Which Invertebrates Usually Have a Concentration of Olfactory Receptors at Their

Question

Which invertebrates usually have a concentration of olfactory receptors at their head end?  
A) Cnidarians
B) Echinoderms
C) Bilateral invertebrates
D) Predatory invertebrates
E) Prey invertebrates

Accepted Answer

Bilateral invertebrates usually have a concentration of olfactory receptors at their head end, which helps them to detect and locate food sources and avoid predators. Examples include insects, crustaceans, and mollusks. Cnidarians and Echinoderms do not have a definitive head region, and while predatory and prey invertebrates may have a strong sense of smell, it does not necessarily mean they have a concentration of olfactory receptors at their head end.