Unicellular organisms

• 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.

Amoeba

• 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.

Euglena

• 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.

Amoeba (left) and euglena (right)