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We will begin our look at animal diversity with a look at the invertebrates , animals

without backbones

Phylum Porifera – the sponges

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• Approx. 5,500 different extant species• All are aquatic or marine• Porous body plan w/out tissues (Parazoa)• Choanocytes – specialized cells (collar cells) with

flagella used for feeding• Sponges are suspension feeders, they filter the

water-column for suspended plankton and food particles

• Amoebocytes – take up food by phagocytosis• Many sponges produces spicules• Most sponges are monoecious

Anatomy of a sponge

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Classification of sponges

• Kingdom Animalia– Phylum Porifera

• Class Calcarea – calcium carbonate spicules– Grantia

• Class Demospongiae – spongin spicules– Common bath and finger sponges

• Class Hexactinellidia – six-rayed spicules made from silica

– Venus-looking-glass sponge

Phylum Cnidaria

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Characteristics of cnidarians• 10,000 spp.• True tissues (eumetazoan)

– Ectoderm –epidermis– Endoderm – gastrodermis

• Radial symmetry• Two growth forms

– Polyp– Medusa

• Only one opening for digestion – mouth – incomplete digestive system• Specialized stinging cells called cnidocytes with nematocysts (stinging

capsule) inside• Some contractile tissue – movement• Very primitive nerves –forms a nerve net• Various sexual and asexual reproductive modes

– Asexual -budding

Basic anatomy and growth forms

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Cnidocyte – used for feeding

Classification of Cnidarians

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Class Hydrozoa• Examples: Hydra,

Obelia, Portuguese-man-o-war

• Sexual reproduction or asexual by budding

Life cycle of Obelia

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Class Scyphozoa

• Medusa growth form dominates

• Includes jellyfish (Aurelia)

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Class Cubozoa

• Box jellyfish, sea wasp

• Highly toxic cnidocytes

• “box-shaped” medusa

• Photoreceptors embedded in medusa fringe

Class Anthozoa• Sea Anemones and

corals• Polyps• Sea anemones are

solitary• Corals often colonial

– Secrete calcium carbonate protective wall around polyps that forms the coral

– Coral reefs are important components of marine ecosystems

– Flower Gardens off Freeport

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Phylum Platyhelminthes

Characteristics of flatworms

• 20,000 spp.• Triploblastic• Bilateral symmetry• Acoelomate• Simple nervous system• Flame cells (protonephridia) – removal of

metabolic waste• Incomplete digestive system

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Classification of flatworms

Class Turbellaria

• Dugesia– Know the parts/functions of the planarian– Eyespots, auricles, gastrovascular cavity, pharynx, ventral nerve

cords, ganglia

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• Tapeworm anatomy – scolex, proglottids (monoecious), no digestive system

• All parasites with direct and indirect hosts

– Direct host – harbors adult parasite– Indirect host harbors larval forms

Class cestoda

Class Trematoda

• Parasitic flukes• Two suckers for attachment to host• Example – Schistosoma, blood fluke

– Infects >200 million people worldwide– Dioecious – male and female– Aquatic snail is intermediate host– Know life cycle

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