Clade Deuterostomia

Phylum EchinodermataPhylum Hemichordata

Phylum Chordata

Protostomes vs. Deuterostomes

• Zygote cleaves to become blastula and then forms gastrula. The blastopore of the gastrula can become either the mouth or the anus of the organism

• Protostome- “first mouth” Blastopore becomes the mouth. Ex-Annelids, Mollusks and arthropods

• Deuterostome- “second mouth” Blastopore becomes anus.

Ex-echinoderms, hemichordates,chordates

3

Embryonic Development

• Protostome– Blastopore becomes mouth

• Deuterostome– Blastopore becomes anus– (Animation)

Coelomates- true body cavity lined with mesoderm

• EX: all other animals

Phylum Echinodermata

Phylum Echinodermata• Includes starfish, sea urchins, sea cucumber & sand

dollars- all marine• Successful for 500 my• “Spiny-skinned”• Pentaradial Symmetry• Coelom, no segmentation• endoskeleton• Lack a centralized brain- have a Nerve ring with radial and lateral nerves -sense touch, light, temp, water conditions Ouch!

Phylum Echinodermata: Anatomy• Bipinnaria larvae(bilaterally symm.)• Water Vascular System:

-- Series of water-filled canals

-- Carries out functions including respiratory, circulation, and movement.

-- Oxygen, food, & wastes are carried by the water vascular system.

Phylum Echinodermata: Anatomy

• Water enters madreporite and flows through the stone canal and then enters the circular ring canal.

• Water then is separated into five radial canals that branch into double rows of bulblike structures called ampullae, which are on each side of the ambulacral ridge.

• The ampullae are connected to suckerlike podia = tube foot

Water Vascular System

Phylum Echinodermata: Anatomy• Have 5 sections or rays or arms

• Tube Feet: -- Act like suction cups-- Extend from the body-- Used to “walk”, capture, and hold prey

*How a single tube foot moves*

Tube Feet

Checkpoint1. What does Echinodermata mean?2. What are the basic characteristics of these

animals?3. What type of symmetry do echinoderms have?4. What are the functions of the water vascular

system?5. What do echinoderms use to move?6. What type of embryological development do

they have?

Class Asteroidea

Star Fish

Starfish: External Anatomy• Typically have 5 arms-

rays thick and short

• Arms emerge from a central disc

• Have an endoskeleton of small calcareous plates called ossicles

Starfish: External Anatomy• From the ossicles project spines & tubercles that

are responsible for their spiny surface

Starfish: External Anatomy

• On the oral surface- ventral side w/ mouth

-- Ambulacral (am-bu-la ‘kral) grooves: Radiate out along the arms from the centrally located mouth

-- Tube feet project from the grooves

Ambulacral Groove

Starfish: External Anatomy

• On the aboral surface- dorsal surface that includes the madreporite and anus.

Starfish: Internal Anatomy• Prey on bivalves

Two stomachs

• Pyloric stomach- used for digestion• cardiac stomach-can be extended outward to

engulf and digest prey.

Digestion• Starfish push their stomach out once prey is caught.

-- cardiac stomach pushes out of mouth to surround prey (ex: clam)

-- pyloric cecae-Pours out enzymes2/arm

-- Digests clam in its own shell

-- Then it pulls its stomach and the partially digested prey into its mouth. Pyloric stomach completes

digestion.

Reproduction

Asexual reproduction-

--Regenerates arms

-- If pulled apart into pieces, each piece will grow into a new animal, as long as it contains a portion of the central disc.

Reproduction

• Sexual- Individual starfish are male or female. Fertilization takes place externally, both male and female releasing their gametes into the environment.

• Resulting fertilized embryos form part of the zooplankton and are called deuterostomes.

Reproduction

• The deuterostomes then become a larva that are bilateral symmetrical.

• As they grow, they then change to radial symmetrical adults.

1 - Ambulacral ossicles

and ampullae.

2 - Madreporite.

3 - Stone canal.

4 - Pyloric caecae.

5 - Rectal glands.

6 - Gonads.

Class EchinoideaSea Urchins & Sand Dollars

• Sea Urchin

-- Eat algae

-- Have calcium carbonate plates covered with spines.

-- Can swivel spines

-- Many animals prey on sea urchins

-- Yes, people eat sea urchins Call it “roe”

Class Echinoidea

Sea Urchins

• Sea urchins are one of the sea otters favorite food.

• Sea otters keep sea urchin populations in check. Without sea otters, the sea urchins can devastate kelp forests which upsets the ecosystem.

Sea Urchins• On the oral surface of the sea urchin is a centrally

located mouth made up of five united calcium carbonate teeth or jaws, with a fleshy tongue-like structure within.

• The entire chewing organ is known as Aristotle's lantern.

Sea Urchins• Shell, which is also called the "test", is globular in

shape and covered with spines.

Sea Urchin• The spines, which in some species are long and

sharp, serve to protect the urchin from predators and aid in locomotion.

• The spines can inflict a painful wound on a human who steps on one, but they are not seriously dangerous, some are venomous.

Sand Dollars

Class Echinoidea

• Sand Dollars

-- Flattened disk

-- Few animals eat/bother sand dollars.

-- Burrows into the sand.

-- Also called sea biscuits.

Class HolothuroideaSea Cucumbers

Class Holothuroidea• Sea Cucumbers:

-- Look like warty moving pickles - - arms or rays absent - - tentacles around mouth

-- Benthic: Live on the ocean floor

Sea CucumbersAre little bull dozers

-- Eat detritus in sand

-- Suck up organic matter & remains of other organisms.

-- Sea cucumbers extract oxygen from water in a pair of 'respiratory trees' that branch off the cloaca just inside the anus, so that they 'breathe' by drawing water in through the anus and then expelling it.

Sea Cucumbers• A variety of fish, most commonly pearl fish, have

evolved a Mutualistic symbiotic relationship with sea cucumbers in which the pearl fish will live in sea cucumber's cloaca (anus) using it for protection from predation,

• The pearl fish’s waste provides a source of food/nutrients to the sea cucumber

Class Holothuroidea

• More Sea Cucumber

-- When threatened, they spill their guts!-- It takes 1 ½ to 5 weeks to re-grow their guts

-- The predator will eat the ejected guts, & leaves the sea cucumber alone. It eventually grows back the lost organs.

-- Yes, people eat them!

The End

Checkpoint

1. List the three classes of Echinoderms studied, facts about each class, and the organisms that belong to these classes.