5.
How would you test whether a phenotypic difference between two populations of a plant
is due to environmentally induced plasticity or evolutionary adaptation?
a. DNA sequencing
b. RNA sequencing
c. Grow both populations in different greenhouses
d. Grow both populations in the same greenhouse
The correct answer is d. Grow both populations in the same greenhouse. This common garden experiment directly distinguishes environmental plasticity from genetic (evolutionary) adaptation by standardizing conditions.
Option Analysis
a. DNA sequencing identifies genetic differences but cannot separate fixed evolutionary changes from plasticity, as sequence data reflects genotype without revealing phenotypic expression under controlled environments.
b. RNA sequencing captures gene expression differences, potentially showing plasticity signatures, yet fails to confirm if differences persist without environmental cues or stem from genetic adaptation.
c. Grow both populations in different greenhouses mimics original environments, preserving plasticity effects without isolating genetic causes, thus confounding results.
d. Grow both populations in the same greenhouse eliminates environmental variation; persistent differences indicate genetic adaptation, while convergence reveals plasticity.
Common Garden Experiment
Plants from two populations showing phenotypic differences (e.g., leaf size, height) get grown under identical conditions like controlled temperature, light, and soil. If differences disappear, plasticity caused them—same genotype expresses variably by environment. Persistent differences signal evolutionary divergence via natural selection on heritable traits. Reciprocal transplants extend this by swapping populations, testing local adaptation via home/away fitness.
Why Not Molecular Methods
DNA/RNA sequencing detects genetic or expression variance but requires phenotypic assays to link to traits. Sequencing alone misses how environments trigger plasticity, while common gardens provide causal evidence fundamental to evolutionary ecology.
CSIR NET Relevance
This tests Unit 5 (Quantitative Genetics, Plasticity, Adaptation) integration with ecology/evolution. Practice distinguishes experimental designs: common garden for genetics vs. plasticity; sequencing for mechanisms post-phenotyping.
