Evidence for Variation

Overview

Students investigate how fossils and comparative anatomy provide evidence that populations change over time and vary from ancestral forms. They use a short teacher-selected, New Zealand curriculum-aligned video, then compare vestigial and analogous structures before making an evidence-based claim.

Learning intentions

• Students will explain how fossils provide evidence of variation and change over time.
• Students will distinguish between vestigial and analogous structures.
• Students will use observations to support a scientific claim about biological variation.
• Students will communicate evidence using appropriate scientific language.

Success criteria

• I can describe at least two observations from fossils that support change over time.
• I can explain the difference between a vestigial structure and an analogous structure.
• I can classify examples accurately and justify my decisions.
• I can use evidence and reasoning to explain how species may be related or adapted to different environments.

Curriculum links

• Science — Physical Science and the wider Nature of Science focus on making observations, identifying patterns, and using evidence to explain natural phenomena.
• Science — students interpret representations and observations, communicate scientific explanations, and evaluate the strength of evidence.
• The lesson develops understanding of variation, adaptation, relationships between organisms, and how scientific explanations are built from evidence.

Lesson structure (50 minutes)

1. 0–5 min · Hook and prior knowledge. Open with the fossil mystery hook showing a sequence of related fossil images and ask, “What could explain changes in a body shape across millions of years?” Students silently write one idea, then share with a partner. Take two or three responses without confirming answers.

2. 5–12 min · Video and guided teaching. Play the short New Zealand curriculum-aligned video embedded or linked by the teacher in the curriculum-aligned evidence video. Students record one observation about fossils and one question. Pause at a suitable point to clarify that fossils are preserved evidence of past life and that the fossil record is incomplete, so scientists combine several types of evidence.

3. 12–20 min · Build key concepts. Use the key concepts slides to teach:

• Fossil evidence: fossils can show organisms with features that differ from both earlier and later forms, helping scientists infer change and variation over time.
• Vestigial structures: inherited structures that have become reduced or have little current function, such as the human tailbone or whale pelvic bones.
• Analogous structures: structures with similar functions but different underlying origins, such as bird wings and insect wings; they are evidence of similar pressures, not necessarily close ancestry.

Students complete a three-column note: term, meaning, and example. Emphasise that one example alone does not “prove” a complete evolutionary history.

4. 20–34 min · Evidence analysis in pairs. Distribute the fossil and comparative anatomy evidence worksheet to pairs. Students examine short descriptions and images of fossil sequences, whale pelvic bones, the human tailbone, bird wings, and insect wings. For each, they identify the evidence type, record an observation, and write what the observation may suggest. Circulate and ask, “What can you observe directly?” and “What inference are you making?”

5. 34–43 min · Classification and discussion. Display the classification challenge. Read each example aloud and ask pairs to hold up or point to “fossil evidence”, “vestigial”, or “analogous” on their worksheet. Invite different answers and require justification using the sentence frame: “I classify this as ___ because the evidence shows ___.” Address the misconception that “vestigial” means completely useless and reinforce that analogous structures have similar functions but different evolutionary origins.

6. 43–50 min · Claim, evidence, reasoning exit check. Students complete the final section of the claim-evidence-reasoning exit task: “Explain how fossils and comparative anatomy can provide evidence for variation and change over time.” They must include one fossil observation, one vestigial or analogous example, and a reasoning sentence. Invite one student to read a strong response, then collect worksheets.

Resources

• the complete evidence and variation slide deck
• the fossil and comparative anatomy evidence worksheet
• A short teacher-selected New Zealand curriculum-aligned video about fossils, variation, and evidence
• Projector or interactive display with speakers
• Images or diagrams of fossil sequences and comparative structures
• Whiteboard and markers
• Pens or pencils

Assessment

• During the video, check students’ recorded observations and questions for the difference between evidence and inference.
• During pair work, listen for accurate use of “vestigial”, “analogous”, “function”, “origin”, and “variation”; question students who classify without justification.
• Use the final claim-evidence-reasoning response to assess whether students connect observations to a scientifically reasonable explanation.

Differentiation

• Provide the sentence frames “I observe…”, “This may suggest…”, and “I classify this as… because…” on the worksheet and board.
• Pre-teach or display visual definitions for fossil, variation, inherited, function, origin, vestigial, and analogous; allow students to discuss ideas before writing.
• Pair students strategically and offer a reduced set of examples for students who need a smaller cognitive load.
• Extend confident students by asking them to explain why fossil evidence is incomplete and why scientists use multiple lines of evidence rather than one observation.
• For EAL learners and students with literacy needs, use labelled diagrams, read the worksheet aloud, and accept a combination of brief notes, oral explanation, and annotated images.