Section 1
Echinoderms
Section 1
Focus
Animal Development
Objectives
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. This lesson describes the
similarities and differences between
protostome and deuterostome
development and introduces students to the groups of organisms
that show each of these developmental patterns. Students will study
echinoderm structure and function
and review examples of several different groups of echinoderms.
Bellringer
Ask students to list the names of as
many non-fish marine organisms as
they can think of. (Most will be either
mollusks or echinoderms.)
Motivate
● Compare the developmental
pattern found in protostomes
with that found in deuterostomes.
8B
If you have been to a saltwater aquarium, you’re sure to have seen
echinoderms, which are spiny invertebrates that live on the ocean
bottom. How could echinoderms like the brittle star shown on the
first page of this chapter be related to animals such as chordates,
which are primarily vertebrates? The answer lies in their early devel● Describe the major characteristics of echinoderms.
8C opment. As an embryo develops, it goes through a gastrula stage. As
TAKS 2 shown in Figure 1, a gastrula has an opening to the outside called
● Summarize how the sea
the blastopore . In acoelomate animals, the mouth develops from or
star’s water vascular system
near the blastopore. This pattern of development also occurs in
functions.
7B TAKS 3
some coelomate animals, such as annelids, mollusks, and arthroKey Terms
pods. Animals with mouths that develop from or near the blastopore
are called protostomes .
blastopore
Some animals follow a different pattern of development. In phyprotostome
lums Echinodermata and Chordata, the anus—not the mouth—
deuterostome
develops from or near the blastopore. (The mouth forms later, on
ossicle
water-vascular system
another part of the embryo.) Animals with this pattern of developskin gill
ment are called deuterostomes , also shown in Figure 1. If you know
the origin of these two terms, it’s easy to remember the differences
between the two developmental patterns. The term protostome is
from the Greek protos, meaning “first,” and stoma, meaning
“mouth.” The prefix deutero- is from the Greek deuteros, meaning
“second.” In deuterostomes, the anus develops first and the mouth
develops second.
Figure 1 Embryonic development
The development of an animal embryo follows one of two patterns.
Demonstration
GENERAL
Bring in several preserved or dried
specimens of echinoderms such as
sea cucumbers, sea stars, and sand
dollars. You can supplement these
specimens with pictures in books.
Allow students to inspect them and
come up with as many common
characteristics as they can. List those
characteristics on the board or
overhead, and refer to the list as
you teach the specific characteristics.
Gastrula
Gastrula
Gut
Embryo
Gut
Embryo
Anus
Mouth
Blastopore
Blastopore
Coelom
Blastopore
becomes mouth
LS Visual TAKS 2 Bio 8C
Protostomes
Coelom
Blastopore
becomes anus
Deuterostomes
692
Chapter Resource File
pp. 692–693
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7A
TAKS Obj 3 Bio 7B
TEKS Bio 7A, 7B, 8B, 8C
Teacher Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7A
TAKS Obj 3 Bio 7B
TEKS Bio 5C, 7A, 7B, 8C
TEKS Bio/IPC 3C
692
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
• Data Sheet for Data Lab
Transparencies
TT Bellringer
TT Patterns of Embryonic Development
TT Evolution of Chordates and
Echinoderms
GENERAL
Planner CD-ROM
• Reading Organizers
• Reading Strategies
Chapter 31 • Echinoderms and Invertebrate Chordates
Vertebrates
Lancelets
Tunicates
Sea
stars
Subphylum
Cephalochordata
Subphylum
Vertebrata
Sea
lilies
Brittle
stars
Class
Asteroidea
Sea
cucumbers
Class
Ophiuroidea
Class
Holothuroidea
Figure 2 Evolution of
chordates and echinoderms.
This phylogenetic tree shows
the relationship of the major
chordate and echinoderm
groups.
