Common Characteristics of Living Organisms

Vocabulary flashcards summarizing key biological terms related to the common characteristics of living organisms.

Cellular Structure

The basic organizational trait of all living things; each organism is composed of one or more cells that carry out life functions.

Prokaryotic Cell

A cell lacking a nucleus and membrane-bound organelles; seen in Bacteria and Archaea.

Eukaryotic Cell

A cell containing a true nucleus and membrane-bound organelles; found in protists, fungi, plants, and animals.

Nutrition

The life process through which organisms obtain materials and energy from their environment.

Autotroph (Producer)

An organism that synthesizes its own food—usually via photosynthesis or chemosynthesis.

Heterotroph (Consumer)

An organism that obtains ready-made organic food by ingesting or absorbing other organisms.

Respiration

A set of reactions that break down food molecules to release usable energy (ATP).

Aerobic Respiration

Energy-releasing pathway that requires oxygen to produce ATP.

Anaerobic Respiration

Energy-releasing pathway that does not require oxygen; typical of certain bacteria and yeast.

Metabolism

The sum of all chemical reactions occurring within a living cell or organism.

Anabolism

Metabolic reactions that build larger molecules from smaller units, consuming ATP (e.g., protein synthesis).

Catabolism

Metabolic reactions that break down larger molecules into smaller units, releasing energy (e.g., digestion, cellular respiration).

Basal Metabolism

The minimum amount of energy an organism uses at complete rest to maintain vital functions.

Homeostasis

The maintenance of a relatively stable internal environment despite external changes.

Excretion

The removal of metabolic wastes such as CO₂, ammonia, or excess water from an organism’s body.

Stimulus

Any internal or external change that evokes a response from an organism.

Response

A measurable or observable reaction of an organism to a stimulus.

Movement

The ability of an organism or its parts to change position or orientation; may involve locomotion or growth-oriented motions.

Adaptation

An inherited characteristic that increases an organism’s chances of survival and reproduction in a specific environment.

Reproduction

The biological process by which new individual organisms are produced, ensuring continuity of the species.

Asexual Reproduction

Reproductive mode involving a single parent that produces genetically identical offspring (e.g., binary fission in amoeba).

Sexual Reproduction

Reproduction involving fusion of gametes from two parents, yielding genetically diverse offspring.

Growth

An increase in size and mass of an organism; in multicellular organisms, chiefly through cell division and enlargement.

Development

The progression of structural and functional changes leading an organism toward maturity.

Organization (Biological Hierarchy)

Ordered levels of complexity in living systems: atom → molecule → organelle → cell → tissue → organ → system → organism.

Contractile Vacuole

A specialized organelle in many freshwater protists that expels excess water to maintain osmotic balance.

Transpiration

Loss of water vapor from plant surfaces, primarily leaves; a form of excretion in plants.

Gutación (Guttation)

Exudation of liquid water from plant leaf margins, helping to remove excess ions and water.

Phototaxis

Movement of a motile organism toward or away from light, exemplified by Euglena swimming toward illumination.

Basal Metabolic Rate (BMR)

Quantitative measure of basal metabolism expressed as energy use per unit time (e.g., kcal/day).