Choose parents with desirable features
In selective breeding, humans deliberately choose which individuals become parents.
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
Who chooses the desired parents in selective breeding?
What you will learn
- Identify human choice of breeding parents
- Make selection criteria measurable and context-specific
Original selection schematic. Population counts and scenarios are supplied teaching models; they are not field observations.
| Stage or record | Meaning |
|---|---|
| Breeding goal | Larger measured seed mass |
| Selected parents | 8 of 40 plants |
| Human role | Chooses parents for the stated feature |
| Next steps | Cross parents; assess and choose offspring |
Identify human choice of breeding parents
Selective breeding begins when humans select individuals with desirable features as parents. A crop breeder might choose plants with a stated seed characteristic; an animal breeder might choose domesticated animals with a wanted wool feature. The human goal is the selection criterion. It should be stated precisely, because “best” can hide several different traits.
Selection begins with existing variation among the available individuals. A measured seed mass, disease score or fibre length can help define the feature, but appearance alone does not guarantee a particular genotype. The case should state whether the feature is inherited or provide evidence linking parents and offspring.
Make selection criteria measurable and context-specific
Choosing parents is only the first step. The chosen individuals must be crossed to produce the next generation, then offspring are assessed against the desired feature. One parent choice does not guarantee every offspring will show it. The breeder makes repeated decisions across generations to increase the frequency of the target trait.
Selective breeding differs from an individual learning or changing a feature. People choose which organisms reproduce; the offspring inherit combinations from their parents. A useful improvement can involve trade-offs, such as prioritising one crop characteristic while monitoring others. Be clear about the chosen trait and do not claim a species has been improved in every respect.
Sources for this lesson
Pause and explain
What is missing after people choose parent plants?
Worked example
A grower chooses 8 bean plants with the highest measured seed mass from a field of 40. Identify the human selection step and two facts still needed for a full selective-breeding sequence.
Show the worked solution
- The grower selects parent plants using a stated seed-mass criterion.
- A cross must produce offspring, and those offspring must later be assessed and selected.
Answer This is selection of individuals with a desirable measured feature by humans. A cross and selection among the next generation are still required; the count alone does not show seed mass is inherited.
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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 breeder records fibre lengths of 25 domesticated sheep and selects the six longest-fibre animals as parents. State the selection criterion and one evidence limit.
Give me a hint
Name the recorded feature and avoid assuming inheritance.
Compare my reasoning
- The criterion is measured fibre length.
- The record does not by itself show how offspring fibre length will vary.
Humans selected the six parents for longer measured fibre. Inheritance and next-generation outcomes still need evidence.
Look for these in your work
- Criterion stated
- Inheritance limit
A crop team chooses parents for larger seeds, but the phrase “largest is best” is the only record. Improve the criterion and explain why the team should also monitor another trait.
Give me a hint
A useful criterion is measurable and linked to the breeding goal.
Compare my reasoning
- Record seed mass or a defined seed-size measurement using the same method.
- Monitor germination or seed number to detect a possible trade-off.
Specify a comparable seed-size measurement and retain another relevant crop outcome; selection for one feature does not prove overall improvement.
Look for these in your work
- Measurable feature
- Trade-off monitoring
A breeder chooses parent fish with brighter colour for a display strain. What ethical or practical information would be needed before claiming this is a useful improvement?
Give me a hint
Consider health, reproduction and the stated goal as separate evidence.
Compare my reasoning
- A colour goal alone does not describe health or breeding outcome.
- Check inherited offspring colour, welfare and other performance measures.
The breeders can state the chosen colour criterion, but a useful improvement claim needs offspring inheritance and relevant health, welfare and performance evidence.
Look for these in your work
- Goal and outcome separated
- No unsupported improvement claim
Common mistakes
- Calling selection complete before offspring are produced
- Assuming phenotype guarantees genotype
- Using “best” without a defined feature
What can you explain now?
What is missing after people choose parent plants?
Compare with the explanation
Crossing them and selecting offspring in a later generation
Both steps follow parent choice in the syllabus sequence.
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Make it stick
Without your notes, identify human choice of breeding parents and make selection criteria measurable and context-specific. 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.