### animal:

Invertebrate animal
* Many invertebrate animals are capable of forming such associations.
* Most invertebrate animals have skeletons.
* Most invertebrate animals live in habitats
  - marine habitats
* Some invertebrate animals have exoskeletons.
* Some invertebrate animals resemble sea snails
* include centipedes.
  - the soil and water and on plants

### animal | invertebrate:

Aquatic invertebrate
* are extremely sensitive to many pesticides.
* lend themselves to education about aquatic conservation very readily.
* live in the bottom parts of our waters.
* serve as the primary food source for many stream fishes.
* swim through the water, crawl along the bottom, or burrow into the bottom.

### animal | invertebrate:

Brachiopod
* All brachiopods are marine animals whose habitats range from the inter tidal zone to deep ocean
  - secrete a mineralized shell composed of two bilaterally symmetrical valves
* Most brachiopods are found attached to rocks or burrowing in soft sediments
  - sessile filter feeders and are incapable of burrowing
  - have their two shell valves held together on a hinge with teeth and sockets
  - live below the low tide level in seawater with normal salinity
  - prefer clear waters, but there are a few which prefer brachish waters
* Some brachiopods also have adjustor muscles which connect to the pedicle
  - have statocysts , which detect changes in the animals' position
* are a very common local fossil.
* are also abundant
  - especially common here
* are among the oldest known fossils
  - shelled invertebrates
  - ancient shellfish that have been found in the layers of the Grand Canyon
  - benthic marine invertebrates that inhabit both deep water and shallow environments
  - entirely marine
  - extremely abundant
  - in the form of the two hinged shell type
* are marine animals that secrete a shell consisting of two parts called valves
  - that, upon first glance, look like clams
  - with one upper and one lower shell
  - invertebrates with two dissimilar shells
  - next in abundance
* are one of most common fossils found in the Pennsylvanian rocks in eastern Kansas
  - the easiest fossils to find
  - quite different
* are rare in the oceans today
  - solitary animals
  - strictly marine and are usually found in shallow seas
  - superficially similar to bivalves , both having two shells
* develop spines and heavier shells as sharks develop broad, flat teeth for crushing.
* have a characteristic lophophore
  - food-gathering organs called lophophores
  - symmetrical shells but the two mating shells are different
* is an invertebrate
* live only in the sea, and most species avoid locations with strong currents or waves
* now live in deeper waters where food is scarcer
  - mainly in cold water and low light
* retain strong bilateral symmetry, even in their feeding organs.
* still live today and most are found on shallow ocean bottoms
  - persist today, but are neither abundant nor diverse
+ Bivalve, Comparison with brachiopods
  * The upshot was that bivalves took over the desirable inshore habitats. Brachiopods now live in deeper waters where food is scarcer.
+ Lingula
  * Brachiopods are superficially similar to bivalves, both having two shells. Bivalves may be attached to a substrate with byssus filaments, that extend from between the shells.