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Invertebrates
BIOZ 341
 Dr, Rafat Khattab
 Biology Department
 E-mail: [email protected]
Invertebrate Zoology
 Study of invertebrate animals
 Inverts make up at least 99% of all extant (living)
animal species on the planet
 Over 1,000,000 described spp. (species) on the
planet (mostly insects)
 Estimated 10 to 30 million spp. have yet to be
described
 We will cover 19 (time permitting) of the approx. 35
animal phyla
Invertebrates
 Invertebrates are those animals without
backbone.
 They can be classified into several taxa
according to several criteria:
 1- Presence or absence of proper tissues,
 2- Number of layers of tissues present
 3- Presence or absence of body cavity.
 Invertebrates include protists , parazoans
and metazoans orgamnisms
 Protista; which includes Protozoa and
other single celled organisms
 Parazoa are those multicellular animals,
which lack proper tissues. Animals belong
to Phylum Porifera (sponges) are good
representatives to Parazoa.
 Metazoa are those multicellular animals,
which have proper tissues.
 Phylum Coelentrata (Cnidaria) includes
diploblastic (two layered) metazoans.
 Acoelomates are triploblastic (three
layered) metazoans without a body cavity
(solid bodied invertebrates), such as
Phylum Platyhelminthes.
 Pseudocoelomates are triploblastic
metazoans with a pseudocoelom (the
cavity originated from the blastocoel),
such as Phylum Aschelminthes.
 Coelomates are triploblastic metazoans
with true coelom (the cavity originated
from the mesoderm).
 These include annelids (segmented
worms), arthropods (jointed legs
invertebrates), molluscs (soft bodied
invertebrates), echinoderms (spined skin
invertebrates), and chordates (animals
with a notochord).
 This course deals with the study of
taxonomy, morphology, and biology of
some major examples representing
Protozoa, Parazoa, lower and some higher
Metazoa of invertebrates.
 Exploring invertebrate diversity
PORIFERA (5,500 species)
A sponge
PLACOZOA (1 species)
CNIDARIA (10,000 species)
A jelly
KINORHYNCHA (150 species)
0.5 mm
250 µm
A placozoan (LM)
PLATYHELMINTHES (20,000 species)
A marine flatworm
ECTOPROCTA (4,500 species)
Figure 33.3
Ectoprocts
A kinorhynch (LM)
ROTIFERA (1,800 species)
A rotifer (LM)
PHORONIDA (20 species)
Phoronids
 Exploring invertebrate diversity
BRACHIOPODA (335 species)
A brachiopod
ACANTHOCEPHALA (1,100 species)
NEMERTEA (900 species)
A ribbon worm
CTENOPHORA (100 species)
5 mm
An acanthocephalan
MOLLUSCA (93,000 species)
A ctenophore, or comb jelly
ANNELIDA (16,500 species)
An octopus
LORICIFERA (10 species)
A marine annelid
PRIAPULA (16 species)
50 µm
Figure 33.3
A loriciferan (LM)
A priapulan
 Exploring invertebrate diversity
ARTHROPODA (1,000,000 + species)
NEMATODA (25,000 species)
A roundworm
A scorpion (an arachnid)
CYCLIOPHORA (1 species)
TARDIGRADA (800 species)
100 µm
100 µm
A cycliophoran (colorized SEM)
Tardigrades (colorized SEM)
HEMICHORDATA (85 species)
ONYCHOPHORA (110 species)
An onychophoran
An acorn worm
ECHINODERMATA (7,000 species)
Figure 33.3
A sea urchin
CHORDATA (52,000 species)
A tunicate
Preview of Phyla We Will Cover
 Protozoa – animal-like
protists
 Do not belong to
kingdom animalia, and
thus are not considered
to be invertebrate
animals
 Important evolutionary
link between
prokaryotes, and
everyday plants and
Volvox
Phylum Porifera
 Sponges
Phylum Cnidaria
 Jellyfish, Anemones, and Corals
Portuguese Man O’ War
Phylum Ctenophora
 Comb Jellies
Phylum Platyhelminthes
 Flatworms
Phylum Nemertea
 Ribbon Worms
Phylum Mollusca
 Chitons, Clams, Snails, Slugs, Squids, and
Octopi
Banana Slug
Phylum Annelida
 Segmented Worms
Phylum Echiura
 Spoonworms
Phylum Sipuncula
 Peanut Worms
Phylum Tardigrada
 Water Bears
Phylum Arthropoda
 Horseshoe Crabs, Arachnids, Crustaceans,
Myriapods, and Insects
Phylum Gastrotricha
 Name means “stomach hair”
Phylum Nematoda
 Roundworms
Caenorhabditis elegans = good
Ascaris lumbricoides = bad
Phylum Rotifera
 Wheel bearers
Phylum Phoronida
 A lophophorate
Phylum Brachiopoda
 Lamp shells, another lophophorate
Phylum Bryozoa
 Bryozoans, the largest phylum in the
superphylum Lophophorata
Phylum Echinodermata
 Starfish, Brittle Stars, Urchins, and Sea
Cucumbers
Phylum Chordata
 Phylum Chordata is
the only phylum
containing
vertebrate animals,
however, there are
some invertebrate
chordates