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by 18SCartwright
Last updated 7 years ago


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Reproduction- asexual reproduction involves the body being split into two parts, and the missing body parts regenerating to form two organisms starting from one: however, it must be split in a way that certain body parts are present in both parts (sea cucumbers are the only subgroup that can regenerate whole internal organs)- sexual reproduction involves eggs from females and spermatozoa from males being expelled into the water, where the eggs are fertilized (this occurs annually)


Defining Characteristics- most have spiny surfaces, which are caused by hard plates under the skin, which are part of an endoskeleton- most adults' external body parts protrude from the center (like spokes on a wheel)

Brittle Star Diagram

Importance- echinoderms used to be used for medicinal purposes by the Greeks and Romans- they were also used as a food source- they help to regulate numbers of small organisms in the ocean by feeding on them- they control the growth of seaweed, allowing the corals to flourish- they change the structure of seafloor sediments, altering its physical and chemical compositions

Diet/Feeding- different kinds of echinoderms feed on different things in the ocean- some examples of food are; plankton, coral, mussels, clams, mollusks, algae, and even its own kind- the way some echinoderms eat is by pulling their stomach out through their mouth and injecting it into their prey (mostly starfish do this), then digesting the food and pulling their stomach back in

Body Structure- adults show radial symmetry, but some reveal bilateral features (opening of the sea star's water vascular system is not central) - larvae are bilaterally symmetrical- they have coeloms, which are fluid-filled cavities formed from a portion of the digestive tube of the early embryo- some echinoderms are segmented, meaning that their bodies are made up of similar segments (a sea urchin is made up of similar spines all around its body)- most echinoderms have hair-like structures protruding from the skin (called cilia), which carry food particles toward the mouth or carry unwanted substances away from the body- each has a water vascular system, which is a network of water-filled canals that branches into tube feet (which are structures that mobilize the animal)

Subgroups and Examples- 6 classes of echinoderms; sea urchins (Echinoidea), sea stars (Asteroidea), brittle stars (Ophuiroidea), sea lilies (Crinoidea), sea cucumbers (Holothuroidea), and sea daisies (Concentricycloidea)




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