Table of Contents – pages iv-v

Unit 1: What is Biology?Unit 2: EcologyUnit 3: The Life of a CellUnit 4: GeneticsUnit 5: Change Through TimeUnit 6: Viruses, Bacteria, Protists, and FungiUnit 7: PlantsUnit 8: InvertebratesUnit 9: VertebratesUnit 10: The Human Body

Unit 1: What is Biology?

Chapter 1: Biology: The Study of LifeUnit 2: Ecology Chapter 2: Principles of Ecology Chapter 3: Communities and Biomes Chapter 4: Population Biology Chapter 5: Biological Diversity and ConservationUnit 3: The Life of a Cell Chapter 6: The Chemistry of Life Chapter 7: A View of the Cell Chapter 8: Cellular Transport and the Cell Cycle Chapter 9: Energy in a Cell

Unit 4: Genetics

Chapter 10: Mendel and Meiosis

Chapter 11: DNA and Genes

Chapter 12: Patterns of Heredity and Human Genetics

Chapter 13: Genetic Technology

Unit 5: Change Through Time Chapter 14: The History of Life Chapter 15: The Theory of Evolution Chapter 16: Primate Evolution Chapter 17: Organizing Life’s Diversity

Unit 6: Viruses, Bacteria, Protists, and Fungi

Chapter 18: Viruses and Bacteria

Chapter 19: Protists

Chapter 20: Fungi

Unit 7: Plants

Chapter 21: What Is a Plant?

Chapter 22: The Diversity of Plants

Chapter 23: Plant Structure and Function

Chapter 24: Reproduction in Plants

Unit 8: Invertebrates

Chapter 25: What Is an Animal?

Chapter 26: Sponges, Cnidarians, Flatworms, and

Roundworms

Chapter 27: Mollusks and Segmented Worms

Chapter 28: Arthropods

Chapter 29: Echinoderms and Invertebrate Chordates

Unit 9: Vertebrates Chapter 30: Fishes and Amphibians

Chapter 31: Reptiles and Birds

Chapter 32: Mammals

Chapter 33: Animal Behavior

Unit 10: The Human Body

Chapter 34: Protection, Support, and Locomotion

Chapter 35: The Digestive and Endocrine Systems

Chapter 36: The Nervous System

Chapter 37: Respiration, Circulation, and Excretion

Chapter 38: Reproduction and Development

Chapter 39: Immunity from Disease

Invertebrates

What is an animal?

Sponges, Cnidarians, Flatworms and Roundworms

Mollusks and Segmented Worms

Arthropods

Echinoderms and Invertebrate Chordates

Chapter 29 Echinoderms and Invertebrate Chordates

29.1: Echinoderms

29.1: Section Check

29.2: Invertebrate Chordates

29.2: Section Check

Chapter 29 Summary

Chapter 29 Assessment

What You’ll Learn

You will compare and contrast the adaptations of echinoderms.

You will distinguish the features of chordates by examining invertebrate chordates.

• Compare similarities and differences among the classes of echinoderms.

Section Objectives:

• Interpret the evidence biologists have for determining that echinoderms are close relatives of chordates.

• 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.

What is an echinoderm?What is an echinoderm?

• 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.

Echinoderms have endoskeletonsEchinoderms have endoskeletons

• Sea stars, sometimes called starfishes, may not appear spiny at first glance, but a close look reveals that their long, tapering arms, called rays, are covered with short, rounded spines.


• The endoskeleton of all echinoderms is made primarily of calcium carbonate, the compound that makes up limestone.

• Some of the spines found on sea stars and sea urchins have become modified into pincerlike appendages called pedicellariae (PEH dih sih LAHR ee ay).



• An echinoderm uses its jawlike pedicellariae for protection and for cleaning the surface of its body.

Pedicellariae

Echinoderms have radial symmetryEchinoderms have radial symmetry• You may remember that radial symmetry is

an advantage to animals that are stationary or move slowly.

• Radial symmetry enables these animals to sense potential food, predators, and other aspects of their environment from all directions.

The water vascular systemThe water vascular system

• The water vascular system is a hydraulic system that operates under water pressure.

• Water enters and leaves the water vascular system of a sea star through the madreporite (mah druh POHR ite), a sievelike, disk-shaped opening on the upper surface of the echinoderm’s body.


• The underside of a sea star has tube feet that run along a groove on the underside of each ray.


• Tube feet are hollow, thin-walled tubes that end in a suction cup.

• Tube feet look somewhat like miniature droppers.

