1. Chapter 29: Echinoderms and Invertebrate Chordates
Section 1: Echinoderms

2. Echinoderms Includes starfish, sea urchins, sand dollars, etc.
Belong to the phylum Echinodermata
Stretches back to the beginning of the Cambrian Period, more than 580 million years ago

3. What Is an Echinoderm? Echinoderms are spiny skinned animals
In addition to having a spiny skin, echinoderms are characterized by five-part radial symmetry, an internal skeleton, a water vascular system, and suction-cuplike structures called tube feet
The internal skeleton, or endoskeleton, is made up of hardened plates of calcium carbonate, which are often bumpy or spiny
The water vascular system consists of an internal network of fluid-filled canals connected to external appendages called tube feet
Water vascular system is involved in many essential life functions in echinoderms

4. Form and Function in Echinoderms
Adult echinoderms have a body plan with five parts organized symmetrically around a center
Typically have neither an anterior nor a posterior end and no brain
The side where the mouth is located is called the oral surface, and the opposite side is called the aboral surface

5. Form and Function in Echinoderms
The water vascular system opens to the outside through a sieve like structure called the madreporite
The entire water vascular system operates like a series of living hydraulic pumps that can propel water in or out of the tube feet
The tube feet act like living suction cups
All echinoderms “walk” with their tube feet, and some use their tube feet for feeding

6. Feeding
Carnivores
Use their tube feet to pry open the shells of bivalve mollusks such as clams and scallops
Once opened, the carnivores flips its stomach out of its mouth, pours out enzymes, and digests its prey in the prey’s own shell
Herbivores
Scrape algae from rocks by using their five-part jaw
Filter feeders
Use tube feet on flexible arms to capture plankton that float by on ocean currents
Detritus feeders
Move like a bulldozer across the ocean floor, taking in a mixture of sand and detritus

7. Respiration Echinoderms need to exchange carbon dioxide for oxygen
In most species the thin walled tissue of the tube feet forms the main respiratory surface
In some species small outgrowths called skin gills also function in gas exchange

8. Internal Transport
The functions of transporting oxygen, food, and wastes are shared by different systems in echinoderms
The distribution of nutrients is performed primarily by the digestive glands and the fluid within the body cavity

9. Excretion
Solid wastes are released through the anus in the form of feces
Excrete nitrogen-containing wastes primarily in the form of ammonia
Wastes seem to be excreted in many of the same places around the body in which gas exchange takes place – the tube feet and the skin gills

10. Response Have primitive nervous systems
Have a nerve ring that surrounds the mouth and radial nerves that connect the ring with the body sections
Also have light sensitive cells to help them tell whether it is night or day
Many echinoderms hide under rocks and in crevices by day, coming out to feed at night, when most predators are asleep

11. Movement
Most echinoderms use tube feet and thin layers of muscle fibers attached to the plates of the endoskeleton to move
Mobility is determined by the structure of the endoskeleton
Some plates are fused
Some have flexible joints

12. Reproduction Most are either male or female Some are hermaphrodites
In starfish, the sperm and egg are produced in testes or ovaries which fill the arms during the reproductive season
Shed their sperm and eggs into the water
Larvae swim around for some time
Eventually, they will swim to the ocean bottom, where they mature and metamorphose into adults that have radial symmetry

13. The Echinoderm Classes
Almost 6000 species of living echinoderms
Found in almost every ocean in the world
No echinoderms have ever entered fresh water, and they cannot survive for long on land
Echinoderms are remarkably diverse in appearance

14. Starfish
Contains the common starfish, which are also known as sea stars
Occur in many colors
Many species have more than 5 arms
Starfish creep slowly along the ocean bottom
Most are carnivores, preying upon the bivalves they encounter as they move
Some species are important predators in rocky areas along the coast

16. Brittle Stars Live in tropical seas, especially on coral reefs
Look much like a common starfish, but they have longer, more flexible arms and are able to move much more rapidly
Brittle stars protect themselves by shedding one or more of their arms when attacked
The detached parts keep wriggling violently, distracting predators, while the rest of the animal escapes
Are filter and detritus feeders that hide by day and wander around in search of food at night

17. The brittle star gets its name
from the fact that it can shed
its arms when it is threatened.
This distracts predators so that
the brittle star can escape. In
time, it will regrow the missing
arm. Some starfish, such as the
sun star, have more than five
arms.

