What is a tissue?

Students define a tissue as a group of similar specialised cells doing a shared job, give animal and plant examples, and explain how a tissue does what single cells can't (AC9S8U02, node 2). About 23 minutes.

Open the teacher guide: answers, solutions, slides and a worksheet.

Students will be able to

• I can define a tissue.
• I can name an animal tissue and a plant tissue and the job of each.
• I can explain how a tissue does a job that one cell can't.

Before class

A concept tutorial for introducing or revising the idea. Set the width with ?width=minimum, typical (default) or wider. It sits between Why are cells different shapes? (node 1) and What is an organ made of? (node 3), which uses the same heart and leaf diagrams for whole organs.

Not a hinge node, but it is the step students skip: they jump from cells to organs without the "similar cells, one job" level. The prediction tests whether they expect one big cell, or every cell equally.

Board notes: the heart wall and leaf are labelled diagrams, not to scale; each layer stands for millions of cells. Blood counts as a tissue (cells in a liquid), which surprises some students.

Running the lesson

1. Engage: tally the predictions. 'One large cell' and 'every kind of cell equally' are the two misconceptions.
2. Explore: ask how the muscle cell's job relates to the muscle tissue's job (the same, at a bigger scale).
3. Explain: the definition and the matching are the success criteria; 'why a tissue' is the collective idea.
4. In your own words: the cell-to-tissue drawings for muscle and xylem are the evidence.

The hard part (on purpose)

Telling a tissue from an organ. Ask 'how many kinds of cell?' and let the student decide which level they are looking at.

When students get stuck

• A student calls the heart a tissue. Ask: How many kinds of cell are in the heart wall? Fix: Several, in different layers: muscle, lining, nervous, connective. Several tissues together make an organ.
• A student says a tissue is any cells in the same place. Ask: Are the cells alike, and do they share one job? Fix: A tissue is similar cells with one job. Cells side by side doing different jobs belong to different tissues.
• A student thinks plants don't have tissues. Ask: How does water get from the roots to the leaves? Fix: Through xylem: a tissue of long, hollow cells joined into tubes.

Stretch and support

Stretch: Blood is called a tissue, though it's a liquid. Does it fit the definition? (Yes: specialised cells, such as red blood cells, carried in plasma, doing shared jobs like carrying oxygen.)

Support: Give the frame: '… tissue is made of many … cells. Together they … , which one cell could not do on its own.'

Where it leads

Next: What is an organ made of? (node 3). Organ systems (node 4) are a class task.

In class: prepared slides of muscle, epithelium (cheek cells) and a plant stem section; matching cards from cell to tissue to organ to system.

What each step is for

• Engage: one cell or many?: Students who think one specialised cell can do an organ's job, or that a tissue is any mix of cells in one place, pick those options; the definition needs 'similar cells, one shared job'.
• Explore: from cell to tissue: Finding the parts of one muscle cell, then the muscle, lining and nerve tissues in the heart wall, moves students from the cell to the group of cells.
• Explain: tissues: Defining a tissue by similar cells and a shared job, with plant and animal examples, is the node; the 'why not one cell' question gets at what a tissue adds.
• Elaborate: tissues in a leaf: Finding plant tissues by their jobs checks that the definition works beyond animals.
• Elaborate: when a tissue goes wrong: What happens when one tissue changes (scar tissue in the heart) shows that an organ's work depends on each tissue doing its job.