aiMOOC

Evolution and inheritance - Unit 1 - Science Year 6

QR-Code

Introduction

How can a rock tell you about a living thing that disappeared long before you were born? You will investigate fossils as evidence, explain a possible route to fossil formation, compare records from different times and judge what the evidence can support.

This Year 6 unit focuses on recognising that living things have changed over time and that fossils tell us about life millions of years ago. Later work can explore inheritance and adaptation in more detail. Here you build the evidence skills needed for those ideas: observing carefully, comparing, explaining and recognising uncertainty.

Look at the coiled shape and its ridges in the photograph. The hammer provides a comparison object; you cannot calculate an exact size unless its dimensions are known. This is a photograph to study, not an instruction to use a hammer. Classroom tasks use images, paper and teacher-approved modelling materials. Collecting at real sites needs permission and appropriate adult organisation; do not approach cliffs, quarries or unstable slopes for this course.

Read fossils as evidence of past life

A fossil is preserved evidence of past life in its geological setting. Fossils include remains of organisms and traces of their activities. A fossil shell can give evidence about the animal's body; a preserved trackway can give evidence that an animal moved across a surface. Not every old-looking rock is evidence of an organism.

Body fossils preserve information from parts of organisms, including bones, shells, wood and leaves. They can include impressions or casts of those parts. Trace fossils record activities such as walking, burrowing or leaving a trail. A footprint is evidence of an action; it is not the animal's foot turned into stone.

The Yellowstone specimen shows fossil fern impressions. Find a larger branching line and several smaller divisions. Compare it with the ammonite photograph: one shows plant material, the other an animal's shell. Fossils are not limited to dinosaurs, and their sizes range from microscopic evidence to very large specimens.

Separate observation from interpretation

An observation describes what you can inspect: “The image shows repeated curved ridges.” An interpretation uses evidence and knowledge: “These ridges belonged to a shell.” A confident interpretation should explain its basis. “The animal was frightened” would require different evidence; a shell photograph alone does not reveal that feeling.

Worked example: a footprint and a stone. In an invented classroom collection, card A shows a repeated three-toed trackway and card B a smooth round pebble. Card A supports an interpretation about movement by an organism. The shape of card B alone does not show that it is a fossil. Ask about its structure, origin and geological context instead of assuming that unusual means fossilised.

Check your understanding: is a fossil leaf impression necessarily a footprint-style trace fossil? No. An impression of a body part records the part itself; evidence of walking records activity. Explain what is preserved rather than relying only on the word “impression”.

Source: National Park Service: fossils, body evidence and traces.

Explain how evidence can be preserved

Most organisms do not become fossils. Remains may decay, be eaten, be broken up or be carried away. Preservation depends on conditions, and later geological processes can also destroy evidence. The fossil record is therefore incomplete rather than a photograph of every organism that ever lived.

One possible route starts when an organism dies and its remains are covered by sediment. Burial can protect some remains from disturbance. Further layers accumulate, sediment may become rock, and minerals can preserve or replace parts of the remains. Weathering and erosion may later expose the fossil. These stages describe a common example, not a process that every fossil follows in exactly the same way.

There are several kinds of preservation. An impression can remain after a body part disappears. Material can fill a cavity and make a cast. Some original material can survive in suitable conditions. Do not explain every fossil as a completely stone-replaced skeleton, or assume that fossilisation itself always takes millions of years. Many fossils provide evidence of life that is millions of years old, which is a different statement about age.

Watch the Natural History Museum animation: identify an event that helps preservation and an event that can expose a fossil later. The animation compresses long periods into a short film; the screen time is not a real geological clock.

Model an impression and identify the limits

With teacher-approved modelling material, press a clean leaf gently into a small flattened piece and lift it away. Sketch the pattern left behind. A paper rubbing or a drawing from the photograph is an alternative. Do not collect protected plants or taste modelling material.

