Select offspring that show the desired feature
The new generation must be assessed against the breeding criterion before the next cross.
Section B17.2 · Selection
Exam scope and assessment notes
Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-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. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.
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
Why record offspring that are not selected?
What you will learn
- Compare offspring with an explicit feature criterion
- Use complete denominators when reporting selection
Original selection schematic. Population counts and scenarios are supplied teaching models; they are not field observations.
| Stage or record | Meaning |
|---|---|
| Offspring assessed | 50 |
| Meet threshold | 18 |
| Selected proportion | 18/50 = 36% |
| Record | All assessed, including those not selected |
Compare offspring with an explicit feature criterion
After a cross, selective breeding requires a choice among offspring. Define the desired feature and a consistent assessment method. For example, if a crop goal is seed mass above a stated threshold, weigh every sampled plant’s seeds using the same units and protocol before deciding which are suitable parents.
Selection is a decision about which individuals will reproduce in the next cycle. It is not a claim that all offspring without the feature disappear from the population or that they are biologically inferior. Keep records of all offspring assessed, including those not selected, so the denominator and selection proportion remain clear.
Use complete denominators when reporting selection
Offspring with the desired appearance may differ genetically, and the same phenotype can arise through different combinations in some inheritance patterns. Do not infer a guaranteed breeding result from a visible trait. The selected offspring become parents only if they are crossed or mated in the next cycle.
This step completes the Core three-part sequence when linked to human choice and crossing: people choose desirable parents, cross them to produce offspring and select offspring showing the desired feature. Repeating the process can alter how common the feature is, but the outcome depends on inheritance and reproductive results.
Sources for this lesson
Pause and explain
What does selecting offspring mean in the breeding sequence?
Worked example
A breeder measures 50 offspring; 18 exceed the agreed seed-mass threshold and are selected as future parents. Calculate the selected proportion.
Show the worked solution
- Use all 50 assessed offspring as the denominator.
- 18/50 = 0.36, so 36% meet the threshold and are selected.
Answer 36% of the assessed offspring were selected. The other 32 are still part of the denominator; the record does not state what happens to them.
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 breeder evaluates 64 crop offspring and selects 16 for the next cross. What percentage were selected?
Give me a hint
Divide selected offspring by all 64 assessed.
Compare my reasoning
- 16/64 = 0.25.
- 0.25 × 100 = 25%.
25% were selected; all 64 belong in the denominator.
Look for these in your work
- Correct full denominator
- Percentage is 25%
Of 30 measured lambs, 11 meet a stated wool criterion. How many were not selected and what is the selected percentage?
Give me a hint
Subtract 11 from 30, then calculate 11/30.
Compare my reasoning
- 30 − 11 = 19 not selected.
- 11/30 × 100 ≈ 36.7%.
19 did not meet the criterion; approximately 36.7% of all assessed lambs were selected.
Look for these in your work
- Count remaining offspring
- Percentage correctly rounded
A farmer changes the target from seed mass to drought survival after seeing offspring results. Explain why earlier selection records should keep the original criterion visible.
Give me a hint
Selection depends on the stated desirable feature.
Compare my reasoning
- The two criteria are not interchangeable.
- Keeping the old measurement allows the farmer to compare outcomes and identify trade-offs.
The record should show which criterion was used at each cycle; changing the goal can alter which offspring are selected and limits comparisons between generations.
Look for these in your work
- Criteria tracked by generation
- Trade-off and comparability
Common mistakes
- Removing unselected offspring from the denominator
- Calling the selected proportion the inheritance probability
- Saying all selected offspring will pass on the feature
What can you explain now?
What does selecting offspring mean in the breeding sequence?
Compare with the explanation
Choosing suitable offspring as parents for a later cross
This is the third step after parents are crossed.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Without your notes, compare offspring with an explicit feature criterion and use complete denominators when reporting selection. 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.