Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, evolution, distribution, and taxonomy.
Modern biology is a vast and eclectic field, composed of many branches and subdisciplines. However, despite the broad scope of biology, there are certain general and unifying concepts within it that govern all study and research, consolidating it into single, coherent field.
In general, biology recognises:
- the cell as the basic unit of life,
- genes as the basic unit of heredity, and
- evolution by natural selection as the mechanism that propels the synthesis and creation of new species.
- all organisms survive by consuming and transforming energy and by regulating their internal environment to maintain a stable and vital condition.
Sub disciplines (areas of studies) of biology are defined by the scale at which organisms are investigated, the kinds of organisms studied, their behaviours, and the methods used to study them:
- Biochemistry examines the rudimentary chemistry of life;
- molecular biology studies the complex interactions among biological molecules;
- cellular biology examines the basic building-block of all life, the cell;
- botany studies the biology of plants;
- zoology studies the biology of animals;
- physiology examines the physical and chemical functions of tissues, organs, and organ systems of an organism;
- evolutionary biology examines the processes that produced the diversity of life; and
- ecology examines how organisms interact in their environment.
source: adapted from http://en.wikipedia.org/wiki/Biology
The term 'life sciences' is also used and can be considered an even broader context that considers the definition of life to include broader implications such as ethics, improvements in life or medicine.