How do sea urchins sense light?

With light-sensitive cells across their bodies

Why have sea urchins been important in biology?

For studying fertilization and embryos

Sea Urchins Quiz: 10 Questions That Test What You Know

A sea urchin has no eyes, yet its whole body seems to sense light, and this sea urchins quiz explores the spiny grazers found in every ocean. Learn how urchin booms stripped kelp forests in California, why urchin roe is prized as uni in Japan and how urchins helped scientists study embryos.

Start Sea Urchins Quiz

🎯 Daily Trivia Challenge • 🧠 10 Questions • ⏱️ 150 Seconds

Question 1 / 10 Time: 150s

Group
Which animal group do sea urchins belong to?
Mouth
What is a sea urchin's mouth called?
Diet
What do most sea urchins eat?
Barrens
What happens when urchins multiply out of control?
Otters
Which predator keeps urchin numbers in check in the North Pacific?
Uni
What is uni in Japanese cuisine?
Sense
How do sea urchins sense light?
Feet
How do sea urchins move?
Science
Why have sea urchins been important in biology?
Sand dollar
Which flat animal is a type of sea urchin?

Explanations: answer key for all 10 questions

Q1: Which animal group do sea urchins belong to?
Answer: Echinoderms
Sea stars are relatives.
Q2: What is a sea urchin's mouth called?
Answer: Aristotle's lantern
Aristotle described it.
Q3: What do most sea urchins eat?
Answer: Algae and kelp
They scrape rocks clean.
Q4: What happens when urchins multiply out of control?
Answer: They create urchin barrens
Kelp forests disappear.
Q5: Which predator keeps urchin numbers in check in the North Pacific?
Answer: Sea otters
Otters are a keystone species.
Q6: What is uni in Japanese cuisine?
Answer: Sea urchin gonads
It is considered a delicacy.
Q7: How do sea urchins sense light?
Answer: With light-sensitive cells across their bodies
Their whole body may act like an eye.
Q8: How do sea urchins move?
Answer: With tube feet and spines
They move slowly across rocks.
Q9: Why have sea urchins been important in biology?
Answer: For studying fertilization and embryos
Their eggs are easy to observe.
Q10: Which flat animal is a type of sea urchin?
Answer: Sand dollar
It has very short spines.

Sea Urchins Quiz – Spiny Grazers of the Seafloor

Sea urchins are spiny echinoderms related to sea stars and sand dollars. There are about 950 species, living on rocky seafloors and reefs from shallow tide pools to the deep sea, in every ocean of the world.

Urchins graze on algae with a five-toothed mouth called Aristotle's lantern. They move with tube feet and spines, and their bodies are covered in light-sensitive cells. Some have venomous spines, while others are harmless to touch.

When predators such as sea otters and sunflower sea stars decline, urchins can multiply and destroy kelp forests, leaving urchin barrens. Urchins are also a valuable seafood, and their eggs have helped scientists understand how embryos develop.

What This Quiz Teaches

Ocean fans and students will enjoy these questions.

What urchins are
How they eat
What urchin barrens are
What uni is
Why scientists study them

Did You Know?

Some urchins live over 100 years.
Pencil urchins have thick spines.
Urchins can regrow spines.
Urchins bore holes into rock.
Fire urchins are venomous.