The word Biology literally breaks down to mean the study of life. But it's further meaning includes the function and structure of life, not only to mean simply human biology, but instead something quite diverse. Biology is also the study of the life function of animals, plants, bacteria, viruses, invertebrates, insects, birds, fishes and the list goes on. Animal Biology, for exapmle, studies the life function and structure of humans and other animals and is just one of the different fields of biology or biological sciences.
Prior to the 19th century the study of Biology was called Natural Science. Modern day Biology has come to mean the science of the structure, function, growth, origins, evolution and distribution (disbursement) of species, including classification of all living things.
There are five Principles that form the foundation of modern Biology. These principles are:
Cell Theory: All living things are made up of at least one cell. A cell is the basic building block that any living organism is made out of. Cells multiply through a process called Cell Division where each cell is an exact copy of the parent cell, except in the case of reproductive sperm and ovum which contain only half the genetic material of the parent cell.
Evolution: Natural selection and genetic drift can cause inherited traits to change from one generation to another.
Gene Theory Every living thing has certain genetic traits encoded into it's unique DNA. Segments of this DNA that specify a given trait are known as genes. These genes pass specific genetic traits from one generation to the next and are further broken down into Genotype and Phenotype.
Energy required for normal cellular function and metabolism
Homeostasis: is the process that maintains an organism's internal environment without regard to the external environment. In other words it is the body's way of maintaining harmony within it's various systems despite disease, temperature, or other external stimuli. Thus maintaining balance and harmony within the cell, organism, or ecosystem
Biology in it's broadest sense studies the unique interactions between the various biological forms found not only on this planet but the universe. Discovering the roots of biodiversity is what this study is all about.