Whole Earth Curriculum WEC

Lesson 05 — Cells: The Basic Unit of Life

Learners learn that cells are the basic unit of life: every living thing is made of cells, and some living things are just one cell. They match cell parts to their jobs, compare plant and animal cells, and meet single-celled organisms — amoebae, yeast, and pond algae — that do all of life's work inside one small cell.

D06 P3: Intellectual & Cognitive Awareness D06.S2 50 minutes Draft

Objectives

Essential question

What are living things made of, and how can one single cell be a whole living thing?

cellorganismsingle-celledmulticellularmembranenucleuscytoplasmmicroscope

Materials

Standard materials

Low-tech / no-cost

Enriched / lab & device

Works in different contexts

A diagram of cells as the basic unit of life. On the left, an animal cell is shown as a rounded shape with a labeled outer membrane, a central labeled nucleus, and labeled cytoplasm filling the inside. In the middle, a plant cell is shown as a more boxy shape with a thick labeled cell wall outside the membrane, a nucleus, cytoplasm, and small labeled chloroplasts. On the right, a single-celled organism (an amoeba) is shown as one irregular cell with a nucleus and a caption reading 'one cell = one whole living thing.' A title reads: cells are the basic unit of life. Labels and shapes, not color alone, carry the meaning so it prints clearly in grayscale.
A diagram of cells as the basic unit of life. On the left, an animal cell is shown as a rounded shape with a labeled outer membrane, a central labeled nucleus, and labeled cytoplasm filling the inside. In the middle, a plant cell is shown as a more boxy shape with a thick labeled cell wall outside the membrane, a nucleus, cytoplasm, and small labeled chloroplasts. On the right, a single-celled organism (an amoeba) is shown as one irregular cell with a nucleus and a caption reading 'one cell = one whole living thing.' A title reads: cells are the basic unit of life. Labels and shapes, not color alone, carry the meaning so it prints clearly in grayscale.

Lesson 5 — Cells: The Basic Unit of Life

Summary

Learners learn that cells are the basic unit of life: every living thing — plant, animal, fungus — is built of cells, and some living things are made of a single cell. They match cell parts to their jobs, compare plant and animal cells, and meet single-celled organisms such as amoebae, yeast, and pond algae, which perform all of life’s tasks inside one tiny cell.

Objectives

  • Explain how cells are the basic unit of life and that some living things are made of a single cell. (D06.S2.06.01)

Connection

Your own body is a city of cells — trillions of them, each too small to see without a microscope. Yet some living things need no city at all: the yeast that makes bread rise is a single cell, and the green algae floating in a pond is a single cell too. From a giant tree to the yeast in dough, the rule is the same: the cell is the small living unit everything bigger is made from. Today you meet that unit up close.

Materials

  • Cell diagram
  • Cell parts cards
  • “One cell, whole life” page

Preparation

  • Print or draw the cell diagram and part cards per pair.
  • Recall Grade 3–4: living things grow, move, and reproduce; now we ask what they are made of.
  • Have the cloth-bag/ball/water model ready if using it.

Facilitator note

Written to the learner (“you”). Three ideas to land: (1) cells are the basic unit of life — all living things are made of cells; (2) some living things are one cell — a single cell can be a whole organism; (3) a few parts and their jobs (membrane = boundary, nucleus = control center, cytoplasm = the gel that fills it; plants add a cell wall for support and chloroplasts for making food). Model the worked example with the bag model: the bag is the membrane (it holds the inside in and lets some things pass), the ball is the nucleus, the water is the cytoplasm. Note the “how do we know” through-line: we know cells exist because microscopes let us see them — that is evidence, not guess. The claim that all life is made of cells is a well-tested scientific theory (cell theory); hold it as evidence-based, not as dogma. Yeast (single-celled fungi) is a welcoming, global example — bread and fermented foods across cultures. See docs/facilitation.md.

Procedure

  1. Gather (5 min). What are you made of? Skin, blood, bone, muscle — and if we could look closer and closer, what is the smallest living piece? Write your guess.
  2. Meet the cell (10 min). Look at the diagram. A cell is the basic unit of life — the smallest part that is itself alive. The membrane is its boundary, the nucleus is its control center, and the cytoplasm is the gel that fills it. A plant cell adds a stiff cell wall for support and chloroplasts for making food from sunlight. Point to each part and say its job.
  3. One cell, whole life (10 min). Not everything is built of many cells. A single-celled organism is a living thing made of exactly one cell — an amoeba in a puddle, yeast in bread dough, algae on a pond. That one cell must eat, grow, and reproduce all by itself. On your page, draw one and write the jobs it does in its one cell.
  4. Match parts to jobs (15 min). With a partner, match each part card to its job: membrane → boundary; nucleus → control center; cytoplasm → filling; cell wall → support; chloroplasts → food-making. Then build your own cell with the bag model (or stand together as one cell) and point to each part.
  5. Close (5 min). From one cell to a whole forest, the cell is where life is built. And some living things never get bigger than a single cell — yet they are complete and alive.

Differentiation

  • Support: Use the bag model and a two-part label (membrane = bag, nucleus = ball); focus on “one cell can be a whole living thing.”
  • Extension: Explain two ways a plant cell differs from an animal cell and why a plant’s cell wall helps it stand tall without a skeleton.

Assessment

  • Formative (observation): Can the learner name the cell as the basic unit of life, name one single-celled organism, and match two parts to their jobs?
  • Self-check: The learner asks, “Can I explain what one cell must be able to do for a single-celled organism to stay alive?”

Home connection

With permission, look at bread yeast or a drop of pond water if a magnifier is available. Tell someone what you think you are seeing: one cell doing all of life’s jobs.

Resources