What are mollusks - what are snails and slugs?
Welcome to Quatr.us Study Guides!

What are Mollusks?

Slug
Slug

Mollusks are animals like mussels, clams, snails and slugs. Cephalopods like octopus and squid are also mollusks. The name Mollusk means "soft", because mollusks don't have any skeletons. The first mollusks probably evolved from early segmented worms around 500 million years ago. At that time, all animals except arthropods still lived in the ocean, and all these early mollusks also lived in the ocean.

Like segmented worms, mollusks were generally long and thin, and they had a mouth and an anus with a long gut in between to digest their food.

Snail
Snail

But mollusks also have some things that segmented worms don't have. Many mollusks have shells made of calcium to protect them.

Most mollusks still live in the ocean, but a few kinds of snails and slugs have evolved to live on land. Snails have probably evolved to live on land not just once, but on several different occasions, independently. The earliest evidence of land snails comes from about 325 million years ago, around the same time that frogs came out of the water, and so frogs love to eat snails. But there weren't so many land snails and slugs until about 145 million years ago, in the time of the last dinosaurs and the first birds - and birds also love to eat snails.


Bibliography and further reading about slugs and snails:

Cephalopods
Biology
Quatr.us home


Celebrating Black History Month with the pharaoh Hatshepsut, the queen Shanakdakhete, the poet Phillis Wheatley, the medical consultant Onesimus, the freedom fighters Toussaint L'Ouverture, Denmark Vesey, Yaa Asantewaa, and Samora Moises Machel, and the civil rights leader Martin Luther King, Jr.
Please help other teachers and students find us: link to this page from your class page.
Karen Carr is Associate Professor Emerita, Department of History, Portland State University. She holds a doctorate in Classical Art and Archaeology from the University of Michigan. Follow her on Instagram or Twitter.
Cite this page
  • Author: K.E. Carr
  • Title:
  • Site Name: Quatr.us Study Guides
  • Publisher: Quatr.us
  • Date Published:
Proud of your class page, homework page, or resource page? Send it in and win a Quatr.us "Great Page!" award!
Sign up for more free articles and special offers in Quatr.us' weekly newsletter:
We will never share your e-mail address unless you allow us to do so. View our privacy policy. Easy unsubscribe links are provided in every email.
Comment on This Article

Cool stuff we've been enjoying: Looking for birthday gifts? Check out these new Chromebooks - all the computer you need for only $229.00!. Then study in peace with these Beats wireless headphones - for the exact same price! When you're done, show off your presentation or watch a movie with this excellent smartphone projector for only $39.99!


Does your class page honor diversity, celebrate feminism, and support people of color, LBGTQ people, and people with disabilities? Let us know, and we'll send you a Diversity Banner you can proudly display!
Looking for more?
ADVERTISEMENT
Quatr.us is loading comments...
(Comments will appear after moderation, if they are kind and helpful. Feel free to ask questions, and we'll try to answer them.)
Cite this page
  • Carr, K.E. . Quatr.us Study Guides, . Web. 23 February, 2017
ADVERTISEMENT