Australian Curriculum v9 / ACiQ Year 10 Science - Unit 1 - Evolution by natural selection and supporting evidence
Evolution by natural selection and supporting evidence
Explain natural selection through heritable variation, differential survival and reproduction, and population change across generations.
Updated 2026-07-26 - 13 min read
Evolution by natural selection and supporting evidence is taught here as a connected set of decisions, not a list of facts. Work through the prerequisite recall, explicit models, carefully faded examples, misconception repairs and transfer task before using the target in Check, Practice, Review or Rapid Revision.
This note is designed to work with the guided lessons, curated practice, flashcards, Tutor context, Review and Rapid Revision for the same canonical target. The same three evidence checks are used throughout, so feedback can route a learner back to the precise idea that needs repair.
Natural-selection mechanism
Heritable variants that improve reproductive success become more common across generations. Use the model to make a prediction, connect it to observable evidence and state any relevant condition or limitation.
A dependable reasoning routine
- Define the system or phenomenon and identify the change being explained.
- Trace the mechanism for natural-selection mechanism in causal order rather than listing disconnected terms.
- Link each claim to an observation, measurement, model or accepted scientific relationship.
- State the boundary of the conclusion: what was tested, what remains uncertain and what evidence would strengthen it.
Repair: Selection changes allele frequencies in populations; it does not purposefully redesign individuals.
The repair matters because the shortcut may appear to work in one familiar example while failing when the system boundary, causal mechanism, variable or evidence limit changes. Use the routine above to make the reasoning visible enough for another learner to verify.
Example 1.1
Which statement correctly explains natural-selection mechanism?
Step 1 - identify the governing idea: Heritable variants that improve reproductive success become more common across generations.
Step 2 - apply it to this evidence: It states the governing scientific relationship and its conditions.
Result: Heritable variants that improve reproductive success become more common across generations.
The evidence-to-mechanism link is: It states the governing scientific relationship and its conditions. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.
Why the alternatives fail:
- Individuals evolve useful traits because they need them. — It conflicts with the stated mechanism or evidence: It states the governing scientific relationship and its conditions.
- A single observation proves the claim in every context. — It changes the system boundary or claims a cause that the supplied observations do not establish.
- The scientific terms can be rearranged without changing the mechanism. — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.
Example 1.2
A student says: "Individuals evolve useful traits because they need them." What is the best correction?
Step 1 - identify the governing idea: Heritable variants that improve reproductive success become more common across generations.
Step 2 - apply it to this evidence: The correction identifies the precise conceptual error and replaces it with a testable explanation.
Result: Selection changes allele frequencies in populations; it does not purposefully redesign individuals.
The evidence-to-mechanism link is: The correction identifies the precise conceptual error and replaces it with a testable explanation. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.
Why the alternatives fail:
- Repeat the claim with more technical vocabulary. — It conflicts with the stated mechanism or evidence: The correction identifies the precise conceptual error and replaces it with a testable explanation.
- Ignore conflicting evidence. — It changes the system boundary or claims a cause that the supplied observations do not establish.
- Treat the model as a literal picture with no limits. — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.
Example 1.3
After antibiotics, resistant bacteria form a larger fraction. Why?
Step 1 - identify the governing idea: Heritable variants that improve reproductive success become more common across generations.
Step 2 - apply it to this evidence: Differential survival changes the population.
Result: Susceptible bacteria die while resistant variants reproduce
The evidence-to-mechanism link is: Differential survival changes the population. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.
Why the alternatives fail:
- A conclusion that ignores the named mechanism — It conflicts with the stated mechanism or evidence: Differential survival changes the population.
- An answer based on one familiar keyword — It changes the system boundary or claims a cause that the supplied observations do not establish.
- A claim that exceeds the available evidence — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.
Variation, fitness and environment
Fitness is reproductive success in a particular environment, so the same trait can be advantageous in one context and costly in another. Use the model to make a prediction, connect it to observable evidence and state any relevant condition or limitation.
A dependable reasoning routine
- Define the system or phenomenon and identify the change being explained.
- Trace the mechanism for variation, fitness and environment in causal order rather than listing disconnected terms.
- Link each claim to an observation, measurement, model or accepted scientific relationship.
- State the boundary of the conclusion: what was tested, what remains uncertain and what evidence would strengthen it.
Repair: Fitness depends on descendants and environmental conditions.
The repair matters because the shortcut may appear to work in one familiar example while failing when the system boundary, causal mechanism, variable or evidence limit changes. Use the routine above to make the reasoning visible enough for another learner to verify.
Example 2.1
Which statement correctly explains variation, fitness and environment?
Step 1 - identify the governing idea: Fitness is reproductive success in a particular environment, so the same trait can be advantageous in one context and costly in another.
Step 2 - apply it to this evidence: It states the governing scientific relationship and its conditions.
Result: Fitness is reproductive success in a particular environment, so the same trait can be advantageous in one context and costly in another.
The evidence-to-mechanism link is: It states the governing scientific relationship and its conditions. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.
Why the alternatives fail:
- The strongest organism is always the fittest. — It conflicts with the stated mechanism or evidence: It states the governing scientific relationship and its conditions.
- A single observation proves the claim in every context. — It changes the system boundary or claims a cause that the supplied observations do not establish.
- The scientific terms can be rearranged without changing the mechanism. — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.
Example 2.2
A student says: "The strongest organism is always the fittest." What is the best correction?
Step 1 - identify the governing idea: Fitness is reproductive success in a particular environment, so the same trait can be advantageous in one context and costly in another.
