Animal Form and Function Chapter 32

What you need to know! The characteristics of animals. The stages of animal development How to sort the animal phyla based on symmetry, development of a body cavity, and the fate of the blastopore The traits used to divide animals into groups

All animals 1. Multicellular 2. Heterotrophic Obtain nutrients by ingestion (eating) 3. Extracellular matrices hold the cells together (tight junctions) No cell walls 4. Mobility (at some point in their life) 5. Diploid dominant 6. Nervous and muscular tissue (most) 7. Sexual Reproduction Gametes fuse to form zygotes

Embryonic Stages a) Morula: mitosis forms cell ball through cleavage of zygote b) Blastula: hollow cell ball c) Gastrula: infolding of cellular layers

Embryonic Germ Layers Endoderm Internal sac that becomes the digestive system Ectoderm Outermost layer that becomes the skin and nerves Mesoderm Cells between the endo- and ectoderm that become muscles and other organs

Embryonic Development

Coelom Fluid filled body cavity for cushioning organs or to form a hydrostatic skeleton Animals with 3 germ layers may develop this Coelomates: organisms with coelom Acoelomates: organisms w/out coelom

Coelom True coelom: body cavity is completely lined by mesoderm cells (segmented worms and vertebrates) Pseudocoelom: mesoderm and other tissue cells form body cavity (roundworms)

Animal Evolutionary Trends Tissue Complexity Cells grouped into tissues according to similar function Tissues develop from germ layers during embryogenesis Organisms are said to be diploblastic when they have 2 layers, triploblastic when they have 3 layers Body symmetry Either radial (circular) symmetry with top and bottom or Bilateral symmetry with front (anterior), behind (posterior), backside (dorsal), and stomach (ventral)

Animal Evolutionary Trends Cephalization In animals with bilateral symmetry progressive accumulation of nerve tissue anterior as animals gain complexity: accessory organs for seeing, feeling, tasting evolve Gastrovascular cavity Digestion of foods can have one opening: saclike gut, or 2 openings: digestive tract Coelom fluid filled cavity cushioning internal organs Segmentation Body is divided into segments sometimes repeating (worms, insects) or are modified into body parts Protostomes and Deuterostomes Forms different cleavage patterns of early morula – spiral cleavage or radial cleavage

Protostome vs. Deuterostome CharacteristicProtoDeutero Early cleavagesspiral(angle)Radial(straight) Infolding ofForms mouthForms anus archenteron Coelom developssplit of archenteronOutpouching of fromsidesarchenteron