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

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

• 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.

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