Grades 6–8 · DNA & methods
Reading the Code: how a genetic test finds a hidden species
One soil sample becomes a hands-on introduction to how genetic identification actually works.
Students choose five soil-dwelling target species, run a whole-class composite soil sampling protocol, and learn step by step how DNA extraction, matching, and reporting work as they wait for and then read their class Field Journal.
Grade band
Grades 6–8
Time required
4 class periods
Class size
20–32 students, one kit
Sample type
Soil, one vial
Standards and outcomes
- MS-LS3-1 — Develop and use a model to describe why structural changes to genes (mutations) may or may not affect proteins
- MS-LS4-2 — Apply scientific ideas to construct an explanation for the anatomical similarities among modern organisms and fossils to infer evolutionary relationships
- MS-LS2-2 — Construct an explanation that predicts patterns of interactions among organisms across multiple ecosystems
- Science & Engineering Practices — developing and using models, planning investigations, analyzing data, constructing explanations
How one kit serves a whole class
The $200 Classroom Starter Kit holds one soil collection vial, targets up to five species, and returns results in 7–10 days for the class Field Journal. Because there's only one vial, the class runs a composite batching protocol: several crews each collect a small soil core from a different spot in the study area, and all cores are combined into a single sample so every student has a hand in the sample that gets tested.
Choose one
Research tracks
Track A — Meet the Decomposers
Genetic identification of soil life
Driving question. What decomposer organisms can genetic testing find in our schoolyard soil that we can't easily see?
Species to pick. Up to five soil organisms commonly present in most regions: an earthworm species, a soil-dwelling beetle, a fungal decomposer group, a soil mite or nematode category, and a soil bacterium group linked to decomposition.
What students take away. Students connect what a genetic test detects to what's actually happening beneath the surface of the soil.
Track B — Same Species, Different Clues
How genetic evidence compares to physical evidence
Driving question. Can a genetic test confirm a species we already suspect is here from physical signs like burrows or shells?
Species to pick. Species chosen because they leave visible physical evidence (burrows, shells, tracks, or fecal pellets) alongside genetic evidence: a burrowing invertebrate, a snail or slug species, and two or three additional soil organisms with known physical signs.
What students take away. Students compare physical-evidence hypotheses against genetic detection results as two independent lines of evidence.
Track C — The Invisible Majority
Microbial diversity and what genetic tests reveal
Driving question. What tiny soil organisms exist that we would never find by digging with a trowel?
Species to pick. A set of five organisms weighted toward microscopic or hard-to-see groups: a fungal group, a bacterial group, a nematode category, a soil mite, and one slightly larger organism as a comparison point.
What students take away. Students use the results to argue that most soil biodiversity is invisible to the naked eye and only detectable genetically.
The lesson sequence
Step by step, with teacher notes
- 01
Choosing our five and predicting the code
45 minutesStudents research candidate soil organisms, propose a five-species list with reasoning, and vote as a class. Each student writes a prediction and a short explanation of how a genetic test could possibly find something buried and invisible in soil.
Teacher notes
- Open with: "How could a machine tell us something is in this soil without anyone digging it up?" — let students guess before explaining.
- Provide a simple regional soil-organism reference list so proposals aren't starting from nothing.
- Require each pitch to include a reason the organism might be present (moisture, plant cover, disturbance history).
- Run the vote and lock in the final five before moving to sampling.
- Introduce the word 'DNA' as 'the instruction code inside every living cell' before going further.
Materials
- Regional soil-organism reference list
- Whiteboard or shared doc for the vote
- Prediction log sheet
Student prompts
- What evidence (soil type, plant cover, moisture) suggests this organism might be present?
- How do you think a lab could detect something too small to see?
- What would it mean if we don't detect an organism we expected to find?
- 02
Collecting the composite soil sample
50 minutesCrews collect small soil cores from several spots in the study area and combine them into one composite sample, so the single vial represents the whole area rather than one shovel-full.
Teacher notes
- Say before digging: "Gloves on first — clean tools, clean hands, no touching the inside of the vial."
- Mark three or four distinct collection spots ahead of time (near roots, open ground, under mulch, compacted path) so the composite reflects real variety.
- Rotate roles (digging, measuring depth, recording, sealing) so every student takes part in producing the one sample.
- Have students note visible organisms (worms, insects, roots) as they dig, separate from the genetic prediction, to compare later.
- Keep a backup collection plan in case of frozen or waterlogged ground.
Materials
- 1 classroom eDNA soil collection vial and prepaid mailer
- Nitrile gloves (one pair per student minimum)
- Small trowels or soil corers
- 3–4 sterile sub-sample bags
- Field data sheet on clipboard
Student prompts
- Digging crew — collects small soil cores from three or four distinct spots.
- Recording crew — logs depth, moisture, and any organisms seen while digging.
- Sealing crew — combines the cores, seals the vial, and preps the return mailer.
- 03
How the lab reads the code
45 minutes, during the 7–10 day turnaroundStudents learn, step by step, how a lab turns a scoop of soil into a list of species: breaking cells open, copying a specific stretch of DNA, and comparing that code against a library of known species.
