Question

Example 4: Fish size varies by pond. The same fish species grows larger in spacious ponds with abundant food.

Effect: _________________ had the bigger effect.

Your Reasoning
Choose one example above. Explain why you think the environment or genetics had the bigger effect.

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Answer 1

Effect: environment had the bigger effect.

Your Reasoning
Choose one example above. Explain why you think the environment or genetics had the bigger effect.

The fish are the same species, so large genetic differences are less likely to explain the size differences; instead the pattern matches environmental causes (spacious ponds with abundant food produce larger fish). Food availability, stocking density, and space directly affect growth rate and final size via nutrition and competition, which are well-known drivers of phenotypic plasticity in fish. Unless there is evidence of distinct genetic populations adapted to each pond, the simplest explanation is that environmental conditions produced the size differences. A common-garden or reciprocal-transplant experiment (raising fish from both ponds in the same controlled conditions) would confirm this by showing whether size differences persist when the environment is held constant.