types of echinoderms

practice iv

Sea cucumbers at National Geographic http://animals.nationalgeographic.com/animals/invertebrates/sea-cucu 1. Where do sea cucumbers live? 2. How do sea cucumbers eat?


Echinoderms are spread all over the world at almost all depths, latitudes, and environments in the ocean. Most feather stars (crinoids) live in shallow water. In the deep ocean, sea cucumbers are common, sometimes making up 90% of the organisms. Most echinoderms, however, are found in reefs just lying beneath the surface of the water. No echinoderms are found in freshwater habitats or on land. This makes Echinodermata the largest animal phylum to only have ocean-based species.

types of echinoderms

The echinoderms can be divided into two major groups: 1. Eleutherozoa are the echinoderms that can move. This group includes the starfish and most other echinoderms. 2. Pelmatozoa are the immobile echinoderms. This group includes crinoids, such as the feather stars. Listed below are the four main classes of echinoderms present in the Eleutherozoa Group ( Table 1.1). Class Asteroidea Ophiuroidea Representative Organisms Starfish and asteroids Brittle stars ( Figure 1.1) Echinoidea Sea urchins and sand dollars Holothuroidea Sea cucumbers Characteristics Capture prey for their own food. Bottom feeders with long, narrow, flexible arms that allow relatively fast movement. Have movable spines which are used for movement, defense, and sensing the environment. Armless, elongated, generally soft-


do echinoderms move

While almost all echinoderms live on the sea floor, some sea-lilies can swim at great speeds for brief periods of time, and a few sea cucumbers are fully floating. Some echinoderms find other ways of moving. For example, crinoids attach themselves to floating logs, and some sea cucumbers move by attaching to the sides of fish. On the underside side of a sea star, there are hundreds of tiny feet usually arranged into several rows on each ray of the star. These are called tube feet, or podia, and are filled with seawater in most echinoderms. The water vascular system within the body of the animal is also filled with seawater. By expanding and contracting chambers within the water vascular system, the echinoderm can force water into certain tube feet to extend them. The animal has muscles in the tube feet, which are used to retract them. By expanding and retracting the right tube feet in the proper order, the animal can walk.

instructional diagrams

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not all echinoderms have the ability to move around.

-->  a. true

b. false

sand dollars can be found both in the ocean and on land.

a. true

-->  b. false

which is a characteristic of a starfish?

-->  a) capture prey for their own food

b) bottom feeders with long, narrow arms

c) have movable spines

d) armless and elongated

which is a characteristic of a brittle star?

a) capture prey for their own food

-->  b) bottom feeders with long, narrow arms

c) have movable spines

d) armless and elongated

which echinoderms are able to move relatively quickly?

a) sea cucumbers

b) sand dollars

c) asteroids

-->  d) brittle stars

which echinoderms have movable spines?

-->  a) sand dollars

b) starfish

c) sea cucumbers

d) brittle stars

echinoderms that cannot move include

-->  a) feather stars

b) starfish

c) sand dollars

d) none of the above

diagram questions

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