Step 2 - apply it to this evidence: The correction identifies the precise conceptual error and replaces it with a testable explanation.
Result: Fitness depends on descendants and environmental conditions.
The evidence-to-mechanism link is: The correction identifies the precise conceptual error and replaces it with a testable explanation. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.
Why the alternatives fail:
- Repeat the claim with more technical vocabulary. — It conflicts with the stated mechanism or evidence: The correction identifies the precise conceptual error and replaces it with a testable explanation.
- Ignore conflicting evidence. — It changes the system boundary or claims a cause that the supplied observations do not establish.
- Treat the model as a literal picture with no limits. — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.
Example 2.3
A pale moth survives better on pale bark but worse on dark bark. What does this show?
Step 1 - identify the governing idea: Fitness is reproductive success in a particular environment, so the same trait can be advantageous in one context and costly in another.
Step 2 - apply it to this evidence: Camouflage changes predation risk differently by background.
Result: Advantage is environment-dependent
The evidence-to-mechanism link is: Camouflage changes predation risk differently by background. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.
Why the alternatives fail:
- A conclusion that ignores the named mechanism — It conflicts with the stated mechanism or evidence: Camouflage changes predation risk differently by background.
- An answer based on one familiar keyword — It changes the system boundary or claims a cause that the supplied observations do not establish.
- A claim that exceeds the available evidence — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.
Evidence for evolution
Fossils, homologous structures, biogeography and DNA similarities provide independent, converging evidence for common ancestry. Use the model to make a prediction, connect it to observable evidence and state any relevant condition or limitation.
A dependable reasoning routine
- Define the system or phenomenon and identify the change being explained.
- Trace the mechanism for evidence for evolution in causal order rather than listing disconnected terms.
- Link each claim to an observation, measurement, model or accepted scientific relationship.
- State the boundary of the conclusion: what was tested, what remains uncertain and what evidence would strengthen it.
Repair: Evidence is evaluated by pattern, mechanism, dating and agreement across sources.
The repair matters because the shortcut may appear to work in one familiar example while failing when the system boundary, causal mechanism, variable or evidence limit changes. Use the routine above to make the reasoning visible enough for another learner to verify.
Example 3.1
Which statement correctly explains evidence for evolution?
Step 1 - identify the governing idea: Fossils, homologous structures, biogeography and DNA similarities provide independent, converging evidence for common ancestry.
Step 2 - apply it to this evidence: It states the governing scientific relationship and its conditions.
Result: Fossils, homologous structures, biogeography and DNA similarities provide independent, converging evidence for common ancestry.
The evidence-to-mechanism link is: It states the governing scientific relationship and its conditions. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.
Why the alternatives fail:
- One similar body part proves direct ancestry. — It conflicts with the stated mechanism or evidence: It states the governing scientific relationship and its conditions.
- A single observation proves the claim in every context. — It changes the system boundary or claims a cause that the supplied observations do not establish.
- The scientific terms can be rearranged without changing the mechanism. — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.
Example 3.2
A student says: "One similar body part proves direct ancestry." What is the best correction?
Step 1 - identify the governing idea: Fossils, homologous structures, biogeography and DNA similarities provide independent, converging evidence for common ancestry.
Step 2 - apply it to this evidence: The correction identifies the precise conceptual error and replaces it with a testable explanation.
Result: Evidence is evaluated by pattern, mechanism, dating and agreement across sources.
The evidence-to-mechanism link is: The correction identifies the precise conceptual error and replaces it with a testable explanation. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.
Why the alternatives fail:
- Repeat the claim with more technical vocabulary. — It conflicts with the stated mechanism or evidence: The correction identifies the precise conceptual error and replaces it with a testable explanation.
- Ignore conflicting evidence. — It changes the system boundary or claims a cause that the supplied observations do not establish.
- Treat the model as a literal picture with no limits. — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.
Example 3.3
Why are shared DNA sequences powerful evidence?
Step 1 - identify the governing idea: Fossils, homologous structures, biogeography and DNA similarities provide independent, converging evidence for common ancestry.
Step 2 - apply it to this evidence: Molecular data provide a separate line of evidence.
Result: Inherited molecular similarities can quantify relatedness independently of appearance
The evidence-to-mechanism link is: Molecular data provide a separate line of evidence. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.
Why the alternatives fail:
- A conclusion that ignores the named mechanism — It conflicts with the stated mechanism or evidence: Molecular data provide a separate line of evidence.
- An answer based on one familiar keyword — It changes the system boundary or claims a cause that the supplied observations do not establish.
- A claim that exceeds the available evidence — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.
Retrieval check
Try these without looking back at the examples.
- A student says: "Individuals evolve useful traits because they need them." What is the best correction?
- A student says: "The strongest organism is always the fittest." What is the best correction?
- A student says: "One similar body part proves direct ancestry." What is the best correction?
Answers
- Selection changes allele frequencies in populations; it does not purposefully redesign individuals. — The correction identifies the precise conceptual error and replaces it with a testable explanation.
- Fitness depends on descendants and environmental conditions. — The correction identifies the precise conceptual error and replaces it with a testable explanation.
- Evidence is evaluated by pattern, mechanism, dating and agreement across sources. — The correction identifies the precise conceptual error and replaces it with a testable explanation.
Transfer task
Find an unfamiliar example from school, daily life, a credible news source or another subject. Explain which of the three evidence checks applies. Complete the task, then audit your own response: identify the evidence used, the relationship applied, one plausible misconception and the final reasonableness check. If a peer could not reproduce your reasoning, add the missing step.