Kingdom Animalia

Kingdom Animalia
  • All Multicellular Eukaryotic heterotrophs
  • Lack cell walls & chloroplasts
  • Have unique embryological development patterns.
  • Animals can be organized by the following categories:
    • Type of symmetry
    • Type of gastrulation
    • Type of coeloem
Symmetry
Animals show 3 types of symmetry
1. Asymmetrical
  • No apparent structure around any axis
2 . Radial Symmetry
  • Has top and bottom, but no front, rear, left or right
3. Bilateral symmetry
  • Has Dorsal (top), Ventral (bottom), Anterior (front), Posterior (rear), left & right
  • Often show cephalization, the concentration of sensory and feeding parts to the anterior
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Embryology & Animal Classification
  • Animals differ in the way they develop embryologically
  • Two ways they can differ
  1. Fate of the blastopore
  2. Type of cleavage in gastrula formation
Gastrulation
  • Sperm fertilizes egg forming a zygote
  • The cells of the zygote divide numerous times.
  • When the number of cells reaches ~32 it forms a hollow ball called a blastula.
  • As division continues an invagination forms a hollow pocket in this ball of cells This is now called a gastrula, the process is known as gastrulation.
  • The opening of the gastrula is known as the blastopore
    • In Protostomes the blastopore becomes the mouth
    • In Deuterostomes the blastopore becomes the anus
  • The hollow space is known as the Archenteron
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  • This results in the formation of three dermal layers
    • The ectoderm (forms outer covering & nervous tissue)
    • The endoderm (gut & outpocketings like liver & lungs)
    • The mesoderm (muscles & other organs, forms later in the blastocoel of the gastrula)
Cleavage
  • 2 types
    • Spiral cleavage
    • Radial Cleavage
  • Spiral Cleavage (Annelid, Arthropods & Molluscs)
    • In spiral cleavage the cellular divisions occur diagonally, in a twisting pattern.
  • Radial cleavage (Echinoderms & Chordates)
    • The cellular divisions occur in perpendicular axes to each other.
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Coelomes
  • A Coeloem refers to the body cavity of an animal
  • These from from the 3 derm layers
  • Three types of coelomes
  1. Acoelomates have no internal body cavity
  2. Pseudocoelomates have an incompletely formed body cavity
  3. Coelomates have a fully developed body cavity completely lined by mesoderm
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