A group of similar cells that carries out a certain job is called a tissue.

Here's a breakdown:

* Cells: The basic building blocks of all living things.

* Tissue: A collection of similar cells that work together to perform a specific function.

* Organ: A structure made up of different tissues that work together to perform a more complex function.

* Organ System: A group of organs that work together to carry out major life processes.

For example, muscle tissue is made up of muscle cells that can contract and relax, allowing for movement. Nervous tissue is made up of nerve cells that transmit signals throughout the body.