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METAZOA=ANIMALIA. Key characteristic features that permitted amazing diversity: a) multicellularity b) ability to move  c) possession of collagend) heterotrophy in feeding( advanced digestive systems)PHYLUM PORIFERA

- are sessile - primitive; they show the least cellular differentiation & integration of all Metazoa - with no true tissues - no mouth or gut - no muscles or reproductive, digestive, respiratory, sensory or excretory organs - no circulatory system - cells are remarkably autonomous - many show no clear axes of symmetry - sometimes put in separate sub-kingdom Parazoa Defining sponge traits include:

a) water-canal system b) Colony form varies from simple to complex

Asconoid

Syconoid

Leucanoid

Referred to as ascon type ,sycon type and leucon typec) Specialized cell types include:

o pinacocytes o archaeocyteso contractile cells o choanocytes o porocyte

d) Reproduction: budding and fragmentation are common ,most sponges are hermaphroditic and fertilization is internal

e) Typesof digestion: Food capture - several levels of filtration: ostia = external filter to exclude big stuff, although porocytes/pinacocytes can phagocytize food that gets stuck

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outside. Pinacocytes lining channel walls can do same. If channel gets clogged by oversize particles, it can reorganize.

Predation - One group of sponges (Cladorhizidae) is predatory and has lost its choanoderm as well as aquiferous system! Instead uses long filaments extended from the body and armed with hooked spicules (Vacelet & Boury-Esnault, 1995), a fundamental abberation to the body plan of Porifera.

Trophic symbioses - In addition to filter feeding, many sponges, like many other sessile organisms on reefs, have microscopic algal symbionts, that may provide nourishment for the host.

f) Three classes of Porifera to note (a fourth class is not covered): CALCARAE,DEMOSPONGIAE and HEXACTINELLIDA that can be grouped into glass and chalk sponges depending on the type of spicules.

Phylum Cnidaria Predatory species divided into three main classes Two body forms predominate: polyp and medusae The basic body plan of all cnidarians is similar:

o a) radially symmetrical o b) the gut has one opening (mouth only, no anus) o c) tentacles (hollow or solid) surround the end bearing the moutho d) the gastric cavity has associated canals

Cnidarians exhibit a true, three-layered, tissue level of organization o a) epidermis and gastrodermis are true tissues o b) the middle layer (mesoglea) mostly non-cellular 

This diverse phylum is united by a unique and complex cell type: o a) a cnidocyte -a cell that bears two important organelles:

nematocyst  cnidocil 

Nematocysts come in 30 forms Only a few other cell types exist; most are in epidermis and gastrodermis:

o a) epithilio-muscular o b) interstitial o c) receptor o d) nerve o e) gland o f) amoeboid

Life cycle: asexual reproduction and coloniality are widespread o a) a distinctive ciliated planula larva forms after gastrulation o b) the planula larva may be the ancestral form of the Bilateria

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Classes:(a) HYDROZOA a) Hydroids

two orders: polyps thecate or naked  polyps show division of labor in colonial forms most possess a medusa stage

b) Trachyline medusaec) Hydrocorals (b) SCYPHOZOA a) new medusae are produced from a polypb) some polyp stages possess septae in the gastrovascular cavity c) ANTHOZOA The class is all polyps and there is no medusa stage a)  Octocorals b) Hexacorals

Phylum Ctenophora all marine, most pelagic; common members of the "gelatinous zooplankton"

o can be significant predators in mid-ocean environment o body length can reach 2m; some have up to 70cm tentacles

share 3 features with Cnidaria which they resemble superficially: o diploblastic organization o possess only a mouth o gastrovascular cavity with radiating canals

exhibit some curious differences from Cnidaria: o asexual reproduction not well-developed o all are hermaphroditic o highly determinate, bi-radial cleavage o lack cnidocytes

four distinctive features: o unique rows of ciliated comb plates: possess 8 vertical "comb rows" (comb cilia are the largest cilia known in Metazoa)o two long, branching tentacles covered with colloblasts o exhibit conspicuous biradial symmetry o Do not exhibit polymorphismo Lack the characteristic stinging organelles called nnematocysts

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evolutionarily enigmatic o middle layer exhibits some tissue-like characters o middle layer develops from mesenchyme cells o wide variety of body forms

Bilateral AnimalsThe Bilateria includes all remaining phyla. Key innovations include:

Bilateral symmetry that adapts the to forward movement Third tissue layer : Triploblastic (ectoderm, mesoderm, endoderm) –tissues defined and

organized into complex functional organs. Compartmentation – nervous tissue highly organized and concentrated at the anterior

end of the animal.(Cephalization)o Most Bilateria exhibit a well-developed coelom o A pseudocoelom is simply a blood-vascular system lacking a heart

Excretory organs – no longer depend on simple diffusion o An excretory system includes 3 steps: i) ultrafiltration, ii) resorption , and iii)

transport o Plame cell and tubules for Platyhelmintheso Nephridial systems come in two general forms:

protonephridia metanephridia

Complete gut (mouth and anus) in the ribbonworms and separated from the circulatory system.

