Annelids: Segmented Worms Phylum Annelida Segmented Worms Phylum Annelida 1. _____ from the Latin word _____ meaning “little ring” 2. All are _____ worms
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Annelids: Segmented Worms Phylum Annelida
1. _____________________ from the Latin word ________________ meaning “little ring”
2. All are ________________________ worms 3. Approximately __________________ species including earthworms, freshwater worms, leeches,
and marine worms
4. 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 Coelom o 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 • Metamerism
o 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 mouth
o _____________________________: first body segment
• ___________________: circular rings • _________________________: the last segment
where the anus is • _________________________: reproductive
structure
• Nervous System o 2 cerebral ganglia o A ventral nerve cord with two ganglia per metamere o 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)
• Locomotion o Both _____________________ and ________________ muscles o Most have _____________ (chitonous bristles secreted by the epidermis) that aid in
locomotion and burrowing o Setae may be modified into appendages called ___________________
• Skeletal System o Fluid in the coelom acts as a _______________________________
PARAPODIA
• Gas Exchange o Mainly by ____________________ through skin o Class Polychaeta often has specialized structures for gas exchange (ex. Parapodia, gills)
• Digestive System o ____________________________ o Regional ________________________ (digestive organs)
• Circulatory System o ________________ circulatory system composed of blood vessels (some of which are
contractile and act as “hearts”) o Some circulation is also accomplished by the _________________ fluid
• Excretion o Excretion is accomplished by organs called _______________________ (singular
nephridium) • Reproduction
o Sexual
5. Three Classes of segmented worms • _________________________________ • _________________________________ • _________________________________
Class Polychaeta Characteristics
• 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 fertilization o Fertilization is usually ___________________ in water o ________________ development à __________________ larvae
swims around until it grows into adult for by adding segments • Ecology
o Polychaetes often have effective defense strategies: Ø some have tubes to hide in Ø some have vicious jaws
Ø some have modified “stinging” setae o Some Polychaetes have a mutualistic relationship with their host
Ø For example, many scaleworms are found near, or in the mouth, of brittlestars, starfish, and sea urchins.
Ø The scaleworm eats its host’s leftovers and with its vicious jaws, it
will attack any predator trying to eat it’s host.
Class Oligochaeta Characteristics
• 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 fungi o 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.
• Locomotion
o Circular muscles contraction o Longitudinal muscle contraction
• Reproduction o Usually ________________________ o Still have to have a partner o Cross-fertilize by exchanging _______________.
• Ecology o 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. • Reproduction
o usually _________________________ o cross-fertilize by exchanging sperm
• Ecology o 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
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