Introduction to Invertebrate Zoology

• Invertebrate classification and relationships involve understanding based on cell number, embryology, body symmetry, developmental pattern, evolutionary relationships, habitat, and lifestyle
• Schaffer and Emerson's 1964 study aimed to identify stages of attachment and patterns in the development of attachment between infants and parents
• Participants in the study were 60 babies from Glasgow, and the findings showed that babies of parents with 'sensitive responsiveness' were more likely to form attachments
• Attachment is a strong reciprocal emotional bond between an infant and a primary caregiver
• Glacial erosion involves abrasion, a sandpapering effect caused by small rocks embedded within the glacier rubbing on bedrock, and plucking, where meltwater from glaciers freeze around broken rock parts, breaking them off as the ice moves down the slope
• Bilateral symmetry in animals allows them to be divided into two mirror images, with the left and right sides being identical
• No symmetry in animals means their body parts are not arranged in any particular order
• Deuterostomes have a mouth opening that did not arise from the blastopore, undergo schizocoelous coelom formation, have a radial, indeterminate cleavage pattern, and have monociliated cells in their larvae
• Biradial symmetry is found in comb jellies, where what is on the left side of the organism is mirrored on the right side
• Cephalization, the concentration of nervous and sensory tissues and organs at one end of an animal, is strongly associated with bilateral symmetry
• A sponge is a suspension feeder
• Acellular organisms include viruses
• Bilaterally symmetrical organisms develop germ layers during embryonic stages, giving rise to tissues and organs
• Radially symmetrical organisms came about before bilaterally symmetrical organisms and became abundant
• Cleavage formation in embryos can be spiral or radial, depending on the type of embryo
• In protostome embryos, cleavages are oblique to the original body axis, resulting in spiral cleavage
• Indeterminate cleavage allows cells to develop into entire organisms on their own, while determinate cleavage does not
• Protostome development (examples: molluscs, annelids):

  • Coelom development differs for protostomes and deuterostomes
• Coelom is the main body cavity in most animals, fluid-filled, positioned inside the body to surround, contain, and protect the digestive tract and other internal organs
• Organisms can be characterized based on how the germ layers in the embryo eventually develop in the organism—whether a coelom will form or not
• Coelom Formation:

  • Acoelomates: gut surrounded by mesoderm
  • Pseudocoelomate: body cavity partially lined by mesoderm and endoderm
  • Coelomate: true body cavity, completely lined by mesoderm
• Gastrulation:

  • Rearrangement of the cells of a blasula to form an embryo with 3 germinal layers: Ectoderm, Endoderm, Mesoderm
• Diploblastic organisms have:

  • Ectoderm only
• Which diagram shows schizocoely?

  • Diagram a
• Mouth Formation:

  • Protostomes: mouth origin from blastopore
  • Deuterostomes: mouth not from blastopore
• Protostomes:

  • Cleavage pattern: spiral, determinate
  • Coelom formation: schizocoely
• Deuterostomes:

  • Cleavage pattern: radial, indeterminate
• Polar lobe formation:

  • A conspicuous bulge of cytoplasm that forms prior to cell division and contains no nuclear material
• Larval morphology provides additional support for the premise that the protostome/deuterostome distinction is a natural one of long evolutionary standing
• Phylogenetic trees constructed on the basis of larval type accord well with those based on other criteria, e.g. molecular sequences
• Two major, well-defined groups emerge from phylogenetic trees: protostomes with downstream larvae and deuterostomes with upstream larvae
• Deuterostomes have monociliated cells in their larvae
• Classification in terms of Evolutionary Relationship:

  • Taxonomy developed by Carolus Linnaeus
  • Hierarchical classification and binomial system of nomenclature
  • Taxon refers to any group of organisms distinct enough to be assigned to a category
• Kingdom Animalia, Phylum Arthropoda, Class Insecta, Order Diptera, Family Muscidae, Genus Musca, Species M. domestica
• Phylogeny is the hypothesis of evolutionary relationships, represented by a phylogenetic tree which is a graphical summary of evolutionary history
• Phylogenetic Terms:

  • Monophyletic Group: forms a clade with an ancestral species and all its descendants
  • Polyphyletic Group: composed of unrelated organisms descended from more than one ancestor
  • Paraphyletic Group: includes an ancestor but not all of its descendants
• Reptilia is not a valid phylogenetic name as the group Reptiles does not form a clade unless birds are included
• Shaded in red is a valid clade: True
• The synapomorphic feature of the groups shaded in red is: Bilaterally symmetrical
• Classification in terms of Habitat and Lifestyle:

  • Habitat: terrestrial, aquatic (freshwater, marine, intertidal, subtidal, open sea)
  • Mobility: mobile, sessile, sedentary, planktonic