Biology Basics

Scott Bauer USDA/ARS

What is biology? Simply put, it is the study of life. With that in mind, how do we know if something is living? Is a virus a living thing? What are the characteristics of life? Living organisms have the ability to be organized, take and use energy from the environment, grow and develop, reproduce, respond to stimuli, and adapt to the demands of an environment. Living things include both the visible world of animals and plants, as well as the invisible world of viruses and bacteria.

The foundation of biology as it exists today is based on five basic principles. They are:

• Cell Theory: all living organisms are composed of cells. The cell is the basic unit of life.
  
  
• Gene Theory: traits are inherited through gene transmission. Genes are located on chromosomes and consist of DNA.
  
  
• Evolution: any genetic change in a population that is inherited over several generations. These changes may be small or large, noticeable or not so noticeable.
  
  
• Homeostasis: ability to maintain a constant internal environment in response to environmental changes.
  
  
• Thermodynamics: energy is constant and energy transformation is not completely efficient.