Question

1. what are the main levels of organization in the respiratory system, from smallest to largest?

cells, tissues, organs, systems
tissues, cells, organs, systems
cells, organs, tissues, systems
systems, organs, tissues, cells

Explanation:

In biological organization, the smallest unit of life is the cell. Groups of similar cells form tissues. Tissues then combine to form organs, and multiple organs working together form an organ system (like the respiratory system). So the correct order from smallest to largest is cells, tissues, organs, systems.

Answer:

A. Cells, tissues, organs, systems