animal diversity

• there are 4 supergroups of Eukarya: excavata, SAR ( stramenophile, alveolate, rhizaria), archaeplastida, and unikonta
• unikonta includes two major clades: amoebozoans and opisthokonts
• animal characteristics

  • multicellular - interconnected cells
  • gap junctions for communication and tight junctions for holding/interconnecting cells together
• animal characteristics

  • no cell walls
  • can move (directional motion at some point in their life cycle; adapt, move from stressful environment)
  • heterotrophic (obtain energy by consuming energy-releasing food substances)
• animal characteristics

  embryonic tissue: ectoderm, mesoderm, endoderm
• animals have a diplontic life cycle
• gametes are haploid cells; zygote are diploid cells
• common ancestor of animals is shared with a group of protists called the Choanoflagellates (unicellular)
• choanaflagellates are a good outgroup of the animal clade because they are closely related but not multicellular
• clade of multicellular organisms called Metazoa clade
• earliest descendant of animals is in phylum Porifera
• multicellular organisms have cells that look almost identical to a single celled choanoflagellate
• 3 lines of evidence that choanoflagellates are closely related to animals

  • cell morphology
  • cell morphology unique to animal cells (no cell wall or plastid)
  • DNA sequence homology
• phylum Porifera

  • basal group known as sponges which have simple body structures
  • 2 cell layers
  • epidermis
  • choanoderm (draws in food particles and passed through amoebocytes)
• phylum Porifera

  middle region

  • porocyte (where water enters sponge known as the spongocoel)
  • mesohyl (amoebocytes, and hardened spicules)
• phylum Porifera

  random growth

  • asymmetrical (grow in all different directions)
• sponge cells are totipotent meaning they can regenerate and change cell fate
• all sponge cells can give rise to any of the other cell types
• sponge can self-assemble with other cells into sponge
• a sponge separated into its constituent cells will spontaneous resassemble
• radial symmetry

  • several planes of symmetry
  • only one body axis
  • top and bottom (oral and aboral)
• tissues are groups of specialized cells
• parazoa have no membranes
• eumetazoa have membranes
• cleavage - mitotic division
• gastrulation

  • primitive gut
  • blastopore (mouth)
• embryonic tissues

  • two germ layers
  • diploblastic
  • ectoderm (outer layer embryo)
  • endoderm (inner layer, and gut)
• phylum cnidaria 


  organisms associated: jellies, anemones, and corals
• phylum cnidaria

  • diploblastic, radially symmetrical bodies
  • epidermis (outer)
  • gastrodermis (inner)
  • mesoglea (jelly layer, between epidermis and gastrodermis, non cellular)
• phylum cnidaria

  • 2 basic body shapes
  • polyp (anemones and hydras)
  • crawling animals
  • cylindrical
  • mouth faces up
  • aboral side moves animal
• phylum cnidaria

  • 2 basic body shapes
  • medusa (free swimming jellies)
  • mouth faces down
  • moves freely in the water
  • tentacles point down
• diploblastic animals have two germ layers

  • ectoderm
  • covers surface of embryo
  • outer covering of the animal
  • endoderm
  • innermost germ layer
  • lines pouch that forms during gastrulation
  • lining of digestive tract, live, lungs
• triploblastic animals have three germ laters

  • mesoderm
  • fills space between ectoderm and endoderm
  • forms muscle and most inner organs
  • ex. flatworms, arthropods, vertebrates
• clades share a common ancestry

  • monophyletic clades
  • implies relationships
  • demonstrates divergent evolution
• grades share key biological feature only

  • no relationship between organisms
  • convergent evolution
  • ex. coelom, segmentation, wings
  • two unrelated groups have found a similar solution to solving different problems
• evolution of bilateral symmetry

  • two sided symmetry
  • derived character
• bilateral symmetrical animals have:

  • dorsal (top) and ventral (bottom)
  • right and left
  • anterior (front) and posterior (back)
• cephalization

  • sensory "equipment" concentrated at the anterior end (development of a head)
• cephalization

  radial symmetry

  • network of individual neurons
  • radial animals often sessile or weakly swimming (drifting)
• cephalization

  bilateral symmetry

  • clustering of neurons
  • ganglia
  • brains
  • clustering of sensory organs
  • active movement