Apply repeated selection to domesticated animals
Animal breeding repeats human choice across generations while monitoring welfare and trade-offs.
Section 18.3 · Selection
Core and Extended; Biology 0610, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked
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
Which evidence shows selection was repeated across generations?
What you will learn
- Describe artificial selection in domesticated animals
- Evaluate more than one inherited feature in a breeding decision
Original selection schematic. Population counts and scenarios are supplied teaching models; they are not field observations.
| Stage or record | Meaning |
|---|---|
| Generation cycles | Three recorded crosses |
| Selection goal | Wool length at a stated age |
| Offspring step | Measured and selected each cycle |
| Other measures | Health, fertility and care conditions |
Describe artificial selection in domesticated animals
People can apply artificial selection to domesticated animals by choosing parents with desired features, crossing them and selecting suitable offspring. A supplied example may use wool length, egg number, milk yield or another stated characteristic. Keep the question’s feature and breeding goal explicit rather than assuming a breed has one universal quality.
The selected animals produce the next generation, whose offspring are assessed against the same criterion. The breeder repeats the process over many generations. A single pair of parents or one litter is not a full multi-generation sequence; show at least repeated parent choice and offspring selection.
Evaluate more than one inherited feature in a breeding decision
Choosing one feature can coincide with changes in other features. Monitor health, fertility, behaviour and the intended production outcome as separate measures. A phenotype may also be influenced by nutrition, age and housing. Comparable records help distinguish a breeding trend from a change in care or environment.
The curriculum asks how artificial selection is carried out to improve domesticated animals and how to apply it to a context. It does not imply that any single production measure proves overall improvement. Avoid moral or welfare conclusions without evidence; state what is measured, what is selected and what remains to be evaluated.
Pause and explain
Why measure animal offspring at comparable ages and conditions?
Worked example
A domesticated flock is assessed over three breeding cycles for wool length. The selected parents each generation are crossed, and offspring are measured at the same age. Which details make this a repeated selection sequence?
Show the worked solution
- Look for repeated human parent choice and crosses.
- Confirm offspring are measured and selected as parents for the next cycle.
Answer The repeated human choices, crosses and offspring selections across three cycles form a multi-generation artificial-selection sequence. Measuring at the same age improves comparability.
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.
In three flock cycles, people choose longer-wool parents, cross them and select offspring at the same age. Name the repeated steps and one additional measure to monitor.
Give me a hint
List selection, crossing and offspring selection.
Compare my reasoning
- Choose parents using the stated wool criterion.
- Cross them, assess offspring, select suitable next parents; monitor health or fertility separately.
The cycle repeats parent selection, crossing and offspring selection; health or fertility should be recorded as a separate outcome.
Look for these in your work
- Sequence complete
- Additional measure distinguished
Later offspring average 8 cm wool versus 7 cm in the earlier group, but they were measured at older ages. Give a cautious interpretation.
Give me a hint
The groups are not comparable in age.
Compare my reasoning
- The numerical difference is 1 cm.
- Age could explain some or all of the difference.
The later recorded average is 1 cm greater, but different ages prevent a clear breeding attribution. Compare same-age animals under comparable conditions.
Look for these in your work
- Difference correct
- Age confound named
A breeding group is selected only for egg number; the next generation has more eggs but lower hatch success in the supplied records. How should the outcome be reported?
Give me a hint
Keep both target and second outcome visible.
Compare my reasoning
- Egg number increased under the stated measurement.
- Hatch success fell and may be a trade-off.
Report both egg number and hatch success; improvement depends on the stated breeding goal and relevant welfare/production criteria, not one measure alone.
Look for these in your work
- Both outcomes kept
- Trade-off evaluated
Common mistakes
- Counting one generation as repeated selection
- Assuming a production trait proves welfare or health
- Comparing animals at different ages without qualification
What can you explain now?
Why measure animal offspring at comparable ages and conditions?
Compare with the explanation
Age and care can affect the observed phenotype
Comparable conditions make generations easier to interpret.
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Make it stick
Without your notes, describe artificial selection in domesticated animals and evaluate more than one inherited feature in a breeding decision. 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.