Biology – New World Encyclopedia

Biology is the "science of life." It is the study of living and once-living things, from submicroscopic structures in single-celled organisms to entire ecosystems with billions of interacting organisms; it further ranges in time focus from a single metabolic reaction inside a cell to the life history of one individual and on to the course of many species over eons of time. Biologists study the characteristics and behaviors of organisms, how species and individuals come into existence, and their interactions with each other and with the environment. The purview of biology extends from the origin of life to the fundamental nature of human beings and their relationship to all other forms of life.

Biology, or "life science," offers a window into fundamental principles shared by living organisms. These principles reveal a harmony and unity of the living world operating simultaneously among a great diversity of species and even in the midst of competition both between and within species for scarce resources. The overlying harmony is seen at each level, from within a cell to the level of systems in individuals (nervous, circulatory, respiratory, etc.), the immediate interactions of one organism with others, and on to the complex of organisms and interactions comprising an ecosystem with a multitude of ecological niches each supporting one species. Such harmony is manifested in many universally shared characteristics among living beings, including interdependence, a common carbon-based biochemistry, a widespread pattern of complementary polarities, sexual reproduction, and homeostasis.

As the science dealing with all life, biology encompasses a broad spectrum of academic fields that have often been viewed as independent disciplines. Among these are molecular biology, biochemistry, cell biology, physiology, anatomy, developmental biology, genetics, ecology, paleontology, and evolutionary biology. While competition among individuals expressing genetic variability has generally been identified as a key factor in evolutionary development, the pivotal roles of cooperation[1] and long-term symbiosis or symbiogenesis (Margulis and Sagan 2002) in living systems have emerged in the late twentieth century as essential complementary focal points for understanding both the origin of species and the dynamics of biological systems.

While biology is unlike physics in that it does not usually describe biological systems in terms of objects that exclusively obey immutable physical laws described by mathematics, it is nevertheless characterized by several major principles and concepts, which include: universality, evolution, interactions, diversity, and continuity.

See also: Life

Living organisms share many universal characteristics, including that they are composed of cells; pass on their heredity using a nearly universal genetic code; need energy from the environment to exist, grow, and reproduce; maintain their internal environment; and exhibit dual characteristics or complementary polarities. This are the common set of characteristics identified by biologists that distinguish living organisms from nonliving things.

With the exception of viruses, all organisms consist of cells, which are the basic units of life, being the smallest unit that can carry on all the processes of life, including maintenance, growth, and even self-repair. Some simple life forms, such as the paramecium, consist of a single cell throughout their life cycle and are called unicellular organisms. Multicellular organisms, such as a whale or tree, may have trillions of cells differentiated into many diverse types each performing a specific function.

All cells, in turn, are based on a carbon-based biochemistry, and all organisms pass on their heredity via genetic material based on nucleic acids such as DNA using a nearly universal genetic code. Every cell, no matter how simple or complex, utilizes nucleic acids for transmitting and storing the information needed for manufacturing proteins.

Every living being needs energy from the environment in order to exist, grow, and reproduce. Radiation from the sun is the main source of energy for life and is captured through photosynthesis, the biochemical process in which plants, algae, and some bacteria harness the energy of sunlight to produce food. Ultimately, nearly all living things depend on energy produced from photosynthesis for their nourishment, making it vital to life on Earth. There are also some bacteria that utilize the oxidation of inorganic compounds such as hydrogen sulfide or ferrous iron as an energy source. An organism that produces organic compounds from carbon dioxide as a carbon source, using either light or reactions of inorganic chemical compounds as a source of energy, is called an autotroph. Other organisms do not make their own food but depend directly or indirectly on autotrophs for their food. These are called heterotrophs.

In development, the theme of universal processes is also present. Living things grow and develop as they age. In most metazoan organisms the basic steps of the early embryo development share similar morphological stages and include similar genes.

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Biology - New World Encyclopedia