What Is Modern Cell Theory? — Reading Comprehension

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Grades

Standards

MS-LS1-1
MS-LS1-2

About This Reader

This NGSS-aligned reading passage introduces middle school students to modern cell theory, building on the original ideas of Schleiden, Schwann, and Virchow. Aligned with MS-LS1-1, the text includes updated ideas such as the presence of DNA in all cells, the chemical similarity between all cells, and the fact that metabolism occurs within cells. With vocabulary like 'organelle,' 'nucleus,' and 'electron microscope,' this science passage strengthens reading comprehension and helps students understand how life operates at the cellular level, linking key concepts in biology and health.

CONTENT PREVIEW

The modern cell theory is an updated version of the original cell theory that explains how cells function and how life works at the microscopic level. While the original cell theory was developed in the 1800s by scientists like Schleiden, Schwann, and Virchow, modern cell theory includes new ideas based on advanced technology and research.

The basic three parts of the original cell theory are still true today:

All living things are made of one or more cells
The cell is the basic unit of structure and function in living things
All cells come from pre-existing cells

Modern cell theory builds on these ideas with a few important additions:

● All cells contain genetic material (DNA) that is passed from one cell to another during cell division.

● All cells are basically the same in chemical composition and activities, even if they look different.

● All energy flow (metabolism) of life happens inside cells.

Thanks to powerful tools like electron microscopes and DNA sequencing, scientists have discovered that cells are more complex than once thought. We now know that organelles, such as the nucleus and mitochondria, carry out specific functions. We also understand how cell membranes, enzymes, and genes play key roles in cell behavior and reproduction.

Modern cell theory is important in many areas of science, including medicine, genetics, and biotechnology. It helps scientists understand how diseases start, how organisms grow, and how cells can be used in treatments like stem cell therapy.

Fun Fact: Your body makes around 25 million new cells every second—all following the same rules of modern cell theory!

What are the three basic parts of the original cell theory?

Cells are invisible, quiet, and dryCells are large, made of water, and never divideAll living things are made of cells, cells are the basic unit of life, and cells come from other cellsOnly animals have cells, and cells live forever

What new idea is part of modern cell theory?

Cells can flyAll cells contain DNACells do not divideOnly bacteria have cells

How is energy related to cells in modern cell theory?

Cells absorb energy from light onlyEnergy never moves through cellsAll energy flow of life happens in cellsCells store energy in air

What tool has helped scientists learn more about cells?

ThermometerCalculatorElectron microscopeTelescope

What is passed from one cell to another during division?

BloodGenesWaterDNA

What part of the cell controls many activities and holds DNA?

Cell wallCytoplasmNucleusRibosome

What is the main idea of the passage?

Cells can become animalsModern cell theory includes new discoveries about how cells workCells never changeCell theory is used only in labs