ANIMAL CLASSIFICATION
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Systematics or Taxonomy is the study of the kinds and diversity of
organisms.
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The modern classification is rooted in the work of Karl von Linne
(Carolus Linnaeus).
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Modern taxonomists use five taxon or more as: Domain, Kingdom
Phylum, Class, Order, Family, genus, and species.
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Many zoologists recognize three major groups within the animal
kingdom: Mesozoa (Phylum Mesozoa), Parazoa (Phylum Porifera), and
Eumetazoa (all other phyla).
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The Eumetazoa are further subdivided into: protestomes
(Platyhelminthes, Nematoda, Mollusca, Annelida, and Arthropoda), and
deuterostomes (Echinodermata, Hemichordata, Chordata, and others)
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Protozoa
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1. Phylum Sarcomastigophora
consists of flagellates and amoeba within a
single type
of nucleus (with over 18,000
described species
Characteristics:
a) unicellular or colonial
b) locomotion by flagella, pseudopodia, or
both
c) autotrophic (self-nourishing), saprozoic
(living in decaying organic matter), or
heterotrophic (obtain energy from organic
compounds)
d)
single type of nucleus
Euglena
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freshwater
contains chloroplast with pyrenoid which
synthesizes and stores polysaccharide
a pigment shield (stigma) permits light to
strike the photoreceptor from only one
direction
haploid and reproduce by longitudinal binary
fission
Trypanosoma
Large and diverse, includes several species that infect
wild and domesticated animals in Africa, particularly
hoofed animals, and humans. Most of the African
trypanosomes are transmitted by vectors, and the most
common vector is the tsetse fly (Glossina sp.).
The species that cause human African trypanosomiasis
("sleeping sickness") also infect wild animals and can be
transmitted from these animals to humans
(zoonotic infections).
Most African trypanosomes are restricted to Africa,
although a few species have been imported into South
America.
Amoeba (Entamoeba histolytica)
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naked
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normally found in shallow water
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engulf food by phagocytosis
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reproduce by binary fission
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particle feeders
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some are pathogenic line
Phylum Porifera - known as sponges; primarily marine
animals consisting of loosely
arranged cells
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Assymmetrical or radially symmetrical
Three cell types: pinacocytes, mesenchyme cells,
and choanocytes
Central cavity, or a series of branching channels
No tissue or organs
Class Calcarea – spicules composed of CaCO3; spicules are
needle-shaped and 3 or 4 rays; ascon, leucon or
sycon body forms; marine. Ex. Grantia
Class Hexactinellida
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Spiculus composed of silica, usually six-rayed;
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spicules often fused into an intricate lattice;
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cup or vase-shaped; scycon or leucon body form;
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Glass sponges.
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Ex. Euplectella (Venus flower basket)
Class Demospongia
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Brilliantly covered sponges with needle-shapec or
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4-rayed siliceous spicules or spongin or both;
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leucon body form;
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Ex. Spongilla, Cliona
Morphology:
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Pinacocytes line the outer surface of a sponge
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Pinacocyte may be mildly contractile, their combination
may change the shape of some sponges
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In some sponges, pinacocytes are specialized into
tubelike, contractile porocytes which regulate
water circulation
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Below the pinacocyte layer is a jelly-like mesohyl
composed of mesenchyme cells
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Mesohyl is specialized for reproduction, secreting skeletal
elements, transporting and storing food and forming
contractile rings around the openings in the sponge
wall.
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Below the mesohyl and lining the inner chamber is a layer
of collar cells or choanocytes which are flagellated
cells that have collarlike ring or microvilli surrounding
a flagellum. The flagellum creates water current
through a sponge and the collar filters microscopic food
particles from the water.
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Sponges are supported by a skeleton consisting of microscopic needle like spikes called spicules. Made up of
calcium carbonate or silica, spicules are formed by
ameboid cells. Skelton is made up of spongin.
Body forms of a sponge
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1) Ascon – vase-like; ostia are the outer opening of porocytes
and lead directly to a chamber called the spongocoel;
choanocytes line the spongocoel.
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2) Sycon – the sponge walls appear folded; water enters
a sycon sponge through openings called dermal pores;
dermal pores are the openings of the incurrent canals
and connect to the radial canals; choanocytes line the
radial canals and the beating of choanocyte flagella
moves water from the ostia through incurrent and
radial canals, to the spongocoel and out the osculum.
