Cell Theory Explained: The Three Big Ideas of Life (Grade 6 and 7 Science)

Hi, I'm Luna from DoodleBeez. Every living thing, from a tiny bacterium to a giant blue whale, has something in common. They are all made of cells. Today we will learn the three big ideas of cell theory.

Cells are too small to see with our eyes alone. In sixteen sixty five, Robert Hooke looked at thin slices of cork through a microscope and saw tiny boxes. He called them cells.

Later, Antonie van Leeuwenhoek built powerful lenses and saw tiny living things swimming in pond water. In the eighteen hundreds, scientists Schleiden, Schwann and Virchow put the ideas together into cell theory.

Idea one. All living things are made of one or more cells. Some organisms, like bacteria, are just one cell. Humans are made of trillions of cells working together.

Idea two. The cell is the basic unit of structure and function in living things. It is the smallest unit that can carry out all the processes of life, like using energy and getting rid of waste.

Idea three. All cells come from existing cells. Cells do not appear out of nowhere. A cell divides to make new cells, which is how you grow and how cuts heal.

Now it's your turn. A scientist claims a new cell formed from nothing in a jar of broth. Which part of cell theory says this is wrong? Pause and try. Idea three, all cells come from existing cells.

Great job! Remember, all living things are made of cells, the cell is the basic unit of life, and all cells come from existing cells. Practice cell theory in the Science Lab at doodlebeez.com. See you next time!