Phylum
Phylum
Chordata Echinodermata
Ancestral
deuterostome
Teach
SKILL
Class
Echinoidea
Class
Crinoidea
Subphylum
Urochordata
Sea
urchins
BUILDER
Interpreting Visuals Have students
examine Figure 2. Ask them to identify the first group of echinoderms
that evolved (sea cucumbers) and the
most recently evolved group(s) of
echinoderms. (sea stars, sea lilies,
brittle stars) Ask them to identify
the evolutionary relationship
between echinoderms and chordates—did one evolve from the
other? (Echinoderms and chordates
evolved from a common ancestor that
was neither an echinoderm nor a
chordate.) LS Visual
TAKS 3 Bio 7A (grade 11 only), 7B; Bio 8B
The first deuterostomes were marine echinoderms that evolved
more than 650 million years ago. They were also the first animals
to develop an endoskeleton. Today, most people are familiar with
echinoderms known as “starfish,” which are not really fish and are
more properly called sea stars. In addition to sea stars, many other
animals commonly seen along the sea shore—sea urchins, sand dollars, and sea cucumbers—are echinoderms. All are marine, and all
are radially symmetrical as adults.
Chordates, as well as a few other small phyla, are also deuterostomes. (Humans and all other vertebrates are chordates.) Like the
echinoderms, chordates have an internal skeleton. This developmental similarity unites these seemingly dissimilar animal phyla. It
also leads scientists to believe that chordates and echinoderms
derived from a common ancestor, as shown in the phylogenetic tree
in Figure 2. The identity of the ancestral deuterostome is not
known. The fossil record indicates that echinoderms, such as the
sea lily in Figure 3, were abundant in the ancient seas.
Group Activity
GENERAL
Symmetry All adult echinoderms
display pentaradial symmetry. Penta
means “five.” Therefore, echinoderms have five or approximately
multiples of five arms. Have groups
of students create displays that
define and model various forms of
symmetry. Encourage them to compare objects made by humans with
those found in nature. They can use
pictures and clay models to make
their comparisons.
LS Kinesthetic Co-op Learning
Bio 5C
Demonstration
Evolutionary Milestone
8 Deuterostomes
Echinoderms are coelomates that have a deuterostome pattern of
embryo development. The same pattern of development occurs in
the chordates.
Figure 3 Fossil sea lily.
Sea lilies such as the one
preserved by this fossil were
plentiful in the ancient oceans.
693
Trends in Medicine
Body Part Regeneration The importance
of chemical signals in the development of
deuterostomes has significant medical implications for the regeneration of lost body parts.
Scientists are working to discover factors that
cause cells to change and grow so that someday it might be possible to re-grow a severed
spinal cord or an amputated limb.
Bio/IPC 3C; Bio 5C
Display any echinoderms you or
your students may have collected
such as sea stars or sand dollars.
Emphasize the five-part radial symmetry of the specimens. Point out
that during drying, the skin of sand
dollars disintegrates, and only the
hard internal skeleton remains. Ask
students how echinoderms differ
from arthropods. (Echinoderms have
endoskeletons, no body segments, and
radial symmetry; arthropods have
exoskeletons, body segments, and
bilateral symmetry.) LS Visual
TAKS 2 Bio 8C; Bio 5C
BIOLOGY
• Unit 7—Exploring Invertebrates
This engaging tutorial introduces
students to invertebrate structure
and function.
Chapter 31 • Echinoderms and Invertebrate Chordates
693
Modern Echinoderms
Teach, continued
continued
Teaching Tip
Sea Urchin Embryology Tell students that sea urchins hatch from
eggs as microscopic floating larvae.
These delicate, elegant-looking
creatures have two mirror-image
halves, just like beetles, birds and
bats. They float for weeks near the
ocean’s surface fanning even tinier
organisms into their mouths. Then,
a change occurs. A small bundle of
cells inside the organism begin to
grow. All of the other cells die, and
the tiny bundle settles to the ocean
floor to grow into something that
looks like a calcified Koosh Ball
several inches in diameter. Instead
of two mirror-image halves (bilateral symmetry) seen in the larva,
the adult urchin is organized more
like five equal pie slices (pentaradial symmetry), a nearly spherical
version of its cousin the starfish.
Adult urchins creep slowly around
the ocean bottom using a fivetoothed structure to scrape food
from rocks. Studies of both body
shape and particularly molecular
composition indicate that their
ancestors were bilateral. Bio 5B, 5C
READING
SKILL
BUILDER
Interactive Reading Assign
Chapter 31 of the Holt Biology
Guided Audio CD Program to
help students achieve greater
success in reading the chapter.
Real Life
Do sand dollars
resemble the sun?
