Biology: The Study of Life

Definition and Etymology

Biology is the scientific study of life. The term is derived from the Greek words bios (meaning "life") and logos (meaning "the study of").

• Prefix: "bio-" means "life"

• Suffix: "-ology" means "the study of"

Biology encompasses the study of all living organisms, from microscopic bacteria to large animals and plants.

Cell Theory and Diversity of Life

Life is incredibly diverse, ranging from ocean life to terrestrial plants and animals. Despite this diversity, all life shares certain fundamental characteristics:

• Cell: The cell is the smallest, most basic unit of life. All living things are composed of one or more cells.

• Organism: Any individual form of life, which can be applied to all forms of life.

Unicellular vs. Multicellular Organisms

Organisms can be classified based on the number of cells they possess:

• Unicellular organisms: Forms of life that consist of a single cell (e.g., bacteria, some protists).

• Multicellular organisms: Forms of life that consist of multiple cells (e.g., plants, animals, fungi).

Unicellular organisms are usually only seen with microscopes, while multicellular organisms have specialized cells for different functions.

Characteristics of Living Things

Shared Properties of Life

All living organisms share several key characteristics that distinguish them from nonliving things:

1. Composed of cells: All living things are made up of one or more cells.

2. Use smaller structures to build larger ones: Biological organization is hierarchical.

3. Respond to environment: Organisms can sense and react to changes in their surroundings.

4. Maintain stable internal conditions (homeostasis): Ability to regulate internal environment.

5. Capacity to produce offspring (reproduction): Living things can reproduce to create new individuals.

6. Acquire and use energy: Organisms obtain energy from their environment and use it to power life processes.

7. Information: DNA functions as genetic material: DNA stores genetic information necessary for growth and reproduction.

8. Time for adaptation & change (evolution): Populations of organisms evolve over generations.

Note: Viruses are NOT considered alive because they do not meet all these criteria.

Organization of Life: Hierarchical Structure

Levels of Biological Organization

Life consists of multiple parts organized into a hierarchical pattern, from the smallest to the largest scale:

Each level builds upon the previous, creating increasing complexity.

Emergent Properties

Emergent properties are characteristics that arise when smaller parts are combined, which the individual parts do not display. At each new level of the hierarchy, the whole is greater than the sum of its parts.

• Example: Individual neurons cannot think, but together they form a brain capable of thought.

• Example: Molecules alone do not have life, but when organized into cells, life emerges.

Key Terms and Concepts

• Homeostasis: The maintenance of stable internal conditions despite changes in the external environment.

• Evolution: The process by which populations of organisms change over generations.

• Autotrophy: The ability of an organism to produce its own food from inorganic substances (e.g., photosynthesis in plants).

• Multicellularity: The state of being composed of multiple cells that work together.

Example Questions and Applications

• Which of the following is NOT a characteristic of life? (e.g., DNA molecule that stores genetic and hereditary information is a characteristic; ability to establish a constant internal temperature is homeostasis.)

• Salt concentration in blood remains steady regardless of diet. This illustrates homeostasis.

• At which point of the organizational hierarchy does life emerge? Cellular level.

Additional info: The notes above expand on brief points and fill in missing context to provide a comprehensive overview suitable for General Biology students.