Annelida Segmented Worms

N0- not that kind of worm!

Common Examples Earthworms

Common Examples Bristle Worms

Common Examples Feather Duster Worms

Common Examples Tube Worms

Common Examples Tube Worms

Common Examples Leeches

Rag Worm How would you like to run into the jaws of this guy!

Characteristics Segmentation Cephalization Bilateral Symmetry Coelomates One way digestive tract Both Filter Feeders and Predators Asexual and Sexual Reproduction Water and Land Examples

Segmentation Each segment repeats Very efficient design. Some are specialized Digestion, reproduction,excretion, etc.

Definite Head End

Annelida has Bilateral Symmetry Yes, Symmetric No, not Symmetric No, not Symmetric

Section 27.2 Summary – pages The basic body plan = a tube within a tube internal tube= suspended w/in coelom = digestive tract. Body Structure

Phylum Annelida Hydrostatic skeleton –Fluid pressure in coelom provides support & locomotion –Circular muscles –Longitudinal muscles –Peristaltic locomotion – squeeze, relax, squeeze!

Section 27.2 Summary – pages SETAE = tiny bristles on each segment help move anchors body in soil so each segment can move the animal along Setae Body Structure

Phylum Annelida Setae (“bristles”) of chitin – a carbohydrate Chitin forms the exoskeleton in insects, shrimp, crayfish, etc. –“anchors” for earthworm –“paddles” for polychaete –Enlarged as jaws in leeches, some polychaetes

Section 27.2 Summary – pages distinguishing characteristic is that bodies are divided into ringed segments In most species, segmentation continues internally as each segment is separated from the others by a body partition. Body Structure Segments

Section 27.2 Summary – pages Each segment has its own muscles, allowing shortening and lengthening of the body. Segmentation also allows for specialization of body tissues. Certain segments have modifications for functions such as sensing and reproduction. Body Structure

Section 27.2 Summary – pages Segmented worms have simple nervous systems in which organs in anterior segments have become modified for sensing the environment = cephalization Nervous system Some sensory organs are sensitive to light, and eyes with lenses and retinas have evolved in certain species.

In some species there is a brain located in an anterior segment. Nerve cords connect the brain to nerve centers called ganglia, located in each segment. Setae Brain Nervous system

Phylum Annelida Closed circulatory system –Multiple “hearts” –Hemoglobin not in blood cells reddish-pink color Blood carries O2 to and CO2 from body cells flow through vessels to reach all parts of the body must live in water or in wet areas on land because they exchange gases directly through their moist skin – like your lungs

Section 27.2 Summary – pages complete internal digestive tract length of body Nutrients diffuse to blood Transported to all cells Digestion and Excretion Food > mouth > crop >gizzard > gut >anus

Section 27.2 Summary – pages GIZZARD a muscular sac Contains hard particles to grind soil and food before they pass into intestine/gut Mouth Crop Gizzard Digestion and Excretion Circulatory System

Section 27.2 Summary – pages have two nephridia in almost every segment. Special cells that collect waste and transport it through the coelom and out of the body. Nephridia Excretion

Section 27.2 Summary – pages Earthworms and leeches are hermaphroditic –exchange sperm. forms a capsule for the eggs and sperm. The eggs fertilized in capsule, then it slips off the worm and left in soil 2-3 weeks, young worms emerge from the eggs. Reproduction

Section 27.2 Summary – pages separate sexes and reproduce sexually. Reproduction in Bristleworms eggs and sperm are released into seawater and fertilize there = external fertilizaton larvae hatch in sea become part of the plankton –important part of food chain Eventually settles to the bottom to live

Section 27.2 Summary – pages ClassOligochaeta - earthworms Class Polychaeta - bristleworms Class Hirudinea - leeches CLASSES OF ANNELIDA

Section 27.2 Summary – pages most well-known annelids Easily seen by most people. Class Oligochaeta: Earthworms burrows through soil Loosens and aerates soil Feces = “castings” = fertilizer Ecologically very important Possible human food source= protein

Section 27.2 Summary – pages Class Polychaeta: Bristleworms Polychaete means “many bristles” Most body segments have many setae has a head with well-developed sense organs, including eyes.

Section 27.2 Summary – pages have parapodia, (paired feet) can be used for swimming or crawling over corals and bottom of sea. Class Polychaeta: Bristleworms Parapodia also function in gas exchange.

Section 27.2 Summary – pages segmented worms with flattened bodies usually no setae Class Hirudinea: Leeches Many are parasites suck blood or other body fluids from hosts (ducks, turtles, fish, and humans).

Section 27.2 Summary – pages saliva contains: – anesthetic chemicals –Anticoagulants – prevent clotting of blood can ingest 2 to 5 times its weight in 1 meal. Hirudinea: Leeches Front and rear suckers for attachment

Section 27.2 Summary – pages Annelids probably evolved in the sea, perhaps from larvae of ancestral flatworms. Origins of Segmented Worms Tubes constructed by polychaetes are the most common fossils of this phylum. Some of these tubes appear in the fossil record as early as 540 million years ago.