Introduction to Biology

Definition and Scope of Biology

Biology is the scientific study of life and living organisms. The term is derived from the Greek words "bios" (meaning "life") and "-logy" (meaning "the study of"). Biologists investigate the structure, function, growth, origin, evolution, and distribution of living things.

• Biology: The study of life and living organisms.

• Prefix "bio-": Means "life".

• Suffix "-logy": Means "the study of".

• Cell: The smallest, most basic/fundamental unit of life.

• Organism: Any individual form of life.

Example: Homo sapiens (humans), Panthera tigris (tiger), and Quercus robur (oak tree) are all organisms studied in biology.

Practice Question

• The area of science that studies life and its processes is called: Biology.

Unicellular vs. Multicellular Organisms

Types of Organisms

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

• Unicellular organisms: Consist of a single cell (e.g., bacteria, many protists).

• Multicellular organisms: Consist of multiple cells that are often specialized for different functions (e.g., plants, animals, fungi).

Example: Escherichia coli is a unicellular bacterium, while humans are multicellular organisms.

Characteristics of Life

Defining Features of Living Things

All living organisms share a set of characteristics that distinguish them from nonliving things:

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

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

• Respond to environment: Organisms detect and respond to stimuli.

• Maintain stable internal conditions (homeostasis): Regulation of internal environment.

• Capacity to produce offspring (reproduction): Ability to generate new individuals.

• Acquire and use energy: Metabolism for growth, maintenance, and reproduction.

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

• Time for adaptation & improved survival (evolution): Populations evolve over generations.

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

Practice Questions

• Which of the following is NOT a characteristic of life? (e.g., DNA molecule that stores genetic and hereditary information is a characteristic; the ability to convert sunlight energy into chemical energy is also a characteristic.)

• Salt concentration in blood remains relatively steady, regardless of a person's diet. This best illustrates: Homeostasis.

Biological Organization: Hierarchy of Life

Levels of Biological Organization

Life is organized into a hierarchy from the smallest chemical building blocks to the entire biosphere. Each level represents an increase in complexity.

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

Practice Questions

• Which of the following options has the correct order in terms of the hierarchy of organization? (e.g., Ecosystem → Community → Population → Organism)

• Use the word bank to complete the pyramid of life's organizational hierarchy.

Emergent Properties

Definition and Examples

Emergent properties are characteristics that arise when smaller parts combine to form more complex structures, and these properties are not present in the individual parts alone. At each new level of the hierarchy, the whole is greater than the sum of its parts.

• Emergent property: A property that appears when individual components are combined to form a more complex system.

Example: A single neuron cannot think, but a network of neurons (the brain) can produce consciousness and thought.

Practice Questions

• Which of the following is the best example of an emergent property? (e.g., Cells are made of simple molecules, but when organized together, these molecules can perform living functions.)

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

Additional info: The study notes above expand on the brief points and fill in missing context to provide a comprehensive overview suitable for introductory college biology students.