Cell is the basic unit of human structure and function, and human body is a tissue formed by cell differentiation. The main tissues of human body include epithelial tissue, muscle tissue, connective tissue, nerve tissue, etc., and then these different tissues are combined together in a certain order to form organs with certain functions, and then multiple organs that can perform one or several physiological functions are combined together in a certain order to form a system. The human body consists of digestive system, respiratory system, circulatory system, urinary system, exercise system, reproductive system, endocrine system and nervous system. Finally, eight systems form a complete human body. The human body is made up of cells, tissues form organs, organs form systems, and then systems form the human body.

Plants are similar to animals, and their growth and development start from fertilized eggs, which divide and differentiate into tissues and organs, and then form plants.

Test center: This question examines that the basic unit of organism structure and function is cell.

Comments: For this kind of topic, students should know that cells are the basic unit of organisms, cells differentiate into tissues, and different tissues form organs in a certain order. Animals, plants and people are all made of cells except viruses.