Biology, the science that deals with living things. The earth is home to a diverse range of living organisms. An estimated 10 million species live on the planet. All living things, despite their diversity, have some characteristics in common. Biology is concerned with all these forms of life—from humans to microbes, from whales and trees to insects and molds. Biologists study the makeup of living things, how they live, and the physical and chemical changes that occur within them.

Biology is important because people themselves are animals and live in a world filled with an enormous diversity of other living things. Medicine, agriculture, and engineering are just three of the many fields that benefit from the knowledge gained from biological studies. Through the study of biology, people have learned how to adapt nature to their own needs—by breeding superior cattle, for example, and by using fertilizers to improve crops. Advanced research in biology has led to the discovery of better ways to prevent and treat diseases. Wildlife conservation has been made possible through research in ecology.

Biology is traditionally classified into botany and zoology. Apart from botany and zoology, biology can also be divided into ecology, physiology, and systematics. Ecology is the study of the relationship between the living things and their environment. Physiology is the study of various biological functions of the living thing, such as respiration, digestion and reproduction. Systematics deals with classification of living things. Systematics is also called taxonomy.

The study of living things involves other sciences as well. To understand various biological functions and processes, biologists use data from physics, chemistry, and statistics.

This article is about the specialized areas biologists work in, the history of biology, and the various advances in the field of biology.

Major fields of biology
Anatomy deals with the structure of living things.
Bacteriology is the study of bacteria.
Biochemistry examines the chemical processes and substances that occur in living things.
Biophysics applies the tools and techniques of physics to the study of living things.
Botany is the study of plants.
Cryobiology analyzes how extremely low temperatures affect living things.
Cytology studies the structure, composition, and functions of cells.
Ecology concerns the relationships living things have with one another and their environment.
Embryology deals with the formation and development of plants and animals from fertilization until they become independent organisms.
Entomology is the study of insects.
Ethology concerns animal behavior under natural conditions.
Evolutionary biology is the study of the evidence supporting the theory of evolution.
Genetics is the study of heredity.
Ichthyology is the study of fishes.
Immunology concerns the body's defenses against disease and foreign substances.
Limnology studies bodies of fresh water and the organisms that live in them.
Marine biology investigates life in the ocean.
Medicine is the science and art of treating and healing.
Microbiology deals with microscopic organisms.
Molecular biology analyzes molecular processes in cells.
Neurobiology deals with the nervous system of animals.
Ornithology is the study of birds.
Paleontology is the study of prehistoric life.
Pathology examines the changes in the body that can cause disease or are caused by disease.
Physiology deals with the functions of living things.
Sociobiology focuses on the biological basis for social behavior in human beings and other animals.
Systematics, also called taxonomy, is the scientific classification of organisms.
Virology concerns viruses and virus diseases.
Zoology is the study of animals.