Final answer:
The statement that insects have both dorsal and ventral blood vessels is false. Insects do not have both dorsal and ventral blood vessels.
Step-by-step explanation:
The statement that insects have both dorsal and ventral blood vessels is false. Insects actually have an open circulatory system, meaning that their blood, called hemolymph, is not confined to blood vessels but flows freely within their body cavity. Insects have a tubular heart that pumps hemolymph towards the head, and the hemolymph bathes the tissues directly. However, the way the question is asked is slightly unclear. Insects, for example, have spiracles that allow air to enter the tracheal respiratory system but these are not related to olfactory senses or the mouth. In the context of vertebrates, which have olfactory systems and jaws, the olfactory receptors are typically located in the nasal cavity, not connected to the mouth.
Mammals, such as dogs, have far more olfactory receptors than humans. These olfactory receptors are connected to the olfactory bulb in the brain, not to the mouth directly. For instance, a typical dog has approximately 40 times more olfactory receptors than a human, vastly enhancing their sense of smell.