Actinopoda Phylum with organisms shaped in the form of a ball with spines radiating from the center. The spines are used to increase the surface area for catching and ingesting food and to improve flotation. This phylum includes radiolarians which are common, beautiful members of the plankton community in the Chesapeake Bay.



Animalia Kingdom which includes organisms which have a true nucleus (eukaryotic), are muticellular, and heterotrophic (do not make their own food). Animals also have nervous and muscle tissue, body semmetry, and identifiable body parts (eg. eyes, legs, antennae, a digestive system).



Annelida Phylum of segmented worms, which appear to be surrounded with rings. Annelids live in wet or moist environments, such as oceans, ponds, and soil. Most annelids are bottom-dwellers which burrow. Annelids are very abundant and diverse in the Chesapeake Bay.



Anterior The part of an animal that faces to the front.



Arthropoda This phylum includes over 80% of the world's known organisms and includes animals which live in almost every habitat on earth. Arthropods all share the following in common: body segmentation, a hard exoskeleton (external skeleton), and jointed appendages. Phylum Arthropoda includes insects, crustaceans, and spiders.





Autotrophic An organism that makes its own food (as in plants).



Bacillariophyta Phylum of diatoms, also called golden-brown algae. Diatoms have an outer covering made of silica. Some diatoms appear singularly and some grow in chain-like colonies. There is a diversity of shapes within this phylum. The three major divisions are disk-like, rod-like, boat-shaped.



Cell Wall The outermost layer of a plant-like cell, usually made of cellulose.



Cerata Soft, finger-like projections from the body of the sea slug.



Cilia Short, hair-like appendages usually found in large numbers. In some organisms cilia function in locomotion and/or feeding.



Ciliophora All organisms in this phylum are ciliates, meaning they posses hair-like cilia at some point in their lives. Cilia are used for locomotion or food acquisition. All ciliates are heterotrophes (do not make their own food). Organisms in this phylum are very fast for their size; if you see something moving on the slide too fast to identify it is usually a ciliate.



Cnidaria Phylum which includes very primitive, carnivorous animals with stinging tentacles. Cnidarians may appear as a sessile polyp (as seen in hydroids and sea anemones) or as a floating medusa (as characterized by jellyfish). Anyone who has ever been swimming in the Chesapeake Bay is familiar with the phylum Cnidaria because of the abundance of of sea nettles in the summer months. The Chesapeake Bay is also home to many other cnidarians, including beautiful sea anemones.



Colony A group of animals of the same species living together and dependant on one another. Some colonies are physically connected and function as a single unit.



Crustacea Subphylum which includes primarily aquatic arthropods with a hard exoskeleton and jointed appendages. Crustaceans are the only arthropods with two pairs of antennae. Animals in this phylum make up the most abundant part of the plankton community. Perhaps the most well known Chesapeake Bay crustacean is the Blue Crab.



Flagellates These are organisms which have at least one flagellum. A flagellum is a whip-like structure used for locomotion. Flagellates may be plant-like, animal-like, or have characteristics of both.



Gastropoda Class of terrestrial and aquatic mollusks with one or two pairs of fleshy tentacles. Most gastropods have shells and a large foot however, both land and sea slugs have lost their shells in evolution. Most gastropods feed on algae or plant material, although a few groups are predatory. In the Chesapeake Bay, gastropods are represented by periwinkles, whelks, and nudibranchs (sea slugs).



Herbivorous Organisms which feed on primary producers, usually green plants.



Heterotrophic An organism that does not make its own food and must consume other organisms.



Larva The free-living, immature form of an animal which changes structurally when it becomes an adult.



Mollusca Phylum which includes soft-bodied organisms either having an external shell which is single, double, or of eight plates or having an internal shell (as in a squid or octopus). This phylum includes many easily recognizable Chesapeake Bay species including oysters and clams.



Nematoda Phylum of roundworms which live in moist habitats, including aquatic environments, wet soil, and animal tissue. Nematodes may survive as decomposers, parasites, and agricultural pests. They are characterized under the microscope by their snake-like bodies and thrashing movements.



Parasite An organism which survives by living on a host organism, using its host for food or protection. A parasite does not benefit its host and often causes it harm.



Phytoplankton Organisms in the plankton community which have plant-like characteristics.



Plankton Group of aquatic organisms which drift or float with the currents and tides. Most species are microscopic, although a few larger species are included such as jellyfish.



Platyhelminthes Phylum of flatworms which live in aquatic and damp terrestrial habitats. Flatworms are soft, unsegemented worms whose bodies are characterized by their dorso-ventral (top to bottom) flattening. Flatworm species are both free-living and parasitic (tapeworms). There are many free-living flatworms in the Chesapeake Bay.



Polychaeta This is the most common class of annelids in the Chesapeake Bay. Over 110 species live in the Bay, residing in almost every habitat. Polychaetes are characterized by having many hairs (setae). They often have head structures including tentacles, and feathered extensions. Polychaetes may burrow, swim, crawl, or build tubes.



Protista Organisms in this Kingdom are unicellular and have a true nucleus (eukaryotic). They may be heterotrophic or autothrophic (able to make their own food). They may also be motile or sessile.



Pseudopodia Flowing extensions of a cell; "fake feet".



Rotifera Phylum of microscopic, transparent animals distinguished by rings of cilia around the anterior end, which cause the appearance of whirling. Rotifers are abundant in the plankton community and are important for nutrient recycling in aquatic systems.



Secrete To pump out or discharge a specific substance from a cell into the surrounding environment.



Sessile Attached to a substrate; non-motile.



Sheath A protective layer of tissue which covers all or part of an organism. The body parts of the organism can expand from or retract into the sheath.



Silica A glasslike substance.