All about sea urchins

Sea urchins are typically spiny, globular animals, echinoderms in the class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal to 5,000 metres. Their tests are round and spiny, typically from 3 to 10 cm across. Sea urchins move slowly, crawling with their tube feet, and sometimes pushing themselves with their spines. They feed primarily on algae but also eat slow-moving or sessile animals. Their predators include sea otters, starfish, wolf eels, triggerfish, and humans.

Like other echinoderms, urchins have fivefold symmetry as adults, but their pluteus larvae have bilateral (mirror) symmetry, indicating that they belong to the Bilateria, the large group of animal phyla that includes chordates, arthropods, annelids and molluscs. They are widely distributed across all the oceans, all climates from tropical to polar, and inhabit marine benthic (sea bed) habitats from rocky shores to hadal zone depths. Echinoids have a rich fossil record dating back to the Ordovician, some 450 million years ago. Their closest relatives among the echinoderms are the sea cucumbers . Both are deuterostomes, a clade which includes the chordates.

The animals have been studied since the 19th century as model organisms in developmental biology, as their embryos were easy to observe; this has continued with studies of their genomes because of their unusual fivefold symmetry and relationship to chordates. Species such as the slate pencil urchin are popular in aquariums, where they are useful for controlling algae. Fossil urchins have been used as protective amulets.

Source: Wikipedia

	Have unlimited access to all exercises on bitgab
	Get discounts on bitgab Academy courses
	Join unlimited group classes
	Get a 100% discount on private classes with bitgab teachers
	Ask questions to our teachers anytime

	Private and unlimited access to bitgab for all students and teachers in your school, using your own unique subdomain (yourschoolname.bitgab.com)
	Teach online classes of up to 15 students
	Custom exercises created by our Editorial team from a content of your choosing
	Ability to create your own language learning activities to use in class or as an alternative to doing homework
	Track student progress with personalized reports and analytics
	Send messages to students, groups, and much more
	24/7 unlimited support

	Have unlimited access to all exercises on bitgab
	Get discounts on bitgab Academy courses
	Join unlimited group classes
	Get a 100% discount on private classes with bitgab teachers
	Ask questions to our teachers anytime

	Have unlimited access to all exercises on bitgab
	Get discounts on bitgab Academy courses
	Join unlimited group classes
	Get a 100% discount on private classes with bitgab teachers
	Ask questions to our teachers anytime

Adding api fields

Getting the list of room occupants

Fields from server

Name To Id

Chat

Chat with XXX

Read the text and answer the questions

Practice your writing skills by discussing the questions below

Conversation

Adding api fields

Getting the list of room occupants

Fields from server

Name To Id

Chat

Chat with XXX

All about sea urchins

Read the text and answer the questions

Practice your writing skills by discussing the questions below

Conversation

bitgab PREMIUM for Schools Step 1 of 2

Payment information Step 2 of 2

Thank you!

Error

Reserve Class Reserve a 1-to-1 conversation class with this teacher

Payment information Reserve a 1-to-1 conversation class with this teacher

Class Reserved!

Error

bitgab PREMIUM for Schools
Step 1 of 2

Payment information
Step 2 of 2

Reserve Class
Reserve a 1-to-1 conversation class with this teacher

Payment information
Reserve a 1-to-1 conversation class with this teacher