Review Core natural and artificial selection
Contrast environmental reproductive effects with human choice and keep both sequences complete.
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Use the stated case, sample and assumptions. Diagrams and numerical records in this pathway are original teaching models; written answers are self-checked.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What is the key distinction between the two Core processes?
What you will learn
- Synthesize the five natural-selection links
- Complete repeated crop or animal breeding steps
Original selection schematic. Population counts and scenarios are supplied teaching models; they are not field observations.
| Stage or record | Meaning |
|---|---|
| Natural process | Environment affects reproductive chances |
| Artificial process | Humans choose parents for a feature |
| Shared biology | Variation, inheritance and reproduction |
| Evidence boundary | Counts and selected traits have defined limits |
Synthesize the five natural-selection links
Natural selection begins with inherited variation within a population, followed by many offspring and a struggle for survival that includes competition for limited resources. In the stated environment, individuals better adapted than others have a greater chance of reproducing. They pass alleles to offspring. Each link explains a different part of the population process.
Artificial selection begins with people choosing individuals with desirable features. People cross those selected parents to produce the next generation, then select offspring showing the desirable features. Repeating this cycle over many generations can improve a stated crop or domesticated-animal feature.
Complete repeated crop or animal breeding steps
Both processes involve inherited variation and reproduction, but the selection pressure differs. In natural selection, environmental conditions affect comparative reproductive outcomes. In artificial selection, people choose the breeding criterion and parents. People can also alter environments, so identify the primary process described instead of relying on whether humans are present.
Use evidence at the correct level. A survival count does not automatically measure reproduction; a phenotype percentage is not automatically an allele frequency; one selected generation is not “many generations.” State the target, denominator, context and limits. Core exam explanations should link all steps without adding unsupported claims about intention or universal superiority.
Sources for this lesson
Pause and explain
Which phrase completes a natural-selection account after differential reproduction?
Worked example
A stated crop line has inherited seed-colour variation and many seeds. People choose parents with red seeds, cross them and select red offspring for three later cycles. Classify the process and outline the repeated sequence.
Show the worked solution
- People set the target and choose which parents reproduce.
- The parents are crossed; offspring are measured and selected as parents for later cycles.
Answer This is artificial selection because people choose the criterion and parents. The repeated cycle is parent choice, crossing, offspring selection, then repeating across generations. The record does not establish improvement in traits beyond seed colour.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A seed-eating bird population has inherited beak variation, many chicks and limited food. One group leaves more offspring and passes its alleles. Identify the process and name the full links.
Give me a hint
Check whether humans set a breeding target.
Compare my reasoning
- The environment affects reproductive chance in the supplied case.
- List variation, many offspring, resource competition, greater reproductive chance, allele transmission.
This is natural selection; the complete sequence includes all five stated links and a conditional environmental context.
Look for these in your work
- Process identified
- All five links included
People choose domesticated tomato parents for firm fruit, cross them and select firm offspring over four cycles. Identify the process and repeated steps.
Give me a hint
Human choice defines the process.
Compare my reasoning
- People select desirable parents.
- Cross, assess offspring, choose suitable future parents and repeat.
This is artificial selection: human parent choice, crossing, offspring selection and repetition across generations.
Look for these in your work
- Process identified
- Sequence complete
A dataset shows that a dark phenotype rises from 30% to 55%, but gives no genotype or breeding records. Evaluate claims that the allele doubled and that humans selected it.
Give me a hint
Separate phenotype proportion from allele copies and ask who/what selected parents.
Compare my reasoning
- The data compare phenotype proportions only.
- No genotype counts or human parent-choice records are supplied.
Neither claim follows. The phenotype share changed in the dataset, but allele frequency and the selection process need additional evidence.
Look for these in your work
- Phenotype boundary
- Selector evidence
Common mistakes
- Calling a human-selected crop example natural selection because it has an environment
- Omitting offspring selection
- Extending a target-trait change to all traits
What can you explain now?
Which phrase completes a natural-selection account after differential reproduction?
Compare with the explanation
The individuals pass alleles to the next generation
Inheritance links parents with population change.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Without your notes, synthesize the five natural-selection links and complete repeated crop or animal breeding steps. Explain the mechanism, use the given population or breeding records and state what the evidence does not establish.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.