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An invertabrate has no backbone. We as humans arevertebrates because we have a backbone. If you look at the octopus below you see that it has no back, meaning no backbone. Remember mollusks have no backbone!!!!!!!!!!!!!!!!!!!!!!!!!
What is a Mollusk?
mollusk or mollusc
(mlsk)
Any of numerous invertebrate animals of the phylum Mollusca, usually living in water and often have a hard outer shell. They have a muscular foot, a well-developed circulatory and nervous system, and often complex eyes. Mollusks include gastropods (snails and shellfish), slugs, octopuses, squids, and the extinctammonites. Mollusks appear in the fossil record in the early Cambrian Period, but it is not known from what group they evolved.
This is a clam. As you can see it only has a shell and no backbone. The clam is a ocean living mollusk that moves or swims by jet propulsion. They propel themselves by ejecting water from their body. For example, the squid ejects water from a cavity within its body, and the scallop ejects water to move by clamping its shell closed.
This is howmollusksevolved over time. The hypothetical ancestor on top is like a slug. You see that the parts under the shell look just like the ancestor. On the right is a shelled animal that is a snail which is in the gastropod group. The bottom right is a squid (in the cephalopod), which most people don't think should be a mollusk. The top left is called a chiton. The bottom left is a picture of abivalve (like a clam). There are 50,000 species of mollusks on earth currently (at least that we know of).
These are some picture examples of mollusks that evolved from the same ancestor. These are all mollusks!!!!!!!!!!!!!!!!! Isn't it just amazing.
Some Mollusk System Facts
System Type
Mollusks System
Muscular-Skeletal
A Mollusk has an outer shell. It has a soft body. It has a muscular foot that it uses for movement.
Digestion
A Mollusk has food brought in through a siphon system and then to its mouth. It then goes to a digestive gland and to its intestine. Wastes leave via the anus.
Nervous
A Mollusk has no formal nervous system, but has a series of ganglia that conduct impulses.
Circulation
A Mollusk has a heart, blood and blood vessels.
Respiration
A Mollusk has tubes called siphons that bring water in and out of their bodies so that they can get oxygen and give off carbon dioxide. They have gills that help with this.
Reproduction
A Mollusk is either male or female and reproduces sexually with a large organ called a gonad.
Excretion
A Mollusk has an excretory system with an anus. It has an organ called the nephridium that gets rid of wastes.
Symmetry
A Mollusk has bilateral symmetry.
Appearance
A Mollusk has a soft, thick, fleshy body. It can be very small or as big as six feet across.
Mollusks bodies
Molluskshave three body regions.
1. The sense organs and the "brain" are in located in the head.
2. The "visceral mass" contains the internal organs.
3. The muscular part of the body is usually the "foot"
What is the Difference Between an Octopus and a Squid?
An octopus has eight arms. A squid has ten: eight of the same length and two extra long ones used in grabbing prey. These extra two arms are called tentacles. The arms of both squids and octopuses have suckers on them used to latch onto prey.
Questions
1. Are mollusks vertebrates or invertebrates?
2. How many species of mollusks are there?
3. is an octopus considered a mollusk?
4,. What are 3 groups of mollusks?
5. Whats the difference of a octopus and a squid?
6. When did the first mollusks appear on earth?
7. What are the 3 body regions of a mollusk?
8. How big can a mollusk be?
Thanks to these sites we were able to find great information. 8-)
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