Your model helps show how a surface can retain a shape. It does not demonstrate mineral replacement, the age of a real fossil or every condition involved in burial. Write a label: “A classroom model of an impression, made today.” A good scientific model explains an idea and also states what it leaves out.

Reason it out: if a class finds more fossil shells than evidence of soft worms, can it conclude that no worms lived there? No. Some organisms or parts are more likely to be preserved and discovered than others. Search effort and the rocks available also affect the sample.

Sources: Natural History Museum: fossil formation and British Geological Survey: preservation and the fossil record.

Reconstruct ancient places from several clues

A fossil is more informative when its location and surrounding rock are recorded. A fossil of a marine organism can support an interpretation that a place was once influenced by the sea. Scientists also examine the sediment, other fossils and evidence about whether material was moved. One specimen alone does not justify a complete picture of a landscape.

Sediments can build up in layers. In a simple sequence that has not been overturned or disturbed, a lower sedimentary layer was deposited before a layer above it. This gives a relative order, not an exact numerical age. Real rocks can be folded, faulted or eroded, so scientists must investigate the sequence rather than apply “lower means older” without checking.

Worked example: a fictional rock sequence

The following is an invented classroom dataset. The layers are stated to be undisturbed. The observations are simplified; they are not records from a real field site.

Layer	Evidence recorded	A cautious interpretation
Top: Cedar	Rooted plant remains and soil-like material	A land surface with plants is a possibility to investigate.
Middle: Brook	Leaf fragments and fine layered sediment	Plant material reached a place where fine sediment accumulated.
Bottom: Shore	Several fossils identified as marine shells	A marine setting is supported by these identifications.

Shore was deposited before Brook, and Brook before Cedar. Together, the observations support a change in the conditions represented by the layers. They do not show that a particular shell animal turned into a plant, or that all changes in a place are evolutionary changes.

Try it: a classmate says the dataset proves the exact temperature in Cedar. What should you reply? Feedback: no temperature measurement or evidence for an exact value is supplied. Ask what additional evidence would be needed. An explanation becomes stronger when you state both the useful clue and the limit.

Sources: National Park Service: geological context and British Geological Survey: using fossils.

Explain change over long periods

Fossils from different geological times show that life on Earth has changed. Some forms known from fossils are extinct; other fossils have features that can be compared with living organisms. An extinction means that a species has no living members left, rather than that one individual has died.

A real example: ammonites. These were marine animals, not coiled land snails. The group became extinct at the end of the Cretaceous, about 66 million years ago. Their fossil shells document a kind of animal that inhabited ancient seas and has no living members today. That is concrete evidence that the living world has changed. It does not establish the exact age of the photographed specimen from its appearance alone. British Geological Survey: ammonites.

Evolution concerns changes in inherited characteristics in populations over generations. A seedling growing into a mature plant is an individual's development. It is not, by itself, evidence that a population has evolved. Evolution is not a ladder on which every organism has to become a larger or “better” version of itself.

The fossil record contributes evidence about when different forms lived and about changes in features. Scientists compare many specimens, their ages and other kinds of evidence when investigating relationships. A single similar-looking fossil is not enough to name a direct ancestor of a living animal. Similarity is a starting point for questions, not permission to invent a family tree.

Make a time scale without inventing a history

Use a fictional scale where 1 centimetre represents 10 million years. A 10-centimetre line represents 100 million years. Label one end “100 million years ago” and the other “present”. An invented record dated 40 million years ago belongs 4 centimetres from the present end. These dates are for practising the scale, not claimed ages of the photographed fossils.

One million years is 1,000,000 years. Such numbers help explain why the fossil record can describe worlds very different from today's. A diagram can also be misleading: if its intervals are unequal, a short-looking gap might represent a long time. Always inspect the scale and labels.

Your conclusion: “Life has changed over time” can be supported by comparing evidence from different times. “Every change in a fossil sample proves direct ancestry” cannot. Keep your observation, explanation and uncertainty together.

Sources: Natural History Museum: the fossil record and British Geological Survey: evidence for evolution.

