Cells and Organisms in the Animal Kingdom

Cell Organization

• In unicellular organisms, a single cell performs all functions like digestion, respiration, and reproduction.
• In multicellular animals, different groups of cells perform specific functions in a well-organized manner.

Tissues

• A group of similar cells, along with intercellular substances, performs a specific function, and is called a tissue.
• There are only four basic types of tissues in complex animals.

Organs

• Tissues are organized in a specific proportion and pattern to form organs like stomach, lung, heart, and kidney.
• Organs are formed when two or more tissues work together to perform a specific function.

Organ Systems

• Organs work together through physical and/or chemical interactions to form organ systems, such as the digestive system, respiratory system, etc.
• Organ systems contribute to the survival of the body as a whole through division of labor.

Body Composition

• The body of a simple organism like Hydra is composed of different types of cells, with thousands of cells in each type.
• The human body is composed of billions of cells performing various functions.

This quiz covers the structure and functions of cells in both unicellular and multicellular organisms, including simple organisms like Hydra and the human body.