Selective Breeding & Genetic Diversity — Practice · Grade 7 Science

Chapter: Evolution, Evidence & Life History

What this practice covers

By the end of Selective Breeding & Genetic Diversity you should be able to:

8 questions, written answer, multiple choice and numeric, each with a worked explanation.

Vocabulary used: artificial selection, selective breeding, gene pool, heritability evidence, selection pressure.

Problem 1

Does training an individual automatically count as selective breeding?
Answer and explanation

No. Selective breeding changes which organisms reproduce based on traits; training changes an individual’s experience.

Problem 2

Why compare environments before selecting for size?
Answer and explanation

Resource differences can affect size; without comparable conditions, the chosen characteristic may not reflect an inherited contribution.

Problem 3

Does improvement in one chosen trait prove improvement in every trait?
Answer and explanation

No. Other outcomes and tradeoffs need separate evidence.

Problem 4

Why can a uniform variety be vulnerable to one particular threat?
Answer and explanation

If individuals share a susceptible inherited response, a threat targeting that response can affect many; the actual effect needs evidence.

Problem 5

Illustrative plants: A averages 12 seeds in favorable soil; B averages 9 in poorer soil. A proposal says breeding only A proves an inherited yield improvement. Explain the confound, propose a stronger comparison, and identify a diversity tradeoff.
Answer and explanation

The observed yield difference does not isolate an inherited advantage because soil differs. Compare parent and offspring performance under suitable matched conditions and independent replicates. Selecting only a narrow group may reduce variation, so measure other outcomes and possible vulnerabilities rather than declaring universal improvement from one trait.

Notice unequal soil conditions.

Compare replicated offspring under matched conditions.

Consider narrowing inherited variation.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 6

Can selecting for an existing trait guarantee a completely new desired trait appears next generation?
Answer and explanation

No. Selection acts on heritable variation and reproductive contribution; new changes are not guaranteed or produced by desire.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 7

Which comparison better tests an inherited yield contribution?
  1. Parents in entirely different conditions only
  2. Offspring groups under matched conditions with replication
  3. Only the highest one result
  4. A label saying best
Answer and explanation

Offspring groups under matched conditions with replication

Matched offspring comparisons address environmental differences and variability.

Problem 8

A sample has 15 plants with a selected variant among 50. Find the share.
Answer and explanation

30 %

15/50×100=30%, without assuming universal advantage.

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