18. Sea Urchins and Sand Dollars
Includes disk-shaped sand dollars, oval heart urchins, and round sea urchins
Most are grazers that eat large quantities of algae
Others are detritus feeders
Heart urchins and sand dollars live hidden in burrows
Most sea urchins wedge themselves in crevices in rock during the day and only come out at night
Many sea urchins have long, sharp spines

19. The slate urchin has thick, strong spines that were once harvested for use as implements for writing on slateboards. Sea urchins have a lanternlike set of bony plates inside their body that power their jaws. The sand dollar gets its name from its flattened, coin-shaped appearance.

20. Sea Cucumbers
Look like warty moving pickles with a mouth at one end and an anus at the other
Most are detritus feeders
Not numerous in shallow water
Herds containing hundreds of thousands of them often cover areas of the sea floor at great depths
A few species expel sticky substances that attach to a predator
The predator is immobilized as it is glued into a helpless ball

22. Sea Lilies and Feather Stars
These filter feeders, which have 50 or more long, feathery arms, comprise the most ancient class of echinoderms
Not common today
Sea lilies are sessile animals that are attached to the ocean bottom by a long, stem like stalk
Many feather stars live on coral reefs, where they perch on top of rocks at night and use their tube feet to catch floating plankton

24. How Echinoderms Fit into the World
Numerous in most marine habitats
Control the populations of other animals
Control the distribution of algae
Considered delicacies by some people
Useful as research subjects and as possible sources of medicine

25. Chapter 29: Echinoderms and Invertebrate Chordates
Section 2:
Invertebrate Chordates

26. Invertebrate Chordates
Phylum Chordata
Fish, frogs, birds, snakes, dogs, cows, and humans
Most of the chordates are vertebrates, which means they have backbones, so they are placed in the subphylum Vertebrata
The invertebrate chordates are divided into two subphyla – tunicates and lancelets

27. What Is a Chordate? Belong to phylum Chordata
Chordates are animals that are characterized by a notochord, a hollow dorsal nerve cord, and pharyngeal (throat) slits
All chordates display these three characteristics at come stage in their life

28. 1st Characteristic
The notochord, is a long, flexible supporting rod that runs through at least part of the body, usually along the dorsal surface just beneath the nerve cord
In most vertebrates, the notochord is quickly replaced by the backbone

29. 2nd Characteristic
The hollow dorsal nerve cord, runs along the dorsal surface just above the notochord
In most chordates, the front end of this nerve cord develops into a large brain
Nerves leave this cord at regular intervals along the length of the animal and connect to internal organs, muscles, and sense organs

30. 3rd Characteristic
Pharyngeal slits, are paired structures in the pharyngeal, or throat, region of the body
In aquatic chordates the pharyngeal slits are gill slits that connect the pharyngeal cavity with the outside
Many invertebrates have gills of some sort in various places, but only chordates have pharyngeal gills

31. 3rd Characteristic
In terrestrial chordates that use lungs for respiration, pharyngeal slits are present only for a brief time during development
These slits soon close up as the embryo develops
In chordates such as humans, pouches form in the pharyngeal region but never open up to form slits
For this reason, some scientists regard pharyngeal pouches, not slits, as the “true” chordate characteristic

32. Tunicates
Small marine chordates that eat plankton they filter from the water
Get their name from a special body covering called the tunic
Only the tadpole-shaped larvae of tunicates have a notochord and a dorsal nerve cord
When tunicate larvae mature, they undergo metamorphosis and become sessile adults that grow into colonies attached to a solid surface
Both larval tunicates and adults filter feed and breathe at the same time through a pharyngeal basket pierced by gill slits

34. Lancelets
Small fishlike creatures that live in the sandy bottom of shallow tropical oceans
Have a definite head
Have a mouth that opens into a long pharyngeal region with up to 100 pairs of gill slits
Feed by passing water through their pharynx, where food particles are caught in a sticky mucus
This mucus is swallowed into a digestive tract that starts at one end of the pharynx and continues straight through the animal to the anus, near the tail

35. Lancelets
Have a simple, primitive heart that pumps blood through vessels in a closed circulatory system
They show evidence of segmentation in the arrangement of their nerves and muscles
Muscles are organized into V-shaped units that are paired on either side of the body
Each muscle unit receives a branch from the main nerve cord
Lancelets have no jaw
Their mouth is composed entirely of soft tissues
Also lack appendages and can move only by bending their bodies back and forth

37. How Invertebrate Chordates Fit into the World
It is important to remember that living vertebrates did not evolve from living lancelets or tunicates
Both these subphyla have evolved over time
However, similarities in structure and embryological development indicate that vertebrates and invertebrate chordates evolved from common ancestors many millions years ago

38. Homework
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