Algae with an eye

Euglena species are often abundant in calm waters, where they can be present in such numbers, that the surface of ponds and ditches can have a green or red color.

Euglena is commonly studied in biology classes because it has both plant (it has chloroplasts and so can photosynthesize) and animal (it moves and can eat) characteristics. Depending on conditions, photosynthesis or eating can predominate. It is a single celled creature with a large flagellum (not visible in this video, see below) that lives in fresh water. It is generally elongate but can change its shape quite dramatically during so-called euglenoid movement. It swims using its flagellum and can orientate itself with respect to gravity and light.

Golden colonial algae

The term colonial as used here applies to algae composed of free-swimming look alike unicells, which form groups that may be large and elaborately interconnected as in Volvox, or smaller and relatively simple as in Synura.

The Synura colonies shown in this video - taken in phase contrast - have ovoid golden-brown cells characteristic of the Chrysophyta, each cell bearing two flagella whose beating propels the colony through the water with a smooth rolling motion.