1. The Invertebrates
Other Invertebrates

2. Phylum Mollusca clams, snails, octopuses
(second largest phylum of animals)

3. General Characteristics
*locomotion by muscular foot
body covering of ciliated epithelium
most have cephalization (“head” region)
*has a mantle
a sheath of tissue enclosing the vital organs
secretes a shell
forms its respiratory apparatus
*shell is multilayered and used for protection or body support

4. Characteristics (cont.)
has a complete digestive system
gills or lungs to control respiration
circulation is by means of heart and colorless blood
has ganglia and nerve cords for nervous system
special sense organs for vision, taste, touch, smell, and balance
sexual reproduction with a trochopore larval stage

5. Characteristics (cont.)
bilateral or asymmetrical
*visceral hump
part of the body with the heart, digestive, and excretory organs
usually covered by the mantle
*radula
small organ with many tiny teeth for scraping food particles

6. Classification
6 Classes based on shape, shell type, and foot; we will look at 3
Class Bivalvia
“two-shelled”
Class Gastropoda
“stomach-footed”
Class Cephalopoda
“head-footed”

7. Class Bivalvia clams, mussels, oysters, scallops
shell (valve) composed of 3 layers
horny layer
prismatic layer
calcium carbonate
pearly layer
foot

8. Class Bivalvia the shell’s job is to
protect animal from external predators and internal irritations
if mantle gets a grain of sand in it, it will secrete the material of the pearly layer around the sand and form a pearl
the strong muscles holding the two shells together keep predators from being able to eat them

9. Class Bivalvia incurrent & excurrent siphons open circulatory system
filter feeders – no radula
gills - oxygen in/CO2 out
open circulatory system
heart helps pump
excurrent siphon
incurrent siphon
gills

10. Class Bivalvia FYI Giant clam of Australia’s Great Barrier Reef
can measure more than 1 yard in length
weighs hundreds of pounds
Shipworm
bivalve who can burrow over 2 feet into wooden ships and wharves
once protected all they have to do is extend their siphons to feed
causes much damage by weakening the wood to collapse

11. Class Gastropoda snails, slugs “stomach-footed” shell (valve) radula
univalves
shell-less
radula
mantle cavity

12. Class Gastropoda most are aquatic
foot is located below the visceral hump where the stomach is located
secretes slime to move over and then the foot contracts over it
enables a snail to glide over an upright razor blade
one shell, univalve
nutrition
food is brought into the mouth by the radula
digestive tract is twisted so that the anus comes out above the mouth

13. Class Gastropoda circulation nervous system
opened
heart located below the stomach and some blood vessels carry blood to dorsal area of the animal
nervous system
ganglia located near the mouth
pair of eyes on tope of tentacles
slugs are unique type of gastropod because they are terrestrial and lack a shell

14. Class Cephalopoda squid, octopus “head-footed” shell (valve) radula
shell-less
internal shell
external shell
radula

15. Class Cephalopoda jet propulsion defense mechanisms
siphon or funnel for expelling water from the mantel
fastest marine invertebrates
defense mechanisms
ink to confuse predators
color changes for camouflage

16. Phylum Echinodermata
“spiny skin”
starfish, sea urchins, sand dollars

17. General characteristics
6 Classes
lives in saltwater environments
radial symmetry in adults
bilateral symmetry in larva
locomotion by a water vascular system and tube feet
support by a series of hard plates beneath the epidermis
has spines to give the animal a rough, spiny appearance
complete digestive system

18. General characteristics (cont.)
respiration using skin gills
no well organized circulatory or excretory organs
asexual reproduction by regeneration
sexual reproduction by separate sexes using external fertilization

19. Echinoderms radial symmetry water-vascular system ring canal
madreporite
tube feet
radial canals

20. Echinoderms: Starfish
coelom
body cavity
regeneration
coelom

21. Class Stelleroidea (starfish)
External features
rays
4-25, but 5 rays are most common
central disc
central area of starfish from which rays extend
spines
originate from the hard plates below the epidermis to give a rough appearance
skin gills
smaller tubing around spines for respiration and excretion by diffusion

22. Class Stelleroidea (starfish)
External features (continued)
anus
opening on dorsal surface of central disc for eliminating waste
Sieve plate (madreporite)
dorsal surface at edge of central disc
regulates the water pressure in the tube feet so it can act like suction
tube feet
ventral surface of rays
used for locomotion and opening shells of bivalves
mouth
ventral surface of central disc

23. Class Stelleroidea (starfish)
Internal Features
stomach
inside central disc
can be everted through the mouth
releases enzymes to break down food and then absorb it, then stomach is brought back in
digestive gland
extends into each ray
looks like plant leaves
finishes the digestion begun by mouth
radial canal
runs through the rays as past of its water-vascular system

24. Class Stelleroidea (starfish)
Internal Features (continued)
ring canal
part of the water-vascular system that circles inside the central disc
gonads
found in each ray
sexes are separate so they will either be all ovaries or all testis

25. FYI
fertilization is external so it is by luck that the sperm and eggs get together
the resulting larva is ciliated and bilateral
they eventually settle to bottom of ocean and develop into radially symmetrical adults
as long as the ray has a small portion of the central disc it can become a complete adult
crown of thorns starfish are causing much problems on coral reefs
sea cucumber has the remarkable ability to regenerate new internal organs
when attacked, they can eject some of their internal organs to appease its attacker and then retreat

26. FYI
The uniqueness of the echinoderms has caused problems for evolutionists.
they claim that starfish are “living fossils”
to solve the problem, evolutionists put starfish in a separate non-evolving branch of the phylogenetic tree (pg 192)
“very old” starfish have led evolutionists to assume that they evolved early but have not changed since

27. Other classes of echinodermata
Echinoidea
sea urchins and sand dollars
Holothuroidea
sea cucumber
Ophiuroidea
brittle stars and basket stars
Crinoidea
sea lilies and feather stars