Echinoderms

A series of 50 flashcards covering the key concepts, characteristics, and ecological importance of Echinodermata.

What are ossicles in echinoderms?

They are small, calcified structures that make up the skeleton of echinoderms.

List the five living classes of Echinodermata.

Crinoidea, Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea.

What type of symmetry do echinoderms exhibit?

Pentamerous radial symmetry.

What is a key feature of echinoderm anatomy?

A mesodermal calcitic endoskeleton.

How many extant and extinct echinoderm classes exist?

7,000+ extant and 15,000+ extinct.

What is the primary habitat of echinoderms?

Mostly marine environments.

Describe the water vascular system in echinoderms.

A network of fluid-filled canals used in locomotion, feeding, and respiration.

What is mutable collagenous connective tissue?

Tissue that can change properties rapidly, allowing echinoderms to adapt their body stiffness.

Name one reproductive strategy used by echinoderms.

Broadcast spawning, where eggs and sperm are released into the water.

What kind of feeders are crinoids?

Filter feeders.

What ecological role do sea stars (Asteroidea) play?

They are often predators and scavengers.

How do echinoderms regenerate lost body parts?

Through their ability to regenerate limbs and even internal organs.

What is a notable characteristic of brittle stars (Ophiuroidea)?

They have distinct, snake-like arms.

Which echinoderm class has the most species?

Ophiuroidea (brittle and basket stars).

What adaptation allows some echinoderms to survive in variable salinities?

Brittle stars can tolerate short periods of low salinity.

What is unique about the tube feet of echinoderms?

They often lack adhesion disks and are used primarily for locomotion and food transport.

What is the function of Cuvierian tubules in holothuroids?

They are expelled as a defense mechanism during evisceration.

Describe the anatomical composition of echinoderms.

Composed of a body wall, skeleton made of ossicles, and a water vascular system.

What does gonochoric mean in the context of echinoderm reproduction?

It refers to species that have separate sexes.

How do sea cucumbers protect themselves from predators?

By expelling their respiratory organs and regenerating them later.

What environmental conditions do echinoderms thrive in?

They are found in a range of environments from intertidal zones to abyssal depths.

What is the importance of the water vascular system in echinoderms?

It plays a critical role in locomotion, feeding, and hydraulic control of their tube feet.

What type of larval stage is ancestral to all echinoderms?

Dipleurula larva.

What is the skeletal structure of sea urchins called?

Test or theca.

What is a commercially important use of echinoderms?

They are collected for food, particularly in Asia.

Why is overharvesting of echinoderms a concern?

Many species face the risk of extinction due to high demand.

What is one way to culture echinoderms in captivity?

By breeding them to prevent overharvesting in the wild.

How are echinoderms categorized in relation to deuterostomes?

Echinoderms are part of the Deuterostomia clade.

Which echinoderm class is known for having photoreceptors at the tip of their arms?

Asteroidea (sea stars).

What environmental extremes can echinoderms tolerate?

Echinoderms are typically marine but can adapt to some brackish environments.

What morphological differences exist between extant and extinct echinoderms?

Extant species differ morphologically from extinct ones, particularly due to historical extinctions.

What do echinoderms use their tube feet for?

Movement, prey transport, and gas exchange.

What unique feature does the echinoderm skeleton have?

It consists of ossicles embedded in a mutable connective tissue.

What type of ecological interactions do echinoderms participate in?

Echinoderms can be hosts in both commensal and parasitic interactions.

What unique strategy for reproduction do some echinoderms employ?

Some species can clone their larvae.

In what periods did the first echinoderms appear?

During the Ordovician period.

What anatomical features distinguish crinoids from other echinoderms?

They have long arms and absence of madreporites.

What reproductive strategy does the class Holothuroidea primarily exhibit?

Most are gonochoric and use broadcast spawning.

What significant feature allows echinoids to reduce coral loss in marine ecosystems?

Their role as grazers can help control algae growth on coral.

Describe the ecological pattern of echinoderm species richness.

Abundance is highest at continental shelves and upper slopes.

What is a potential risk associated with the collection of sea cucumbers?

Overharvesting may lead to their extinction.

Which echinoderm class has individuals that can swim?

Some feather stars within the class Crinoidea.

Explain how echinoderms achieve locomotion.

They use their tube feet powered by their water vascular system.

What is the significance of the fossils found dating back to the Ordovician period?

They provide insight into the early evolution of echinoderms.

What adaptation allows echinoderms to quickly respond to threats?

Autotomy (the ability to shed limbs) as a stress response.