Question

If one is attempting to determine the influence of genes or the environment on phenotypic variation, inbred strains with individuals of a relatively homogeneous or constant genetic background are often used. Variation observed between different inbred strains reared in a constant or homogeneous environment would likely be caused by genetic factors. What would be the source of variation observed among members of the same inbred strain reared under varying environmental conditions?

Short answer

Answer: The primary source of variation in the phenotype is the influence of the environment on phenotypic development.

Step-by-step solution

Understand the inbred strain condition

Since the inbred strains have a relatively constant genetic background, the genetic differences between the individuals will be minimal.

Consider the influence of varying environments

When members of the same inbred strain are reared under varying environmental conditions, these conditions might lead to differences in their phenotypic traits.

Identify the source of variation

As there is minimal genetic variation within the same inbred strain, the source of variation observed among members of the same inbred strain reared under varying environmental conditions is likely due to the influence of the environment on their phenotypic development.

Conclusion

The source of variation observed among members of the same inbred strain reared under varying environmental conditions is the influence of the environment on phenotypic variation.