Chapter
33 - Invertebrates
Parazoa
Back to Biology 1402 page
No tissue
Phylum Porifera (sponges)
sole representative
Phylum Porifera - Sponges
Sessile aquatic organisms (fresh water and marine)
Most are suspension feeders
Most are hermaphrodites (single organism produces both
male and female gametes)
Radiata
Radial symmetry
Diploblastic (2 germ layers)
Phylum Cnidaria - hydras, jellyfishes, corals, anemones,
sea fans
Phylum Ctenophora - comb
jellies
Phylum Cnidaria-
jellyfish, corals, anemones
Aquatic - sessile (polyp) and mobile (medusa) stages
in life cycle
Carnivorous
Sexual and asexual reproduction
3 major classes - Hydrozoa, Scyphozoa
and Anthozoa
Phylum Ctenophora -
Comb Jellies
Aquatic organisms - all marine - use cilia for
locomotion
Plankton feeders
Bilateria
Bilateral symmetry
Triploblastic
All remaining animal phyla
Bilateria
Lineage 1 - Acoelomates
No body cavity
Phylum Platyhelminthes
(flatworms) sole representative
Phylum Platyhelminthes -
Flatworms
Flattened dorsoventrally
Aquatic, terrestrial, parasitic
Turbellarians - nearly all free-living
Monogeneans, trematodes (flukes) and cestodes (tapeworms) parasitic- complex life cycles
involving several hosts - important in human health
Bilateria -
Lineage 2 - Pseudocoelomates
Body cavity present - not lined with mesoderm
Phylum Rotifera - Rotifers
Phylum Nematoda Nematodes
Phylum Rotifera - Rotifers
Mobile aquatic organisms
Characterized by crown of cilia used in feeding
Complete digestive tract
Reproduce by parthenogenesis (females develop from
unfertilized eggs; eggs fertilized by disfunctional
males form resistant zygotes)
Phylum Nematoda -
Nematodes (Roundworms)
Aquatic, terrestrial, parasitic
Complete digestive tract, lack circulatory system
Reproduction usually sexual
Parasitic forms important in human health and
agriculture
Bilateria -
Lineage 3 - Coelomates
Body cavity present - lined with mesoderm
Remaining animal phyla
Two main branches - Protostomes
& Deuterostomes
Protostomes
Spiral-determinate cleavage; schizocoelous;
mouth develops from blastopore
Includes the Phyla Nemertea,
Bryzoa, Brachiopoda, Phoronida, Mollusca, Annelida & Arthropoda
Phylum Mollusca -
the Molluscs
Characterized by muscular foot, visceral mass & mantle
Aquatic & terrestrial
Includes the bivalves (clams), gastropods (snails)
& cephalopods (squids, octopus & nautilus)
Important components of food web, human food, vectors
of disease organisms
Phylum Annelida -
the Segmented Worms
Body wall & internal organs segmented (except
digestive tract)
Aquatic & terrestrial
Includes the oligochaetes
(earthworms), polychaetes (marine segmented worms)
& leeches
Important in soil aereation
(earthworms) and as components of food web
Phylum Arthropods -
the Arthropods
Characterized by segmented body, jointed appendages,
exoskeleton from ectoderm
Aquatic and terrestrial
Includes the arachnids (spiders, scorpions, ticks,
mites), crustaceans (crabs, lobsters), and insects
Largest group of organisms - extremely important in
food web, in agriculture & human disease
Deuterostomes
Radial-indeterminate cleavage; enterocoelous;
anus develops from blastopore
Includes the Phyla Echinodermata
& Chordata
Phylum Echinodermata -
the Echinoderms
Characterized by a water vascular system, tube feet,
secondary radial symmetry & endoskeleton from mesoderm
Entirely marine
Includes the sea stars, brittle stars, sea urchins,
sand dollars, sea lillies & sea cucumbers
Important components of food web
Phylum Chordata -
the Chordates
Characterized by notochord, hollow nerve cord,
pharyngeal slits & muscular postanal tail
Aquatic & terrestrial
Includes the lancelets, tunicates & vertebrates
This is the Phylum that man belongs to