• The round, muscular structure called the ampulla (AM pew lah) works something like the bulb of a dropper.

The water vascular systemThe water vascular system• Each tube foot

works independently of the others, and the animal moves along slowly by alternately pushing out and pulling in its tube feet.

Ampullae


• Tube feet also function in gas exchange and excretion. Gases are exchanged and wastes are eliminated by diffusion through the thin walls of the tube feet.

Echinoderms have varied nutritionEchinoderms have varied nutrition

• All echinoderms have a mouth, stomach, and intestines, but their methods of obtaining food vary.

• Sea stars are carnivorous and prey on worms or on mollusks such as clams.

Echinoderms have varied nutritionEchinoderms have varied nutrition

• Most sea urchins are herbivores and graze on algae.

• Brittle stars, sea lilies, and sea cucumbers feed on dead and decaying matter that drifts down to the ocean floor.

Echinoderms have a simple nervous systemEchinoderms have a simple nervous system

• Echinoderms have no head or brain, but they do have a central nerve ring that surrounds the mouth.

Ring canal


• Nerves extend from the nerve ring down each ray.

• Each radial nerve then branches into a nerve net that provides sensory information to the animal.

• Echinoderms have cells that detect light and touch, but most do not have sensory organs.


• Sea stars are an exception. A sea star’s body consists of long, tapering rays that extend from the animal’s central disk.

• A sensory organ known as an eyespot and consisting of a cluster of light-detecting cells is located at the tip of each arm, on the underside.


• Eyespots enable sea stars to detect the intensity of light.

• Sea stars also have chemical receptors on their tube feet.

Echinoderms have bilaterally symmetrical larvaeEchinoderms have bilaterally symmetrical larvae

• If you examine the larval stages of echinoderms, you will find that they have bilateral symmetry.

• Through metamorphosis, the free-swimming larvae make dramatic changes in both body parts and in symmetry.

Echinoderms are deuterostomesEchinoderms are deuterostomes

• Echinoderms are deuterostomes.

• This pattern of development indicates a close relationship to chordates, which are also deuterostomes.

• Approximately 6000 species of echinoderms exist today.

• About one-fourth of these species are in the class Asteroidea (AS tuh ROY dee uh), to which the sea stars belong.

Diversity of EchinodermsDiversity of Echinoderms

Diversity of EchinodermsDiversity of Echinoderms• The five other classes of living echinodems

are Ophiuroidea (OH fee uh ROY dee uh), the brittle stars; Echinoidea (eh kihn OY dee uh), the sea urchins and sand dollars.

• Holothuroidea (HOH loh thuh ROY dee uh), the sea cucumbers; Crinoidea (cry NOY dee uh), the sea lilies and feather stars; and Concentricycloidea (kon sen tri sy CLOY dee uh), the sea daisies.

Sea Cucumber

Diversity of EchinodermsDiversity of Echinoderms

Sea starsSea stars• Most species of sea stars have five rays, but

some have more. Some species may have more than 40 rays.

Sea starsSea starsEndoskeleton

Madreporite

Tube feet

Pedicellariae

Anus

Stomach

Digestive gland

Eyespots

Ray

Nerve ring

Mouth

Reproductive organ

Endoskeletal plates

Radial nerve Ampullae

Radial canal

Ring canal

Brittle starsBrittle stars

• Brittle stars are extremely fragile.

• This adaptation helps the brittle star survive an attack by a predator.

• While the predator is busy with the broken off ray, the brittle star can escape. A new ray will regenerate.

Brittle starsBrittle stars

• Brittle stars propel themselves with the snake like, slithering motion of their flexible rays.

• They use their tube feet to pass particles of food along the rays and into the mouth in the central disk.

Sea urchins and sand dollarsSea urchins and sand dollars

• Sea urchins and sand dollars are globe or disk-shaped animals covered with spines; they do not have rays.

• A living sand dollar is covered with minute, hair-like spines that are lost when the animal dies.

• A sand dollar has tube feet that protrude from the petal-like markings on its upper surface.


• These tube feet are modified into gills and are used for respiration.

• Tube feet on the animal’s bottom surface aid in bringing food particles to the mouth.


• Sea urchins look like living pincushions, bristling with long, usually pointed spines.

• Sea urchins have long, slender tube feet that, along with the spines, aid the animal in locomotion.

Sea cucumbersSea cucumbers

• Sea cucumbers are so called because of their vegetable-like appearance.

• Their leathery covering allows them flexibility as they move along the ocean floor.

