Ch 32: Animal Diversity

• Nutrition mode 

• Heterotrophs that ingest their food 

• Body plans

• A set of morphological and developmental traits 

• Hox genes 

• Regulates the development of body form 

• Larva 

• Sexually immature state that eventually undergoes metamorphosis 

• Radial symmetry 

• Have top and bottom

• Bilateral symmetry 

• Have dorsal (top) & ventral (bottom) side, left & right side, anterior (front) and posterior (back) sides

• Cephalization 

• Development of a head region 

• Multicellularity in animals 

• Requires the evolution of new ways for cells to adhere (attach) and signal (communicate) to each other 

• Choanoflagellates 

• Closest living relative to animals 

• Cell structure 

• Cells are supported by structural proteins like collagen instead of cell wall 

• Cell specialization 

• Nervous & muscle tissue 

• Tissues 

• Groups of similar cells that act as a functional unit 

• Reproduction and development 

• Sperm fertilizes egg 

• Zygote forms cleavage (rapid mitosis) 

• Formation of multicellular, hollow blastula 

• Blastula undergoes gastrulation (formation of a gastrula with different layers of embryonic tissue)

• Ectoderm 

• Germ layer covering the embryo’s surface 

• IE skin, central nervous system

• Endoderm 

• Innermost germ layer and lines the developing digestive tube called the archenteron 

• Diploblastic animals

• Only have ectoderm and endoderm 

• Triploblastic animals 

• Have ectoderm, endoderm, and mesoderm 

• Protostome development 

• The blastopore becomes the mouth 

• Cleavage = spiral and determinate (embryonic cells determined)

• Coelom = splitting of solid masses of the mesoderm forms the coelom 

• Deuterostome development 

• The blastopore becomes the anus 

• Cleavage = radial and indeterminate (embryonic stem cells) 

• Coelom = mesoderm buds from the archenteron to form the coelom 

• Blastopore 

• Forms during gastrulation and connects the archenteron (early gut tube) to the exterior of gastrula

• Coelom 

• True body cavity derived from mesoderm 

• Coelomates 

• Animals that possess a true coelom 

• Pseudocoelomates 

• Posses a body cavity derived from the mesoderm and endoderm 

• Acoelomates 

• Triploblastic animals that lacks a body cavity 

• Functions of body cavity

• Fluid cushions suspended organs 

• Fluids acts like a skeleton against muscles 

• Allows internal organs to grow and move independently of the outer body wall 

• What is the sister group to all other animals?

• Sponges are the sister group to all other animals 

• Eumetozoa (“true animals”) 

• A code of animals with tissues 

• Most animal phyla belongs to which clade?

• Bilateria

• Clades of bilaterian animals 

• Deuterostomia

• Ecdysozoa 

• Lophotrochozoa