Phylum Annelida (segmented worms)

• OMG! (gosh) A COELOM

Very successful phylumANYONE SEEN THESE SCUBA DIVING? Polychaetes.

Let’s start with what we know- EARTHWORMS

Developmental Stages• What does it mean to say that an earth worm is a

protostome?

• Develops mouth first.

ONLY BILATERAL ANIMALS CAN BE CLASSIFIED AS PROTOSTOME OR DEUTEROSTOME

We have the first Coelom

Advantages of a Coelom

- independent movement of body wall and enclosed organs - more space for complex organs and organ systems- storage area for eggs and sperm.

-It also contains fluid that protects internal organs, and can provide oxygen and nutrients to cells, collect wastes, and function as a hydrostatic skeleton.

Movement via Setae (also called Chaetae)

• The worms anchor the Setae to create friction. They then elongate and contract accordingly.

Digestion• Mouth Pharynx Esophagus Crop Gizzard Intestine

Anus• More evolved digestive system.

Circulation• First heart that we have seen• Simple closed circulatory system• Along with nematodes, annelida have developed hemoglobin. In these

animals it floats freely in the blood and is not attached to cells.

Blood is pumped by the 5 hearts through the Ventral Vessel and then returns via the dorsal

(back) blood vessel.

Respration

• DIFFUSION through body wall

• Must keep its cuticle moist!

Reproduction

Get a Room!

Reproduction

• Even though worms are hermaphroditic most reproduction is sexual.

• They align their Clitellum's • clitellum secrets mucus ring to release sperm

fertilization. Eggs are then transported to the sperm.

Excretion• Nephridia- coiled tubes• The tubule opens to the outside through the body wall. Filtration of the

blood across the tubule wall can occur because of the close association between capillaries and the nephridium.

Reading

• Hand out earthworm labelling sheet

Label the earthworm parts (as a class)

Dissection time

• A reminder of vocabulary for dissection.

Cut it open like this.