Euglenoids, Definition, Structure, Classification, and Reproduction

Euglenoids are single-celled, flagellated organisms found primarily in freshwater environments. They possess both plant-like and animal-like characteristics, featuring chlorophyll for photosynthesis and flagella for movement. This unique combination makes them an important subject of study, bridging the gap between plant and animal life.

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Definition of Euglenoids

Classification of Euglenoids

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Structure of Euglenoids

• Cell Shape and Pellicle : Euglenoids have an elongated cell body covered by a flexible, protein-rich layer called the pellicle, rather than a rigid cell wall. This pellicle provides support and allows the cell to twist and change shape as it moves.
• Flagella : Euglenoids possess one or two flagella, which aid in movement. Typically, only one flagellum is visible externally, while the other is shorter and located within the reservoir (a pocket-like structure inside the cell).
• Chloroplasts : The presence of chloroplasts in Euglenoids allows them to perform photosynthesis, using sunlight to produce energy. These chloroplasts contain the pigment chlorophyll, giving Euglenoids a green color similar to plants.
• Eyespot (Stigma) : Euglenoids have an eyespot near the base of the flagellum, which is sensitive to light. The eyespot helps Euglenoids detect light sources, enabling them to move toward optimal lighting for photosynthesis.
• Contractile Vacuole : Euglenoids also have a contractile vacuole that helps maintain osmotic balance within the cell by expelling excess water.

Nutrition of Euglenoids

• Autotrophic Nutrition : When exposed to sufficient light, euglenoids carry out photosynthesis using chloroplasts. They capture sunlight and convert carbon dioxide and water into glucose, similar to plant cells.
• Heterotrophic Nutrition: In the absence of light, euglenoids switch to heterotrophic nutrition, absorbing dissolved organic matter from the environment. They can ingest small particles or feed on organic molecules, making them adaptable to changing conditions.

Locomotion of Euglenoids

Reproduction of Euglenoids

MCQs of Euglenoids

Q1. Euglenoids have flexible body due to the presence of;

1. chlorophyll.
2. cell wall.
3. pellicle.
4. cellulose.

Q2. Which of these bears two unequal flagella?

1. Euglenoids
2. Slime molds
3. Diatoms
4. Dinoflagellates

Q3. Which of the following is NOT present in Euglena?

1. Chloroplasts
2. Flagella
3. Cellulosic cell wall
4. Proteinaceous pellicle

Answers of MCQs of Euglenoids