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The biological sciences developed slowly over the course of human history. Early humans practiced an inexact form of biology when they established agriculture. They observed the environment around them to determine what types of seeds yielded consumable food, when to plant, when to water, and when to harvest the seeds for planting in the next season. Early humans improved their way of life as a result of their primitive forays into science.

It wasn't until modern times that biology developed into an exact science. Our ancestors learned to differentiate between desirable and undesirable plants (taxonomy), to seek out and live in more habitable environments (ecology), to domesticate plants (agronomy and horticulture) and animals (animal husbandry), and to eat a suitable diet (nutrition). Eventually, plants and animals were classified; later they were studied to see how they functioned and how they related to other organisms around them. This was the beginning of zoology (animal science) and botany (plant science).

The Greek philosopher Aristotle created one of the first documented taxonomic systems for animals. He divided animals into two types: blooded (mammals, birds, amphibians, reptiles, and fishes) and bloodless (insects, crustaceans, and other lower animals). He also studied reproduction and theorized, incorrectly, how embryos developed in animals.

From the second century to the 11th century, the Arabs and Persians made important advances in biological understanding. Unlike the Europeans, they continued to study from the base of knowledge established by the Greeks. Avicenna, a Persian philosopher and physician, wrote the Canon of Medicine, one of the most influential and important publications on medical knowledge in the world at its time—and for the next seven centuries.

The field of biology has expanded rapidly in the last two centuries. The French physician Louis Pasteur developed the field of immunology, and his studies of fermentation led to modern microbiology. Many other achievements became possible because of improvements in the microscope. Scientists could isolate much smaller structures than ever before possible. Matthias Schleiden and Theodor Schwann formulated the idea that the cell is the fundamental unit of all organisms. Gregor Mendel discovered the principles of heredity through crossbreeding pea plants.

While the 19th century can be considered the age of cellular biology, the 20th and early 21st centuries have been dominated by studies and breakthroughs in biochemistry and molecular biology. The discovery of the atomic structure allowed the fundamental building blocks of nature to be studied. Living tissues were found to be composed of fats, sugars, and proteins. Proteins were found to be composed of amino acids. Discoveries in cell biology established the manner in which information was transmitted from one organism to its progeny. Chromosomes were recognized as the carriers of this information. In 1944, Oswald Avery and a team of scientists were able to isolate and identify DNA as the transmitter of genetic information. In 1953, James Watson and Francis Crick deciphered the complex structure of DNA and hypothesized that it carried the genetic code for all living matter.

Today, advances in biotechnology have allowed biologists and other scientists to study and manipulate the DNA of plants and animals to create healthier organisms and more productive yields, as well as seek cures to human diseases. In addition to medicine, scientists are using biotechnology in agriculture and environmental remediation.

Biological science is the foundation for most of the discoveries that affect people's everyday lives. Biologists break new ground to improve our health and quality of life and help us to better understand the world around us.

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