Gabriel Dominguez Marisa Ramunas Biology – Period 8 ECHINODERMS

What Is An Echinoderm? Echinoderms are characterized by spiny skin, an internal skeleton, a water vascular system, and suction-cup like structures called tube feet. Most adult echinoderms have a five-part radial symmetry. Meaning that the body parts usually occur in multiples of five and are arranged around the center of the body like a wheel.

About Them The phylum name comes from the words echinos, meaning “hedgehog”, and derma meaning “skin”. Kingdom = Amimalia Phylum = Echniodermata

Water Vascular System A unique feature of echinoderms is a system of internal tubes called a water vascular system. The water vascular system, which is filled with fluid, carries out many essential body functions in echinoderms, including respiration, circulation, and movement.

Feeding Echinoderms have several methods of feeding, for example: Sea urchins use five-part jaw like structures to scrape algae from rocks. Sea stars usually feed on mollusks such as clams and mussels. Once the preys shell is open, the sea star pushes its stomach out through its mouth, pours out enzymes, and digest the mollusk in its own shell. The sea star then pulls its stomach in and the some what digested prey into its mouth.

Movement Most echinoderms move using tube feet. An echinoderms movement relies on its structure of the endoskeleton. For example, sea urchins have movable spines attached to the endoskeleton that help it get around.

Reproduction Echinoderms reproduce by external fertilization. In most sea star species, the sexes are separate. Sperm are produced in testes, and the eggs are produced in ovaries. Both types of gametes are shed into open water, where fertilization takes place. The larvae swim around for a while and swim to the bottom of the ocean, where they are able to develop into adults.

Groups Of Echinoderms (There are about 7,000 species!) Sea Urchins & Sand Dollars: Have large, solid plates that form a box around their internal organs. Eat large amounts of algae. Brittle Stars: Are commonly found on coral reefs. They have slender, flexible arms that help them get away from predators quickly. Are filter feeders. Hide by day and come out at night.

Groups (cont.) Sea Cucumbers: Look like warty, moving pickles. Are detritus feeders that move along the sea floor while sucking up organic matter and the remains of other animals and plants. Sea Stars: Best-known group of echinoderms. They move by creeping slowly across the ocean floor. Most are carnivorous.

Groups (cont.) Sea Lilies & Feather Stars: Are filter feeders. Have long feathery arms. Makes up the oldest class of echinoderms. Live on top of coral reefs.

Pictures Of The Groups of Echinoderms

Ecology Of Echinoderms In many areas, a sudden rise or fall in the number of echinoderms can cause major changes in population of other organisms. Sea urchins help control the distribution of algae. Sea stars are important predators in the ocean because it helps control the number of other organisms such as clams and coral.

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