently good illumination.

Mobility (Locomotion)

Some living organisms, such as animals and bacteria, are capable of moving from one place to another; in other words, they are motile. They need this to acquire food, unlike other organisms, such as plants, which can manufacture their own necessary food from "raw materials" obtained in one and the same Location. Nevertheless, movements of certain parts can also be observed in plants. For instance, leaves reach towards the light, and the flowers of some plants close at night.

Excretion

Excretion is the removal of "waste products"—unwanted metabolic by-products—from the organism. Waste products include, for example, carbon dioxide, which must be eliminated because its accumulation in excess has a harmful effect. Animals ingest a large amount of protein in their food; these substances are not stored in the body and therefore must be broken down and excreted. Thus, excretion in animals consists primarily of the elimination of nitrogenous wastes.

Reproduction

The lifespan of organisms is limited, yet all possess The ability to continually "sustain life", ensuring the survival of the species. A species survives because parents pass on their core characteristics to their offspring, regardless of whether the offspring resulted from sexual or asexual reproduction. In searching for the causes underlying this TRANSMISSION OF TRAITS (inheritance), "reductionists" discovered Nucleic Acids—DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). The molecules of these acids contain coded information that is passed from one generation of organisms to the next.

Growth

Non-living objects (such as crystals or stalagmites) grow by accumulating material on their outer surface. Living creatures, on the other hand, grow from within, using nutrients supplied to the organism through food. The assimilation of these substances results in The formation of new living matter.

The seven Main characteristics of life listed above are present in all organisms to varying degrees. All these features are merely observable manifestations of the primary properties of matter, namely its ability to extract, store, and utilize external energy. However, Living matter is also capable of not only maintaining but increasing its energy reserves. Unlike living matter, dead organic matter is easily destroyed by mechanical and physical environmental factors. Living creatures possess a built-in system of self-regulation that sustains life processes, prevents the uncontrolled breakdown of structures and substances, and guards against the purposeless release of energy. Such regulation is directed towards maintaining Homeostasis at all Levels of Organization in living systems—Cell/3.html">From Molecules to entire communities.

All the features of living things listed here are examined in greater detail in the relevant sections of the book, with many chapters describing the chemical and physical mechanisms underlying particular phenomena. We owe this to the successful research of recent years. Our knowledge of what happens within a cell or an organism has undoubtedly been enriched by the discovery and study of DNA, Protein Synthesis, mechanisms of heredity, Enzymes, Hormones, the Immune Response, and many Other Aspects of the Structure and function of living organisms.

In the Appendices located at the end of the third volume, you will find information essential to any biologist, including: fundamentals of chemistry, descriptions of scientific Research Methods, experimental approaches, and much more. The appendices are designed to provide necessary information to students who have significant gaps in a particular field. Once this information has been mastered, one can begin to develop the ability to critically evaluate and describe observed phenomena. After all, this exact mindset lies at The Heart of any scientific inquiry.