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animals that lack a backbone

example of invertebrate

Christmas tree worm

what accounts for ninety percent of known animal species?


what has produced diversity of forms

adaptation to the varied environments.

Sponges are ____ animals that lack ___ tissues

basal; true



sponges are


what are the simplest of animals?

sponges, and they are sedentary, sometimes mistaken for plants by the ancient Greeks

sponges are what kind of feeders?

suspension feeders

suspension feeders-

capture food particles suspended in the water that passes through the body (sac perforated with pores)

where is water drawn in the body?

the pores, and into a central cavity, the spongocoel

where does the water flow out the body?

through a larger opening called the osculum

sponges are what kind of animals?

basal animals

basal animals

represent a lineage that originates near the root of the phylogenetic tree of animals

sponges lack

true tissues, groups of similar cells that act as a functional unit and are isolates from other tissues by membranous

a sponge body containes

several different cell types

the interior of the spongocoel are

flagellated choanocytes, or collar cells

what are collar cells named for?

finger like projections that form a collar around the flagellum

these cells engulf bacteria and other food cells by


what supports the evidence that animals evolved from a choanoflagellate-like ancestor

similarity between choanoctyes and cells of choanoflagellates

the body of a sponge consists of

two layers of cells separated by a gelatinous region called the mesophyl

what allows gas exchange and waste removal ?

both cell layers are in contact with water, and diffusion across the membrane

what are other tasks performed by?

amoebocytes- named for their psuedopodia

functions of amoebocytes

take up food from surrounding living water and from choanocytes, digest it, and carry nutrients to other cells. can also manufacture tough skeletal fibers within the mesophyl, made from calcium carbonate or sillica

other sponges produce more flexible fibers composed of

a protein called spongin- bath sponges

amoebocytes are capable of

becoming other types of sponge cells

becoming other types of sponge cells enables it to adjust its shape

in response to physical change in the environment, direction of water currents


each individual functions as both male and female in sexual reproduction by producing sperm and eggs

sequential hermaphroditism

they function first as one sex and then the other

where do sponge gametes arise?

choanocytes or amoebocytes

eggs reside in

the mesophyll

sperm are carried out of the sponge by

the water current

what results from some of the sperm being drawn into neighboring individuals?

cross fertilization

where does fertilization occur?


in the mesophyl

zygotes develop into a flagellates, swimming larvae that disperse from the parent sponge

Cnidarians are an ancient phylum of


wat clade do all animals except sponges and a few other groups belong to?


clade with animals with true tissues?


one of the oldest lineages in this clade is the phylum


cnidarians have diversified into a wide range of sessile and motile forms including:

hydras, corals, and jellies

basic body plan of a cnidarian

sac with a central digestive componet, the gastrovascular cavity

the single opening to the gastrovascular cavity functions as

both the mouth and the anus

two variations of the body plan of cnidarian:

the sessile polyp and the motile medusa


cylindrical forms that adhere to the sunstrate by the aboral end of their body (the end opposite of the mouth) and extend their tenticles, waiting for prey.

examples of polyp:

hydras and sea anemones


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

medusae include

free swimming jellies

where do the tentacles of a jelly dangle from?

the oral surface, which points downward

some cnidarians only exist as ___, others exist as ____

polyps or medusae; both a polyp stage or a medusae stage

cnidarians are ___ that often use ____ to capture prey and push the food into the ____

carnivores; tenticles arranged in a ring around their mouth; gastrovascular cavity.

what is secreted into the cavity?

enzymes, breaking down the prey into a nutrient rich broth

cells lining the cavity do what?

absorb these nutrients and complete the digestive process

any undigested remains is expelled through the


the tenticles are armed with

batteries of cnidoctytes, function in defense and prey capture

what is uniqe to cnidarians?


cnidcytes contain

cnidae, capsule like organelles that are capable of exploding outward and that give phylum Cnidaria its name

specialized cnidae


stinging thread that can penetrate the body wall of cnidarian's play is contained in the


other kinds of cnidae

have long thread that stick to or entangle small prey that bump into the cnidarian's tentacles

simplest formes of nervves and tissues is in?


what have bundles of microfilaments arranged into contractile fibers

cells of the epidermis (outer layer); gastrodermis (inner layer)

gastrovascular cavity acts as a

hydrostatic skeleton against which the contractile cells can work

when a cnidarian closes its mouth

the volume of its cavity is fixed and contraction of selected cells causes the animal to change shape

movements are coordinated by a


why can cnidarian detect and respond to stimuli from all directions?

they have no brain, and the noncentralized nerve net is associated with sensory structures that are distributed around the body.

phylum cnidaria is divided into four clades:

hydrozoa, scyphozoa, Cubozoa and anthozoa

hydrozoans alternate betweeb

polyp and medusa forms

when an environment is favorable

a hydra produces asexually by budding

when conditions deteriorate

hydras can produce sexually, forming resistant zygots that remain dormant until conditions improve

prominante stage of scyphozoans


where do the medusa of most species live

plankton, as jellies

many schyphozoans go through a stage of being

small polyps during their life cycle


have a boxed shaped medusa stage

cubozoans also have

complex eyes imbedded un the fringe of their medussae, strong swimmers


occur only as polyps

corals live in

solitary or colonial forms

form symbioses with algar

secrete a hard externaml skeleton of calcium carbonate

each polyp genetation does what

builds on the skeletal remains of earlier generations contructing rocks

!!the skeletons are what?


