Which of the following animals isn't considered a type of mollusk?
Considering snail, clam, octopus and lobster, the answer is: lobster.
A mollusk is an invertebrate that has a soft body. This animal group is one of the most diverse groups in the animal kingdom, with nearly 100,000 different species. Examples include the squid, octopus, clams, oysters, and snails.
Generally speaking, mollusks are essential elements of their food chain and ecosystem. They can be hosts for smaller organisms, filters for fresh and saltwater, and have played important roles in human culture for thousands of years. One species of mollusk, known as a Cephalopod, has been recorded in fossil form dating back as far as 500 million years ago. Since then, mollusks like the Cephalopod have played important roles in fishing industries and food consumption.
In such a highly varied species, there are few definitions that fit all categories. Mollusks can range from too small for visible sight, to as long as 45 feet in length. Their lifespans can range from several hours to hundreds of years -- one species of mollusk has been recorded for living over 500 years. Mollusks account for 23% of all recorded marine life.
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