Biology is the natural science that studies life and living organisms. It covers their structure, function, growth, development, behaviour, origin, evolution and distribution. Biology works at every scale, from molecules inside a cell to whole populations and the ecosystems they share. It draws heavily on chemistry and physics, and it supports applied fields such as medicine, agriculture and biotechnology. A few broad ideas hold the discipline together. All organisms are made of cells. Organisms pass on hereditary information in genes. Living things take in and transform energy, keep a stable internal state, and have descended with modification from common ancestors.
Etymology
The word comes from the Greek bios ("life") and -logia ("study of"). The term in its modern sense was proposed in 1802 by two naturalists who appear to have arrived at it independently. One was the German Gottfried Reinhold Treviranus. The other was the French naturalist Jean-Baptiste Lamarck, who used it in his Recherches sur l'organisation des corps vivants (1802). Latin forms of the word had appeared earlier in the eighteenth century, but they did not carry the modern meaning.
History
People studied living things long before biology had a name. In ancient Greece, Aristotle described and classified hundreds of animals from his own observation and dissection. His student Theophrastus wrote systematic works on plants. Medical traditions also built up anatomical and physiological knowledge, including Greek, Roman, Islamic, Indian and Chinese medicine.
Modern biology started to take shape in the early modern period. In 1628 William Harvey showed that blood circulates through the body. The microscope revealed a previously hidden world. Robert Hooke used the word "cell" in his Micrographia (1665), and Antonie van Leeuwenhoek described microorganisms in the 1670s. In the eighteenth century Carl Linnaeus set out a consistent system of classification and binomial nomenclature, which gave the description of species a common language.
The nineteenth century produced the main unifying theories of the field. Matthias Schleiden and Theodor Schwann formulated cell theory in 1838–1839, and Rudolf Virchow later added that every cell arises from an existing cell. In 1859 Charles Darwin published On the Origin of Species, which explained how natural selection drives evolution. Alfred Russel Wallace had reached the same idea independently. Gregor Mendel worked out the laws of inheritance from experiments on pea plants. His results drew little attention until they were rediscovered in 1900, and that rediscovery launched genetics. During the same period Louis Pasteur and Robert Koch established the germ theory of disease.
In the 1930s and 1940s the "modern synthesis" combined Darwinian selection with Mendelian genetics. In 1953 James Watson and Francis Crick proposed the double-helix structure of DNA, drawing on X-ray data from Rosalind Franklin and Maurice Wilkins. This opened the era of molecular biology. Later milestones include cracking the genetic code, recombinant DNA technology, and the sequencing of the human genome.
Foundational principles
- Cell theory. The cell is the basic unit of structure and function in all living things.
- Genes and heredity. Hereditary information is stored in genes made of DNA (RNA in some viruses). It is copied when cells divide and passed from parents to offspring. Genes are expressed through RNA to make proteins, which do most of the work in cells.
- Evolution. Populations change over generations through natural selection, genetic drift, mutation and gene flow. Common descent explains both the unity and the diversity of life.
- Energy and metabolism. Organisms capture and convert energy. Autotrophs such as plants make organic matter through photosynthesis. Heterotrophs, including animals, get energy by breaking down organic compounds, for example through cellular respiration.
- Homeostasis. Organisms regulate their internal environment, including temperature, pH and solute concentrations. This process is called homeostasis.
Levels of organization
Biological systems are usually described as a hierarchy: molecules, organelles, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems and the biosphere. Each level has properties that the level below it does not. For example, a single neuron cannot learn the way a brain can, and an immune system coordinates many cell types to defend the body.
Branches
Biology has many subdisciplines, often grouped by the kind of organism studied or by the level of organization:
- By organism: botany (plants), zoology (animals), microbiology (microorganisms), mycology (fungi) and virology (viruses).
- By level or approach: biochemistry and molecular biology study the chemical processes and molecules of life. Cell biology studies cells. Physiology studies how organisms function. Anatomy studies their structure. Developmental biology covers how organisms grow from a single cell. Genetics deals with heredity and variation.
- By scale and history: ecology studies how organisms interact with each other and their environment. Evolutionary biology studies how life has changed over time. Systematics and taxonomy classify organisms and reconstruct their relationships. Paleontology studies fossil life.
Many newer fields overlap these boundaries, including neuroscience, bioinformatics, systems biology and synthetic biology.
Diversity of life
Biologists commonly sort life into three domains, a scheme proposed by Carl Woese in the late twentieth century. Two domains, Bacteria and Archaea, consist of prokaryotes. The third, Eukarya, includes protists, fungi, plants and animals. Fossil evidence suggests that life on Earth had appeared by at least about 3.5 billion years ago. Roughly two million species have been formally described, but estimates of the true number vary widely and run much higher, especially for microorganisms. Documenting and conserving this biodiversity is a major focus of modern research.
Methods
Biologists use the scientific method: they observe, form hypotheses, run controlled experiments and analyse data statistically. Common tools include light and electron microscopy, DNA sequencing, gene editing, model organisms, field surveys and computational modelling. Biology deals with variable living systems, so its methods often depend on comparisons between groups, large sample sizes and repeated experiments.
Applications
Biological knowledge underpins medicine, from understanding disease to developing drugs and vaccines. It also supports crop and livestock breeding, food production, environmental management and conservation. Biotechnology applies biology in industry, producing enzymes, biofuels and engineered organisms. More and more, artificial intelligence is used to analyse genomic data and predict protein structures.
References
- Biology - Etymology, Origin & Meaningetymonline.com
- Jean-Baptiste Lamarcken.wikipedia.org
- Jean-Baptiste Lamarckbritannica.com
- Gottfried Reinhold Treviranusen.wikipedia.org