Animalia Phyla
Porifera
Poriferas are invertebrates, and are informally known as
sponges. They lack true tissues but have several different cell types, and Porifera
are suspension feeders who trap passing particles with their bodies. They are
sedentary and among the simplest of animals (often mistaken for plants). They
are a lineage which originates near the base of the phylogenetic tree, so they
are referred to as basal creatures. Sponges are hermaphrodites and switch sexes
as needed. An example is the stove-pipe sponge.
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Cnidaria
With a radially symmetrical body and incomplete gastrovascular
system, Cnidaria are an ancient phylum. They have true tissues, and are either
sessile or motile. They are carnivores who use tentacles to push prey into
their gastrovascular cavity. Once digested, the remains are ejected out the
same opening. Cnidarian tentacles are armed with cnidocytes, unique cells which
function in defense and prey capture. An example is the Pacific Sea Nettles
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Platyhelminthes
Known as flatworms, they have bilateral symmetry and a central
nervous system. They have flattened bodies, and are often found in marine,
freshwater and damp terrestrial environments. They are diverse, with some being
free-living and others being parasitic. Some are microscopic while others can
be nearly 20 meters longs. Their uniquely flat shape allows them to rely on
diffusion with the environment for most movement of gas and waste. An example is the
Blue Pseudoceros Flatworm |
Nematoda
Known as roundworms, they have a tough cuticle which
surrounds their body and are often parasitic of both plants and animals. They
do not have segmented bodies and can range to nearly 1 meter long. They have a
complete gastrovascular system, running from their posterior to anterior ends. Due
to their lack of a circulatory system, roundworms transport nutrients
throughout the body via the fluid in the pseudocoelom. An example is the Caenorhabditis elegans,
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Annelida
Annelids, which are often called segmented worms, are unique
for their segmented body plan. Most internal organs are repeated within each
segment. Each segment also contains a pair of excretory tubes which remove
waste through external pores. Tiny blood vessels run through an Annelid’s skin,
allowing respiration. They have a complete gastrovascular system. Annelids can
be found in the sea, in freshwater habitats and damp soil. An example is the Asian earthworm.
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Mollusca
Mollusks have soft bodies and most have a hard shell made of
calcium carbonate. Despite being very diverse, from snails to squids, Mollusks
all share a common body plan. They have a muscular foot for movement, a
visceral mass containing the internal organs and a mantle, which covers the
visceral mass and usually secretes a shell. Most mollusks use a strap-like
organ, radula, to scrape up food. Mollusks can be male, female or a hermaphrodite. An example is the Tonicella lineata.
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Arthropoda
Consisting
of over a million species ,including insects, Arthropods are the most successful
phylum to exist. They have a segmented exoskeleton and jointed appendages. Over
the course of evolution, the number of segments have decreased while the
appendages have become more specialized. Arthropods are covered in an
exoskeleton constructed from chitin. Their bodies are divided into the head,
abdomen and thorax. Arthropods have well-developed sensory organs and an open
circulatory system. An example is the African field cricket.
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Echinodermata
Bilaterally symmetrical as larvae but not as adults,
Echinoderms move and feed by using a system of internal canals to pump water to
different areas of their bodies. Closely related to Chordata. Echinoderms have
are slow-moving or sessile creatures. They have a thin epidermis which covers a
hard exoskeleton. In relation to their names, Echinoderms have tough spines and
ridges on their outer layers. Unique to Echinodermata is the water vascular
system, consisting of a network of hydraulic canals which extend into the tube
feet, for movement and feeding. An example is the Malaysian sea cucumber.
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Chordata
Chordata
are bilateral, consisting of vertebrates and invertebrates. They have a
notochord which is a vertical, flexible rod from the digestive tube to the
nerve cord. The basic chordate body plan includes the notochord, a dorsal,
hollow nerve cord and a complete gastrovascular tract. The appearance of the
head and backbone were major transitions in chordate evolution. An example is the golden pristella tetra.
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Click on the following link to learn about the Subphyla Vertebrata and associated classes within Chordata: