Add your Article
- E Learning Jamaica
- 2014 GSAT Results for Jamaican Kids
- E Learning in Jamaica WIN PRIZES and try our Fun Animated Games
- Results of GSAT are in schools this week
- Environment
- Snow Traps
- Animal CSI or from Science Lab to Crime Lab
- Will Climate Change Depose Monarchs?
- GSAT Exam Preparation Jamaica
- Ministry of Education Announces 82 GSAT Scholarships for 2010
- March 21-22, 2013: Over 43,000 students will take the GSAT Exam
- Results of GSAT are in schools this week
- GSAT Exams Jamaica Scholarships
- GSAT Practice Papers | GSAT Mathematics | Maths
- GSAT stars reap scholarship glory
- GSAT Scholarship
- GSAT Mathematics
- Losing with Heads or Tails
- GSAT Mathematics Quiz, Teaching Math, teaching anxiety
- A Sweet Advance in Candy Packing
- Parents
- Raise a Lifelong Reader by Reading Aloud
- How children learn
- Expert report highlights the importance to parents of reading to children!
Mollusks
Published: 07/01/2010
Although mollusks are probably best known for their unique shells, the word itself actually comes from he Latin word for "soft." Beneath their shells, mollusks are actually very soft-bodied invertebrates (no spine) -- and some of the most well-known mollusks (like the octopus, for example) have no shells at all. Mollusks share a mantle (a fold of skin that lines the shell, when present) and a muscular foot that they use for motion. Many types of mollusks are raised and captured for food -- squid and clams, for example -- and some people consider eating snails a true delicacy. The mollusks are members of the large and diverse phylum Mollusca, which includes a variety of familiar creatures well-known for their decorative shells or as seafood. These range from tiny snails, clams, and abalone to the octopus, cuttlefish and squid (which are considered the most intelligent invertebrates). There are some 70,000 described species within this phylum. The giant squid, which until recently had not been observed alive in its adult form, is the largest invertebrate; although it is likely that the Colossal Squid is even larger. The scientific study of mollusks is called malacology. The mollusk's body is often divided into a head, with eyes or tentacles, a muscular foot and a visceral mass housing the organs. Mollusks have a mantle, which is a fold of the outer skin lining the shell, and a muscular foot that is used for motion. Many mollusks have their mantle produce a calcium carbonate external shell and their gill extracts oxygen from the water and disposes waste. All species have a complete digestive tract that starts from the mouth to the anus. Many have a feeding structure, the radula, mostly composed of chitin. Radulae are diverse within the Mollusca, ranging from structures used to scrape algae off rocks, to the harpoon-like structures of cone snails. Cephalopods (squid, octopuses, cuttlefish) also possess a chitinous beak. Unlike the closely related annelids, mollusks lack body segmentation. Development passes through one or two trochophore stages, one of which (the veliger) is unique to the group. These suggest a close relationship between the mollusks and various other protostomes, notably the Annelids. Mollusk fossils are some of the best known and are found from the Cambrian onwards.
Mollusks
