Phylum Echinodermata: The Echinoderms

Explanation
Echinoderms have an endoskeleton made up of ossicles. Ossicles are small, calcified structures that are interconnected to form a rigid framework within the body of echinoderms. These structures provide support and protection to the internal organs of echinoderms. The ossicles are made up of calcium carbonate, which gives them strength and durability. They also play a role in the movement and locomotion of echinoderms, as the muscles attach to these ossicles, allowing for coordinated movement.

Explanation
The water vascular system is a unique feature found in echinoderms. It is made up of a series of canals that deliver water to the tube feet, which are used for attachment and movement. This system allows echinoderms to control the movement of their tube feet and perform various functions such as locomotion, feeding, and respiration. It also helps in maintaining the internal water balance and waste elimination in these organisms.

Explanation
Autotomy is a behavior observed in certain echinoderms where they intentionally shed or detach a body part in order to escape from predators. This process allows them to distract or confuse the predator, as the detached body part continues to move and attract attention while the echinoderm escapes. Autotomy is a remarkable adaptation that enables these organisms to survive and regenerate lost body parts over time.

Explanation
The genus Antedon belongs to the class Crinoidea. Crinoidea is a class of marine animals commonly known as sea lilies or feather stars. These organisms are characterized by their feather-like arms that they use for filter feeding. Antedon is a specific genus within this class, indicating that it is a particular group of sea lilies or feather stars.

Explanation
Class Crinoidea is found in the subphylum Pelmatozoa. Crinoidea refers to a class of marine animals known as crinoids or sea lilies, which are characterized by their flower-like appearance and long, feathery arms. Pelmatozoa is a subphylum of echinoderms, which includes organisms such as sea stars, sea urchins, and sea cucumbers. Therefore, it is correct to say that Class Crinoidea is found in the subphylum Pelmatozoa.

Explanation
Genus Echinaster is found in the class Asteroidea. Asteroidea is the class that includes starfish or sea stars. Since Echinaster is a genus of starfish, it belongs to the class Asteroidea.

Explanation
The correct answer is Eleutherozoa. Eleutherozoa is a subphylum of the phylum Echinodermata, which includes the class Asteroidea (starfish). This subphylum consists of marine animals that have a water vascular system and spiny skin.

Explanation
Class Ophiuroidea is found in the Subphylum Eleutherozoa. Eleutherozoa is a subphylum of the phylum Echinodermata, which includes organisms such as sea stars, sea urchins, and sea cucumbers. Ophiuroidea, commonly known as brittle stars, are a class of echinoderms characterized by their long, slender arms and distinct central disk. They are closely related to sea stars but have some anatomical differences. By being classified under the Subphylum Eleutherozoa, it indicates that Ophiuroidea shares certain common characteristics and evolutionary history with other echinoderms in this group.

Explanation
The correct answer is Eleutherozoa. Class Echinoidea belongs to the subphylum Eleutherozoa. This subphylum includes all the echinoderms that have a free-living adult stage and are not attached to a substrate. Echinoidea, commonly known as sea urchins, are characterized by their spherical shape and spiny exoskeleton. They are part of the diverse group of marine animals known as echinoderms, which also includes starfish, sea cucumbers, and brittle stars.

Explanation
Genus Echinarachnius is found in the class Echinoidea. This is because Echinoidea is the class that includes all sea urchins, which is the group that Genus Echinarachnius belongs to.

Explanation
The genus Holothuria is found in the class Holothuroidea. Holothuroidea is a class of marine animals commonly known as sea cucumbers. These animals have elongated bodies and are typically found on the ocean floor. The genus Holothuria is one of the largest genera within the class Holothuroidea, comprising numerous species of sea cucumbers. Therefore, the correct answer is Holothuroidea.

Explanation
Feather Star

Explanation
This species belongs to the genus Echinaster.

Explanation
Sea Urchin

Explanation
Sand Dollar

Explanation
Sea Cucumber