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Monday, December 17, 2012
What is Euglena?
Euglena is unicellular organisms grouped into the Kingdom Protista, and the Phylum Euglenophyta. All euglena have chloroplasts and can make their own food by photosynthesis. They are not absolutely autotrophic though, euglena can also process food from their surroundings; euglena generally lives in silent ponds or puddles.
Movement of Euglena:
Euglena move by a flagellum (flagella), which is a burrs from some cells that assist in cellular locomotion. The flagellum is found on the anterior end, and twirls in such a way as to pull the cell via the water. It is connected at an inside pocket known as the reservoir.
Characteristics and Arrangements of Euglena:
The Euglena is special in that it is both heterotrophic (must consume food) and autotrophic (can make its own food). Chloroplasts within the euglena trap sunlight that is used for photosynthesis, and can be observed as various rods like structures all over the cell. Euglena also have an eyespot at the anterior end that detects light, it can be seen close to the reservoir. This assists the euglena find bright locations to collect sunlight to make their food. Euglena can also get nutrients (vitamins and minerals) by absorbing them throughout their cell membrane, therefore they grow to be heterotrophic when light is not available, and they cannot photosynthesize.
When feeding as a heterotroph, the Euglena surrounds a particle of food and consumes it by phagocytosis. When there is sufficient sunlight for it to feed by phototrophy, it uses chloroplasts containing the pigments Chlorophylla and Chlorophyll b to produce sugars by photosynthesis. Euglena's chloroplasts are surrounded by three membranes, while those of plants and the green algae (among which earlier taxonomists often placed Euglena) have only two membranes. This fact has been taken as morphological evidence that Euglena's chloroplasts evolved from a eukaryotic green algae. Thus, the intriguing similarities between Euglena and the plants would have arisen not because of kinship but because of a secondary endosymbiosis. Molecular phylogenetic analysis has lent support to this hypothesis, and it is now generally accepted.
The euglena has a stiff pellicle outside the cell membrane that assists it retain its form, though the pellicle is relatively flexible and some euglena can be noticed scrunching up and moving in an inchworm type fashion.
In the center of the cell is the nucleus, which includes the cell's DNA and controls the cell's actions. The nucleolus can be observed within the nucleus.
The interior of the cell includes a jelly-like liquid substance called cytoplasm. Toward the posterior of the cell is a star-like structure: the contractile vacuole. This organelle assists the cell eliminate extra water, and without it the euglena could take in some much water due to osmosis that the cell would explode