 Tomales
Bay is home to all major forms of life. Within the bay and
along its shores, a wide range of physical conditions provide
niches for a wide range of life strategies. Bay environments
extend from the intertidal zone to it deepest channels where
mud and gravel receive little light penetration under 50 feet
of water. Plankton and fishes flourish in the water column,
and varying salinity levels are suited to a variety of life
forms and life stages. The intertidal shores of the bay vary
in structure from wide mud flats to sandy beaches, rocky shores
and cliffs. Numerous wetlands line the edges of the bay. These
diverse habitats harbor a wide diversity of organisms. Additionally,
numerous land-dwelling animals, including us, go to the bay
to forage. The bay is thus an intersection point of many life
strategies.
Chordata
 The phylum Chordata includes the animals most familiar to
us, those with backbones. These organims are within the major
subphylum Vertebrata. Vertebrates include mammals, amphibians,
reptiles, birds, and fish. Chordata also includes two other
subphyla, the Urochordata and Cephalochordata. The Cephalachordates
are known as lancelets because of their bladelike shape. They
are small creatures, a few centimeters long, that live in
the sand below marine waters along the coast. Urochordates
are commonly known as tunicates. They exhibit an exoskeletal
tunic and a perforated pharynx, but lack the notochord and
nerve cord. Tunicates include the Ascidiacea, or sea squirts.
All members of the phylum Chordata share four identifying
characteristics at some time during their lifecycle: 1.) The
notochord (a rod that extends most of the length of the body).
It stiffens the body and acts as support during locomotion.
2.) Postanal tail. 3.) Pharyngeal pouches (gill slits). 4.)
A single, dorsal, hollow nerve cord.
Mollusca
 This phylum contains some of the most common and well known
invertebrates. It includes oysters, clams, squid, snails,
and octopuses. All mollusks have a muscular foot used for
locomotion, as well as a mantle, an outgrowth that covers
the animal. Many of them produce a calcium carbonate shell,
which hangs over the mantle. Mollusks are found in salt water,
in fresh water, and on land. The major classes of the phylum
are: Polyplacophora (chitons), Aplacophora (without shells),
Monoplacophora (with one shell), Scaphopoda (with a tubular
shell), Bivalvia (with two part shells such as clams), Gastropoda
(having a single part shell, e.g. snails), and Cephalapoda
(little or no shell, e.g. octopus).
Arthropoda
 The Arthropoda phylum is a highly diverse and recognizable
group, including Insects, Arachnids (scorpions, spiders, and
mites), Crustaceans (lobsters, crabs, shrimps, barnacles,
etc.), Centipedes and millipedes (worm-like, segmented animals
with a single pair of legs on each body segment). Arthropods
have segmented bodies and an exoskeleton that may or may not
be further stiffened with calcium carbonate.
Annelida
 This
is a group commonly referred to as segmented worms. Annelids
are distinguished by ring-like external bands along their
muscular body wall that coincide with internal partitions
dividing their bodies into segments. They are common in marine
substrates, though earthworms and leeches are the most familiar
annelids for most people. However, the polychaetes make up
the bulk of Annelida's diversity and abundance in Tomales
Bay. Classes of Phylum Annelida include Clitellata (leeches
and earthworms), Pogonophora (beard worms) and Polychaeta
(paddle-footed worms).
Cnidaria
 The
phylum Cnidaria is an ancient and successful group of animals
that include colorful corals, sea anemones, and jellyfish.
Cnidarians have a basic body shape of a sack with a central
digestive organ. A single opening to this cavity serves as
both the mouth and the anus. Cnidarians are all carnivores.
They use a ring of tentacles placed around the mouth, in order
to trap prey and force it into the gastrovascular cavity.
The tentacles are also used as a defense mechanism to defend
against predators. Classes within Cnidaria are Hydrozoa (Portuguese
man-of-war, hydras), Cubozoa (box jellyfish, sea wasp), Scyphozoa
(jellyfish, sea nettle) and Anthozoa (sea anemones, sea fans,
most corals).
Ectoprocta (Bryozoans)
 Bryozoans
are animals that live in colonies, and resemble mosses in
structure. Each member of a colony lives in a chamber secreted
by its epidermis. The exoskeleton varies according to the
species and may be gelatinous, chitinous, stiffened with calcium
or impregnated with sand. Though reefs do not occur in Tomales
Bay it is noteworthy that in other habitats many species of
bryozoans contribute to reef formation. Marine bryozoans belong
to the class Gymnolaemata. The other class in the phylum Ectoprocta,
which includes the freshwater bryozoans, is Phylactolaemata.
Echinodermata
 Echinodermata, (from the Greek meaning 'spiny skin'), are
a large and successful group of marine animals. Most living
echinoderms are pentameral; that is, they have five-fold symmetry,
with rays or arms in fives or multiples of five. Echinoderms
have a system of internal water-filled canals, which in many
echinoderms form suckered "tube feet", with which
the animal may move or grip objects. Classes of Echinodermata
include Stelleroidea (sea stars), Echinoidea (sand dollars
and sea urchins), Crinoidea (feather stars and sea lilies)
and Holothuroidea (sea cucumbers).
Protozoa
 Protozoa
are the most abundant animals in the world in terms of numbers
and biomass. They comprise a diverse grouping of about 80,000
different single cell organisms. Many are mobile and animal
like. They were once grouped together as a single phylum within
the Animal Kingdom, the phylum Protozoa. Recently they have
been classified within a number of unicellular phyla, where,
along with most algae, make up the kingdom Protista, or Protoctista.
Protozoans are found wherever there is enough moisture; in
the sea, in fresh water, and in soil. Their principal importance
is as consumers of bacteria. Bacteria play a vital role in
maintaining the earth as a suitable place for inhabitation
by other forms of life, and protozoa play a vital role in
controlling their numbers and biomass. Protozoa are also important
as parasites and symbionts of multi-cellular animals.
Algae
 Algae are an ancient group of photosynthetic organisms. Some
are microscopic, single celled organisms which float freely
in water, while others are attached to the substrate and grow
into large congregations of cells. Some can grow as large
as 100 feet tall. None have true roots. Recently, some taxonomists
have placed algae in the Protoctista kingdom, which includes
molds, protozoans and other obscure nucleated aquatic organisms.
Others assign them to a variety of phyla within the Plant
kingdom. Algae includes the familiar macroalgae, or seaweed,
as well as diatoms, stoneworts, and dinoflagellates.
Many conspicuous macroalgae can be found in the mid to lower
intertidal zones. Microscopic algaes are abundant in the water
column and can also be found growing on a variety of shoreline
surfaces, including rocks, driftwood and the surfaces of plants.
Plantae
 The plant kingdom includes all the familiar photosynthetic
leafy trees, shrubs, grasses and herbs. It also includes mosses
and ferns. A great variety of plant life can be found in the
salt marshes along the perimeter of Tomales Bay. Some plants
also grow in subtidal habitats. Eelgrass (Zostera marina)
is abundant along the subtidal margins of Tomales Bay and
provides habitats to numerous invertebrates and young fish.
Fungi
 This kingdom of organisms are distinct
from plants in that they are heterotrophic, i.e. they cannot
photosynthesize and must derive their energy by consuming
matter around them. In addition to the familiar mushrooms,
Fungi include yeasts and many inconspicuous symbionts, such
as mychorrizal fungi living in plant roots. Fungi are rare
in marine environments and are most likely to be found within
lichens on rocks along the shoreline.
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