Annelids Flashcards
True or False: Phylum Annelida largely consists of segmented worms
True
Some ____ are grotesque in appearance, whereas others are graceful and beautiful.
polychaetes
Segments of the bodies of most Annelids are ___
metameres
Circular rings that externally mark metameres
annuli
Division of the body into a series of units, each of which contains similar components of all major organ systems.
metamerism
In annelids the segments are delimited internally by ___
Septa
Annelids are sometimes called _____ because, with the exception of leeches, most annelids bear tiny chitinous bristles called setae
Bristle worms
Short, needlelike setae help anchor segments during ____ and long, hairlike setae aid ____
locomotion; aquatic forms in swimming
_____ are chiefly marine formd
Polychaetes
Oligochaetes and leeches occur predominantly in _____
freshwater or terrestrial soils.
Many leeches are predators, specialized for _____
piercing their prey and feeding on blood or soft tissues.
A few leeches are _____, but most live in ____ or in damp regions.
marine; freshwater
____ are typically found at both ends of the body for attachment to the substratum or to their prey
Suckers
Composes the two-part head of the Annelid body
Prostomium and peristomium
A terminal portion in the annelid body that bears an anus
pygidium
New segments differentiate during development just in front of the _____
pygidium
Te oldest segments are at the ____ end and the youngest segments are at the ____ end.
Anterior; posterior
True or False: Each segment typically contains respiratory, nervous, and excretory structures, as well as a coelom.
True
True or False: Flaps called parapodia may be present on each segment.
True
lines the body wall of each compartment, forming dorsal and ventral mesenteries that cover all organs
Peritoneum
Peritonea of adjacent segments meet to form ___, which are perforated by the gut and longitudinal blood vessels
Septa
True or False: The body wall surrounding the peritoneum and coelom contains strong circular and longitudinal muscles adapted for swimming, crawling, and burrowing
True
The coelom of most annelids is filled with fluid and serves as a hydrostatic skeleton except in ____.
Leeches
Crawling motions are produced by ______
alternating waves of contraction by longitudinal and circular muscles passing down the body
Swimming forms use ____ rather than peristaltic movements in locomotion.
undulatory
An annelid body has a thin outer layer of ____ surrounding the epidermis
nonchitinous cuticle
_____ are ancestral for annelids, although they have been reduced or lost in some.
Paired epidermal setae
True or False: The annelid digestive system is segmented
False; the gut runs the length of the body perforating each septum
True or False: Longitudinal dorsal and ventral blood vessels follow the same path, as does the ventral nerve cord
True
Historically, annelids were divided among three classes: ____, ____, and ____.
Polychaeta, Oligochaeta, Hirudinida
Phylogenetic analyses show polychaetes and oligochaetes to be ___ groups; leeches form a ___.
paraphyletic; clade
Clitellata are characterized by presence of a reproductive structure called a ____
clitellum
a term used to denote any of 80 morphologically distinct families of worms, typically those with many setae
Polychaete
The division of annelids into two such groups, one ___ and the other ___ was proposed long ago on morphological grounds and later rejected.
Errant; Sedentary
Differentiate Errant and Sedentary
Spelling; Errant (freely moving); Sedentary (spending most of their lives in tubes or burrows)
Consists of about 250 species of benthic marine worms, living at depths ranging from the intertidal to more than 5000 m.
Sipuncula
True or False: Sipuncula live sedentary lives in burrows in mud or sand, occupy borrowed snail shells, or live in coral crevices or among vegetation.
True
Some Sipuncula are commonly called ____ because, when disturbed, they can contract to a peanut shape
Peanut worms
Sex cells are released in Sipuncula through the ____.
nephridia
The larval form of Sipuncula is usually a ____
trochophore
Members of _____ are unusual tube-dwelling annelids with three distinct body regions
Chaetopteridae
The parchment worm, Chaetopterus feeds on ____
suspended particles
(Chaetopteridae) The worm attaches to the side of the tube by ____
ventral suckers
What are fans? (Chaetopteridae)
Modified parapodia on segments 14 to 16 that pump water through the tube by rhythmical movements.