To the Chumash Indians of
southern California, the
lines radiating from a sand
dollar’s mouth resemble
the sun’s rays. Sand dollars, once plentiful in the
Pacific Ocean, became the
Chumash’s symbol
for the “newborn”
sun of the
winter solstice.
The term echinoderm is
from the Greek echinos,
meaning “spiny,” and
derma, meaning “skin.”
Many of the most familiar animals seen along the seashore—sea
stars, sea urchins, sand dollars—are echinoderms. Echinoderms
are also common in the deep ocean. While all echinoderms are
marine, the different classes of echinoderms vary considerably in
the details of their body design. Despite their apparent differences,
all echinoderms share four fundamental characteristics.
1. Endoskeleton. Echinoderms have a calcium-rich endoskeleton
composed of individual plates called ossicles . When ossicles
first form in young echinoderms, they are enclosed in living tissue, so they are a true endoskeleton. Even though the ossicles of
adult echinoderms appear to be external, they are covered by a
thin layer of skin (although sometimes the skin is worn away).
In adult sea stars and in many other echinoderms, a large number of these plates are fused together. The fused plates function
much like an arthropod exoskeleton. They provide sites for muscle attachment and shell-like protection. In most echinoderms,
the plates of the endoskeleton bear spines that project upward
through their skin.
2. Five-part radial symmetry. All echinoderms are bilaterally symmetrical as larvae. During their development into adults, the
larvae’s body plan becomes radially symmetrical. Most adult
echinoderms, such as the one shown on the left in Figure 4, have
a five-part body plan with arms that radiate from a central point.
However, the number of arms can vary. Echinoderms have no
head or brain. Instead, the nervous system consists of a central
ring of nerves with branches extending into each of the arms.
Although echinoderms are capable of complex response patterns, each arm acts more or less independently. Many species,
including sea stars, can regenerate a new arm if a portion of an
arm is lost. In some species of sea stars, a complete animal can
regenerate from an arm connected to a portion of the central
disk. However, a complete sea star cannot regenerate from an
arm alone.
Figure 4 Five-part body
plan. The echinoderm fivepart body plan is easily seen
in this colorful African species.
Other sea stars, such as
the sunstar, have more than
five arms.
LS Auditory
pp. 694–695
Student Edition
TAKS Obj 1 Bio/IPC 2C
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 2 Bio 10B
TAKS Obj 3 Bio 12B
TEKS Bio 8C, 10A, 10B, 12B
TEKS Bio/IPC 2C
Teacher Edition
TAKS Obj 1 Bio/IPC 2C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 12B
TAKS Obj 4 IPC 7D
TEKS Bio 5B, 5C, 10A, 12B, 12C,
12D, 12E
TEKS Bio/IPC 2C
TEKS IPC 7D
694
694
IPC Benchmark Fact
Have students locate the element calcium on the periodic
table and state the number of its outer or valence electrons,
bonding pattern, physical properties, and chemical behavior
based on its location on the periodic table.
TAKS 4 IPC 7D (grade 11 only)
Chapter 31 • Echinoderms and Invertebrate Chordates
3. Water-vascular system. Echinoderms have a waterfilled system of interconnected canals and thousands of
tiny hollow tube feet called a water-vascular system.
In some echinoderms, such as the sea star, the tube feet
extend outward through openings in the ossicles. In
some species, each tube foot has a sucker at its tip.
Many echinoderms use their tube feet to crawl across
the sea floor. The water-vascular system also functions
in feeding and gas exchange. A sea star can use the
hundreds of tube feet on its arms to pull the valves of a
bivalve open. Some gas exchange and waste excretion
takes place through the thin walls of the tube feet.
Teaching Tip
4. Coelomic circulation and respiration. The echinoderm body
cavity functions as a simple circulatory and respiratory system.
Particles, including respiratory gases, move freely throughout
the large, fluid-filled coelom. Many echinoderms have skin gills
that aid respiration and waste removal. Skin gills, shown in
Figure 5, are small, fingerlike projections that grow among the
echinoderm’s spines. These projections create an increased surface area through which respiratory gases can be exchanged.
Skin gills also function as excretory structures, and wastes that
accumulate in them are released into the surrounding water.
Figure 5 Skin gills. An
echinoderm’s skin gills
function as both respiratory
and excretory organs.