Platyhelminthes-  Worm-like forms occur in 12 different phyla1) Ph. PLATYHELMINTHES includes the flatworms, flukes, and tapeworms

  o generally small in size o have a blind gut: mouth but no anus o no circulatory system or coelomo depend on a network of protonephridiao have a simple ladder-like nervous system with anterior brain o tremendous capacity for regeneration and asexual reproduction o most are hermaphroditico classification is a problemo the most primitive taxon within the Protostomia:

has some protostome characteristics lacks others (coelom, circulatory system, anus, trochophore larvae)

2) Class TURBELLARIA- mostly free-living flatworms a) have an extensively ciliated, glandular epidermis b) vary body shape with circular, longitudinal and dorsoventral muscles c) gut may be absent, complex, tripartite, or unbranched  d) 3 forms of pharynx: simple, plicate, bulbous e) gonads may be absent, few, or many; those with gonads are hermaphroditic; 3) Cl. TREMATODA (digenic flukes)

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 a) definitive host nearly always a vertebrateb) oral (and often ventral) sucker, bulbous pharynx, gut has two branches ,Chinese liver fluke has 2 intermediate hosts 4) Cl. CESTOIDEA (tapeworms) a) common gut parasites of all vertebrate classes b) distinctive head end; no mouth and no gut c) produce many segments d) encyst in intermediate host

NemerteaNEMERTEA (ribbon worms; 1,150 spp); predatory, mostly marine a) can reach quite large sizeb) share many traits with flatwormsc) differ from flatworms: body is circular in cross-section, complete gut; unique blood-vascular system lined with endothelium; spectacular proboscis housed in a rhynchocoel   PSEUDOCOELOMATE ANIMALS AschelminthesA grouping of convenience whose origins and membership remain controversial

General Adaptive Features:a) triploblastic organization  b) complete gut c) small size   d) odd determinate cleavage e) retractile or eversible spiny head end  f) an acellular outer-body covering

Larger aschelminthes posses a fluid-filled pseudocoelom a) it differs little from a hemocoel anatomically b) it develops like a hemocoel in other protostomes except the gut is often free of mesodermal tissue c) it is not associated with a pumping heart

Most have a collagen or chitin cuticle that has many functions: a) as a skeleton  b) it lines the pharynx c) in some groups it must be molted to grow

THE PHYLUM NEMATODA (round worms) a) most are free living, but many are also parasitic b) they are a group of many paradoxes:- may be the most diverse phylum but only 22,000 named spp. - may be the most numerous metazoans on earth - most are tiny  - though rarely seen, some are serious human parasites - although few have seen them, one species (Caenorhabditis elegans) is one of the most intensively studied 'model' animals c) surprisingly little morphological diversity

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- cylindrical or spindle-shaped bodies surrounded by tough cuticle - have a mouth, straight gut and terminal anus - body wall muscles are exclusively longitudinal  - 4 nerve cords: dorsal and ventral (locomotory), 2 lateral (sensory) d) large forms have an extensive pseudocoelom e) many exhibit chromosome diminution2) Ph. ROTIFERA ("wheel bearer" worms) a) are among the smallest of metazoans b) exhibit a huge variety of body forms and life cycles c) often have a 3-part body d) most are suspension feeders e) some are predatory f) some prey rotifers exhibit dramatic changes in body form3) Three other aschelminth phyla worth mentioning include: a) Ph. NEMATOMORPHA (horsehair worms; 325 sp.) - extremely long, slender worms resembling nematodes - single large pseudocoelom - like nematodes, they lack circular muscles - larvae are parasitic in terrestrial insects - only the larvae have a spiny, eversible head end b) Ph. PRIAPULIDA (penis worms; 18 spp.) - thick-bodied (0.5 - 40 cm long), typically predatory worms- distinctive, plumose caudal appendages in some - single large pseudocoelom - although few living species persist, they were a common invertebrate of Cambrian seasc) Ph. ACANTHOCEPHELA (spiny-headed worms; 1150 spp.) - small-bodied (typically 1-2cm), exclusively endoparasitic - require two hosts - no mouth or gut - single large pseudocoelom - spiny, eversible head end to anchor in the gut lining - related to rotifers d) The Aschelminthes may also include the newest animal phylum (1995): CYCLIOPHORA Protostomes and DeuterostomesTwo major divisions of the Bilateria (Protostomia and Deuterostomia) exhibit many differences: 1) Origin of mesoderm is from very different cell types:

o   mesenchyme cells ( protostomes)o epithelial cells inpocket from archenteron ( Deutero)

2) Origin of coelom is via two different mechanisms: o   schizocoely ( splitting of the mesoderm)o enterocoely ( as outpocketing of primitive gut- Deutero)

3) Origins of mouth and anus differ. The blastopore gives rise to the: o   mouth; the anus arises secondarily (Protostomia) o anus ; the mouth arises secondarily (Deuterostomia)

4) Other differences include: PROTOSTOMIA: spiral and determinate cleavage –TRONCHOPHORE LARVA

multiciliated cells DEUTEROSTOMIA: radial and indeterminate cleavage-DIPLUERA LARVAmonociliated cells, deuterostomes may only include echinoderms, hemichordates and chordates

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