Sea cucumbersSea cucumbers

• When sea cucumbers are threatened, they may expel a tangled, sticky mass of tubes through the anus, or they may rupture, releasing some internal organs that are regenerated in a few weeks.

• Sea cucumbers reproduce by shedding eggs and sperm into the water, where fertilization occurs.

Sea lilies and feather starsSea lilies and feather stars

• Sea lilies and feather stars resemble plants in some ways.

• Sea lilies are the only sessile echinoderms.

• Feather stars are sessile only in larval form. The adult feather star uses its feathery arms to swim from place to place.

Sea daisiesSea daisies

• Sea daisies are flat, disk-shaped animals less than 1 cm in diameter.

• Their tube feet are located around the edge of the disk rather than along radial lines, as in other echinoderms.

Origins of EchinodermsOrigins of Echinoderms

• The earliest echinoderms may have been bilaterally symmetrical as adults, and probably were attached to the ocean floor by stalks.

• Another view of the earliest echinoderms is that they were bilateral and free swimming.

Origins of EchinodermsOrigins of Echinoderms

• The echinoderms represent the only major group of deuterostome invertebrates.

• This pattern of development is one piece of evidence biologists have for placing echinoderms as the closest invertebrate relatives of the chordates.

Origins of EchinodermsOrigins of Echinoderms• Most echinoderms have been found as

fossils from the early Paleozoic Era.• Fossils of brittle

stars are found beginning at a later period. Not much is known about the origin of sea daisies.

Question 1 Why is radial symmetry an advantage

to animals that are stationary or slow moving? (TX Obj 2; 8C)

Radial symmetry enables stationary or slow moving animals to sense potential food, predators, and other aspects of their environment from all directions.

Question 2

What is the similarity between the endoskeleton of echinoderms and the exoskeleton of crustaceans? (TX Obj 2; 8C, 10A, 10B)

Both of these features are composed of calcium carbonate.

Answer

Question 3 Pincerlike appendages from modified

spines on sea stars are called _______.(TX Obj 2; 8C, 10A, 10B)

A. rays

B. pedicellariae

C. madreporites

D. tube feet

Pedicellariae

The answer is B, pedicellariae.

Question 4 Which of the following terms does NOT

describe an echinoderm’s method of obtaining food? TX Obj 2; 8C, 10A, 10BTX Obj 3; 12B, 12E)A. carnivoreB. herbivoreC. parasiteD. scavengerThe answer is C, parasite.

Question 5

What stimulates a sea star to move in a given direction? (TX Obj 2; 8C, 10A, 10B)

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

• Summarize the characteristics of chordates.

Section Objectives:

• Explain how invertebrate chordates are related to vertebrates.

• Distinguish between sea squirts and lancelets.

What is an invertebrate chordate?What is an invertebrate chordate?

• The phylum Chordata includes three subphyla: Urochordata, the tunicates (sea squirts); Cephalochordata, the lancelets; and Vertebrata, the vertebrates.

• Invertebrate chordates have a notochord, a dorsal hollow nerve cord, pharyngeal pouches, and a postanal tail at some time during their development.

What is an invertebrate chordate?What is an invertebrate chordate?

• In addition, all chordates have bilateral symmetry, a well-developed coelom, and segmentation.

Postanal tail

AnusMuscle blocksPharyngeal

pouches

Mouth

Dorsal hollow nerve cord

Notochord

All chordates have a notochordAll chordates have a notochord• The embryos of all

chordates have a notochord (NOH tuh kord) — a long, semirigid, rod-like structure located between the digestive system and the dorsal hollow nerve cord.

Gill slits

Nerve cord

Notochord

• In invertebrate chordates, the notochord may be retained into adulthood. But in vertebrate chordates, this structure is replaced by a backbone.

• Invertebrate chordates do not develop a backbone.

All chordates have a notochordAll chordates have a notochord

• The notochord develops just after the formation of a gastrula from mesoderm on what will be the dorsal side of the embryo.

• The notochord anchors internal muscles and enables invertebrate chordates to make rapid movements of the body.

All chordates have a notochordAll chordates have a notochord

• The dorsal hollow nerve cord in chordates develops from a plate of ectoderm that rolls into a hollow tube.


Outer layer of ectoderm

All chordates have a dorsal hollow nerve cordAll chordates have a dorsal hollow nerve cord

• This tube is composed of cells surrounding a fluid-filled canal that lies above the notochord.

