Euglena. Euglena are often classified as their own phylum because they exhibit
both the characteristics of protozoa and algae. Euglena move making them like
protozoans. Euglena contain chloroplasts which allow them to carry out
photosynthesis, making them more like algae, although they do not contain a cell
wall. That is why euglena can be classified as either as algae or a protozoan.
Euglena sense light by using the eyespot. Since the euglena is like algae, it goes
through the process of photosynthesis. The eyespot is typically red and is found
near the ‘head’ where the flagellum is found. The euglena uses the eyespot to help
find food, at times, when no light is present, the euglena captures and feeds like an
amoeba.
As has already been stated euglena move mainly through the use of flagellum.
During active locomotion it is swung backward, and waves pass rapidly from its base
to its tip. However, the euglena cell is also surrounded the pellicle. The flexibility
of the pellicle allows the euglena to crawl through mud or water that is littered
with debris. The euglena may also move like a worm drawing up its rear half and
sliding forward, this is not the usual method of movement.
Euglena is a single-celled microorganism that has both animal and plant
characteristics. Like many plant cells they have bright green chloroplasts that
contain chlorophyll and carry on photosynthesis. Like animal cells, they have a long
whip like flagellum used for locomotion. The body is typically elongated and
somewhat spindle-shaped. It is enclose by a flexible, striated pellicle made chiefly
of protein. The front end of the body forms a flask-shaped cavity, or reservoir. A
red eyespot, or stigma, is located near one wall of the reservoir at about the same
level as a swelling on the flagellum. These two structures are responsible for light
sensitivity and enable individuals to become oriented toward light. In addition to
the numerous chloroplasts, there are reserves of carbohydrate in the cell. A large
nucleus is located in the posterior half of the body.
Reproduction is asexual, in which the body cleaves longitudinally while the
nucleus undergoes splitting. This is the same way in which the amoeba reproduces.
Euglena is a common inhabit of freshwater ponds and streams, where it forms
part of the plankton living in the upper layers within the range of sunlight. A
combination of sunlight, warm temperatures, and polluted conditions often
promotes their growth so that they form an opaque green scum on the water’s
surface.
The euglena breathes and removes in the same manner as the amoeba. The cell
membrane recognizes the nutrients and keeps them from leaving while at the same
time allows waste material to leave. Breathing is done in the same manner; oxygen
moves in through the cell membrane and carbon dioxide leaves.