The uptake of water and solutes from the environment by a cell or a multi-celled organism; that is, the movement of nutrients, fluid, and ions across the gut lining and into the internal environment.

Dark narrow lines that represent absorption of energy at a particular wavelength of light.

Each element on the periodic chart absorbs energy at specific wavelengths of light which looks like a bar code.

A nebula seen in silhouette as it absorbs light from behind; also, called a dark nebula.

The spectrum resulting when light from one source is passed through another material; for example, a tenuous gas.

The result is a series of dark bands crossing the spectrum, known as absorption lines.