Annelids: Segmented WormsPhylum Annelida

1. _____________________ from the Latin word ________________ meaning “little ring”2. All are ________________________ worms3. Approximately __________________ species including earthworms, freshwater worms,

leeches, and marine worms4. Annelid Characteristics

_________________________: 3 cell (body) layers Highest level of organization: _____________________ Bilateral symmetry Cephalization Eucoelomate

o Have a true body cavity that is completely surround by ____________.o Draw the coelom below:

The Coelomo The coelom is a closed, fluid filed cavity that surrounds the gut.o The fluid within acts as a ______________________________ (blood)o Tissue membranes (____________________) suspend the organs in the coelom

Metamerismo The body is made up of serially repeating coordinated segments called

_____________________ that are separated from one another by _________________.o Each metamere contains sets of repeating organs. Ex. Gut, blood vessels, nerve

cord, excretory organs.

Two part head consisting of:

o _____________________________: fleshy lobe that overhangs the moutho _____________________________: first body segment

___________________: circular rings _________________________: the last segment where the anus is _________________________: reproductive structure Nervous System

o 2 cerebral gangliao A ventral nerve cord with two ganglia per metamereo In some species, sensory organs such as _____________, ____________, and

__________________ have arisen.(________________ are appendages that may or may not be covered in cilia that help the worm find and pull in food)

Locomotiono Both _____________________ and ________________ muscleso Most have _____________ (chitonous bristles secreted by the epidermis) that aid

in locomotion and burrowingo Setae may be modified into appendages called ___________________

Skeletal Systemo Fluid in the coelom acts as a _______________________________

PARAPODIA

Gas Exchangeo Mainly by ____________________ through skino Class Polychaeta often has specialized structures for gas exchange (ex.

Parapodia, gills) Digestive System

o ____________________________o Regional ________________________ (digestive organs)

Circulatory Systemo ________________ circulatory system composed of blood vessels (some of which

are contractile and act as “hearts”)o Some circulation is also accomplished by the _________________ fluid

Excretiono Excretion is accomplished by organs called _______________________ (singular

nephridium) Reproduction

o Sexual

5. Three Classes of segmented worms _________________________________ _________________________________ _________________________________

Class PolychaetaCharacteristics

• All _________________• This class contains 2/3 of all known Annelids• Common species are _________________ , ___________________ , and _____________________• Have a well developed head with specialized sense organs• Commonly called _____________________________ because….

o Have many ________________ (chitonous bristles secreted by the epidermis)

o (Poly = many, chaeta= setae) o These setae are arranged in bundles on paddle-like appendages called

____________________o The parapodia function in ______________________, locomotion, and

__________.• _____________________ (tagmosis): the fusion and specialization of formerly

metameric segments• Many are ____________________ feeders with specialized structures• Many are __________________________ with specialized structures• Many construct their own homes out of __________ (calcium carbonate),

__________________, and _______________________.• Reproduction

o Usually ___________________o No permanent sex organs; gametes are shed into coelom where

they stay until time for fertilizationo Fertilization is usually ___________________ in watero ________________ development à __________________ larvae swims

around until it grows into adult for by adding segments• Ecology

o Polychaetes often have effective defense strategies: some have tubes to hide in some have vicious jaws some have modified “stinging” setae

o Some Polychaetes have a mutualistic relationship with their host For example, many scaleworms are found near, or in the mouth, of

brittlestars, starfish, and sea urchins. The scaleworm eats its host’s leftovers and with its vicious jaws, it

will attack any predator trying to eat it’s host.

Class OligochaetaCharacteristics

Earthworms are the most common Habitats: __________________________, freshwater, and __________________ Have few setae (“Oligo” = ________________, “chaeta” = setae Usually feed on ___________________________ (decaying organic matter) Depends on habitat, but they can feed on…

o Dead leaves and plant roots

o Living things such as other worms, bacteria and fungio Decomposing remains of other animals

Do earthworms eat dirt?o Yes and n.o Earthworms ________________________ dirt as they burrow, so yes they swallow it.o HOWEVER, they do not get ______________________ from dirt. Their nutrients come

from decaying plant and animal remains that are in the dirt. Earthworms have a specialized digestive system to obtain the maximum amount of

nutrients out of the detritus.o Example: pharynx, crop, gizzard, etc.

Locomotiono Circular muscles

contractiono Longitudinal muscle

contraction

Reproductiono Usually ________________________o Still have to have a partnero Cross-fertilize by exchanging _______________.

Ecologyo Earthworms are essential soil ___________________,

meaning they allow air to enter the soil.o Mix the soil with their tunnels.o Worm feces are great plant food =

____________________!

Class Hirudenia

Includes ____________________. Usually freshwater but there are some ____________________ and terrestrial species. No __________________ between metameres No ___________________ or parapodia Have two suckers Have an extendable ____________________ for feeding Usually have a fixed number of segments (34). Each metamere consists of several annuli Lack septa between metameres, so they are incapable of moving like Oligochaetes. Instead, they use their anterior and posterior suckers to move.

Reproductiono usually _________________________o cross-fertilize by exchanging sperm

Ecologyo Although some leeches are parasitic blood suckers (can be temporary or

permanent), many are predators. o Leeches have been used medicinally since the 19th century.o Currently they are used to increase blood flow following reconstructive surgery o _______________________ is a powerful anticoagulant that is found in the salivary

glands of leeches