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3) Leucon – have an extensively branched canal system;
water enters the sponge through the ostia and moves
to the incurrent canals which lead to choanocyte-lined
chamber; the exit point of water is called oscula.
Reproduction
Most are monoecious (both sexes occur in the same
individual); asexual reproduction involves the
formation of gemmules (contain masses of ameboid
cells).
Phylum Cnidaria – hydra, anemone, jellyfish, coral
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Radial, or biradial symmetry
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Diploblastic tissue level organization
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Gelatinous mesoglea between the epidermal
and gastrodermal tissue layers
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Gastrovascular cavity
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Nervous system in the form of a nerve net
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Specialized cells called cnidocytes, used in
defense, feeding, and attachement
Class Hydrozoa – majority are marine; have colonial polyps
in which individuals may be specialized for feeding,
producing medusae by budding or defending the colony
Ex. Obelia, Hydra
Class Scyphozoa – “true jellyfish”, all are marine; often
deliver dangerous stings; Their primary food include
small plankton organisms such as mollusks, rotifers,
crustaceans, tunicate larvae, copepods, etc;
Ex. Aurelia aurita
Class Cubozoa – live in warm tropical waters; some possess
dangerous nematocyst.
Ex. Chironex flecken (sea wasp)
Class Anthozoa – marine, colonial, solitary, and lack medusae;
Ex. Sea anemone, corals. Corals are invertebrates that
are in symbiosis with an algae; they have an alternation
of generations during their life cycle (this cycle
alternates from a polyp to medusa stage). However, the
class anthozoa's medusa stage is absent because they
become sessile once they fix themselves in one place.
They only move during their developing stages.
To obtain food, corals filter feed, feeding on
invertebrates and fishes.
Phylum Ctenophora –sea walnuts or comb jellies; marine,
have a spherical form, although several groups
are flattened and/or elongate; bands of cilia called
comb rows are present for locomotion.
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Diploblastic tissue-level of organization
Biradial symmetry
Gelatinous mesoglea between the epidermal and
gastrodermal tissue layers
Gastrovascular cavity
Nervous system in the form of a nerve net
Class Tentaculata – with tentacles; Ex. Pleurobranchia
Class Nuda – without tentacles; Ex Beroe
Phylum Platyhelminthes – “flatworms”
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Usually flattened dorsoventrally, triploblastic, acoelomate,
bilaterally symmetrical, unsegmented worms
Incomplete gut usually present; gut absent in Cestoidea
Cephalization present, with an anterior cerebral ganglion
and usually longitudinal nerve cords
Protonephridia as excretory/osmoregulatory structure
Hermaphroditic, complex reroductive systems
Class Turbellaria – mostly free-living and aquatic; predaceous,
monoecious with reproductive systems adapted for
internal fertilization. Ex. Dugesia
Class Monogenea – monogenetic flukes; mostly ectoparasites
on vertebrates
Class Trematoda – all are parasitic; several holdfast devices
present; gut is present and most are monoecious
Ex. Paragonimus westermani
Class Cestoidea – are tapeworms and gut parasites of vertebrates;
structurally more specialized than the flukes, having
scolex and attachment organs, a neck region, and a
strobila which consists of a chain of segment; gut is
absent and the reproductive system is repeated in each
proglottid.
Phylum Nemertea – elongate flattened worms found in marine
and sand, are called “proboscis worms” because they
have long proboscis.
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Triploblastic, acoelomate, bilaterally symmetrical
unsegmented worm, possessing a ciliated epidermis
containing mucous gland
Complete digestive tract and with an anus
Protonephridia present
Cerebral ganglion, longitudinal nerve cords, and
transverse commissures
Closed circulatory system
Body musculature organized into 2 or 3 layers
Dioecious
Phylum Gastrotrichia – microscopic aquatic animals with a
head, neck, and trunk; numerous adhesive glands
are present; hermaphroditic; parthenogenesis is
common in freshwater species.
Phylum Rotifera – small animals, abundant in freshwater
habitats; ciliated “corona” in the anterior region of
the body; triploblastic, bilateral unsegmented,
complete digestive system; body covered by a cuticle
called “lorica”; feed on plankton organisms; reproduce
by parthenogenesis.
