EUGLENA

Introduction

The Euglena is a unicellular protist that is considered to be eukaryotic since they have true nucleus', and have both animal and plant-like characteristics.They are most commonly found in pond water; and are both heterotrophic <when eating as an animal> and autotrophic <when using photosynthesis>. They lack a cell wall which makes them difficult to classify. However, they are mostly classified as protists due to their heavy reliance on photosynthesis for the absorption of nutrients. They can appear red due to "an extraplastidial carotenoid". They are able to lie dormant as a spore when living in bad conditions, and can also survive in fresh and salt water.

Digestion and Metabolism:

The Euglena absorbs nutrients through photosynthesis since they contain chloroplasts, making them autotrophic. However, they are also able to eat like animals. During the night time, the Euglena becomes heterotrophic and absorbs nutrients straight through their cell surface,  feeding off of dead organic matter that surrounds it. 

Circulation:

They have chlorophyll, which allows them to use photosynthesis. Using photosynthesis means that they are able to produce carbohydrates by using sunlight which is trapped by the chlorophyll.

Gas Exchange:

The Euglena uses diffusion for gas exchange. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration, the oxygen is diffused best when the cell has a moist membrane. 

Reproduction:

There is no proof of the Euglena being able to reproduce sexually, therefore they reproduce asexually. Following nuclear division, longitudinal binary fission occurs, which is when a cell divides lengthwise. Organelles are replicated as the cell circumference grows.  

Life Cycles:

The Euglena reproduces by longitudinal binary fission and asexually; fission occurs when one cell splits into two. The average life span differs among different Euglenas. 

Habitat:

They are most commonly found in ponds, where there is an abundance of organic matter such as green algae which provides them with food when not using photosynthesis. They also appear in marine, brackish habitats, mud, sand, or ice and snow. 

Relationship with Humans:

Euglena are mostly harmless to humans, although they do signal to humans when water is polluted; there is a larger population of euglena if there is a lot of green algae to eat since they feed off of algae and organic matter. Therefore, if a pond has a large population of euglena the pond is most likely to be polluted.