alga

/ ăl′gə /

, Plural algae ăl′jē

1. Any of various green, red, or brown organisms that grow mostly in water, ranging in size from single cells to large spreading seaweeds. Like plants, algae manufacture their own food through photosynthesis and release large amounts of oxygen into the atmosphere. They also fix large amounts of carbon, which would otherwise exist in the atmosphere as carbon dioxide. Algae form a major component of marine plankton and are often visible as pond scum and blooms in tidal pools. Land species mostly live in moist soil and on tree trunks or rocks. Some species live in extreme environments, such as deserts, hot springs, and glaciers. Although they were once classified as plants, the algae are now considered to be protists, with the exception of the cyanobacteria, formerly called blue-green algae. The algae do not form a distinct phylogenetic group, but the word alga serves as a convenient catch-all term for various photosynthetic protist phyla, including the green algae, brown algae, and red algae.

Example Sentences

Another example of conjugation is that of Pandorina, an alga allied to the well-known volvox.

From Project Gutenberg

It is carpeted with a bright-pink alga, Hildenbrandtia rosea, which incrusts the basin of the pool.

From Project Gutenberg

The alga Polysiphonia violacea floats in long feathery tufts from the stakes.

From Project Gutenberg

It is a simple one-celled alga containing protoplasm and endochrome (red coloring-matter).

From Project Gutenberg

When young this alga consists of an annulated tube formed of a single cell.

From Project Gutenberg