Animal Phyla: Ecdysozoans, Arthropods, Echinoderms, and Chordates

What are ecdysozoans?

The most species-rich animal group covered by a tough coat called a cuticle.

What is the process of shedding the cuticle in ecdysozoans called?

Ecdysis.

What are the two largest phyla of ecdysozoans?

Nematodes and arthropods.

Where can nematodes be found?

In most aquatic habitats, soil, moist plant tissues, and body fluids of animals.

What type of reproductive system do nematodes usually have?

Sexual reproduction by internal fertilization.

What percentage of known animal species are arthropods?

Two out of every three known species.

What are the main characteristics of arthropods?

Segmented body, hard exoskeleton, and jointed appendages.

What functions can the appendages of arthropods serve?

Walking, feeding, sensory reception, reproduction, and defense.

What is the composition of the arthropod exoskeleton?

Layers of protein and the polysaccharide chitin.

What type of circulatory system do arthropods have?

An open circulatory system.

What is the unique system found in echinoderms?

A water vascular system.

What are echinoderms?

Marine animals like sea stars and sea urchins.

What defines deuterostomes?

Echinoderms and chordates that share developmental characteristics.

What is the body plan of cnidarians?

A sac with a central digestive compartment and a single opening functioning as mouth and anus.

What are nematocysts?

Specialized organelles within cnidocytes that eject a stinging thread.

What is a typical habitat for planarians?

Fresh water.

What type of body symmetry do bilaterally symmetrical animals have?

A dorsal (top) side, ventral (bottom) side, right and left sides, and anterior (head) and posterior (tail) ends.

What is the germ layer covering the embryo's surface called?

Ectoderm.

What type of animals lack true tissues?

Sponges and a few other groups.

What are the two major groups of metazoa?

Parazoa (sponges) and Eumetazoa (all other animals).

What is a coelom?

A true body cavity derived from mesoderm.

What are the three main parts of a mollusc's body plan?

Muscular foot, visceral mass, and mantle.

What are bivalves?

Marine molluscs that include clams, oysters, mussels, and scallops.

What do earthworms do as they move through soil?

Extract nutrients.

How do planarians reproduce?

They can reproduce sexually or asexually through fission.

What is the primary function of choanocytes in sponges?

Generate a water current and ingest suspended food.

What is the significance of molecular data in animal phylogeny?

It helps in recognizing relationships among animal groups.