• In most adult chordates, the cells in the posterior portion of the dorsal hollow nerve cord develop into the spinal cord.

All chordates have a dorsal hollow nerve cordAll chordates have a dorsal hollow nerve cord

All chordates have a dorsal hollow nerve cordAll chordates have a dorsal hollow nerve cord• The cells in the

anterior portion develop into a brain.

• A pair of nerves connects the nerve cord to each block of muscles.

Neural fold

Neural plate

Outer layer of ectoderm



Cells that form bones and muscles


Notochord

NotochordEctoderm

MesodermEndoderm

Neural foldNeural plate

All chordates have pharyngeal pouchesAll chordates have pharyngeal pouches

• The pharyngeal pouches of a chordate embryo are paired openings located in the pharynx, behind the mouth.

• In aquatic chordates, pharyngeal pouches develop openings called gill slits.

• In terrestrial chordates, pharyngeal pouches develop into other structures.

• At some point in development, all chordates have a postanal tail.

• Humans are chordates, and during the early development of the human embryo, there is a postanal tail that disappears as development continues.

Postanal tail

All chordates have a postanal tailAll chordates have a postanal tail

All chordates have a postanal tailAll chordates have a postanal tail• In most animals that have

tails, the digestive system extends to the tip of the tail, where the anus is located.

• Chordates, however, usually have a tail that extends beyond the anus.

• Muscle blocks aid in movement of the tail.

• Muscle blocks are modified body segments that consist of stacked muscle layers.

• Muscle blocks are anchored by the notochord, which gives the muscles a firm structure to pull against.

All chordates have a postanal tailAll chordates have a postanal tail

Homeotic genes control developmentHomeotic genes control development

• Homeotic genes specify body organization and direct the development of tissues and organs in an embryo.

• Studies of chordate homeotic genes have helped scientists understand the process of development and the relationship of invertebrate chordates to vertebrate chordates.

Diversity of Invertebrate ChordatesDiversity of Invertebrate Chordates

• The invertebrate chordates belong to two subphyla of the phylum chordata: subphylum Urochordata, the tunicates (TEW nuh kaytz), also called sea squirts, and subphylum Cephalochordata, the lancelets.

Tunicates are sea squirtsTunicates are sea squirts

• Although adult tunicates do not appear to have any shared chordate features, the larval stage, has a tail that makes it look similar to a tadpole.


• 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.


• 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.


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

A TunicateA TunicateExcurrent siphon

Pharynx

Ciliated groove

Incurrent siphon

Heart

Tunic

Water

Mouth

Gill slits

Esophagus

StomachIntestine

Reproductive organs

Anus

Lancelets are similar to fishesLancelets are similar to fishes

• Lancelets are small, streamlined, and common marine animals, usually about 5 cm long.

• Like tunicates, lancelets are filter feeders.

Lancelets are similar to fishesLancelets are similar to fishes• Unlike tunicates, however, lancelets retain

all their chordate features throughout life.

Postanal tail

Anus

Muscle blocks

Intestine

Notochord


Oral hood with tentacles

Mouth

Gill slits in pharynx


• Although lancelets look somewhat similar to fishes, they have only one layer of skin, with no pigment and no scales.


• Lancelets do not have a distinct head, but they do have light sensitive cells on the anterior end.

• They also have a hood that covers the mouth and the sensory tentacles surrounding it.

• The tentacles direct the water current and food particles toward the animal’s mouth.

Origins of Invertebrate ChordatesOrigins of Invertebrate Chordates

• Biologist are not sure where sea squirts and lancelets fit in the phylogeny of chordates.

• According to one hypothesis, echinoderms, invertebrate chordates, and vertebrates all arose from ancestral sessile animals that fed by capturing food in tentacles.

Origins of Invertebrate ChordatesOrigins of Invertebrate Chordates

• Recent discoveries of fossil forms of organisms that are similar to living lancelets in rocks 550 million years old show that invertebrate chordates probably existed before vertebrate chordates.

Which of the following features is NOT shared by all chordates? (TX Obj 2; 8C, 10A, 10B)

Question 1

D. protostome developmentC. segmentationB. coelomA. bilateral symmetry

The answer is D, protostome development.

In vertebrates the notochord is replaced by the _______. (TX Obj 2; 8C, 10A, 10B)

Question 2

D. medullaC. spinal chordB. brainA. backbone

The answer is A, backbone.

How does a notochord aid in the movement of a chordate? (TX Obj 2; 8C, 10A, 10B)

Question 3

The notochord anchors internal muscles and enables invertebrate chordates to make rapid movements of the body, which they use to propel themselves.

