Echinoderms and Invertebrate Chordates

Section Objectives: Compare similarities and differences among the classes of echinoderms. Interpret the evidence biologists have for determining that echinoderms are close relatives of chordates.

What is an echinoderm? Echinoderms move by means of hundreds of hydraulic, suction-cup-tipped appendages and have skin covered with tiny, jawlike pincers. Echinoderms are found in all the oceans of the world.

Echinoderms have endoskeletons If you were to examine the skin of several different echinoderms, you would find that they all have a hard, spiny,or bumpy endoskeleton covered by a thin epidermis.

Pretty Starfish

Echinoderm marine invertebrate characterized by spiny skin, radial symmetry, a water vascular system, and an endoskeleton. Slow moving or sessile. Most reproduce sexually.

Evolution of Echinoderms Deuterostomes thought to be 500 million years old.

7 Structures of Echinoderms -

1. Water vascular system network of fluid filled tubes that enable the sea star to move.

Starfish Movement

2. Tube Feet external structures of the water vascular system. Function in gas exchange and excretion.

3. Ampulla – (am - pyoo - luh) muscular sac that helps force water through the water vascular system. Ampullae

4. Pedicellariae – (ped - ih - sihl - ahr - ee ay) pincer like appendages used for protection and for cleaning the surface of its body.

5. Rays long, tapering arms.

Movement

6. Madreporite - (mah - ddray - pohr - ite) sievelike disk shaped opening where water enters and leaves. Part of the water vascular system.

7. Nervous System Primitive nervous system, no head or brain.

Spine Part of the water vascular system. The are on a plate made of calcium carbonate. Firm but flexible.

Sea Star

5 Types of Echinoderms

brittle stars and basket stars

Sea Stars

Sea Lilies and Feather Stars Ex: sea lilies and feather stars, most primitive, resemble exotic plants

Sea Cucumber bilateral symmetry, may shoot out sticky tubules from its anus for protection.

Sea Cucumber

Urchins and Sand Dollars Skeletal plates are fused, forming a solid internal shell

Attack of the Sea Slug

Regeneration the ability to regenerate body parts.

Predator Crown of thorns sea star destroys a huge amount of coral reef each year. Live on the polyps of the coral, one sea star can eat the polyps from about 6 sq meters. Also eat clams and other shell fish. ( Ingests food by pulling its lower stomach into open shells.)

Sea stars Most species of sea stars have five rays, but some have more. Some species may have more than 40 rays.

Sea Star eating

Question 1 What is the similarity between the endoskeleton of echinoderms and the exoskeleton of crustaceans? Answer Both of these features are composed of calcium carbonate.

Question 2 A. rays B. pedicellariae C. madreporites D. tube feet Pincerlike appendages from modified spines on sea stars are called _______. A. rays B. pedicellariae C. madreporites D. tube feet

The answer is B, pedicellariae.

Question 3 A. carnivore B. herbivore C. parasite D. scavenger Which of the following terms does NOT describe an echinoderm’s method of obtaining food? A. carnivore B. herbivore C. parasite D. scavenger The answer is C, parasite.

Question 4 What stimulates a sea star to move in a given direction?

Sea stars move toward light and toward chemical signals emitted from potential prey animals.

Chordata (invertebrae)

Tunicates or sea squirt. Have a leathery outer covering, most adults are sessile.

Tunicates are sea squirts Tunicate larvae do not feed and are free swimming after hatching. They soon settle and attach themselves with a sucker to boats, rocks, and the ocean bottom. Many adult tunicates secrete a tunic, a tough sac made of cellulose, around their bodies.

Tunicates are sea squirts Colonies of tunicates sometimes secrete just one big tunic that has a common opening to the outside. Only the gill slits in adult tunicates indicate their chordate relationship. Adult tunicates are small, tubular animals that range in size from microscopic to several centi-meters long.

Tunicates are sea squirts If you remove a tunicate from its sea home, it might squirt out a jet of water-hence the name sea squirt.

Lancelets Can swim, although spend most of their time buried in the sand. Retain its chordate features throughout its life.

5 Characteristics of Chordates Notochord- a long semi rigid rod like structure. Located between the digestive system and the dorsal hollow nerve cord. (In vertebrates replaced by a backbone.)

5 Characteristics of Chordates Dorsal Hollow Nerve Cord- In folding of the ectoderm that later becomes your spinal cord and brain.

5 Characteristics of Chordates Pharyngeal Pouches – Pair of structures locate in the pharyngeal region behind the mouth. In aquatic chordates (fish) develop into gill slits.

5 Characteristics of Chordates Post anal tail – Appendage or extension of the backbone posterior to the anus. (At some point all chordates have a post anal tail, including humans.)

5 Characteristics of Chordates Muscle Blocks – Modified body segments that consists of stacked muscle layers that are anchored to the notochord. (locomotion or movement)