--- title: "What is a tissue?" subtitle: "Year 8 Biology · From cells to organs · Lesson 6" --- # What is a tissue? **Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}} > **Key question:** One muscle cell is thinner than a hair and can pull with only a tiny force. Yet your heart beats about 100 000 times a day without a rest. :::teacher-note **In one sentence:** 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). **Students should be able to say:** 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. **Width:** the unmarked parts are the floor every student does (Engage, Explore, Explain, Evaluate). Typical and Wider sections add contexts, not difficulty. Students work in the online tutorial alongside this sheet. ::: ## Engage :::keep-together **Your heart pumps with a strong squeeze. What does the squeezing?** ☐ A layer of millions of muscle cells contracting together ☐ The blood pushing itself ☐ Every kind of cell in the heart, equally ☐ One very large muscle cell My prediction, and why: {{lines-3}} ::: :::teacher-note **What happens:** A layer of millions of muscle cells, all contracting together: muscle tissue. One muscle cell is tiny and weak; together they are strong. ::: ## Explore Try it on the board in the tutorial. Was your prediction right? What was different? {{lines-2}} ## Explain: tissues :::keep-together ### What a tissue is **What is a tissue?** ☐ A group of similar specialised cells working together to do one job ☐ Any group of cells in the same place ☐ One very large specialised cell ::: :::teacher-note **Answer:** A group of similar specialised cells working together to do one job Similar cells, one job. Cells → tissues → organs → systems. ::: :::keep-together ### Tissue jobs **Match each tissue to its job.** A. Carries water up a plant from the roots B. Carries electrical signals C. Contracts to move the body or pump blood D. Carries sugar around a plant E. Lines and protects surfaces, inside and out {{columns 60% 40%}} {{rows 1}} | Part | Letter | |---|---| | `Muscle tissue` | | | `Epithelial tissue` | | | `Nervous tissue` | | | `Xylem` | | | `Phloem` | | ::: :::teacher-note **Answer:** Muscle tissue → C. Contracts to move the body or pump blood; Epithelial tissue → E. Lines and protects surfaces, inside and out; Nervous tissue → B. Carries electrical signals; Xylem → A. Carries water up a plant from the roots; Phloem → D. Carries sugar around a plant Animals and plants both have tissues: each is a group of similar specialised cells doing one job. ::: :::keep-together ### Animal or plant **Animal tissue or plant tissue?** Groups: Animal, Plant - Muscle: {{field-15}} - Nervous tissue: {{field-15}} - Blood: {{field-15}} - Xylem: {{field-15}} - Phloem: {{field-15}} - Palisade mesophyll: {{field-15}} ::: :::teacher-note **Answer:** Muscle → Animal; Nervous tissue → Animal; Blood → Animal; Xylem → Plant; Phloem → Plant; Palisade mesophyll → Plant ::: :::keep-together ### Why a tissue **Why does the body use muscle tissue, not just single muscle cells?** ☐ Millions of cells pulling together can make a force no single cell could ☐ Tissues don't need energy ☐ Single muscle cells can't contract ::: :::teacher-note **Answer:** Millions of cells pulling together can make a force no single cell could A tissue does a job at a scale no one cell can. That is why tissue function comes from the cells working together. ::: :::typical ## Elaborate: tissues in a leaf :::keep-together ### Xylem tubes **Xylem is made of long, hollow cells joined end to end. How does that suit its job?** ☐ Each hollow cell stores water for itself ☐ Hollow cells are lighter, so the plant can grow taller ☐ Together they form tubes that water can flow through from the roots to the leaves ::: :::teacher-note **Answer:** Together they form tubes that water can flow through from the roots to the leaves No single cell could carry water up a tree. Joined end to end, xylem cells make a continuous pipe. ::: ::: :::wider ## Elaborate: when a tissue goes wrong :::keep-together ### Scar tissue **After a heart attack, part of the cardiac muscle can be replaced by tough scar tissue (connective tissue). Why does the heart pump less well?** ☐ The nervous tissue stops working everywhere ☐ Scar tissue's cells can't contract, so that part no longer helps squeeze ☐ Scar tissue is heavier than muscle ::: :::teacher-note **Answer:** Scar tissue's cells can't contract, so that part no longer helps squeeze A tissue's job comes from its cells. Replace muscle cells with connective tissue cells and that part of the wall can no longer contract. ::: ::: ## Evaluate: look back Write one sentence: "At first I thought… Now I think… because…" **Revision summary** - A **tissue** is a group of similar specialised cells working together to do one job. - Animal tissues include muscle (contracts), epithelial (lines and protects), nervous (carries signals) and blood. Plant tissues include xylem (water), phloem (sugar) and palisade (photosynthesis). - A tissue can do what one cell can't do alone. - Next: **organs** are made of several tissues working together. ## Exit ticket :::keep-together **Name one animal tissue and one plant tissue, and say the job each does.** {{lines-3}} ::: :::teacher-note **Answer:** For example: muscle tissue contracts to move the body; xylem carries water up the plant. :::