What Are the Three Parts of the Cell Theory? — Reading Comprehension

The cell theory is one of the most important ideas in life science. It helps us understand how living things are built and how they function. This theory was developed over time by several scientists, including Matthias Schleiden, Theodor Schwann, and Rudolf Virchow. Together, their discoveries led to the formation of a three-part scientific explanation we call the cell theory.

The first part of the cell theory states that all living things are made of one or more cells. This means that whether a living thing is as small as a bacterium or as large as an elephant, it is made of cells. Some organisms are unicellular, meaning they are made of just one cell. Others, like humans, are multicellular, made of trillions of cells.

The second part of the cell theory says that the cell is the basic unit of structure and function in living things. This means cells are the smallest units that carry out all the jobs needed for life—like getting energy, growing, and responding to the environment. Just as bricks build a house, cells build the body of an organism.

The third part of the theory states that all cells come from pre-existing cells. New cells are made when older cells divide. This part of the theory was added by Rudolf Virchow, who helped disprove the idea of spontaneous generation, the belief that life could appear from non-living things.

These three parts of the cell theory apply to all living organisms, and they continue to guide scientific research today.

Fun Fact: Even the largest creatures on Earth—like blue whales—are made up of cells that are microscopic in size!

What does the first part of cell theory state?

What is the basic unit of structure and function in living things?

What does the third part of cell theory explain?

Which scientist helped add the third part of the theory?

What does “unicellular” mean?

Why is the cell compared to a brick in the passage?

What is the main idea of the passage?

If new cells did not come from old ones, what would that suggest?