The rigid outer layer of Earth, comprising the crust and upper mantle, broken into tectonic plates.

Relating to the shore zone of a lake, sea, or ocean, where light penetrates to the bottom.

The coastal area of a body of water, extending from the high-water mark to the depth where rooted plants cease to grow.

A vital organ in vertebrates involved in detoxification, protein synthesis, and production of biochemicals for digestion.

The state of being alive, characterized by growth, reproduction, metabolism, and response to stimuli.

Organisms (e.g., coelacanth, ginkgo) that have remained virtually unchanged over millions of years compared to their fossil ancestors.

An organism that exhibits all the characteristics of life, including growth, reproduction, and metabolism.

A shorthand for the scientific term for the lethal dose of a substance in toxicology, LD50.

The border or transitional zone between two structures, such as the edge of the cornea and sclera in the eye.

A sedimentary rock composed primarily of calcium carbonate (CaCO₃), often formed from marine organisms.