Interactive Tasks

Quiz: Test Your Knowledge

Which example is a trace fossil? (A preserved trackway made by an ancient animal) (!A recently manufactured plastic dinosaur) (!An unlabelled ordinary pebble) (!A photograph of a living pet)

What can a fossil leaf impression record? (The form of a part of a past plant) (!The exact thoughts of the plant) (!A modern photographer turning into a fern) (!Proof that every rock contains a dinosaur)

Which statement about the fossil record is accurate? (It is incomplete because preservation and discovery are uneven) (!It includes every organism that has ever lived) (!It contains only dinosaur skeletons) (!It cannot tell us anything about past life)

In the common example in this course, what can burial by sediment do? (Help protect remains from some disturbance) (!Guarantee that every soft part survives unchanged) (!Give a classroom model an ancient age) (!Make every fossil by exactly the same process)

What does a classroom leaf impression demonstrate directly? (How pressing a surface can leave a pattern) (!That a real fossil formed millions of years ago) (!Every stage of mineral replacement) (!The complete history of a species)

In the stated undisturbed fictional sequence, which layer was deposited first? (Shore at the bottom) (!Cedar at the top) (!All layers necessarily formed at the same moment) (!The label tells us no possible order)

What does an undisturbed layer order provide on its own? (Relative order rather than an exact numerical age) (!The birthday of every fossil animal) (!A guaranteed exact temperature) (!Proof that the sequence has never been studied)

What does extinction of a species mean? (No living members of that species remain) (!One animal has gone to sleep) (!Every species becomes larger) (!A seedling grows into an adult plant)

Which statement correctly distinguishes growth from evolution? (An individual growing is different from inherited population change over generations) (!Every individual evolves into a new species as it gets older) (!Evolution is the same as a single animal learning a trick) (!All fossils must be direct ancestors of living people)

On a scale of one centimetre per ten million years, where is forty million years ago? (Four centimetres from the present end) (!Forty centimetres from the present end) (!Four millimetres from the present end) (!At the present end without any gap)

Memory Game

Body fossil	Preserved information from an organism's body part
Trace fossil	Preserved evidence of an organism's activity
Sediment	Material such as sand or mud that can accumulate in layers
Relative order	A sequence from earlier to later without exact dates
Extinction	The loss of all living members of a species
Fossil record	The known preserved evidence of past life

Drag and Drop

Match the evidence with the appropriate explanation.	Explanation
A preserved shell form	Information about part of an ancient animal
A fossil trail in sediment	Evidence that an organism moved
A leaf pressed into modelling material today	A classroom impression model
A known undisturbed lower layer	Material deposited before the layer above
Different fossil forms from different times	Evidence to compare when investigating changes in life

Crossword Puzzle

FOSSIL	What word names preserved evidence of past life in its geological setting?
SEDIMENT	What material can accumulate as sand or mud and bury remains?
EXTINCTION	What is the loss of all living members of a species called?
TRACE	What type of fossil records an activity such as walking?
MILLION	What number word means one thousand thousand?
EVIDENCE	What must a scientific explanation be supported by?

LearningApps

Your teacher should check these external activities for suitability. Compare their explanations with the museum and geological sources below.

Cloze Text

Open Tasks

Easy

Make an observation card: Sketch a detail from one verified photograph and write three observations. Check that each describes something you can see, not an invented behaviour or age.
Sort the evidence: Create cards for a fossil tooth, a trackway, a fossil leaf and a burrow. Sort evidence of body parts from activity and explain each choice. Check that the leaf is not classified as an activity just because it left an impression.
Create an impression model: Use a drawing or teacher-approved material to represent a leaf impression. Label the model with today's date and one limit. Check that you do not call it an ancient fossil.
Build a scale: Draw the course's ten-centimetre fictional time line and mark forty million years ago. Check the present end and explain the conversion used.

