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Key Ideas

  • Cells are the basic unit of life, each with a specific purpose.
  • Cells, tissues, organs, and systems work together to form the structures and perform the functions of the human body.
  • Cells are small, thus maintaining a vast surface area per unit volume to enhance cell efficiency.


The unit begins by inviting students to think about cells as the building blocks of life. Multicellular organisms are composed of different types of cells. These cells work together forming tissues, organs, and systems. Being small, cells maintain a vast surface area per unit volume to enhance efficiency. Students use a microscope to observe the similarities and differences among the cells that comprise different tissues. They also explore the effect an increase in the size of a cell has on the cell's efficiency.



\checkmark identify different structural and functional characteristics of cells.

\checkmark distinguish between a cell, tissue, organ, and system.

\checkmark explain why cells are so small.


cells, cell theory, connective tissue, epithelial tissue, muscle tissue, nervous tissue, organ, system, tissue

Student Materials

Activity 1-1: Why Are Cells Small?

  • Resource
  • Activity Report
  • Plain paper for constructing a model of a cube; Scissors; Metric ruler; Clear tape

Teacher Materials

Activity 1-1: Why Are Cells Small?

  • Activity Report Answer Key
  • Demonstration cube models, 1 cm, 2 cm, 4 cm, and 8 cm on an edge

Advance Preparation

See Activity 1-1 in the Student Edition.

Activity 1-1: Why Are Cells Small?

  • Gather student materials.
  • Prepare demonstration cube models, 1 cm, 2 cm, 4 cm, and 8 cm on an edge. Models can be constructed from paper, as in the student activity procedure. More durable models can be cut from wood or made from modeling clay.
  • Consider planning this activity with math teacher.

Interdisciplinary Connections

Math Students use formulas to calculate and graph the relationship between surface area and volume of cubes.

Students use mathematical formulas and discuss questions such as, “How is it that a fly getting out of a bathtub carries a film of water many times its own weight, whereas a person coming out of the bath carries away a film of water weighing about a pound?”

Art Use cube shapes of varying sizes to create a painting, drawing, or collage that shows relationships and perspectives of cube omparisons.

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