characteristics of an animal
-no cell wall
two major divisions
-invertebrates (no back bone)
-vertebrates (back bone)
a group of cells that have the same function
layers of cells that give rise to organs
nervous system, sense, skin
skeletal system, muscle system, circulatory system
symmetry (three types)
fluid filled cavity laying within cells produced by mesoderm
animal with no coelom
coelon that is within cells produced from mesoderm and endoderm
an embryonic stage that marks the end of cleavage during animal development; a hollow ball of cells in many species.
the embryonic stage resulting from gastrulation in animal development. most animals have a gastrula made up of three layers of cells: endoderm, ectoderm, and mesoderm
a fluid containing space between the digestive tract and the body wall.
a skeletal system composed of fluid held under pressure in a closed body compartment; the main skeleton of most cnidarians, flatworms, nematodes, and annelids.
the animals with "true tissues" (all animals except sponges)
animals that exhibit bilateral symmetry