TAKS 2 Bio 10A; Bio 5C, 12C
Demonstration
www.scilinks.org
Topic: Echinoderms
Keyword: HX4065
Background
2C 12B TAKS 1, TAKS 3
Sea stars can be very effective predators,
and they frequently eat mollusks. The chart
at right shows the relative number of two
species of mollusks before and after the
introduction of a predatory sea star. Study
the chart, and answer the Analysis questions.
Percentage of
original population
0100010110
011101010
0010010001001
1100100100010
0000101001001
1101010100100
0101010010010
Sea Star Predation of Mollusks
Species A
Species B
100
75
50
25
0
Sea
stars
introduced
0100010110
011101010
0010010001001
1100100100010
0000101001001
1101010100100
0101010010010
Time
Analysis
1. Compare the relative sizes
of the two mollusk populations before the introduction
of the sea star.
2. Identify the preferred prey
of the sea star, and use the
data presented in the graph
to support your answer.
3. Critical Thinking
Analyzing Data When
the sea star began preying
on the nonpreferred species,
the preferred species had
dropped to what percent
of its original population?
4. Critical Thinking
Inferring Relationships
What factors might cause
the sea star to begin
consuming a nonpreferred
species, even when its preferred prey is still present?
5. Critical Thinking
Predicting Outcomes
Predict the relative abundance
of the two species of mollusks
if the sea star remains in the
area indefinitely.
OCEANOGRAPHY
CONNECTION
A single otter consumes more than 5,000
pounds per year of crab, snails, sea stars,
urchins, and other invertebrates. When 17thand 18th-century hunters slaughtered otters
for their fur, the kelp forests were decimated.
Kelp populations in many areas have
rebounded since, and once again provide a
home for a wide variety of invertebrates and
vertebrates, including many fish species.
TAKS 3 Bio 12B; Bio 12C, 12D, 12E
Determining
How Predators
Affect Prey
TAKS 1 Bio/IPC 2C; TAKS 3 Bio 12B
Skills Acquired
Analyzing data,
predicting results
Teacher’s Notes
Show students a picture of a sea
star eating a mollusk.
695
Along the coast in parts of California and
Alaska, sea otters and kelp forests flourish
together. What’s the connection? Sea urchins.
Sea urchins eat giant kelp, and when there are
enough sea urchins, they can roam the forest
floor and graze entire forests. Where urchins
abound, it’s hard for new giant kelp plants to
survive and grow. But, otters eat urchins. And
where otters are present, urchins have to hole
up in deep crevices to survive. By controlling
sea urchins, sea otters help kelp forests thrive.
GENERAL
You can use an ordinary dropper to
represent tube feet. Show students
that when an ampulla is filling with
water, suction is created at the open
end. When the ampulla is expelling
water, the suction is gone, and
water leaves the open end. This may
be easier for students to see if you
add a small amount of glitter to the
water. LS Visual Bio 5C
You can learn more about the structure of one particular echinoderm, the sea star, in Up Close: Sea Star, on the following page.
Determining How
Predators Affect Prey
Strength of Tube Feet Tell students that the legs of sea stars can
be very powerful when working
together. An individual foot can be
pulled off a surface easily. However,
when hundreds of tube feet work
together, a sea star can exert
tremendous strength—enough to
pull apart the valves of a clam or
hold the animal to a rock when a
wave pounds on it.
Answers to Analysis
1. The populations were approximately the same size.
2. Species A; species A’s population was the first to decline
and declined more rapidly than
species B’s population.
3. about 50 percent
4. Accept any reasonable answer.
The most obvious factor is
relative abundance—
non-preferred prey will be
easier to find as preferred prey
becomes scarce.
5. There will be about 10 percent
of the original population of
species A and 25 percent of the
original population of species
B as long as both populations
continue to reproduce and
replace lost individuals.
Chapter 31 • Echinoderms and Invertebrate Chordates
695
Up Close
Up Close
Sea Star
Sea Star TAKS 2, TAKS 3
TAKS 2 Bio 8C, 10A;
10B (grade 11 only); TAKS 3 Bio 12B
Teaching Strategies
Ask students to explain the
evolutionary link between sea
stars and chordates. Point out
that although the relationship
between adult echinoderms
and chordates may not be
apparent, the embryos of both
groups have certain developmental stages in common.
