Introduction to Biology

Definition and Etymology

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

• Prefix "bio-": means life.

• Suffix "-logy": means the study of.

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

Levels of Biological Organization

Life is incredibly diverse, but all living things share certain fundamental characteristics and organizational patterns. The smallest, most basic unit of life is the cell, which can be applied to all forms of life.

• Cell: The smallest unit that can carry out all life processes.

• Organism: Any individual form of life.

Unicellular vs. Multicellular Organisms

Cellular Organization

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

• Unicellular organisms: Forms of life that consist of a single cell (usually only seen with microscopes).

• Multicellular organisms: Forms of life that consist of multiple cells.

Examples:

• Unicellular: Amoeba, Bacteria

• Multicellular: Humans, Trees, Animals

Characteristics of Life

Defining Features of Living Organisms

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

• 1. Composed of cells: The basic unit of life.

• 2. Use smaller structures to build larger ones: Hierarchical organization.

• 3. Respond to environment: Ability to sense and react to stimuli.

• 4. Maintain stable internal conditions: Homeostasis.

• 5. Capacity to produce offspring: Reproduction.

• 6. Acquire and use energy: Metabolism.

• 7. Information: DNA functions as genetic material: Stores hereditary information.

• 8. Time for adaptation & change: Evolution.

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

Biological Organization: Hierarchy of Life

Levels of Organization

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

Example: The correct order from smallest to largest is Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere.

Emergent Properties

Definition and Examples

Emergent properties are characteristics that arise when combining smaller parts, 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: Neurons alone cannot think, but when organized into a brain, they produce consciousness.

• Example: Molecules form cells, which can perform life functions that molecules alone cannot.

Formula:

Emergent properties are observed at the cellular level and above.

Key Terms and Concepts

• Homeostasis: The maintenance of stable internal conditions.

• Metabolism: All chemical reactions that occur within an organism.

• Evolution: Change in the genetic makeup of a population over time.

• Reproduction: The process by which organisms produce offspring.

• DNA: The molecule that stores genetic and hereditary information.

Practice Questions (for Review)

• Which of the following is NOT a characteristic of life?

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

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

• Which is the best example of an emergent property?

Additional info: The notes above expand on brief points and fill in missing context to provide a complete, self-contained study guide suitable for General Biology students.