Biology
Biology is the science that deals with living things and their vital processes.
Contents
Definition (Encyclopedia Britannica)
- Biology, study of living things and their vital processes. The field deals with all the physicochemical aspects of life. The modern tendency toward cross-disciplinary research and the unification of scientific knowledge and investigation from different fields has resulted in significant overlap of the field of biology with other scientific disciplines. Modern principles of other fields—chemistry, medicine, and physics, for example—are integrated with those of biology in areas such as biochemistry, biomedicine, and biophysics.
- Biology is subdivided into separate branches for convenience of study, though all the subdivisions are interrelated by basic principles. Thus, while it is custom to separate the study of plants (botany) from that of animals (zoology), and the study of the structure of organisms (morphology) from that of function (physiology), all living things share in common certain biological phenomena—for example, various means of reproduction, cell division, and the transmission of genetic material.
- Biology is often approached on the basis of levels that deal with fundamental units of life. At the level of molecular biology, for example, life is regarded as a manifestation of chemical and energy transformations that occur among the many chemical constituents that compose an organism. As a result of the development of increasingly powerful and precise laboratory instruments and techniques, it is possible to understand and define with high precision and accuracy not only the ultimate physiochemical organization (ultrastructure) of the molecules in living matter but also the way living matter reproduces at the molecular level. Especially crucial to those advances was the rise of genomics in the late 20th and early 21st centuries.
Three laws of biology
The First Law of Biology: all living organisms obey the laws of thermodynamics. This law is fundamental because the laws of the inanimate world determine the course of the universe. All organisms on all planets, including humans, must obey these laws. The laws of thermodynamics govern energy transformations and mass distributions. Cells that comprise living organisms (see The Second Law) are open systems that allow both mass and energy to cross their membranes. Cells exist in open systems so as to allow acquisition of minerals, nutrients, and novel genetic traits while extruding end products of metabolism and toxic substances. Genetic variation, which results in part from gene transfer in prokaryotes and sexual reproduction in higher organisms, allows tremendously increased phenotypic variability in a population as well as an accelerated rate of evolutionary divergence.
A corollary of the First Law is that life requires the temporary creation of order in apparent contradiction to the second law of thermodynamics. However, considering a completely closed system, including the materials and energy sources provided by the environment for the maintenance of life, living organisms affect the system strictly according to this law, by increasing randomness or chaos (entropy). Resource utilization by living organisms thus increases the entropy of the world. A second corollary of the First Law is that an organism at biochemical equilibrium is dead. When living organisms reach equilibrium with their surrounding environment, they no longer exhibit the quality of life. Life depends on interconnected biochemical pathways to allow for growth, macromolecular synthesis, and reproduction. Thus, all life forms are far from equilibrium with their environments.
The Second Law of Biology: all living organisms consist of membrane-encased cells. Enveloping membranes allow physical separation between the living and the non-living worlds. Viruses, plasmids, transposons, prions, and other selfish, biological entities are not alive. They cannot “self” reproduce. They are dependent on a living cell for this purpose. By definition, they therefore, are not alive. A corollary of the Second Law is that the cell is the only structure that can grow and divide independently of another life form. A second corollary of the Second Law is that all life is programmed by genetic instructions. Genetic instructions are required for cell division, morphogenesis, and differentiation. From single-celled prokaryotic organisms to normal or cancerous tissues in multicellular animals and plants, genetic instructions are required for the maintenance of life.
The Third Law of Biology: all living organisms arose in an evolutionary process. This law correctly predicts the relatedness of all living organisms on Earth. It explains all of their programmed similarities and differences. Natural selection occurs at organismal (phenotypic) and molecular (genotypic) levels. Organisms can live, reproduce, and die. If they die without reproducing, their genes are usually removed from the gene pool, although exceptions exist. At the molecular level, genes and their encoding proteins can evolve “selfishly,” and these can combine with other selfish genes to form selfish operons, genetic units and functional parasitic elements such as viruses.
Two corollaries of the Third Law are that (1) all living organisms contain homologous macromolecules (DNA, RNA, and proteins) that derived from a common ancestor, and (2) the genetic code is universal. These two observations provide compelling evidence for the Third Law of Biology. Because of his accurate enunciation of the Third Law, Charles Darwin is considered by many to be the greatest biologist of all time.[1]
See also
External links
- Race biologie or biological anthropology (Rassenbiologie)
- Culture biology (Kulturbiologie)
