applies to forms that can be divided into similar halves by more than two planes passing through the longitudinal axis

applies to animals that can be divided into two mirrored portions with definite right & left halves

typically the front or belly, thinner skinned, lighter color, less hair, flexes

typically the back, thicker skin, darker color, extends outward away from the body

head end of an animal

tail end of an animal

formation of a head end of an animal with a concentration of nervous tissue & sense organs in the head region

eliminates nitrogenous wastes from the body & regulates water, electrolyte, & pH balance

responsible for breaking down food into absorbable units & eliminating indigestible foodstuffs (feces)

fast acting control system of the body

animals that typically have radial or bi-radial symmetry; all have stinging cells; all have tentacles; most primitive animals to have tissues

simplest of all animals; loose collection of cells, no tissues; body made up of a system of canals

acoelomates; simplest animals to display cephalization, bi-lateral symmetry; simplest animals to have organs; includes flatworms, flukes, tapeworms

gelatinous matrix lining spongocoel

opening in which water enters the sponge

opening in which water leaves the sponge

flagellated cells that line the inside of the sponge body; move water, nutrients, & wastes

internal bud typically of a freshwater sponge; parent dies during cold weather, offspring emerges during warm weather

simplest of all sponge canal systems; canals lead directly from outside to interior

canal systems in which there is a thickening and folding of the body wall

digestion that occurs inside individual cells

digestion that occurs outside individual cells

having two distinct layers of tissues

having three distinct layers of tissues

having both male and female gametes in one individual

separate male and female individuals

2 basic body forms; typical of many cnidarians

forms when a bud detaches & floats away from the parent

asexual stage of cnidarians; attached to a substrate; hydroid form

sexual stage of cnidarians; jellyfish form; free-swimming or floating; inverted bowl/umbrella-shaped

blind gut cavity with a single opening for both food & wastes

collection of nervous cells that help coordinate movement of cnidarians

animal that lack a fluid-filled body cavity

animal that has a fluid-filled body cavity, but it is not completely lined by mesodermal tissue

animal that has a fluid-filled body cavity that is completely lined by mesodermal tissue

life cycle that requires multiple hosts; typical of many parasitic flatworms

host species in which parasitic worm larvae undergo a portion of development

parasites of the vertebrate digestive tract; they do not have their own digestive system; they absorb nutrients through their skin; they have scolex for attachment to host

reproductive segments of tapeworms; break off; contain eggs

host's cells that have been reprogrammed by parasitic worm larvae to protect and nourish the growing worm larvae

anterior end curves dorsally to look like a hook; large plates in mouth cut into intestinal wall; juveniles penetrate skin

most common human roundworm parasite

parasitic nematode that lives in the lymphatic system & is transmitted by mosquitoes (or other insect)

transmitted by mosquitoes; most common filarial in the US; lives in the arteries of the host's lungs and hearts

horsehair worms; adults are free-living; juveniles parasitic in arthropods & make their terrestrial hosts enter water

area of a mollusk's body that houses digestive, circulatory, respiratory, & reproductive organs

2 folds of skin that protect the soft insides of a mollusk's body; extend from visceral mass & hang down either side of the body; secrete the shell

tongue-like structure that removes fine particles of food & moves it to the digestive tract

used in locomotion of a mollusk; can be modified to form a funnel for jet propulsion; can be used in attachment to a substrate

hard, protective outer layer of some mollusks; made of calcium carbonate

inner layer of a mollusk's shell, lies next to the mantle; secreted continuously in thin layers; gives the shell its thickness

middle layer of a mollusk's shell; made of layers of calcium carbonate; can be very colorful

mollusks with either a one-piece shell or no shell; shell can be coiled or uncoiled; marine, freshwater, or terrestrial

mollusks that are all active predators, all marine; can have a reduced shell or no shell; closed circulatory system; most complex brain of all invertebrates

mollusks that have a two-piece shell; filter feeders; lack a radula and cephalization

form when sand, a parasite, or other foreign object gets lodged between the shell and mantle of a bivalve

mollusk/cephalopod heart that pumps blood throughout the body

smaller hearts associated with gills of a cephalopod

skin cells that contain pigments; muscles control color & pattern by controlling pigment concentrations

releases melanin when a cephalopod is threatened

thick, non-living outer layer of many invertebrates

excretory tubules that remove/filter nitrogenous wastes from an annelid's body

substances that reduce blood clotting

substances that numb skin