Invertebrates

Sponges are very simple animals that live permanently attached to a location in the water.

The body of this animal has thousands of pores which let water flow through it continually. Sponges obtain nourishment and oxygen from this flowing water. The flowing water also carries out waste products. 


Suck the water in, filter out the food, and send the water out. 

These invertebrates range in size from a few millimeters to 2 meters tall.




Cnidarians : they have soft bodies with tentacles to catch their prey. Some can move about ( jellyfish); others are attached to surfaces beneath the sea (coral).

Echinoderms are marine animals. They have an internal skeleton made up of plates. Many echinoderms have spines.



If you ever turn a starfish over you will see hundreds of little tubes on each arm. Those tubes attach to an object, suck in, and attach to help the creature move.


Worms have long, soft bodies. They do not have legs. Some worms are terrestrial and some are aquatic.

Molluscs are a large group of invertebrate animals. Molluscs have soft bodies, and their bodies are not divided into rings like the segmented worms called annelids . Molluscs don't have legs, though some have flexible tentacles for sensing their environment or grabbing things. Most mollusc species grow a hard shell for protection, but their shell grows in only one or two pieces. It doesn't have joints like the exoskeletons of insects and crustaceans .

There are three main groups of molluscs. 

1)Snails ( Gastropoda (gas′trə pod′), ) are the most diverse group, there are tens of thousands of species. Nearly all snails grow a spiral shell that is all one piece. A few snail groups have stopped growing shells; they're called slugs . 

   

2) Bivalvia  (/ˈbaɪˌvælv/ )  , the clams, oysters, and mussels . These are molluscs with two shells that they can close up tight for protection.

     

 3)Cephalopoda (sef′ə lə pod′), the squids and octopuses. They only live in salt water. They have no shells, but are larger, smarter, and faster than their relatives in the other groups. Squids and octopuses are all predators; they eat fish, crustaceans, and other mollusks.

  


Arthropods:

The easiest way to distinguish an arthropod from any other animal is to see if they have:

1) A segmented body.

This means that they will have a body made up of more than one part.  Spiders have two segments and flies have three segments.

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2) Many jointed legs or limbs.   

Spiders have 8 legs, millipedes can have...  Hundreds!

   

3)  An exoskeleton.

This is an external skeleton. Like armor, it protects the arthropods body.  When arthropods are born the exoskeleton is soft but hardens quickly and it can be shed as the creature grows.  Arthropods are invertebrates; which means that they do not have a backbone.

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4)  Cold blooded

Arthropods are cold blooded -- which means, their body temperature depends on the temperature of the environment surrounding them.