Echinoderms and Hemichordates

What type of symmetry is observed in adult echinoderms?

Basic pentaradial symmetry.

What is the key feature of the water-vascular system in echinoderms?

It is a hydraulic system involved in locomotion, food gathering, respiration, and excretion.

How do echinoderms primarily reproduce?

They are broadcast spawners, releasing large quantities of eggs and sperm directly into the water.

What are pedicellariae in echinoderms?

Jawlike pincers found on their body surface, often stalked and sometimes equipped with poison glands.

What do hemichordates share with chordates?

They share pharyngeal gill slits.

What are the three parts of the coelom in echinoderms and hemichordates?

Protocoel, mesocoel, and metacoel.

What is the function of the madreporite in echinoderms?

It leads to the water-vascular system and allows water to enter.

Name an example of a class within Phylum Echinodermata.

Class Asteroidea (sea stars), Class Echinoidea (sea urchins), or Class Holothuroidea (sea cucumbers).

What is the significance of the Ambulacraria hypothesis?

It predicts gill slits in the pharynx as an ancestral deuterostome character.

How do irregular echinoids differ from regular echinoids?

Irregular echinoids (like sand dollars) exhibit bilateral symmetry, while regular echinoids (like sea urchins) exhibit nearly spherical symmetry.

What does evisceration refer to in sea cucumbers?

The act of removing an organism's internal organs as a defense mechanism to escape predators.

What is the main feeding strategy of brittle stars?

They can be scavengers, browsers, deposit or filter feeders, or predators.

How are the sexes organized in echinoderms?

Most echinoderms have separate sexes.

What is the composition of the nervous system in echinoderms?

The nervous system comprises a nerve ring surrounding the gut and radial nerves running along the arms.

What challenges do echinoderms face regarding osmoregulation?

Most echinoderms are unable to osmoregulate against a strong concentration gradient and rarely venture into brackish water.

What are the three basic regions of the body in acorn worms (Class Enteropneusta)?

Proboscis, collar, and trunk.