lophotrochozoans have the widest range of

animal body forms

the vast majority of animal species belongs to the clade


bilaterian animals members exhibit

bilateral symmetry and triploblastic development

most bilaterians have a

digestive tract with two openings (a mouth and an anus) and a coelom

when did the most recent common ancestor of living bilaterians exists?

late Proterozoic eon

three major clades of bilaterally symmetrical animals are:

Lophotrochozoa, Ecdysozoa and Deuterostomia

Lophotrochozoa's name comes from

features found in some of its members

three features of lophotrochozoas

1) some develop a structure called a lophophore (crown of ciliated tentacles that functions in feeding)
2) some go through a distinctive stage caked the trochophore larva
3) some have none of those features

lophotrochozoans are the most

diverse bilaterian clade in terms of body plan

where does the diversity in form reflected in?

the number of phyla classified in the group (18)`

six diverse lophotrochozoan phyla

flatworms, rotifers, ectoprocts, brachiopods, molluscs, and annelids

where do flatworms live?

marine, fresh water and damp terrestrial habitats

flatworms include many ___ species such as

parasitic species such as flukes and tapeworms

why are flatworms named this?

they have thin bodies that are flattened doesoventrally


flat worm

flatworms undergo ___ development

triploblastic development

flatworms are

acoelomates (animals that lack a body cavity)

what does the flatworm's flat shape do?

places all their cells slose to the water in the surrounding environment or in their gut

how does elimination and gas exchange occur

diffusion across the body surface

flatworms simple excretory apparatus functions in

maintaining osmotic balance with the surroundings

the apparatus consists of


what are protonephridia?

networks of tubules with ciliated structures called flame bulbs that pull fluid through branched ducts opening to the outside

most flatworms have a gastrovascular cavity with how many openings?


flatworms separated into two lineages:

Catenilida and Rhabditophora


small clade about 100 flatworm species, reproduce by budding at the posterior end; offspring can produce own buds before detatching from the parent, thereby forming a chain of two to four genetically identical individuals "chain worms"


diverse clade about 20000 freshwater and marine species- free living and parasitic members

free living rhabditophora

predators and scavengers in a wide range of marine habitats

best known members of free living rhab. are

freshwater species in the genus Dugesia, commonly called planarians

planarians are abundant where? and they prey on..

unpolluted ponds and streams; smaller animals or feed on dead animals

how do planarians move?

using cilia on their ventral surface, gliding along a film of mucus they secrete

planarians head

equipped with a pair of light sensitive eyespots and lateral flaps that function mainly to detect specific chemicals

planarians nervous system

more complex and centralized than the nerve nets of cnidarians

some planarians reproduce?

asexually through fission

decribe the fission of planarians

parent constricts roughly in the middle of its body, separating into a head in and a tail end; each end then regenerates the missing parts; sexual rep also occurs

planarians are

hermaphrodites and mates typically cross fertilize each other

how do half of the known species of rhabditophorans live

as parasites in or on other animals, many have suckers that attach to the internal organs or outer surfaces of the host animal

in most species, what helps protects the parasites within the hosts?

a tough covering

what do reproductive organs occupy?

nearly the entire interior of these worms

two ecologically important subgroups of parasitic rhabditophorans:

trematodes and tapeworms

reproduction of trematodes

alternating sexual and asexual stages

many trematodes require an

intermediate host in which larvae develop before infecting the final host where the adult worms live

infectuois tremotodes are called

blood flukes

how does a blood fluke create a partial immunological camouflage for itself?

mimicking the surface proteins of its hosts and releases molecules that manipulate the hosts immune systems into tolerating the parasite's existence


large and diverse clade of parasitic rhabditiphorans

where do the adult tapeworms live?

mostly inside vertebrates, including humans

in many tapeworms, the anterior end, or scollex, is armed with

suckers and often hooks that the worm uses to attach itself to the intestinal lining of the host

how do tapeworms get nutrients without a mouth and vascuar cavity??

absorb nutients released by digestion in the host's intestine.. absorption occurs across the tapeworm's body surface

what is posterior to the scolex?

a long ribbon of units called proglottids- little more than sacs of sex organs

what happens after sexual reproduction?

proglottids loaded with thousands of fertilized eggs are released from the posterior end of a tapeworm and leave the hosts body in feces

clade Ecdysozoa includes animals that do what?

shed a tough external coat (cuticle) as they grow.



two largest ecdysozoan phyla

nematodes and arthopods



nematodes do not have..

segments bodies, they have cylindrical bodies.

describe the cylindrical body of the nematode:

a fine tips at tip at the posterior end and to a blunter tip at the anterior end

a nematode's body is covered by a

tough cuticle (type of exoskeleton)

what happens to the cuticle periodically?

it periodically sheds its old cuticle and secretes a new, larger one.

nematodes have a ___ but they lack a ___

alimentary canal; circulatory system

how are nutrients transported through the body of a nematode?

via fluid in the pseudocoelom

the body wall muscles of a nemotode are ___


what does nematodes muscle contraction produce?

thrashing motion

reproduction of nematode

sexually, by internal fertilization

decomposition and nutrient cycling are..

important roles of nematodes

nematode species that humans are hosts to

pinworms and hookworms

what redirects some of the cellular functions of their host and thus envade their immune systems

parasitic nematodes

plant host in regards to parasitic nematodes?

inject plant hosts with molecules that induce the development of root cells, supply nutrients to the parasites

infected muscle cell releases signals that

promote thte growth of new blood vessels which then supply nematode with nutrients


billion billion species 10e18, most = insects

what contributes to success of arthopods?

body plan: segmented, hard exoskeleton, jointed appendages

fossils of arthopods

Cambrian explosion

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