Like this study set? Create a free account to save it.

Sign up for an account

Already have a Quizlet account? .

Create an account

when animal life began

precambrian seas with the evolution of multicellular creatures that ate other organisms


eukaryotic, multicellular, heterotrophic organisms that obtain nutrients by ingestion


eating food


once an egg is fertilized, the zygote develops into an early embryonic stage called this which is usually a hollow ball of cells


layers of cells that will eventually form the adult body parts. It has a primitive gut which will develop into the animals digestive compartment


a sexually immature form of an animal that is anatomically distinct from the adult form, usually eats different foods, and may even have a different habitat


a change in body form that eventually remodels the larva into the adult form

the evolution of this equipment for coordinated movement enabled some animals to search for or chase food

most animals have muscle cells, as well as nerve cells that control the muscles

animals probable evolved from a...

colonial, flagellated protist that lived in precambrian seas

cambrian explosion

at the beginning of the cambrian period, 542 millions years ago, animals underwent a relatively rapid diversification

one hypothesis for the cambrian explosion

emphasizes increasingly complex predator-prey relationships that led to diverse adaptations for feeding, motility, and protection

the hypothesis for the cambrian explosion helps explain...

why most cambrian animals had shells or hard outer skeletons, in contrast to precambrian animals, which were mostly soft-bodied

radial symmetry

identical all around a cetral axis

bilateral symmetry

there's only one way to split it into equal halves--right down the midline

a bilateral animal has..

a definate head end, that encounters food, danger, and other stimuli first when the animal is traveling

a body cavitiy

a fluid filled space separating the digestive tract from the outer body wall. Its fluid cushions internal organs, helping to prevent injury. It enables the internal organs to grow and move independantly of the outer body wall

the cavity is at least partly lined by

a middle layer of tissue called mesoderm which develops between the inner (endoderm) and outer (extoderm) layers of the gastrula embryo

a pseudocoelom

if the body cavity is not completely lined by tissue derived from mesoderm, it is termed...

a true coelom

the type of body cavity humans and many other animals have, is completely lined by tissue derived from mesoderm


vertebrates make up less than .... of all animal species


animals without backbones


phylum Porifera. sessile animals that appear so sedate than were mistaken for plants. range in height 1 cm-2m. have no nerves or muscles, but individual cells react to changes in the environment. only about 100 live in fresh water, the rest are marine.

how sponges get water

water is drawn through pores into a central cavity, then flows out of the sponge through a larger opening.

how sponges feed

collecting bacteria from the water that streams through their porous bodies. Flagellated called called choanocytes trap bacteria in mucus and then engulf the food by phagocytosis, digest it, and carry the nutrients to other cells.


the "do-all" cells of sponges, moving by means of pseudopodia, they digest and distribute food, transport oxygen, and disposes of waste. they manufacture the fibers that make up a sponges skeleton


phylum Cnidaria characterized by the presence of body tissues and radial symmetry and tentecles with stinging cells. Most are marine.

the basic body plan of a cnidarian

a sac with a central digestive compartment, the gastrovascular cavity. A single opening to this cavity functions as both mouth and anus

the basic body plan of the cnidarians has two variations

the sessile polyp and the floating medusa


adhere to larger objects and extend their tentacles, waiting for prey


a flattened, mouth down version of a polyp. it moves freely in the water by a combination of passive drifting and contractions of its bell shaped body


carnivores that use tentacles arranged in a ring around the mouth to capture prey and push the food into the gastrovascular cavity where digestion begins


phylum Platyhelminthes. simplest animals with bilateral symmetry. range from 1mm to 20 m. most have gastrovascular cavity with a single opening


parasitic flat worms, ribon like with repeated parts, no digestive tract at all


aka nematodes. phylum Nematodes. cylindrical body, tapered at both ends. most diverse and widespread animals. found in most aquatic habitats, in wet soils, and as parasites in the body fluids and tissues of plants and animals

free living roundworms in the soil are...

important decomposers

roundworms exhibit two innovations not found in flatworms

1)roundworms have a complete digestive tract, meaning they have two openings, a mouth and an anus 2) a body cavity, which in this case is a pseudocoelom ( a body cavity not completely lined by mesoderm-derived tissues


phylum Anthropoda. named for their jointed apendages, crustaceans, arachnids, and insects are examples. over 1 million species. regarded as the most successful animal phylunm

general characteristics of anthropods

anthropod segments and their appendages have become specialized for a great variety of functions.

body of an anthropod is completely covered by an ....



external skeleton, constructed from layers of protein and polysaccharide called chitin. doesnt grow with the body so has to shed it and secrete a larger one


sheding an old exoskeleton and secreting a larger one, leaves the animals temporarily vulnerable to predators and other dangers

four major groups of arthropods

arachnids, crustaceans, millipedes/centipedes, insects


live on land (scorpians, spiders, ticks, mites) four pairs of walking legs and specialized pair of feeding appendages


nearly all aquatic (crabs, lobsters, crayfish, shrimps, and barnacles) multiple pairs of specialized appendages

millipedes and centipedes

similar segments over most of their body and superficially resemble annalids but have jointed legs. mill. are landlubbers that eat decaying plant matter with two pairs of short legs per segment. cent. are terrestrial carnivors with a pair or poison claws used in defense and to paralyze prey


in species diversity...outnumber all other forms of life combined . they live in almost every terrestrial habitat and in fresh water and flying insects


branch of biology that specializes in the study of insects

400 millions years ago

oldest insect fossils date back to... during the paleozoic era

three part body

insects have a...the head, thorax and abdomen

the head of an insect

usually bears a pair of sensory antennae and a pair of eyes. several kinds of mouthparts are adapted for particular kinds of eating


Phylum Mollusca. (ex. snails, slugs, oysters, clams, octopusses, squids). soft bodied animals but protected by a hard shell. most are marine, though some are in fresh water and some land dwelling molluscs in the form of snails and slugs

how molluscs feed

using a straplike rasping organ called a radula to scrape up food

body parts of a mollusc

a moscular foot used for movement, visceral mass containing most of its organs, and a fold of tissue called the mantle

the mantle of a mollusc

drapes over the visceral mass and secretes the shell (if on is present)

three major groups of molluscs

gastropods (including snails and slugs), bivalves (including clams and oysters) and cephalopods (including squids and octopuses


protected by a single spiraled shell into which the animal can retreat when treatened. have distinct head with eyes at the tips of tentacles


including many species of clams, oysters, mussles, and scallops, have shells divided into two halves hinges together. most are sedentary, living in sand or mud in marine and freshwater environments. use their muscular foot for digging and anchoring


differ from gastropods and sedentary bivalves in being built for speed and agility. have large brains and sophisticated sense organs, which contributeto the success of these animals as mobile predators


phylum Echinoderm. named for their spiny surfaces, such as sea urchins, the porcupines, sea stars, sand dollars, and sea cucumbers. they are all marine. most are sessile or slow moving. lack body segments and most have radial symmetry as adults. most have an endoskeleton. and the water vascular system


interior skeleton, constructed from hard plates just beneath the skin.

water vascular system

a network of water filled canals that circulate water throughout the echinoderms body, facilitating gas exhange

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions and try again


Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

Voice Recording