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Student Activity: What Are These Things?

Identify These Chesapeake Bay Organisms
Using A Dichotomous Key

The Key | The Organisms | What Are These?



The Key

1.  
a.  Has a shell
b.  No shell
 
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go to 2
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2.  
a.  Mobile
b.  Sessile
 
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 . . . . . . . . . .  
 
Atlantic Ribbed Mussel
Barnacle

 
3.  
a.  Lives as a colony
b.  Lives independently
 
 . . . . . . . . . .  
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go to 4
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4. 
a.  Individuals connected by compartments
b.  Individuals connected by stalks
 
 . . . . . . . . . .  
 . . . . . . . . . .  
 
Bryozoan
Entoprocts

 
5.  
a.  Has tentacles
b.  No tentacles
 
 . . . . . . . . . .  
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go to 6
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6.  
a.  Has more than 2 tentacles
b.  Has 2 tentacles
 
 . . . . . . . . . .  
 . . . . . . . . . .  
 
White Anemone
Whip Mud Worm

 
7.  
a.  Segmented body
b.  Body not segmented
 
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 . . . . . . . . . .  
 
Isopod
Limpet Nudibranch

 

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The Organisms

Atlantic Ribbed Mussel
[Atlantic Ribbed Mussel]
Phylum - Mollusca, meaning "soft bodied", over 100,000 living species and 35,000 fossil species identified. Sizes range from the elusive giant squid to nearly microscopic forms.

Class - Pelycypoda (Bivalves), meaning "2 shells" (the name for the shells are valves), well known to seafood lovers- oysters, mussels, clams, scallops. Filter feeders, some are sessile and some are mobile by the use of a muscular foot.


Barnacle
[Barnacle]
Phylum - Arthropoda, meaning "jointed legs", most numerous of all phyla.

Class - Crustacea, meaning "hard shell", well known to seafood lovers- crabs, crayfish, lobster, and shrimp; barnacles are not the edible type. Barnacles are sessile but most of this class are highly mobile using all of their 10 legs for movement. Barnacles are filter feeders using their legs to snare plankton from the water.


Bryozoan
[Bryozoan]
Phylum - Bryozoa, sometimes known as "moss animals", this is a group of colonial animals that take on a variety of shapes. They have 2 forms- shrub-like colonies or hardened crusty colonies made from calcium. The lacy crust bryozoan in the picture forms colonies on living and nonliving substrate. They capture their food with the use of small tentacles that extend from each compartment of the colony.


Entoprocts
[Entoprocts]
Phylum - Entoprocta, these unique animals can grow as colonies or individuals. The species shown in the photograph is a colinial type known as loxosoma and is common in estuaries like the Chesapeake Bay.


White Anemone
[White Anemone]
Phylum - Coelenterata, meaning "hollow cavity" or Cnidaria, meaning "stinging cell". Both names have been used for this Phylum. Most familiar species tend to be jellyfish, sea anemones, and freshwater hydra.

Class - Anthozoa, species include anemones and coral, yes there is one species of coral in the Chesapeake Bay known as whip coral.


Whip Mud Worm
[Whip Mud Worm]
Phylum - Annelida, meaning "segmented worm".

Class - Polychaeta, meaning "bristle worm". This class consists of mostly marine species that are found worldwide. Each has characteristic bristles that are found covering or lining the exterior of the body. Mud worms build a burrow in which they live. They use their two tentacles to snare food floating by and transport it along cilia to the mouth, like a conveyer belt.


Isopod
[Isopod]
Phylum - Arthropoda, meaning "jointed legs", most numerous of all phyla.

Class - Crustacea, meaning "hard shell" well known to seafood lovers- crabs, crayfish, lobster, and shrimp; isopods are not the edible type.

Order - Isopoda, shrimp-like animals that have their body flattened dorso-ventrally, in other words they are flattened like a pancake.


Limpet Nudibranch
[Limpet Nudibranch]
Phylum - Mollusca, meaning "soft bodied".

Class - Gastropoda, meaning "stomach foot", includes species like slugs, snails, and sea slugs (nudibranchs). Some are herbivorous and others are carnivorous feeding on bivalves, cnidarians, or other species.

Order - Nudibranchia, nudibranchs are carnivorous sea slugs as compared to sacoglossans which are herbivorous sea slugs. Most Chesapeake Bay species are less than half an inch long.

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