Postanal tail

AnusMuscle blocksPharyngeal

pouches

Mouth


Notochord

How is a tunicate heart unusual?(TX Obj 2; 8C, 10A, 10B)

Question 4

The tunicate heart pumps blood in one direction for several minutes and then reverses direction.

Heart

What is the only feature of adult tunicates that indicates their chordate relationship?(TX Obj 2; 8C, 10A, 10B)

Question 5

D. dorsal hollow nerve cord

C. postanal tail

B. gill slits

A. notochord

The answer is B, gill slits.

Gill slits

• Echinoderms have spines or bumps on their endoskeletons, radial symmetry, and water vascular systems. Most move by means of the suction action of tube feet.

Echinoderms

• Echinoderms can be carnivorous, herbivorous, scavengers, or filter feeders.

• Echinoderms include sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers, sea lilies, feather stars, and sea daisies.

• Deuterostome development is an indicator of the close phylogenetic relationship between echinoderms and chordates.

Echinoderms

• A good fossil record of this phylum exists because the endoskeleton of echinoderms fossilizes easily.

• All chordates have a dorsal hollow nerve cord, a notochord, pharyngeal pouches, and a postanal tail at some stage during development.

Invertebrate Chordates

• All chordates also have bilateral symmetry, a well-developed coelem, and segmentation.

• Sea squirts and lancelets are invertebrate chordates.

Invertebrate Chordates

• Vertebrate chordates may have evolved from larval stages of ancestral invertebrate chordates.

Question 1

Which of the following is not a function of tube feet? (TX Obj 2; 8C, 10A, 10B)

D. movement

C. gas exchange

B. excretion

A. digestion

The answer is A, digestion.

Tube feet

Question 2

What is the difference in the way sea stars and brittle stars use their tube feet?(TX Obj 2; 8C, 10A, 10B)

Sea stars use their tube feet to move. Brittle stars use their feet to pass particles of food along their rays and into their mouth.

Question 3

The only sessile echinoderms belong to the _______. (TX Obj 2; 8C, 10A, 10B)

D. Crinoidea

C. Echinoidea

B. Ophiuroidea

A. Asteroidea

The answer is D. The Crinoidea include the sea lilies which are sessile.

Question 4Describe the sea cucumber’s method of protection from predators. TX Obj 2; 8C, 10A, 10B)

When sea cucumbers are threatened they may expel portions of themselves through the anus or a ruptured part of the skin to confuse predators. The expelled portions are regenerated later.

Question 5What is the adaptive value of colonies of sea cucumbers all shedding eggs and sperm into the water at the same time? (TX Obj 2; 8C, 10A, 10B )

AnswerThe adaptive value of this behavior is that the fertilization of many eggs is assured.

Question 6Endoskeleton

Madreporite

Tube feet

Pedicellariae

Anus

Stomach

Digestive gland

Eyespots

Ray

Nerve ring

Mouth

Reproductive organ

Endoskeletal plates

Radial nerve Ampullae

Radial canal

Ring canal

TX Obj 2; 8C, 10A, 10B

The sea star displays radial symmetry because each ray is a duplicate of the others and all organs extend around a central point in a radial or circular arrangement.

Question 7

Why is the fossil record of invertebrate chordates incomplete? (TX Obj 2; 8C, 10A, 10B)

AnswerSea squirts and lancelets have no bones, shell, or other hard parts that could form fossils.

Question 8

Where is a tunicate’s postanal tail?(TX Obj 2; 8C, 10A, 10B)

AnswerA tunicate possesses a postanal tail only in its larval stage.

Question 9Lancelets and tunicates are both _______.(TX Obj 2; 8C, 10A, 10B, TX Obj 3; 12B, 12E)

D. decomposers

C. parasitesB. filter feeders

A. predators

The answer is B, filter feeders.

Question 10The tunic of Urochordates is composed of _______. (TX Obj 2; 8C, 10A, 10B)

D. celluloseC. calcium carbonate

B. chitinA. mesoderm

The answer is D, cellulose.

Photo CreditsPhoto Credits

• General Biological Inc.

• Ward's Natural Science Establishment, Inc.

• Digital Stock

• Ed Shay

• American Petrolium Inst.

• Harris Biological Supply LTD

• Susan Marquart

• Carolina Biological Supply Co.

• PhotoDisc

• Alton Biggs

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Table of Contents – pages iv-v