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
  • Have a true body cavity that is completely surround by ______.
  • Draw the coelom below:
  • The Coelom
  • The coelom is a closed, fluid filed cavity that surrounds the gut.
  • The fluid within acts as a ______(blood)
  • Tissue membranes (______) suspend the organs in the coelom
  • Metamerism
  • The body is made up of serially repeating coordinated segments called ______that are separated from one another by ______.
  • Each metamere contains sets of repeating organs. Ex. Gut, blood vessels, nerve cord, excretory organs.

  • Two part head consisting of:
  • ______: fleshy lobe that overhangs the mouth
  • ______: first body segment
  • ______: circular rings
  • ______: the last segment where the anus is
  • ______: reproductive structure
  • Nervous System
  • 2 cerebral ganglia
  • A ventral nerve cord with two ganglia per metamere
  • 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
  • Both ______and ______muscles
  • Most have ______(chitonous bristles secreted by the epidermis) that aid in locomotion and burrowing
  • Setae may be modified into appendages called ______
  • Skeletal System
  • Fluid in the coelom acts as a ______


PARAPODIA

  • Gas Exchange
  • Mainly by ______through skin
  • Class Polychaeta often has specialized structures for gas exchange (ex. Parapodia, gills)
  • Digestive System
  • ______
  • Regional ______(digestive organs)
  • Circulatory System
  • ______circulatory system composed of blood vessels (some of which are contractile and act as “hearts”)
  • Some circulation is also accomplished by the ______fluid
  • Excretion
  • Excretion is accomplished by organs called ______(singular nephridium)
  • Reproduction
  • Sexual
  1. 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….

  • Have many ______(chitonous bristles secreted by the epidermis)
  • (Poly = many, chaeta= setae)
  • These setae are arranged in bundles on paddle-like appendages called ______
  • 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

  • Usually ______
  • No permanent sex organs; gametes are shed into coelom where they stay until time for fertilization
  • Fertilization is usually ______in water
  • ______development ______larvae swims around until it grows into adult for by adding segments

•Ecology

  • Polychaetes often have effective defense strategies:

some have tubes to hide in

some have vicious jaws

some have modified “stinging” setae

  • 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 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…
  • Dead leaves and plant roots
  • Living things such as other worms, bacteria and fungi
  • Decomposing remains of other animals
  • Do earthworms eat dirt?
  • Yes and n.
  • Earthworms ______dirt as they burrow, so yes they swallow it.
  • 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.
  • Example: pharynx, crop, gizzard, etc.

  • Locomotion
  • Circular muscles contraction
  • Longitudinal muscle contraction
  • Reproduction
  • Usually ______
  • Still have to have a partner
  • Cross-fertilize by exchanging ______.
  • Ecology
  • Earthworms are essential soil ______, meaning they allow air to enter the soil.
  • Mix the soil with their tunnels.
  • 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
  • usually ______
  • cross-fertilize by exchanging sperm
  • Ecology
  • Although some leeches are parasitic blood suckers (can be temporary or permanent), many are predators.
  • Leeches have been used medicinally since the 19th century.
  • Currently they are used to increase blood flow following reconstructive surgery
  • ______is a powerful anticoagulant that is found in the salivary glands of leeches