______ is the fundamental structural unit of living organisms.

The correct answer is Cell.

Key Points

• The smallest and most basic unit of life is the cell.
• Cells make up the majority of living things, and it is the processes that cells perform that allow life to continue.
• Because of this, cells are also referred to as the fundamental building block of living things.
• The smallest building blocks of all living things are called cells.
• A cell has the ability to live independently and do all the tasks required of a living thing.
• Nutrition, respiration, excretion, transportation, and reproduction are all carried out by a cell.
• Since they contribute to the structure of the organism, cells are structural units.

Additional Information

• Cell:
  • Unicellular organisms are able to I live independently and carry out the fundamental tasks of life.
  • Independent living cannot be guaranteed if a cell's structure is incomplete.
  • As a result, the cell is the basic structural and functional unit of all living things.
  • Cells come together to form the body of every organism, much as how bricks come together to form a house.
  • A tissue is made up of a number of cells that have a certain job to do.
  • An organ is made up of a group of tissues, while an organism is made up of a group of organs.
  • Because of this, cells are regarded as the fundamental building blocks of living things.
  • Cells are the building blocks of all living things.
  • The cell is where all biological activities take place.
• An organism is made up of various organs.
• Organ system: 
  • ​A group of organs that cooperate to carry out one or more functions is known as an organ system in biology.
  • Each organ in a plant or animal body is composed of certain tissues and serves a specific purpose.
• Tissue:
  • ​Tissue is a collection of cells with a common structure and function that work as a single unit.
  • The body's tissues give it form and aid in energy storage and heat retention.
  • Connective tissue, epithelial tissue, muscle tissue, and nervous tissue are the four different types of tissues.
• Organ:
  • ​An organ sits between a tissue and an organ system in the hierarchy of life.
  • Similar cell types come together to form tissues that perform a certain purpose.
  • An organ is made up of a variety of tissues that work together to provide a certain function.
  • For instance, the intestinal wall is made of both smooth muscle and epithelial tissue.