Definition : The cell is the basic unit of structure and function of a living thing.           Explain : Cells are specialized by size and shape for the job they do.

Definition: Tissues are made of a group of similar cells that work together to do a specific job in the body.

Explain: Tissues are made of a group of similar cells that work together to do a specific job in the body.

Definition : Organs are made up of two or more tissues that work together to do a specific job.

Explain :  a heart is an organ made of all four tissues.

Definition : Human organ systems include circulatory, reproductive, digestive, nervous, respiratory.

Explain :  Human organ systems include circulatory, reproductive, digestive, nervous, respiratory.

Definition :  Sum of all cells, tissues, organs and organ systems makes an organism. An organisms is made when a group of organ systems work together.

Explain :A group of the same type of organisms all living together in the same place.

                         Population

A group of the same type of organisms all living together in the same place.

                           Ecosystem

Populations living together in one area