Ajellyfish is a type of cnidarian, a squid is a type of mollusk and a dolphin is a type of vertebrate which two characteristics are present in both a squared and a dolphin but not present in a jellyfish

Ans.  

Jellyfishes are multicellular, marine organisms that belong to phylum Cnidaria. Squids are a type of mollusks, having eight arms and tentacles. Dolphin is a vertebrate that belongs to class mammalia. They produce young, have fur or hairs on the body and complex organ system.

Both squid and dolphin have complex organ systems, nervous system, while complex organ systems are absent in jellyfish.

Both squid and dolphin are triploblastic (having three tissue layers), while jellyfish is diploblastic (having two tissue layers).

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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