Invertebrates

• What is the definition of invertebrates?

  Animals lacking a spinal column or backbone
• What does the term "invertebrate" derive from?

  Latin "in-" meaning without and "vertebra"
• How long ago did the α-proteobacterium get ingested by a prokaryote?

  2-2.7 billion years ago
• What significant event gave rise to the modern eukaryotic lineage?

  The primary endosymbiotic event
• From which kingdoms did the Eukaryota evolve?

  Protista, Metazoa, Fungi, Plantae
• What are protozoa?

  Eukaryotic largely unicellular organisms
• What is the etymology of the term "protozoa"?

  Latin "proto-" meaning first and Greek "zōia" meaning animals
• What is the significance of protozoa in evolution?

  They are the ancestors of metazoans
• What are the theories explaining the evolution of multicellularity?

  • Symbiotic theory: different protozoa join as symbionts
  • Colonial theory: asexual reproduction of cells that remain together
  • Cellularisation: multinucleate protist evolves cell membranes
• Which theory is most likely responsible for the evolution of multicellularity?

  Colonial theory
• What is a disadvantage of cell differentiation in multicellular organisms?

  Cells are less adapted for survival alone
• What is a blastea?

  A hollow ball of cells
• What is the process of gastrulation?

  Formation of a multilayered embryo called a gastrula
• What are the three embryonic cell layers?

  Ectoderm, Endoderm, Mesoderm
• What does the ectoderm form?

  The epithelium and outer structures
• What does the endoderm form?

  The lining of the gut
• What does the mesoderm form?

  The muscles and internal structures
• How many phyla are invertebrates divided into?

  Approximately 32 phyla
• What is the etymology of the term "metazoa"?

  Latin "meta-" meaning change and Greek "zōia" meaning animals
• How are invertebrates classified based on body symmetry?

  • Asymmetrical (Non-Bilateria)
  • Radially symmetrical (Non-Bilateria)
  • Bilaterally symmetrical
• Why is differentiation among cells significant in multicellularity?

  It allows for specialized functions in organisms
• What is the role of germ cell layers in development?

  They give rise to tissues and organs
• How is phylogeny reconstructed in invertebrates?

  Using genetics and morphological characteristics
• What kingdom do invertebrates belong to?

  Animalia
• What is the classification of non-Bilateria?

  Includes Porifera, Placozoa, Cnidaria, Ctenophora
• How many species are in Phylum Porifera?

  7,000-15,000 species
• What does the term "Porifera" mean?

  Bearer of pores
• What level of organization do Porifera exhibit?

  Cellular level of organization
• What do Porifera lack?

  Nerve and muscle cells, tissues, organs
• What are pinacocytes?

  Flattened cells in the pinacoderm
• What is mesohyl?

  Gelatinous non-living layer
• What are spicules made of?

  CaCO₃ or SiO₂
• What are archaeocytes?

  Ameboid cells that are totipotent
• What is the function of choanocytes?

  Generate current and filter feed
• What is the role of the central flagellum in choanocytes?

  Generates a current
• What is the significance of the evolution of a true epithelium?

  Gives rise to the phylum Placozoa
• What does the evolution of the nervous system lead to?

  Gives rise to the phylum Cnidaria
• How many species are in Phylum Cnidaria?

  11,000+ species
• What type of symmetry do Cnidaria exhibit?

  Radial or bilateral symmetry
• What is the tissue level of organization in Cnidaria?

  Nerve net