What is an Animal

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What is an Animal?

• Multicellular heterotrophs
• Ingest their food
• Lack cell walls
• Structural proteins called collagen
• Junctions tight junctions, desmosomes and gap
  junctions
• Most reproduce sexually, with swimming sperm and
  non-motile egg
• Cleavage ? blastula ? Gastrula (with tissue
  layers)
• Some have sexually immature larval stage
• Monophyletic Kingdom

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• Tissues
• Symmetry
• Coelom
• Protostome / Deuterostome

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Porifera

• No True tissues
• No symmetry
• Suspension feeders
• Most are hermaphroditic

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Cnidaria

• Radial symmetry
• All have cnidocytes
• Diploblastic
• Gastrovascular cavity (no anus)
• Carniverous
• Body plan
• Polyp
• Medusa
• Simple muscle system
• Simple nerve net nervous system, no brain

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Cnidarian Classes

• Hydrozoa
• Alternate polyp and medusa in life cycle, with
  polyp as dominant stage
• Examples colonial hydroids, hydra, Portuguese
  Man of War
• Scyphozoa
• Prominent medusa
• Examples jellyfish
• Anthozoa
• Polyps are dominant
• Sea anemonies, and coral

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Ctenophore

• Comb jellies
• Only 100 species
• Have pair of long retractable tentacles

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Acoelomates

• Lack coelom
• Bilateral symmetry
• What evolutionary novelty comes with bilateral
  symmetry?
• Cephalizaton

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Platyhelminthes

• What new novelties are seen in this phylum?
• Triploblastic, so has muscular system
• Organs
• Cephalization, more complex nervous system

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Three classes

• Turbellaria
• Carnivorous
• Moves by cilia
• Eyespots on head
• Rudimentary brain
• Diffusion for gas exchange
• Excretion through flame cells
• Hermaphroditic

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Trematodes

• Often called flukes
• All members are parasitic
• What makes a parasite in good standing?
• Become an egg machine since it is hard to find a
  host
• Use intermediate hosts
• Develop hooks and suckers
• Hermaphroditism, so that limits need to find
  others

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Cestode

• Tapeworms
• Parasitic
• Scolex in adult hooks onto the host intestines
• Proglottids for reproduction
• Eggs eaten by intemediate host and larva develops
• Final host infected by eating intermediate host
  encysted with larva forms
• Do not eat poorly cooked meats

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Pseudocoelomates

• Not quite a true coelom, missing the inner lining
  of muscle

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Rotifera

• Mostly marine
• 1st to get an anus
• Organs lie in the pseudocoelm
• Parthogenesis unfertilized eggs develop into
  females

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Nematoda

• Many found in soil, useful for nutrient recycling
  
• Complete digestive tract
• Some are parasitic, e.g. trichanella and hookworm
  (dogs)

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