Final answer:
The biomagnification of DDT concentration would be most obvious in the Vulture, the apex consumer in the given food chain, due to accumulating higher levels of the toxin from lower trophic levels.
Step-by-step explanation:
In the food chain Grass → Cricket → Prairie chicken → Coyote → Vulture, the biomagnification of DDT concentration would be most obvious in the Vulture. Vultures, as the apex consumers in this food chain, would accumulate the highest concentrations of DDT because of their position at the top of the food chain. Biomagnification results in increasing concentrations of DDT as one moves up each trophic level, from primary producers to apex consumers. The persistent nature of DDT in the environment leads to its accumulation in fat tissues and significant impacts on predators, causing issues like thinning of eggshells in birds and declining populations.