Lesson 5 & 6

• What is the definition of protozoa?

  Assemblage of eukaryotic unicellular organisms
• What does the term 'zoa' in protozoa signify?

  Absence of cell wall and motile stage
• Why are unicellular eukaryotes not considered monophyletic?

  Phylogenetic studies suggest great diversification
• What occurred after the first eukaryote originated?

  A great diversification of organisms
• What are the characteristics of Phylum Protozoa?

  • Unicellular
  • Mostly microscopic
  • Variable or constant shape
  • No germ layer present
• What types of relationships do protozoans exhibit?

  • Free-living
  • Mutualism
  • Commensalism
  • Parasitism
• What are the types of nutrition found in protozoans?

  • Autotrophic
  • Heterotrophic
  • Saprozoic
• How are choanoflagellates morphologically similar to sponges?

  They resemble choanocytes of sponges
• What are sponges classified under?

  Phylum Porifera
• What is the body structure of sponges?

  Cells embedded in a gelatinous matrix
• Why were sponges not accepted as animals until the 19th century?


  They neither look nor behave like other animals
• What are the characteristics of Phylum Porifera?

  • Multicellular
  • Body with pores and canals
  • All aquatic, mostly marine
  • Radial or no symmetry
  • Adults are sessile
• What is the function of choanocytes in sponges?

  They create water currents
• How do sponges perform digestion?

  Intracellular digestion
• How do sponges reproduce asexually?

  By buds or gemmules
• What are the two types of spicules found in sponges?

  Calcareous and siliceous spicules
• What are the classes of sponges in Phylum Porifera?

  • Class Calcarea
  • Class Hexactinellida
  • Class Demospongiae
• What distinguishes Class Calcarea sponges?

  Spicules composed of calcium carbonate
• What is a characteristic of Class Hexactinellida sponges?

  Skeleton of six-rayed siliceous spicules
• What percentage of sponge species does Class Demospongiae comprise?

  Approximately 80%
• What is the adaptive radiation in Class Demospongiae focused on?

  Water circulation and filter-feeding system
• What are the characteristics of Phylum Cnidaria?

  • Aquatic, mostly marine
  • Radial or biradial symmetry
  • Two body layers: epidermis and gastrodermis
  • Presence of nematocysts
• What is the function of nematocysts in Cnidaria?

  Stinging organelles for defense and prey capture
• What type of cavity do Cnidarians have?

  Gastrovascular cavity
• How do Cnidarians achieve locomotion?

  Muscular contractions
• What are the two basic types of individuals in Cnidaria?

  • Polyps
  • Medusae
• How do Cnidarians reproduce asexually?

  By budding in polyps
• What type of nervous system do Cnidarians possess?

  Nerve nets without a central nervous system
• What are the classes of Cnidaria?

  • Class Hydrozoa
  • Class Scyphozoa
  • Class Cubozoa
  • Class Anthozoa
• What is a characteristic of Class Hydrozoa?

  Includes both freshwater and marine species
• What distinguishes Class Scyphozoa?

  Reduced polyp stage and bell-shaped medusae
• What is a defining feature of Class Cubozoa?

  Bell-shaped medusae square in cross-section
• What are the characteristics of Class Anthozoa?

  All polyps, no medusae
• What is adaptive radiation in Cnidaria?

  • Both polyp and medusa share a common structure
  • Efficient predators feeding on large prey
  • Colonial forms can grow to great sizes
• What is the order of true corals in Cnidaria?

  • Order Scleractinia
• How can Scleractinian corals be sorted morphologically?

  By solitary individuals or colonies of polyps
• What do polyps of Scleractinian corals resemble?

  Miniature sea anemones