Question

biologists take multiple measurements of head traits in grasshoppers. they find distinct differences among different populations, and reclassify what had been populations of the same species as several different species. which species concept are they employing?
morphological
lineage
cryptic
biological
dobzhansky - muller

Explanation:

The morphological species concept classifies species based on physical traits. Since biologists are using head - trait measurements (physical characteristics) to reclassify populations, they are using the morphological species concept. The lineage concept focuses on evolutionary history, cryptic species are morphologically similar but reproductively isolated, the biological species concept is based on reproductive isolation, and the Dobzhansky - Muller model is about genetic incompatibilities in speciation.

Answer:

Morphological