Echinoderms & Chordates

A comprehensive set of question-and-answer flashcards covering the major classes, anatomy, physiology, and evolutionary relationships of Echinodermata and Chordata as presented in Dr. Franks’ lecture notes.

What material makes up the echinoderm endoskeleton?

Calcitic plates of calcium carbonate reinforced with proteins.

Which unique vascular system is found only in echinoderms?

The water-vascular system.

How are echinoderm ossicles held together, allowing posture without muscle effort?

By collagen ligaments.

What symmetry characterizes adult echinoderms?

Pentaradial (five-fold) symmetry.

Are echinoderms dioecious or monoecious, and where does fertilization occur?

Dioecious; fertilization is external in the sea.

Do echinoderms possess a centralized brain?

No— they have a decentralized nervous system with no true brain.

Which echinoderm class contains sea lilies and feather stars?

Class Crinoidea.

How do crinoids obtain food?

Filter feeding with arm pinnules that direct particles toward the mouth.

What appendages allow sea lilies to anchor to reef surfaces?

Cirri.

Which echinoderm class includes the typical sea stars?

Class Asteroidea.

Describe the feeding method of many asteroid sea stars on coral.

They evert their stomach onto coral, secrete enzymes, and absorb liquefied tissue.

Trace the main pathway of water through a sea star’s water-vascular system.

Madreporite → stone canal → ring canal → radial canals → ampullae → tube feet.

What remarkable ability allows a sea star to regrow lost arms?

Regeneration; a single arm with part of the central disk can regrow a whole animal.

Which class of echinoderms possesses Aristotle’s lantern?

Class Echinoidea (sea urchins).

What is Aristotle’s lantern used for?

Scraping algae and microbes from surfaces with five continuously replaced teeth.

What respiratory structures do sea cucumbers use and through which opening do they ventilate them?

Paired respiratory trees ventilated through the anus.

Which echinoderm class is known for long, snake-like arms used in crawling?

Class Ophiuroidea (brittle stars).

Together with chordates, echinoderms belong to which embryological group?

The deuterostomes.

In deuterostomes, which embryonic opening becomes the mouth?

The second opening; the blastopore becomes the anus.

List the four key characteristics shared by all chordates.

1) Notochord; 2) dorsal hollow nerve cord; 3) pharyngeal gill slits; 4) post-anal tail.

Name the three subphyla of Chordata.

Urochordata, Cephalochordata, Vertebrata.

What common name is given to most urochordates?

Tunicates or sea squirts.

Why must Molgula larvae quickly find a substrate?

They must attach and metamorphose within 1–2 days or they die.

Which chordate subphylum contains Amphioxus (Branchiostoma)?

Cephalochordata.

What unique muscle blocks drive the swimming of amphioxus?

Myomeres.

Which structure protects the nerve cord in vertebrates?

Vertebral bones (the vertebral column).

What class of jawless vertebrates includes lampreys?

Class Agnatha.

How many gill openings are found on each side of a lamprey?

Seven.

Cartilaginous fish such as sharks belong to which vertebrate class?

Class Chondrichthyes.

Why must most sharks keep swimming continuously?

To force water over their gills for respiration.

What organ gives bony fish buoyancy control?

The swim bladder.

Which external feature covers the gills of most bony fish and enables them to breathe without swimming?

The operculum.

Amphibian larvae breathe with , whereas adults usually breathe with .

Gills; lungs (and skin).

What adaptation allows reptile eggs to be laid on land?

The amniotic egg with a water-retaining amnion.

Birds are living descendants of which dinosaur group?

Theropod dinosaurs.

Name two functions of feathers besides flight.

Insulation (warmth) and display/camouflage.

Which three unique features define mammals?

Hair, mammary glands, and three middle-ear bones.

What is the principal difference between marsupial and placental mammals regarding development?

Marsupials complete development in a pouch; placentals develop internally via a placenta.

What sensory system runs along the side of many fish and detects water vibrations?

The lateral line.

In sea urchins, what structure contains the gonads and is commonly called the 'test'?

The rigid, fused endoskeletal shell.

Where is the madreporite located on most sea urchins?

On the aboral (upper) surface of the test.

Which echinoderm developmental stage follows the blastula?

Gastrula.

What name is given to the free-swimming echinoderm larva with bilateral symmetry?

Bipinnaria larva.

Identify two reasons Dr. Franks’ lab is not dissecting starfish this term.

The prevalence of Sea Star Wasting Syndrome and conservation/ethical concerns.

Which heart structure is present in sharks but not in ray-finned fish?

Trick question—both have a two-chambered heart (atrium and ventricle); difference is not structural but phylogenetic.

What term refers to cold-blooded vertebrates that rely on environmental heat?

Ectothermic animals.

How many chambers are in the hearts of birds and mammals?

Four chambers.