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Cells and organisms

Review your understanding of cells and organisms in this free article aligned to NGSS standards.

Key points:

  • Living things are called organisms. All organisms are made up of cells.
  • Cells are the smallest unit that can carry out all of the functions of life. These functions include taking up nutrients and water, getting rid of waste, getting and using energy, and interacting with the environment.
  • Unicellular organisms are made up of one cell. Multicellular organisms are made up of many cells. The cells in multicellular organisms are often specialized to carry out specific functions.
  • All cells come from other cells. New cells are made through a process called cell division. During cell division, one cell grows and splits into two.
  • Single cells are typically too small to be seen with the naked eye. So, people often view cells through a microscope.
A magnified plant leaf.
Plant cells viewed under a microscope. Image credit: "Bryum capillare leaf cells" by Des_Callaghan, CC BY-SA 4.0.

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