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Module 4: Kingdom Animalia/Metazoa

General Characteristics of Animals

  • Multicellular eukaryotic organisms, heterotrophic, cannot manufacture food.
  • Mobile in seeking food/shelter; specialized cells, tissues (e.g., nervous, digestive).
  • Lack cell walls; fixed growth pattern with embryonic stages.
  • Adaptations include camouflage, migration, and bioluminescence.
  • Divided into two sub-kingdoms: Parazoa (no true tissues) and Eumetazoa (true tissues).
  • Invertebrates: 9 phyla; Vertebrates: 1 phylum.

Parazoa

Phylum: Porifera (Sponges)
  • Simplest multicellular animals, mostly marine, colonial.
  • Asymmetrical, vase-shaped with internal cavity, lacking true tissues/organs.
  • Filter feeders using flagellated collar cells; reproduce asexually (budding/gemmules) or sexually (hermaphroditic).
  • Provide habitats for organisms and clean aquatic ecosystems.
  • Three body types: Asconoid, Syconoid, Leuconoid.
  • Classes: Calcarea, Demospongiae, Sclerospongiae, Hexactinellida.

Eumetazoa

Phylum: Cnidaria (Coelenterates)
  • Aquatic, mostly marine; diploblastic with true tissues.
  • Radial symmetry, have a coelenteron with one opening for digestion.
  • Exhibit polymorphism (polyp and medusa forms).
  • Reproduction: asexual (budding) and sexual (hermaphroditic or separate sexes).
  • Examples include Hydra, jellyfish, and corals.
Phylum: Platyhelminthes (Flatworms)
  • Triploblastic, acoelomate, bilateral symmetry; some free-living, some parasitic.
  • Lack digestive cavity or have an incomplete system.
  • Hermaphroditic, with a nervous system and simple sensory structures.
  • Classes: Turbellaria, Trematoda, Cestoda.
Phylum: Nematoda (Roundworms)
  • Cylindrical, unsegmented, pseudocoelomates; complete digestive tract.
  • Mostly free-living; some parasitic.
  • Separate sexes; significant ecological presence.
Phylum: Rotifera (Wheel Animalcules)
  • Mostly microscopic; free-living but some parasitic.
  • Triploblastic, acoelomate; distinct body structure with crowns of cilia.
  • Complete alimentary canal; reproduction mainly sexual with parthenogenesis in some.
Phylum: Annelida (Segmented Worms)
  • Body segmented, metamerically organized with specialization in body parts.
  • Closed circulatory system, complete digestive system with metameric excretory organs.
  • Classes: Polychaeta, Oligochaeta, Hirudinea.
Phylum: Arthropoda
  • Largest animal phylum; highly diverse and widespread.
  • Bilaterally symmetrical, triploblastic, segmented, jointed appendages.
  • Exoskeleton made of chitin; undergo ecdysis.
  • Open circulatory system