34-2 Animal Bodies 3 structural features used to classify animals 1. Symmetry 2. Germ layers 3. Body cavities

Animal bodies range from those which have no body and lack tissues (sponges) to those that have tissues and body shape (most animals).

1. Symmetry Symmetry * (constant overall pattern of structure) a. Asymmetrical b. Radial c. Bilateral

Symmetry

A. Asymmetrical No symmetry (sponge)

B. Radial Similar parts branch out from a central line (ex. Hydra)

C. Bilateral Two similar halves (most animals have this type of symmetry) dorsal: upper surface ventral: lower surface anterior: head region posterior: tail region right left

Cephalization Bilateral symmetrical animals exhibit cephalization  Sensory and brain are in anterior region  Have a head As move through their environment, the head proceeds to sense danger, prey or mate

Lab A21 Sponge p.694 Jellyfish p. 48 Sea urchin p. 783 Sea star p. 784 Snail p.727 Grasshopper p.765 Crayfish p. 748 Frog p. 821 Lizard p. 852 Sea cucumber p. 784 Starfish p. 785

2. Germ Layers  issue type found in embryos of all animals except sponges.  ll body features, organs and tissues arise from a germ layer. All animals but cnidarians ( Jellyfish) and ctenophores ( relative) have 3 germ layers. The two listed here have only 2 germ layers.

Germ Layers

3. Body Cavities (coelom)   Fluid filled space between digestive tract and outer wall of body Flatworms lack a body cavity (tapeworms). a. Aids in movement by providing a firm structure against which muscles can contract b. Allows movement of exterior of body, gives more freedom of movement c. Fluid acts as medium to transport nutrients and wastes

Coelom

Animal Diversity  Similarities in body parts and patterns of development allow scientists to classify animals and hypothesize about their evolutionary history.  Animals on same branch are more closely related. Chordates more closely related to echinoderms Fig p. 672

Invertebrates: 10 phyla 1.Annelida: earthworm 2.Arthropoda: lobster, crab, spiders 3.Echinodermata: starfish, sea star 4.Cnidarians: hydra, jellyfish 5.Mollusca: clams, snails, octopus, slugs, squids 6. Rotifera: rotifers 7. Protista: amoebas, paramecium, euglena

Vertebrates: 1 phylum   Phylum: Chordata (chordates) *has notochord: firm, flexible rod of tissue located in dorsal part of body and has dorsal nerve cord *in most vertebrates, the notochord forms backbone and dorsal nerve cord develops into the brain and spinal cord.   Subphylum: vertebrata 1. Chordata: amphibians (frogs), reptiles ( lizards), birds, mammals, fish