Traits come from genes and environment together
- The idea
- Predict
- See it
- Why
- Check
The idea
“A trait is either genetic or environmental. If the environment can change it, it isn't really genetic.”
Genetic sounds like fixed. So when soil or diet changes a trait, it's easy to give the environment all the credit.
The short version
The mistake: A trait is either genetic or environmental. If the environment can change it, it isn't really genetic.
What's actually true: Many traits depend on both. Genotypes differ in a shared environment, and each genotype's phenotype shifts as conditions change.
- A genotype sets a range of possible phenotypes, and conditions decide where the organism lands. Its pattern across environments is its norm of reaction.
- Corn uses nitrogen to build proteins and chlorophyll, so poor soil stunts both lines. In any shared soil, A still beats B.
- To see a genetic effect, compare genotypes in the same environment. To see an environmental effect, grow one genotype in different environments.
- A and B in different soils differ in genes and soil at once, so their heights can't show which has alleles for greater height.
On the exam: Same environment, different results: genes. Same genes, different results: environment. Both can be true.