Inside and Outside Skeletons

Overview

In this sixth lesson of the Support and Movement unit, students compare internal and external skeletons using humans, wētā, spiders and shellfish. They connect the position of a skeleton with its jobs: providing support, protecting important body parts and helping movement.

Learning intentions

• WALT identify internal and external skeletons.
• WALT compare how different skeletons support and protect animals.
• WALT use observations and scientific vocabulary to explain our thinking.
• WALT recognise that muscles and skeletons work together to create movement.

Success criteria

• I can explain the difference between an internal and an external skeleton.
• I can classify examples such as humans, wētā, spiders and shellfish.
• I can describe one way a skeleton supports or protects an animal.
• I can use evidence from a picture or model to explain my answer.

Curriculum links

• Biological Science — Body Systems / Support and movement: humans and some other animals have skeletons and muscles that work together for support, protection and movement.
• Biological Science — Support and movement: investigating how muscles and bones interact during physical activities and how body structures provide protection and support.
• Biological Science — Support and movement: observing and classifying animals as vertebrate or invertebrate.
• Science practices: observing, comparing, classifying and recording evidence.

Lesson structure (30 minutes)

1. 0–4 min · Hook and revisit. Open with the hook and learning intention slides and show a striking comparison of a human arm, a wētā and a spider; students silently predict where each animal’s skeleton is and share one reason with a partner. Briefly revisit that bones and muscles work together to support movement.

2. 4–9 min · Direct teach. Use the internal and external skeleton slides to introduce internal skeleton as a skeleton inside the body and external skeleton as a hard covering on the outside; students make a quiet “inside” or “outside” action and repeat the key meanings. Explain that an internal skeleton supports the body from within, while an external skeleton can protect the soft body and provide support.

3. 9–17 min · Observe and classify. Display the animal examples in the animal comparison slides and distribute the skeleton comparison worksheet to pairs. Students classify humans, wētā, spiders and shellfish as internal or external, circle evidence they can see, and record one support or protection job for each; clarify that a shellfish’s shell is an external protective structure, while its soft body is inside.

4. 17–23 min · Movement investigation. Ask students to gently bend and straighten one arm while feeling the muscles above and below the elbow; use the muscles-and-movement prompt slide to ask what changes when the arm moves. Students draw a simple arrow showing movement and explain to a partner that muscles pull on bones inside the body; remind them not to press hard or test another person’s body.

5. 23–27 min · Compare and discuss. Present the questions on the compare-and-explain slides: “Which skeleton gives a wētā protection?” and “How is a human skeleton different from a spider’s?” Pairs compare two animals using the frame, “Both ___ and ___ have ___, but ___ has ___”; invite several students to justify their ideas with observations.

6. 27–30 min · Plenary and exit check. Return to the final recap slide and ask students to complete the final section of the worksheet: draw one internal and one external skeleton and write one job for each. Collect responses as students leave, asking selected students to explain one answer aloud.

Resources

• the Inside and Outside Skeletons slide deck
• the skeleton comparison worksheet
• Projector or interactive display
• Pencils and colouring pencils
• Board and marker
• Optional animal photographs or simple plastic animal models
• Clear floor or seating space for the arm movement observation

Assessment

• Listen during the hook and direct teaching for accurate use of “internal” and “external”; address reversed or vague explanations immediately.
• Check pair worksheets for correct classification and a relevant support or protection function. Ask, “What evidence helped you decide?”
• Use the final drawing and explanation as an exit check: students should identify both skeleton types and link each to support or protection.

Differentiation

• Provide a word bank with inside, outside, skeleton, bone, muscle, support and sentence starters such as “The ___ has an external skeleton because…” and “Its skeleton protects…”.
• Pair students deliberately and allow students to explain orally before writing. Use enlarged, uncluttered animal images and read worksheet instructions aloud for students who need literacy or visual support.
• For EAL learners, demonstrate each term with gestures and explicitly connect “internal” with “inside” and “external” with “outside”; accept labelled drawings and oral responses.
• Extend confident students by asking them to explain one advantage and one limitation of an internal or external skeleton, or to predict how movement might be affected if the skeleton were soft.