Asymmetry Animals have different patterns of symmetry, the arrangement of body parts around a central axis Asymmetry – no general body plan Example: Sponges 1

Radial Symmetry Radial symmetry – body can be divided into equal parts around a central axis Example: starfish, jellyfish Oral = side containing the mouth Starfish Morro Bay, CA 2

Bilateral Symmetry Bilateral symmetry – body can be divided along one plane of symmetry into two mirror halves Example: humans, crocodiles, crayfish 3

Compare the Difference Symmetrical Compare the Difference versus no symmetry 4

Ventral – underside (belly) Dorsal – back (top side) Bilaterally symmetrical animals can be divided into the following planes: Anterior – front end Posterior – back end Ventral – underside (belly) Dorsal – back (top side) Dorsal Anterior Posterior Ventral 5

Cephalization Bilaterally symmetrical animals also have cephalization, which is the concentration of nerve and sensory tissue at the anterior end of the organism 6 6

CNS – Central Nervous System

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Note the formation of the embryonic tissue layers: endoderm, mesoderm, ectoderm 9

Animals have different body plans based on the development of body cavities Acoelomate Pseudocoelomate Eucoelomate 10

Body Cavities Acoelomate – animal that lacks a body cavity Pseudocoelomate – animal that has a cavity between the mesoderm and endoderm (Not a true body cavity.. thus pseudo) 11

Body Cavities Coelomate / Eucoelomate – animal that has a cavity that develops within the mesoderm ( a true coelom/body cavity) 12

Animalia One main distinction between the phyla is the presence of a notochord, which can develop into a vertebral column (backbone) If animals do NOT possess a backbone, they are invertebrates, and if they do possess a backbone, they are called vertebrates Vertebrate Invertebrate 13

Porifera Invertebrate Animals The following phyla will be discussed in more detail in class: Phylum Porifera Phylum Cnidaria Phylum Platyhelminthes Phylum Nematoda Cnidaria Nomura Jellyfish Nematoda Platyhelminthes 14

Invertebrate Animals Phylum Mollusca Phylum Annelida Phylum Arthropoda Phylum Echinodermata Arthropoda Echinodermata Annelida Polychete worm 15

Vertebrate Animals Phylum Chordata Class Agnatha Class Chondrichthyes Class Osteichthyes Class Amphibia Class Reptilia Class Aves Class Mammalia 16