Invertebrate Phyla: Arthropoda, Porifera, Cnidaria, Mollusca, Echinodermata

Arthropoda

Hard skeleton made of chitin and protein.

Possess numerous jointed appendages and a segmented body.

They can fly fast; they must molt to grow.

Porifera

Most of them are marine while a few are freshwater forms.

These are multicellular organisms which are sedentary in nature.

Body is cylindrical, asymmetrical, or has radial symmetry.

Most of them are marine while a few are freshwater forms.

Cnidaria

Two tissue layers with nerve and muscle tissue.

A mouth and stomach.

Nematocysts: harpoon-like structures contained in special cells called cnidocytes.

Two main life forms: free-swimming medusa and attached polyp.

Basic anatomy of cnidarians

They are similar to sponges. Cnidarians are diploblasts, meaning that they develop from two basic germ cell layers: an ectoderm (outer layer) and an endoderm (inner layer).

The cnidarians have two main life forms which are the free-swimming medusa and the attached polyp.

Mollusca

Molluscs have a rasping organ called a radula.

A sheath of tissue called the mantle covers the body and secretes the shell.

A mantle cavity houses gills or lungs.

Calcium shell: some molluscs have greatly reduced shells.

Mollusca: Three Major Classes

Class Bivalvia

Is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts (clams).

Class Gastropoda

Belong to a large taxonomic class of invertebrates. This class comprises snails and slugs from saltwater, from freshwater, and from the land.

Class Cephalopoda

A small group of highly advanced and organized, exclusively marine animals. The octopus, squid, cuttlefish, and chambered nautilus are familiar representatives.

Echinodermata

Internal skeleton made of small calcium carbonate plates.

Five-part symmetry, without a head, eyes, or centralized brains.

Special fluid-filled system that operates tube feet.

Include: sea stars, sea lilies, sea urchins, sea cucumbers, and brittle stars.

How Sponges Eat

Sponges are filter feeders. Most of them eat tiny, floating organic particles and plankton that they filter from the water that flows through their body. Food is collected by specialized cells called choanocytes and brought to other cells by amoebocytes.

Arthropods

Arthropods: have an exoskeleton, brown colored, and are found around the coasts of the northern and southern seas.

Echinoderms

Echinoderms regenerate tissue, organs, and limbs, are found in intertidal zones, and have a central disk.

Similarities

• Both have bilateral symmetry.
• Both start off as planktonic and have spiny skin.