In 1842, Charles Darwin penned his first sketch of On the Origin of Species. Georges-Louis Leclerc, Comte de Buffon, treated species as artificial categories and living forms as malleable-even suggesting the possibility of common descent. Carl Linnaeus published a basic taxonomy for the natural world in 1735, and in the 1750s introduced scientific names for all his species. Meanwhile, taxonomy and classification became the focus of natural historians. However, Robert Remak and Rudolf Virchow were able to reify the third tenet, and by the 1860s most biologists accepted all three tenets which consolidated into cell theory. In 1838, Schleiden and Schwann began promoting the now universal ideas that (1) the basic unit of organisms is the cell and (2) that individual cells have all the characteristics of life, although they opposed the idea that (3) all cells come from the division of other cells, continuing to support spontaneous generation. In the early 19th century, biologists pointed to the central importance of the cell. Advances in microscopy had a profound impact on biological thinking. Investigations by Jan Swammerdam led to new interest in entomology and helped to develop techniques of microscopic dissection and staining.

It was then that scholars discovered spermatozoa, bacteria, infusoria and the diversity of microscopic life. Medicine was especially well studied by Islamic scholars working in Greek philosopher traditions, while natural history drew heavily on Aristotelian thought.īiology began to quickly develop with Anton van Leeuwenhoek's dramatic improvement of the microscope. Scholars of the medieval Islamic world who wrote on biology included al-Jahiz (781–869), Al-Dīnawarī (828–896), who wrote on botany, and Rhazes (865–925) who wrote on anatomy and physiology. His successor, Theophrastus, began the scientific study of plants. He explored biological causation and the diversity of life. Ancient Greek philosophers such as Aristotle (384–322 BCE) contributed extensively to the development of biological knowledge. Their contributions shaped ancient Greek natural philosophy. The earliest of roots of science, which included medicine, can be traced to ancient Egypt and Mesopotamia in around 3000 to 1200 BCE. Main article: History of biology Diagram of a fly from Robert Hooke's innovative Micrographia, 1665 These various organisms contribute to the biodiversity of an ecosystem, where they play specialized roles in the cycling of nutrients and energy through their biophysical environment. Biologists have sought to study and classify the various forms of life, from prokaryotic organisms such as archaea and bacteria to eukaryotic organisms such as protists, fungi, plants, and animals. Life on Earth, which emerged more than 3.7 billion years ago, is immensely diverse. Like other scientists, biologists use the scientific method to make observations, pose questions, generate hypotheses, perform experiments, and form conclusions about the world around them.

Hence, there are multiple subdisciplines within biology, each defined by the nature of their research questions and the tools that they use. īiologists are able to study life at multiple levels of organization, from the molecular biology of a cell to the anatomy and physiology of plants and animals, and evolution of populations.

Finally, all organisms are able to regulate their own internal environments. Energy processing is also important to life as it allows organisms to move, grow, and reproduce. Another major theme is evolution, which explains the unity and diversity of life. For instance, all organisms are made up of cells that process hereditary information encoded in genes, which can be transmitted to future generations. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field.

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