1. Worm-like Animals

2. Characteristics Invertebrates. Cephalization. Coelom.
Sense organs and nerve cells located at anterior end.
Coelom.

3. Characteristics

4. Phylum Platyhelminthes “Flatworms”
Flattened with no coelom.
Unsegmented.
No circulatory or respiratory system.
Digestive cavity with one opening.
Mostly parasitic.
1 mm to 5 m in length.

5. Phylum Platyhelminthes
Class Cestoda
Parasitic tapeworms.
Suckers and hooks attach tapeworm to intestines.
Watch This!!!

6. Phylum Nematoda “Roundworms”
Unsegmented cylindrical bodies.
Pseudocoelom.
Complete digestive tract.
No circulatory or respiratory system.
Mostly parasitic.
2 mm to 2 m in length.
Watch This!!!

7. Phylum Nematoda
The body of a nematode is long and narrow, resembling a tiny thread in many cases, and this is the origin of the group's name. The word "nematode" comes from a Greek word nema that means "thread". The epidermis(skin) of a nematode is highly unusual; it is not composed of cells like other animals, but instead is a mass of cellular material and nuclei without separate membranes. This epidermis secretes a thick outer cuticle which is both tough and flexible. The cuticle is a feature shared with arthropods and other ecdysozoans. As in those other groups, the cuticle is periodically shed during the life of a nematode as it grows, usually four times before reaching the adult stage. The cuticle is the closest thing a roundworm has to a skeleton, and in fact the worm uses its cuticle as a support and leverage point for movement. Long muscles lie just underneath the epidermis. These muscles are all aligned longitudinally along the inside of the body, so the nematode can only bend its body from side to side, not crawl or lift itself. A free-swimming roundworm thus looks rather like it is thrashing about aimlessly.
The muscles are activated by two nerves that run the length of the nematode on both the dorsal (back) and ventral (belly) side. Unlike other animals, where the nerves branch out to the muscle cells, a nematode's muscle cells branch toward the nerves. The ventral nerve has a series of nerve centers along its length, and both nerves connect to a nerve ring and additional nerve centers located near the head.
The head of a nematode has a few tiny sense organs, and a mouth opening into a muscular pharynx (throat) where food is pulled in and crushed. This leads into a long simple gut cavity lacking any muscles, and then to an anus near the tip of the body. Food digested in the gut is not distributed by any specialized vascular system, and neither is there a respiratory system for the uptake or distribution of oxygen. Rather, nutrients and waste are distributed in the body cavity, whose contents are regulated by an excretory canal along each side of the body.

8. Phylum Annelida “Segmented Worms”
Segmented bodies.
Presence of a coelom.
Complete digestive tract.
Has a circulatory system.
Gas exchange via gills or skin.

9. Phylum Annelida
Many have bristles on outer surface to aid with movement.
0.5 mm to 3 m in length.
E.g., Earthworms and leeches.
Watch This!!!

10. Phylum Mollusca 10

11. Characteristics Soft-bodied. Coelom. Two body openings.
Bilateral symmetry. 11

12. Body Plan Three unsegmented body parts: Foot: 2. Mantle:
Locomotion and feeding.
2. Mantle:
Wraps around body and secretes shell.
In some, shell may be reduced or absent.
3. Visceral Mass:
Internal Organs. 12

13. Body Plan

14. Body Plan Complete digestive and circulatory system.
Gills for respiration.
<1 cm to 20 m in length.

15. Class Bivalva E.g., clams, oysters, scallops & mussels.
Hinge connects two shells.
Primarily sessile.
Foot may be modified to burrow.
No head.
Filter feeders.
0.5 mm to 1.4 m in size.
Watch This!!! 15

16. Class Gastropoda E.g., snails and slugs. Foot used for locomotion.
Respiration through gills and moist skin.
Spiral shell except for slugs.
0.5 mm to 75 cm in size.
Watch This!!! And This!!! 16

17. Class Cephalopoda E.g., squids and octopi.
Shell reduced to internal rod.
Only mollusk with closed circulatory system.
Tentacles with suckers.
Well-developed brains; capable of learning.
Move via jet propulsion (by funnel).
10 mm to 20 m in size. 17

18. Class Cephalopoda
Watch This!!! And This!!!

19. Phylum Echinodermata

20. Phylum Echinodermata
E.g., sea stars, sea urchins, sand dollars and sea cucumbers.
Larvae: Bilaterally symmetrical.
Adults: Radially symmetrical around 5+ arms.

21. Phylum Echinodermata Complete digestive system.
Simple circulatory and nervous system.
No respiratory or excretory system.
No head.
Endoskeleton with spiny projections.
Watch This!!!