Cells to Systems for Kids: Levels of Organization (Grade 6 and 7 Science)

Hi, I'm Luna from DoodleBeez. Your body has trillions of cells, yet it works as one living thing. How? It is organized in levels, like building blocks. Today we will climb from cells to systems.

The cell is the smallest unit of life. Every living thing is made of one or more cells. Many cells are specialized. A nerve cell is long to carry signals, and a red blood cell is shaped to carry oxygen.

A tissue is a group of similar cells working together on the same job. Muscle tissue contracts to create movement. Nervous tissue carries signals. Plants have tissues too, like the tubes that carry water.

An organ is made of different tissues working together. The heart contains muscle tissue, nervous tissue and connective tissue. Together they pump blood. The stomach, lungs and brain are organs too.

An organ system is a group of organs that work together. The heart, blood vessels and blood form the circulatory system. The mouth, stomach and intestines form the digestive system.

All the organ systems together make an organism, a complete living thing. Systems depend on each other. Your respiratory system brings in oxygen, and your circulatory system delivers it to every cell.

Now it's your turn. Put these in order from smallest to largest. Organ, cell, organ system, tissue. Pause and try. Cell, tissue, organ, then organ system.

Great job! Remember, cells form tissues, tissues form organs, organs form organ systems, and systems form an organism. Practice levels of organization in the Science Lab at doodlebeez.com. See you next time!