Biology 11- 27.3 (segmented worms)

Segmentation in Annelids

present

Digestion in annelids

a long tube that extends from mouth to anus

path of food

mouth, pharynx, esophagus, crop, gizzard, intestine, anus

types of feeders/how they feed

-Carnivores: 2 or more sharp jaws that shoot out grabbing the prey
-Herbivores: Jaws to tear up plant material
-Detritus feeders: thick mucus to suck up food particles

crop

food storage

gizzard

grinds food

respiration in annelids

Aquatic annelids: use delicate gills to take in o2 and co2
Terrestrial annelids: use diffusion to breathe through skin

internal transport system of annelids

-Closed circulatory system delivers blood to every segment
-2 blood vessels: run length of body
-Dorsal vessel:
Blood, head
-Ventral vessel:
blood, body

open circulatory system

A circulatory system that allows the blood to flow out of the blood vessels and into various body cavities so that the cells are in direct contact with the blood

closed circulatory system

A circulatory system in which the oxygen-carrying blood cells never leave the blood vessels

excretion in annelids

-2 types of waste produced
-Solid waste passed through anus
-Other was excreted by nephridia
-One pair per segment
Simple tube shaped excretory organs

response in annelids

-Two large nerves pass around gut to a pair of ganglia below
-Ganglia merge to form the ventral nerve cord
-Each segment has a pair of small ganglia that carry information to ventral nerve cord

longitudinal muscles

contract to make worm shorter

circular muscles

contract to make worm skinnier

response in free-living marine species

-Best developed sense organs
-Sensory tentacles: statocysts
-Most eyes are simple light detectors
-Some can perceive objects
-Other sense organs scattered along epidermis

response in terrestrial species

-Simpler sensory systems
-Rely on sensory organs similar to marine annelids

reproduction in annelids

-Few reduce asexually (budding)
-Some have separate sexes, some are hermaphrodites
-Can self-fertilize
Received sperm is stored in special sacks, when eggs need to be fertilized a band of thickened segments called clitellum secrete a mucus ring with the sperm and eggs are released into
-Mucus forms a cocoon to protect eggs

Polychatea

-Many setae (bristles that anchor worm as it moves)
-Paddle like lobes called parapoda on each segment
-Has chitinous jaws on head to capture and eat small animals
-Cephalization

oligochataeta

-Earthworms
-Lack a well-developed head
-Setae protrude in small clusters from body surgace to grip soil when segments bulge; withdraw when segments contract

septum

internal walls between each segment

free-living

organism that does not depend on another for food or a place to live

ganglion

A mass of nerve cells

parapodia

Paddlelike appendages that assist aquatic annelids to move

aortic arches (worm)

organ which helps pump oxygenated blood- similar to heart

cuticle (worm)

outermost layer on worms body- exoskeleton

ring vessels

distribute blood to different segments

nerve chord

it is a tubelike structure that has nerve fibers in it- similar to spinal chord

nephridia

organ that remove wastes from the body

clitellum

Band of thickened, specialized segments in annelids that secretes a mucus ring into which eggs and sperm are released

prostomium

cephalized first body segment in the worms anterior end

setae

bristles attached to annelid segments

body cavity

space created in an organism to house organs

pharynx

a muscular structure that pushes out of their mouth to grasp food, then pulls back inside