WormsWorms

FlatwormsFlatworms

Flatworms are invertebrate.

It has a head, or anterior end,

and tail, or posterior end.

Like most animals, flatworms are bilaterally symmetrical.

Examples: Tape worms & blood flukes.

Bilateral SymmetryBilateral Symmetry

Body plan in which an animal can be divided Body plan in which an animal can be divided into two equal sides.into two equal sides.

StructureStructure

Gastrovascular cavity – gut with a single Gastrovascular cavity – gut with a single opening. opening.

Cephalization – concentration of sensory Cephalization – concentration of sensory organs towards the anterior end. organs towards the anterior end.

Digestion & ExcretionDigestion & Excretion

Pharynx – takes up Pharynx – takes up food.food.

Enzymes excreted to Enzymes excreted to break down material.break down material.

Nutrients diffuse to Nutrients diffuse to other parts of the body.other parts of the body.

Flame cells – collect Flame cells – collect excess water.excess water.

Water travels through Water travels through network of tubules network of tubules and is eliminated and is eliminated through pores on the through pores on the body surface. body surface.

Roundworms (Nematodes)Roundworms (Nematodes)

Examples: hookworms, Examples: hookworms, pinwormspinworms

Pseudocoelomates: Pseudocoelomates: hollow fluid filled cavity hollow fluid filled cavity - lined by mesoderm on - lined by mesoderm on the outside and the outside and endoderm on the side. endoderm on the side.

The body of a roundwormThe body of a roundworm

It has a complete digestive tract: It has a complete digestive tract: Two openings: mouth and an anus at opposite ends. Two openings: mouth and an anus at opposite ends. Food only travels one way.Food only travels one way.

Segmented Worms:Segmented Worms:Annelids Annelids

Their bodies are Their bodies are divided in segments, or divided in segments, or sections.sections.

Example: Earth Worm, Example: Earth Worm, leeches leeches

CharacteristicsCharacteristics

Symmetry – BilateralSymmetry – Bilateral

A segmented coelom – allows different parts A segmented coelom – allows different parts of the body to move independently.of the body to move independently.

Setae – external bristles. Setae – external bristles.

CoelomCoelom

The body cavity of annelids is called coelom.The body cavity of annelids is called coelom. A coelom is a fluid-filled cavity completely lined by A coelom is a fluid-filled cavity completely lined by

tissue that originated from mesoderm tissue.tissue that originated from mesoderm tissue.

Structure and MovementStructure and Movement

Anchor middle section Anchor middle section using setae.using setae.

Contraction of the Contraction of the longitudinal muscles longitudinal muscles causes the worm to causes the worm to move forward. move forward.

Feeding and DigestionFeeding and Digestion Pharanx – muscular structure that sucks in soil.Pharanx – muscular structure that sucks in soil.

Esophogus – food passes through here.Esophogus – food passes through here.

Crop – temporary storageCrop – temporary storage

Gizzard – grinds soil, breaking Gizzard – grinds soil, breaking up organic matter.up organic matter.

Intestine – absorbs organic Intestine – absorbs organic compounds and nutrients. compounds and nutrients.

Anus – expels waste.Anus – expels waste.

CirculationCirculation OO22, CO, CO22, nutrients & , nutrients &

wastes transported wastes transported through blood vessels. through blood vessels.

Aortic arches connect Aortic arches connect the dorsal and ventral the dorsal and ventral blood vessels.blood vessels.

Contraction of vessels Contraction of vessels and arches circulates and arches circulates the blood.the blood.

RespirationRespiration

Obtaining Oxygen:Obtaining Oxygen:– Diffusion through skin Diffusion through skin

Nephridia:Nephridia:– Tubes that eliminate excess water and wastes.Tubes that eliminate excess water and wastes.

ReproductionReproduction HermaphroditesHermaphrodites

Setae and mucus secreted by the clitellum hold Setae and mucus secreted by the clitellum hold the worms together. the worms together.

Secrete sperm into the Secrete sperm into the mucus and it is stored mucus and it is stored in the seminal receptacle.in the seminal receptacle.

ReproductionReproduction

After they separate the clitellum secretes a After they separate the clitellum secretes a tube made of mucus and chitin. tube made of mucus and chitin.

This tube picks up the worm’s eggs and This tube picks up the worm’s eggs and sperm sperm fertilization. fertilization.