Introduction to Animals. Chapter 34. What makes an animal an animal?. Multicellular Heterotrophy Sexual reproduction & development Movement. Body Symmetry. Radial symmetry- a body plan in which the parts are organized in circle around an axis. Body Symmetry.
Animals with a Backbone or Spinal Column: (All these animals are in the phyla Chordata and the subphyla Vertebrata.)
Cleavage- the series of cell divisions that occurs immediately following fertilization
Blastula- dividing cells become a hollow ball
Gastrulation- transforms the blastula into a multilaytered embryo called the gastrula