Summary
Marine animals with radial symmetry as adults and a water vascular system, like starfish.
In depth
Phylum Echinodermata. Water vascular system with tube feet, dermal endoskeleton of ossicles, five-part radial symmetry in adults and bilateral larvae, deuterostomes. Can regenerate arms.
Tube feet allow movement and feeding. The skeleton comprises ossicles. Larvae are bilateral. They have no brain.
Example: starfish evert their stomach to digest prey.
Echinoderms (sea stars, brittle stars, sea urchins, sea cucumbers, sea lilies) are all marine, with larvae that are bilateral and adults with pentaradial symmetry, and are deuterostomes, closer to chordates than to most other invertebrates. The water vascular system, powered by a madreporite and ampullae, drives tube feet for locomotion, feeding and gas exchange. Sea stars can evert their stomach to digest prey outside the body, and many regenerate lost arms.
They have no brain and a nerve ring with radial nerves. Sea urchin embryos are classic models in developmental biology, where fertilisation and early cleavage were studied. Crown-of-thorns sea stars harm coral reefs in outbreaks. Sea cucumbers are harvested for food, and some eject sticky threads for defence.
Key idea: pentaradial symmetry in adults is derived from bilateral ancestors.
Frequently asked questions
What is Echinoderms?
Marine animals with radial symmetry as adults and a water vascular system, like starfish.
Which area of biology covers Echinoderms, and how advanced is it?
Echinoderms is one of the 53 topics in Zoology & Animal Diversity. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Protostomes and Deuterostomes, Animal Symmetry, Cnidarians.
Can you give an example of Echinoderms?
Sea stars pry open clams using tube feet.
What should I learn before Echinoderms?
Echinoderms is a Beginner topic, so no earlier topic is required. Other Beginner topics in Zoology & Animal Diversity that pair well with it include Animal Kingdom, Vertebrates and Invertebrates, Sponges.
What topics are related to Echinoderms?
The closest topics to Echinoderms are Protostomes and Deuterostomes, Animal Symmetry, Cnidarians, Annelids. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Echinoderms?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Echinoderms. To practise the whole of Zoology & Animal Diversity, use the Zoology & Animal Diversity quiz.
How is Echinoderms different from Protostomes and Deuterostomes?
Echinoderms: Marine animals with radial symmetry as adults and a water vascular system, like starfish. Protostomes and Deuterostomes: Two animal lineages differing in embryonic development; deuterostomes include echinoderms and chordates. Read both side by side and note what each one explains.
How should I study Echinoderms step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Protostomes and Deuterostomes and explain the difference aloud. Finally, take the Zoology & Animal Diversity quiz and come back to this page for any question you miss.