levels of organization
The cell is the basic unit of structure and function of a living thing. They are extremely small and can only be seen through a microscope.
Cells are specialized by size and shape for the job they do
Red Blood Cell
Tissues are made of a group of similar cells that work together to do a specific job in the body. They are cells put together.
Organs are made up of two or more tissues that work together to do a specific job. They make our body function and move properly.
An organ system is a group of organs working together to perform particular jobs. They all come to together and form the organism itself.
Sum of all cells, tissues, organs and organ systems makes an organism. Organisms come alive when all of the organ systems come ad work together.
Without cells a organism couldn't do anything. Cells make up everything so there would be no tissue, organs, organ systems, and there would ultimately be no organism. With no tissue there would be nothing that needs tissue to be formed so the organism would fail. This will keep happening without even one level the organism would again fail.