Grade 6 · Cells and Living Systems · Cell Structure and Function
Cells: The Basic Unit of Life
Why every living thing is built from cells, and how we know.
Learning objectives
- State the cell theory in your own words.
- Describe how a light microscope reveals cells.
- Compare unicellular and multicellular organisms.
NGSS alignment
MS-LS1-2
Develop and use a model to describe the function of a cell as a whole and ways the parts of cells contribute to the function.
MS-LS1-1
Conduct an investigation to provide evidence that living things are made of cells; either one cell or many different numbers and types of cells.
MYP criteria
- Criterion A — Knowing and Understanding
- Criterion D — Reflecting on the Impacts of Science
ENGAGE
A drop of pond water
A single drop of pond water placed under a microscope is crowded with moving green specks. Each speck is a whole living organism.
Think about it
- What must an organism be able to do to count as alive?
- Why could nobody study cells before the 1600s?
EXPLAIN
Cell theory
Every living thing is made of one or more cells. A cell is the smallest unit that can carry out all life processes on its own.
The three ideas of cell theory
- All living things are made of cells.
- The cell is the basic unit of structure and function in living things.
- New cells are produced from existing cells.
| Organism | Number of cells | Example |
|---|---|---|
| Unicellular | One | Amoeba, bacteria, yeast |
| Multicellular | Many, specialised | Human, oak tree, mushroom |
Common misconception
Cells are not simply tiny bags. Each one is an organised system with structures that do specific jobs.
INVESTIGATION
Estimating cell size
research question
How does the estimated width of a cheek cell compare with the width of an onion cell?
variables
Independent: cell type. Dependent: estimated width in micrometres. Controlled: microscope magnification, eyepiece graticule.
method
View each prepared slide at the same magnification. Count how many cells fit across the field of view, then divide the field width by that number. Repeat with three fields of view.
safety
Handle slides by the edges. Never force the objective lens down onto a slide.
analysis
Calculate the mean width for each cell type and comment on the spread of your repeats.
Watch
Introduction to Cells: The Grand Cell Tour
Amoeba Sisters · 9 min
A clear tour of what cells are and why they matter.
Before you watch: What do you already think a cell looks like inside?
- Name two structures shared by all cells.
- How does the video support the cell theory?
Interactive simulation · PhET
Gene Expression Essentials
Open the Expression tab and watch how a cell builds a protein from its instructions.
While you explore
- Which part of the cell holds the instructions?
- Why does a cell need to make proteins?
Key vocabulary
- Unicellular
- Made of only one cell.
- Cell
- The smallest living building block of an organism.
Practice questions
0/2 correct
Level 1 · Criterion A
Which statement is part of the cell theory?
Level 2 · Criterion A
A yeast organism is made of one cell. It is therefore described as:
MYP criterion tasks
Level 3 · Criterion D
Explain how the invention of the microscope changed what scientists could know about living things.
Reflect & track
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