Which one of the following organisms is likely to show the highest concentration of DDT, once it has been introduced into the ecosystem?

Answer: (c) Snake

The snake eats toads, so it sits highest in this chain and carries the most DDT.

The idea

DDT dissolves in fat and is broken down and excreted very slowly. Each predator eats many prey and retains much of their DDT, so the concentration multiplies up the chain.

Grass → Grasshopper → Toad → Snake — highest DDT

Why the others are wrong

(a) The grasshopper is a primary consumer — lowest dose among the animals.

(b) The toad eats grasshoppers, so it holds more — but it is not the top.

(d) Cattle are herbivores — a short chain, so less accumulation.

The trap

Cattle are the biggest animal. Size doesn’t matter — the level in the food chain does.

Also know

Chemicals that behave like DDT are called persistent organic pollutants and are controlled by the Stockholm Convention (2001), which began with a list of twelve, the “dirty dozen”. Mercury behaves the same way in water food chains.