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ch 18


Animals are multicellular, heterotrophic eukaryotes that obtain nutrients by ingestion


a body cavity completely lined with mesoderm = the middle germ layer that develops into muscle and bone and cartilage and blood and connective tissue


a body cavity that is in direct contact with the wall of the digestive tract., body cavity between the endoderm and mesoderm tissues that is partially lined with mesoderm tissue, fluid filled in contact w/digestion tract

radial symmetry

the body parts radiate from the center, body plan in which body parts repeat around the center of the body; characteristic of sea anemones and sea stars

bilateral symmetry

has mirror-image right and left sides, body plan in which only a single, imaginary line can divide the body into two equal halves; characteristic of worms, arthropods, and chordates


the innermost of three embryonic cell layers in a gastrula; forms the anchenteron in the gastrula and gives rise to the innermost linings of the digestive tract and other hollow organs in the adult (repsiratory)


the middle layer of the 3 embryonic cell layers in a gastrula; gives rise to muscles, bones, the dermis of the skin, and most other organs in the adult.,


the outer layer of 3 embryonic cell layers in a gastrula; forms the skin of the gastrula and gives rise to the epidermis and nervous system in the adult.

complete digestive system

have a distinct mouth and anus, allows for different compartments and function associated with particular activies that becomes organs associated with digestion

incomplete digestive system

a single opening to a pouch-like cavity serves as both mouth and anus

open circulatory system

blood is pumped through vessels that open into body cavities where organs are bathed directly in blood

closed circulatory system

blood remains enclosed in vessels as it distributes nutrients and oxygen throughout the body.


the simplest animals and have no true tissues. Their flagellated choanocytes filter food from water passing through the porous sponge body, have no tissues, no organs and no symmetry; have pores, invertabrate


have true tissues and radial symmetry. Their two body forms are polyps and medusa. They have cnidocytes on tentacles that sting prey and a gastrovascular cavity.


bilateral animals with no body cavity. A planarian has a gastrovascular cavity and a simple nervous system. Flukes and tapeworms are parasitic flatworms with complex life cycles.


Nematodes have apseudocoelom and a complete digestive tract and are covered by a protective cuticle. Many nematodes are free-living decomposers; others are plant or animal parasites, (round worms) round smooth body; have a tube within a tube body plan, separate mouth and anus; no circulatory system; some free living, some parasite


include gastropods (snails and slugs), bivalves (clams), and cephalopods (squids). All have a muscular foot and a mantle, which may secrete a shell and which encloses the visceral mass. Many mollusks feed with a rasping radala.


segmented worms and include earthworms, polychaetes, and leeches., (segmented worms) tube shaped bodies divided into sections; has a coelom, a body cavity with organs inside;simplest animals with a circulatory system; have specialized organs for digestion; earthworms the farmers friend help aerate soil and breakdown organic matter


segmented animals with exoskeletons and jointed appendages. The four lineages are chelicerates (arachnids), the aquatic crustaceans (lobsters and crabs), the lineage of millipedes and centipedes, and the terrestrial insects. insects: have a three-part body (head, thorax, and abdomen) and three pairs of legs; most have wings. These most successful arthropods are grouped in about 26 orders. Their development often includes metamorphosis. Specialized appendages and protective color patterns, which frequently result from changes in the timing and location of homeoticene expression, have played a major role in this group's success.


have a dorsal, hollow nerve cord, a stiff notochord, pharyngeal slits, and a muscular post-anal tail. The simplest chordates are lancelets and tunicates, marine invertebrates that use their pharyngeal slits for suspension feeding.

9 major animal phyla

phylum poriefera (spongs) , phylum coelenterata (jellyfish), phylum platyhelminthes (flateworms), phylum nematoda (roundworms, phylum annelida (segmented worms), phylum arthropoda (insects), phylum mollusca (molluscs), phylum echinodermata (sea stars), phylum chordata (fish, bird, mammals)

8 classes of vertebrates

1. Agnatha - jawless fishes
2. Placodermi - jawed armored fishes (extinct)
3. Chondrichthyes - cartilaginous fishes
4. Osteichthyes - bony fishes
5. Amphibia - Amphibians
6. Reptilia - Reptiles
7. Aves - Birds
8. Mammalia - Mammals

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