Characteristics of Life

Metabolism is the set of life-sustaining chemical reactions in organisms that allow them to convert food into energy and build cellular components.

A stimulus is a signal to which an organism responds. The bright light acts as the external signal that triggers the pupil's contraction.

The genetic code is nearly universal across all known life forms on Earth, which is strong evidence for a common evolutionary ancestor.

Homeostasis is the process by which an organism maintains a stable internal environment, such as body temperature, despite external changes or infections.

Sexual reproduction involves the fusion of gametes from two parents, resulting in offspring with a unique genetic combination different from either parent.

Evolution is a process that occurs in populations over many generations, not within the lifetime of a single individual.

Metabolism encompasses all chemical reactions within an organism that build up (anabolism) or break down (catabolism) materials to maintain life.

Homeostasis is the fundamental biological process of maintaining internal stability, such as pH, temperature, and water balance, in a changing environment.

Asexual reproduction involves a single parent producing offspring that are genetically identical to the parent, as no genetic mixing occurs.

The cell is the basic structural, functional, and biological unit of all known living organisms.

A stimulus is the change in the environment that triggers a response. In this case, the heat from the stove is the stimulus that causes the hand to pull away.

Development refers to the process of change in an organism's life cycle, such as metamorphosis. A tadpole becoming a frog is a classic example of developmental change, whereas simple growth in size is distinct from developmental transformation.

DNA (deoxyribonucleic acid) is the molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known organisms.

In biology, an entity must exhibit all fundamental characteristics of life (such as metabolism, reproduction, and homeostasis) to be classified as a living organism.