What is the correct order of structural levels of organization from smallest to largest?

The correct order of structural levels of organization from smallest to largest is indeed Cells, Tissues, Organs, and Systems. This hierarchy reflects the complexity of biological organization:

• Cells are the basic unit of life and the smallest structural unit that can carry out all the functions of living organisms. Each cell operates independently, performing processes such as metabolism and reproduction.

• Tissues are formed when similar cells group together to perform a specific function. There are four primary types of tissues in the body: epithelial, connective, muscle, and nervous tissue.

• Organs are made up of different types of tissues that work together to perform a particular function. For example, the heart consists of muscle tissue, connective tissue, and nerve tissue, all collaborating to pump blood.

• Systems, often referred to as organ systems, are groups of organs that work together to carry out complex functions necessary for survival. The circulatory system, for example, includes the heart, blood vessels, and blood, all working together to transport nutrients and oxygen throughout the body.

This hierarchical organization is vital for understanding the functioning of living organisms, as each level builds on the previous one to create the complex structures and systems necessary for life.