1. Themes of Biology

2. Definition of Biology  Biology is the study of life, or all living things.  An individual living thing is referred to as an organism.  There are 6 main themes of biology.

3. 1. Cell Structure and Function  The cell is the basic unit of life.  Some organisms are unicellular—have only one cell.  Other organisms are multicellular—composed of more than one cell.  Cells are highly organized and contain specialized structures that carry out different processes.  Multicellular organisms usually have differentiated cells. (Different cells perform different functions.)

4. 2. Stability and Homeostasis  This is the ability of a cell to maintain a stable level of internal conditions.  For example, humans maintain a stable body temperature under controlled or normal conditions.

5. 3. Reproduction and Inheritance  Reproduction—the process where organisms transmit hereditary information to their offspring.  This hereditary info. is in the form of DNA (deoxyribonucleic acid).  There are two types of reproduction: Sexual reproduction Asexual reproduction

6. 4. Evolution  Evolution is the process of change in a population over a period of time.  Scientists suggest that this process occurs due to natural selection (the process by which organisms with favorable variations reproduce at higher rates than those without such variations).  There is both microevolution and macroevolution.

7. 5. Interdependence of Organisms  Ecology studies the interactions of organisms with each other and their environments.

8. 6. Matter, Energy, and Organization  Living things are highly organized structures that must be maintained in their orderly state by a constant supply of energy. How organisms obtain, use, and transfer energy is a major portion of the study of biology.  Organisms obtain their energy by either being heterotrophs or autotrophs.