Standard

Sequence a possible preservation story: Draw a four-panel common burial-and-preservation example. Include the word “possible” and explain why a real organism might not be preserved. Check against the museum animation.
Interpret the fictional layers: Explain which of Shore, Brook and Cedar was deposited first and what the marine shells suggest. Check that you use the stated undisturbed condition and avoid inventing an exact date.
Improve a museum label: Rewrite “This fossil proves everything about the animal” into a useful label with an observation, a supported interpretation and a limit. Check that another learner can tell the three apart.
Explain a difference: Make a short audio or written explanation distinguishing one animal dying, a species becoming extinct and an individual growing. Use original examples and check that the meanings are different.

Advanced

Investigate a sampling problem: In an invented collection, most specimens are shells. Suggest two explanations besides “only shelled animals existed”. Explain how preservation or searching could affect the result and what additional evidence you would seek.
Challenge a misleading family tree: A poster joins one fossil shell directly to a living animal because both are curved. Explain why this is not enough to establish ancestry. Propose more evidence rather than drawing a confident new lineage.
Design a small exhibition: Create three original labels about past life, preservation and change. Use the verified photos with credit, or your own clearly labelled drawings. Check that each label states what its evidence can and cannot show.
Ask an expert question: Prepare questions for a museum's public information service, a teacher or a virtual collection about a specimen's context and interpretation. Do not contact strangers independently or collect at a site. Explain how two different answers might change your interpretation.

Learning Check

The ammonite evidence: Explain how ammonite fossils support the claim that life has changed over millions of years. Feedback: the fossils document marine animals from the past, and the group became extinct about 66 million years ago. A specimen photograph alone does not provide its exact age or prove a direct ancestor.
The trackway label: A label says footprints are the animal's fossilised feet. Correct it and explain what a trackway can show. Feedback: tracks preserve evidence of activity and can record movement; they are not the feet themselves.
The missing worm: A collection contains shell fossils but no worm fossils. Can you conclude that worms were absent? Feedback: no; preservation, exposure and the search can produce an uneven sample. More evidence is needed.
The upside-down sequence: Someone applies the fictional layer rule to a real folded rock face without investigating it. What is missing? Feedback: the course rule was conditional on an undisturbed sequence; the real structure and history must be checked.
The growing seedling: Explain why one seedling growing taller does not on its own demonstrate evolution. Feedback: individual development is different from inherited change in populations over generations.
The model claim: A pupil says a fresh classroom impression proves the exact age of the ammonite photograph. Explain two problems. Feedback: the model represents an aspect of shape preservation, not geological time; a photograph and an unknown comparison object do not supply an exact fossil age.

Learning evidence

Your portfolio should include careful fossil observations, a body-versus-activity comparison, a labelled impression model with limitations, a correctly ordered fictional rock sequence and a time scale with its units. Your explanations should connect a claim to evidence and identify information that is still missing.

You should be able to explain that the fossil record provides evidence about past life and changes over time, while recognising that it is incomplete. Use “relative order” accurately and distinguish evolution across generations from an individual's growth. Do not infer a direct ancestor from one superficial similarity.

Show one improved explanation: save an early statement and the version you changed after checking a source. Explain the specific reason for the change. You can provide equivalent spoken, drawn or written evidence; a collecting trip is not required.

OER and Wikipedia

Reference sources, checked 10 November 2026: Department for Education: science programmes of study; Natural History Museum: what is a fossil?; Natural History Museum: fossil formation; British Geological Survey: fossils; US National Park Service: fossil evidence and geological context. Museum and survey pages are reference material; not all their media are openly licensed.

Media credits: Ammonite-Fossil.jpg, FluffyBiscuit, CC BY 3.0; YELL 11626 Fossil fern leaf (30485564712).jpg, Yellowstone National Park, photograph by Megan Norr, public domain. The original photographs are embedded without alteration. How do dinosaur fossils form?, Natural History Museum, embedded from its official YouTube channel; not relicensed as OER. A photographed geological hammer is a comparison object, not a pupil equipment recommendation.

The article below offers further reading; museum and geological sources should guide the lesson's scientific explanations.