In wild barley and wheat, the seed head shatters to aid seed dispersal. During domestication, farmers selected for non-shattering varieties to

Question

BlackTom AI · Accepted Answer

Non-shattering mutations cause seeds to remain attached to the spike (rachis), enabling humans to harvest grain rather than losing it to natural dispersal.

1. Relevant knowledge points and concepts
- Wild cereals (barley, wheat) have a “shattering” habit: mature seed heads break apart so seeds disperse naturally (an evolutionary advantage for the plant).
- Domestication is artificial selection by humans: traits that aid harvesting and use are favored.
- A “non-shattering” phenotype results from mutations that make the rachis (the seed-head axis) tough rather than brittle, so seeds stay on the plant.

2. Step-by-step reasoning
- In the wild, shattering causes mature grains to fall off before or during human attempts to harvest, reducing recoverable yield per plant.
- Early farmers who gathered from plants with fewer lost seeds collected more grain from those patches.
- They saved and sowed seed from non-shattering plants, increasing the frequency of the non-shattering allele in cultivated populations.
- Over generations, cultivated varieties fixed the non-shattering trait, producing plants adapted to human harvesting.

3. Calculations / intermediate steps
- No numerical calculations are required for this conceptual question. The logical “steps” above show the selection process.

4. Why the correct answer is correct
- The primary selective advantage of non-shattering in domestication is that it keeps the grain attached so humans can harvest it efficiently and with less loss. This directly matches “retain the grain on the plant for harvesting.”

5. Why the other options are incorrect
- “Ensure grains are softer and more palatable.” Grain texture/palatability are separate traits not caused by shattering vs non-shattering.
- “Reduce the water needed by shattering varieties.” Shattering is unrelated to plant water use or drought tolerance.
- “Increase the amount of grains produced by the plant.” Non-shattering does not inherently increase number of grains per plant; it preserves harvested grain but does not by itself increase production.

6. Conclusion
The correct choice is “retain the grain on the plant for harvesting.” This aligns with the provided answer and the domestication history of cereals.

In wild barley and wheat, the seed head shatters to aid seed dispersal. During domestication, farmers selected for non-shattering varieties to单项选择题

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