Phylum Kinorhyncha – minute worms living in marine habitats
bodies composed of 13 or 14 zomites, which have
cuticular scales, plates, spines. Ex. Echinoderes
Phylum Nematoda – roundworms, triploblastic, bilateral
vermiform; unsegmented, pseudocoelomate; complete
digestive tract; live in aquatic and terrestrial environments;
many are parasitic and of medicinal and agricultural
importance. Ex. Ascaris lumbricoides (intestinal roundworm), Trichinella spiralis (porkworm)
Phylum Nematomorpha – elongate worms commonly called
horsehair worms or Gordian worms
Phylum Acantocephala – “spiny-headed worms” because of
their spiny proboscis; endoparasites in vertebrates
Phylum Loricifera – microscopic animals which have spiny head
and thorax; live in gravel and marine environments;
Ex. Nanaloricus mysticus
Phylum Priapulida – cucumber-shaped, wormlike animals;
live buried in the sand and mud in marine habitats;
Ex. Priapulus caudatus
Phylum Mollusca – soft-bodied animals
Body of 2 parts: head-foot and visceral mass
Mantle that secretes a calcareous shell and covers
the visceral mass
Mantle cavity functions in excretion, gas exchange,
elimination of digestive wastes, and release of
reproductive products
Protostome characteristics, including trochophore
larvae, spiral cleavage, and schizocoeleous coelom
formation
Coelom reduced to cavities surrounding the heart,
nephridia, and gonads
Open circulatory system in all but one class
(Cephalopoda)
Radula usually present and used in scraping food
Class Bivalvia – bivalves such as mussels and clams;
Ex. Mytilus
Class Gastropoda – Snails and coiled shells; Ex. Nerita
Class Cephalopoda – squids and octopus; foot modified
into a circle of tentacles and a siphon;
Ex. Octopus, Loligo, Nautilus
Phylum Annelida – segmented worms; triploblastic,
coelomate animals, shows metamerism, have complete
digestive tract
Class Polychaeta – “tubeworms”; predators, scavengers,
or filter-feeders; mostly marine and possess parapodia
with numerous setae. Ex. Nereis, Sabella
Class Oligochaeta – “earthworms”; includes primarily
freshwater and terrestrial annelids; possess few
setae, lack head and parapodia; scavengers;
Ex. Tubifex
Class Hirudinea – “leeches”; complex arrangement of
body-wall muscles, and the loss of septa influence
patterns of locomotion; predatory and feed on body
fluids, such as blood of vertebrates
Ex. Hirudo
Phylum Arthropoda – “jointed legs” animals
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Metamerism modified by the specialization of body
region for specific functions (tagmatization)
Chitinous exoskeleton
Paired, jointed appendages
Growth is accompanied by ecdysis or molting
Ventral nervous system
Coelom reduced to cavities surrounding gonads and
excretory organs
Open circulatory system
Complete digestive tract
Metamorphosis often present
Subphylum Trilobitomorpha
Subphylum Chelicerata
Class Arachnida – spiders, mites, ticks, scorpions
Subphylum Crustacea – mostly aquatic; head with 2 pairs of
antenna, I pair of mandible, 2 pairs of appendages;
biramous appendage
Class Branchiopoda – “water fleas”
Class Malacostraca – lobsters, crayfish, crabs, shrimps
Class Cirripedia – barnacles
Class Copepoda – copepods
Subphylum Uniramia
Class Hexapoda - with three pairs of legs; usually
two pairs of wings; with body, head, thorax and
abdomen; insects
Phylum Echinodermata – postradial symmetry; have an
endoskeleton of interlocking calcium carbonate and
ossicles; have a water vascular system that is used for
locomotion, food gathering, attachment, and exchanges
with the environment
Class Asteroidea – sea stars
Class Ophiuroidea – brittle stars and basket stars
Class Echinoidea – sea urchins, heart urchins, sand dollars
Class Holothuroidea – sea cucmbers
Phylum Hemichordata – live on marine sediments; includes
the acorn worms and the pterobranchs
Ex. Balanoglossus
Phylum Chordata – marine, freshwater and terrestrial habitats;
a notochord, pharyngeal slits, a dorsal tubular nerve
cord, and a post anal tail are all present at some time
in life histories
Subphylum Urochordata- sea quirts, tunicates
Subphylum Cephalochoradata – Amphioxus
Subphylum Vertebrata – lampreys, hagfishes, sharls,
bony fishes, frogs, reptiles, birds, mammals