(Chaetopteridae) A pair of ____ on segment 12 secretes a long mucous net that reaches back to a small food cup just in front of the fans.
enlarged parapodia
One of two large subgroups within Pleistoannelida that comprises the motile polychaetes.
Errantia
Most errant polychaetes are (habitat) ____
Marine
Colors of Erantia
They may be brightly colored in reds and greens, iridescent, or dull.
Errantia play a significant part in marine food chains because they are _____
eaten by fish, crustaceans, hydroids, and many other predators.
Errantia have many setae, usually arranged in bundles on the ____.
parapodia
A polychaete typically has a ____, which may or may not be retractile and which often bears eyes, tentacles, and sensory palps
prostomium
True or False: The peristomium surrounds the mouth and may bear setae, palps, or, in predatory forms, chitinous jaws
True
A polychaete’s digestive system consists of a ___, a ___, and a ___.
foregut; midgut; hindgut
The foregut of errant polychaetes includes a ___, a ____, and an anterior ____.
stomodeum; pharynx; esophagus
In Errantia, The more ____ portions of the midgut secrete digestive enzymes but absorption occurs toward the ____ end.
anterior; posterior
In Errantia, a short ____ connects the midgut to the exterior via the anus, which is on the pygidium.
hindgut
True or False: Sense organs are highly developed in polychaetes and include eyes, nuchal organs, and statocysts.
True
The highest degree of eye development occurs in the family ____, which has large, image-resolving eyes similar in structure to those of some cephalopod mollusks, with cornea, lens, retina, and retinal pigments.
Alciopidae
True or False: Polychaetes have no permanent sex organs, and they usually have separate sexes.
True
Errant polychaetes that live in mucus-lined burrows in or near low tide.
Clam worms
Clam worms are most active at ____, when they wiggle out of their hiding places and swim or crawl over the sand in search of food
Night
Why are Hermodice carunculata called fireworms?
Their hollow, brittle setae contain a poisonous secretion.
____ contains many polychaetes and oligochaetes that live in tubes or burrows, including members of the former phyla
Sedentaria
Clade ____ contains earthworms and their relatives as well as leeches in class Hirudinida.
Clitellata
Earthworms feed mainly on _____
decaying organic matter, bits of leaves and vegetation, refuse, and animal matter.
Earthworms feed mainly on ____
decaying organic matter, bits of leaves and vegetation, refuse, and animal matter.
Annelids have a double transport system: ____ and a ____ circulatory system.
coelomic fluid; closed
The nervous system in earthworms consists of a ____ and peripheral nerves.
central system; peripheral nerves.
True or False: Earthworms react negatively to mechanical stimuli when such stimuli are moderate and positively to a strong stimulus
False; positively to mechanical and negatively to strong
True or False: Earthworms do not avoid light
False; they avoid unless it is very weak
____ aid earthworms in the choice of food.
Chemical responses
True or False: Earthworms are monoecious
True
Freshwater oligochaetes usually are ____ and have more conspicuous setae than earthworms.
smaller
True leeches have ___ segments, entirely lack setae, and possess anterior and posterior suckers.
34
Members of order Acanthobdellida have ___ segments, bear setae on the first ___ segments, and have a ___ sucker.
27; 5; posterior
Members of order Branchiobdellida have __ or __ segments, no setae, and an ___ sucker
14; 15; anterior
Leeches occur predominantly in ___ habitats
Freshwater
Leeches are usually flattened ____
dorsoventrally
Sa leeches, the ____ secretes a cocoon for reception of eggs.
clitellum
True or False: Unlike other annelids, leeches have a fixed number of segments
True
Leeches lack distinct ____ compartments
coelomic
Explain gas exchange in leeches
Occurs only through the skin except in some fish leeches, which have gills.
Leeches have two “brains”: one is ___ and composed of ___ pairs of fused ganglia; the other is ____ and composed of ___ pairs of fused ganglia
anterior - six; posterior - seven
Leeches are ____ but cross-fertilize during copulation
hermaphroditic
Fluid pressure in fluid-filled coelomic compartments is used to create a _____, which in turn permits precise movements such as burrowing and swimming.
hydrostatic skeleton
