Unicellular organisms

Define unicellular organisms.
Describe the key structures, nutrition, and reproduction methods of example unicellular organisms such as Amoeba and Euglena.
Compare and contrast the main features and ways of life of Amoeba and Euglena.

Not all living organisms are as complex as humans.
The first organisms on Earth were made up of just one cell, and there are still many unicellular organisms alive today.
These simple organisms, though small, are capable of carrying out all the essential life processes.
A unicellular organism is an organism that is made up of just one cell. Unlike plants and animals, which are made up of many cells, unicellular organisms consist of a single cell that performs all the necessary functions for survival.

Amoebas are microscopic unicellular organisms that are found in various environments, including freshwater, saltwater, wet soil, and even inside animals.
Structure:
- They have a flexible cell membrane that allows them to change their shape and move around.
Nutrition:
- Amoebas are heterotrophs, meaning they obtain their food from other organisms.
- They engulf tiny particles of food, such as algae, bacteria, and plant cells, by surrounding them and forming a food vacuole.
- The food is then digested within the vacuole.
Reproduction:
- Amoebas reproduce asexually through a process called binary fission.
- In binary fission, the nucleus of the cell divides, followed by the cytoplasm, resulting in two identical daughter cells.

An amoeba cell

Euglenas are another type of unicellular organism found in freshwater.
Structure:
- Euglenas have a flagellum, a tail-like structure that helps them to move through water.
- They also have an eye spot, which detects light and helps them to navigate towards areas with more sunlight for photosynthesis.
Nutition:
- They are unique because they contain chloroplasts, which enable them to produce their own food through photosynthesis.
- However, they can also switch to a heterotrophic mode of nutrition when sunlight is limited.
Reproduction:
- Like amoebas, euglenas reproduce asexually through binary fission.

A euglena cell

Unicellular organism: A living organism that consists of only one cell.
Heterotrophs: Organisms that obtain nutrients by consuming other organisms.
Binary fission: A type of asexual reproduction where a single cell divides into two identical daughter cells.
Amoeba: A type of unicellular organism known for changing shape and engulfing food.
Euglena: A type of unicellular organism that can perform photosynthesis but also consume food.
Flagellum: A whip-like or tail-like structure that helps some unicellular organisms, like Euglena, move.
Chloroplasts: Organelles found in plant cells and some unicellular organisms like Euglena, where photosynthesis takes place.
Food vacuole: A temporary compartment within a cell where food particles are digested.

Research other examples of unicellular organisms (such as Paramecium, bacteria, or yeast) and compare their structures and life processes to those of Amoeba and Euglena.
Investigate the diverse ecological roles that unicellular organisms play in various environments, including their importance in food chains and nutrient cycling.