Introduction to Animals

Unifying Characteristics Eukaryotic Heterotrophic Carnivores, parasites, filter feeders, detritus feeders Multicellular Lacking cell walls and chloroplasts   Respiration – consume oxygen and give off carbon dioxide

More Unifying Characteristics Movement   Reproduction Produce egg and sperm in multicellular structures Specialized cells

Body Structure Body structure basically a hollow tube Inside of tube is specialized for digesting and absorbing food (may be closed) Outer part responds to the environment Space in between may also be specialized Internal transport in larger animals (circulation) Excretory systems in larger animals

Symmetry Asymmetric Radial symmetry Bilateral symmetry Has no symmetry (usually simplistic) Ex. sponges Radial symmetry All wedge shaped sections around a vertical line are similar Ex. starfish Bilateral symmetry Only one plane that can divide the body into equal parts Tend to have a head region (anterior) for quick response to stimuli Ex. Butterflies, humans Other terminology: posterior (“butt”), dorsal (back), ventral (front)

Two Major Divisions Vertebrates (backbone) Invertebrates (no backbone)

Trends Cell specialization Levels of organization More complex symmetry Cephalization Body cavity formation