Biology: Single-Celled Organisms

Organism

• An individual living thing that performs basic life functions.
• Examples include ducks, trees, and algae.
• Basic unit of life is the cell; organisms can be unicellular (simple) or multicellular (complex).

Bacteria

• Single-celled organisms without organized nuclei.
• Found on and inside the human body, in soil, water, and plants.
• Some bacteria are harmless; others can cause illness.

Amoeba

• A type of single-celled organism from kingdom Protista capable of movement.
• Changes shape while moving and can only be seen with a microscope.
• Moves by extending parts of its body, resembling living gelatin.

Functionality of Single-Celled Organisms

• Single-celled organisms carry out all life processes within one cell.
• They can eat, grow, respond to the environment, and reproduce.
• Requires a microscope for visibility.

Microorganism

• Organisms too small to be seen with the naked eye.
• Present in air and water; can be unicellular or multicellular.
• Some microorganisms are disease-causing, while others are beneficial.

Cell and Nucleus

• The basic unit of life where all organisms are composed of cells.
• The nucleus functions as the cell's "brain," controlling activities and holding DNA.
• Contains hereditary information influencing physical traits.

Abdomen

• The body part located between the thorax and pelvis in animals.
• Also refers to the hind section of insects or spiders.

Movement of Single-Celled Organisms

• Amoebas move by shifting cytoplasm to form pseudopods that capture food.
• Some bacteria use flagella (long tails) for movement.

Cytoplasm

• The liquid interior of a living cell that supports organelles and cellular processes.

Cilia

• Tiny hair-like structures that move back and forth to facilitate movement, seen in organisms like paramecium.

Harmful and Helpful Aspects of Single-Celled Organisms

• Some bacteria can spoil food and cause diseases like pneumonia.
• Certain amoebas in contaminated water can lead to severe health issues.
• Bacteria in the intestines aid digestion and vitamin production.
• Phytoplankton produce oxygen through photosynthesis and form the base of ocean food chains.