Teacher notes
- Draw the pipeline as a simple flow chart: soil sample → break open cells → copy a target DNA section → compare to reference library → match or no match.
- Use an analogy: "It's like scanning a barcode at a store — the scanner just needs to read one short label to know exactly what product it's looking at."
- Explain that only DNA that is copied enough times becomes detectable, which is why very rare organisms might be missed.
- Introduce 'reference library' and explain that a species can only be matched if its code is already known and catalogued.
- Ask students to revisit their Phase 1 predictions and note anything they'd like to change now that they understand the process better.
Materials
- Genetic testing pipeline diagram
- Vocabulary handout (DNA, extraction, amplification, reference library, match)
- Barcode scanner analogy handout or image
Student prompts
- Why does a species need to already be in a reference library to be identified?
- What might cause a real organism to be missed by the test?
- How is matching DNA similar to and different from scanning a barcode?
- 04
Reading our Field Journal results
40 minutesThe class reveals the Field Journal together, compares genetic detections to predictions and to any organisms physically observed while digging, and writes a short explanation of what the genetic evidence shows.
Teacher notes
- Project the Field Journal and read results aloud as a shared class moment.
- Have students check off predictions as matched or unmatched before any discussion.
- Ask: "Did the genetic results agree with what we physically saw while digging? What does it mean if they don't?"
- Reinforce that relative signal reflects the strength of the genetic detection, not a body count of organisms.
- Close by asking each student to write one new question this raised about soil life.
Materials
- Class Field Journal report (projected)
- Prediction log sheets from Phase 1
- Simple claim-writing frame
Student prompts
- Which predictions were supported by the Field Journal, and which were not?
- Did the genetic evidence match what you saw while digging? Explain any differences.
- Write one sentence claiming what this soil sample tells us about hidden biodiversity, with one piece of evidence.
Student handout
For every student
Thinking prompts
- Write your prediction for each of the five target species before the sample is sent to the lab.
- Explain the reasoning (soil type, moisture, plant cover) behind each prediction.
- Describe, step by step, how the lab turns a soil sample into a species match.
- Explain why a species must already be in a reference library to be identified.
- List any organisms you physically observed while digging, separate from your genetic prediction.
- After the reveal, mark which predictions matched the Field Journal results.
- Write one question you still have about how genetic testing works.
Data sheet
- Date and time of collection:
- Site description and number of collection spots:
- Soil moisture and approximate depth of each core:
- Weather conditions on collection day:
- Organisms physically observed while digging:
- Target species list with pre-reveal predictions:
- Any visible plant cover or disturbance near the site:
Discussion questions
- Why can a genetic test find organisms that digging by hand would never reveal?
- What does it mean if a species is physically observed but not genetically detected, or the reverse?
- Why does an organism need to already be catalogued in a reference library to be matched?
- What did this project teach you about how much life might be invisible in ordinary soil?
Field checklist
- Nitrile gloves worn before touching any sampling equipment.
- Soil cores collected from at least three distinct spots.
- Depth, moisture, and visible organisms recorded at each spot.
- Weather conditions logged on the data sheet.
- Sample combined, sealed, and labeled without touching the inside of the vial.
- Predictions recorded in writing before results were revealed.
Analysis
CER: What does the genetic evidence tell us about our soil?
- 1.Claim — write one sentence stating what the genetic results reveal about biodiversity in our soil.
- 2.Evidence — list specific detections and relative signal values from the Field Journal.
- 3.Reasoning — explain how the lab's process (extraction, matching, reference library) makes this claim reliable.
- 4.Counter-evidence — note any organism observed by digging but not detected genetically, and suggest why.
Assessment
20-point rubric
Species selection and prediction reasoning
6 ptsEach of the five species predictions is supported by a clear reason tied to soil conditions.
Field procedure and data logging
5 ptsComposite soil sampling steps were followed correctly and site conditions fully recorded.
Understanding the genetic process
4 ptsStudent can explain, in their own words, the steps from soil sample to species match.
CER conclusion
5 ptsThe written claim is clearly supported by specific Field Journal evidence and sound reasoning.
Go further
Extensions
- Compare soil composite results from two different areas of the schoolyard using a second kit.
- Have students design their own simple diagram explaining DNA matching to a younger grade.
- Research one detected organism's role in decomposition and present it to the class.
- Invite a local science teacher or lab technician to explain how genetic testing is used in their field.
For the teacher
Answer key and misconceptions
- Expected: most classes will detect at least a couple of their five target species; zero detections should prompt discussion of soil conditions, not be treated as a failed test.
- Common misconception: 'if we dug it up, the test should find it too.' Correct framing: genetic tests and physical observation are two different lines of evidence that can disagree for good reasons.
- Common misconception: 'stronger signal means more organisms.' Correct framing: relative signal reflects how much DNA was present in the sample, not an exact count of individuals.
- Expected: students should be able to explain that a species can only be matched if it's already catalogued in a reference library, which is why some real organisms may go unidentified.