Chapter 33 Lower Invertebrates

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Chapter 33Lower Invertebrates
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Animals

• 1 million species of animals
• 95 are invertebrates!

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34-36 phyla of the AnimalKingdom

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1. Phyla Calcarea Silicea(formerly
known as Phylum Porifera)

• 5,500 species, mostly marine sponges
• Parazoans
• 2 layers unspecialized cells, no tissues
• Asymmetrical
• Suspension (filter) feeders
• Sessile
• Hermaphroditic, but cross fertilize
• Regenerative abilities

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opening
CaCO3 skeletal fibers
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2. Phylum Cnidaria

• 10,000 species (jellyfish, sea anemones)
• Live in shallow coastal marine waters
• Eumetazoa
• Organized into tissues
• Diploblastic 2 germ layers
• Radially symmetrical
• Carnivorous
• Have stinging tentacles called cnidocytes
• Gastrovascular cavity
• Digestive system (only one opening)

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Life Cycle
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Class Hydrozoa hydra
Class Scyphozoa sea nettle
Class Cubozoa box jelly
Class Anthozoa brain coral
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3. Phylum Ctenophora

• All Marine (100 species)
• Comb Jellies
• Resemble Cnidarians
• Lack stinging cells have sticky cells to capture
  prey

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4. Phylum Platyhelminthes

• Bilaterally symmetrical
• Triploblastic (all germ layers)
• Gastrovascular cavity (both ends)
• Sexual and asexual reproduction
• Complex tissues nerves and brain
• Acoelomate
• Mostly parasitic

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Class Turberellaria planaria
Class Trematoda liver fluke
Class Monogenea Dermophthirius
Class Cestoda tapeworm
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5. Phylum Rotifera

• Mainly freshwater
• Pseudocoelomate
• Complete digestive system
• Use cilia to draw water into mouth
• wheel bearer
• Parthenogenesis sexual-female dominate

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6. Phylum Braciopoda

• Bilateral symmetry
• Coelomates
• Triploblastic
• Marine
• Lophophores for feeding
• Horseshoe-shaped/circular crown of ciliated
  tentacles surrounding mouth

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7. Phylum Nemertea

• Bilateral symmetry
• Triploblastic
• Acoelomate
• Mostly marine
• Proboscis used to probe environment
• Simple circulatory system no heart, blood
  movement through body contractions
• Complete digestive system

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8. Phylum Nematoda

• 25,000 species
• Bilateral Symmetrical
• Organized into Tissues
• Complete digestive tract
• Sexual reproduction
• Pseudocoelomic