Echinoderms not only share
our deuterostome pattern of
embryonic development, but
also have bilateral symmetry
as larvae and endoskeletons
as adults. LS Logical
●
Scientific name: Asterias vulgaris
●
Size: Typically from 15 to 30 cm (6 to 12 in.) in diameter
●
Range: East coast of North America
●
Habitat: Intertidal; often on hard, rocky surfaces
●
Diet: Slow-moving or sessile species, including mollusks,
crustaceans, polychaetes, and corals
Characteristics
Water-vascular system
Tube feet Hundreds of tube feet extend from the bottom of
Water enters and leaves the
system through pores in the
madreporite (ma druh PAWR it), a
the radial canals, and each foot is connected to a waterfilled
sac called an ampulla (am PUHL uh). When water is
pumped from the sacs into the tube feet, they expand outward. Suckers on the ends of the tube feet attach firmly to
Tube feet
sievelike structure that filters out
large particles. Water then moves
into the ring canal and passes
into the radial canals.
solid surfaces. When muscles force water back into the
ampulla, the tube feet shorten, pulling Asterias forward.
▲ Ampullae
▲ Radial canal
Madreporite
Ring canal
Ray (arm)
SKILL
BUILDER
Interpreting Visuals Pose the
following questions as you discuss
the illustration.
1. What makes a tube foot extend?
(contraction of the water-filled
ampulla)
2. What makes it withdraw?
(The ampulla relaxes and refills
with water.)
3. Why can’t sea stars live in terrestrial environments? (They wouldn’t
be able to move about because
they need water to operate their
water vascular system.)
4. Why doesn’t a sea star have a
head? (A sea star has no brain, so
it has no need for a head to
enclose one.) LS Visual Bio 12C
Anus
Pyloric stomach
▼ Cardiac stomach
Reproductive system
In most species of Asterias
the sexes are separate. The
gonads lie at the base of the
Digestive system The
mouth, located in the center of
Central
disk
the body on the bottom side,
is connected by an esophagus to a stomach located
in the central disc. During feeding, a portion
of the stomach is
thrust out through
the mouth. Strong digestive juices liquefy the
prey, which is then ingested.
▼ Reproductive organs
arms and, when filled with
eggs or sperm, may occupy
almost the entire arm.
Digestive
glands
▼ Skin
Skin Asterias has a delicate skin
stretched over an endoskeleton
of spiny plates.
696
Transparencies
pp. 696–697
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 12B
TEKS Bio 7B, 8C, 10A, 12B
Teacher Edition
TAKS Obj 2 Bio 4B, 8C, 10A, 10B
TAKS Obj 3 Bio 12B
TEKS Bio 4B, 8A, 8C, 10A, 10B,
12B, 12C
696
Sea Star Reproduction In addition to asexual
reproduction (any arm can regenerate a new
body as long as part of the central disc is
present), starfish normally undergo sexual
reproduction. A female sea star can deposit
as many as 2.5 million eggs at one time. The
eggs are deposited in the water, where they
are fertilized by the sperm of a male sea star.
Bio 12C
Chapter 31 • Echinoderms and Invertebrate Chordates
TT Anatomy of a Sea Star
Echinoderm Diversity
Echinoderms are one of the most numerous of all marine phyla. In
the past, they were even more plentiful than they are now. There are
more than 20 extinct classes of echinoderms and an additional six
classes of living members. As you saw on the phylogenetic tree that
appeared earlier in this section, the living classes include sea stars, sea
lilies, brittle stars, sea urchins, and sea cucumbers. The recently discovered sea daisy does not appear on the phylogenetic tree because its
relationship to the other echinoderms is not fully understood.
Sea Stars
Sea stars are the echinoderms most familiar to people. Almost all
species of sea stars are carnivores, and they are among the most
important predators in many marine ecosystems. For example, the
crown-of-thorns sea star eats coral polyps. In 1 year, a single crownof-thorns can consume up to 6 m2 of a reef. Over time, this sea star
can destroy an entire coral reef ecosystem. Other sea stars prey on
bivalve mollusks, whose shells they pull open with their powerful
tube feet, as shown in Figure 6.
The ossicles of many species of sea stars produce pincerlike
structures called pedicellaria (ped uh suh LAH ree uh). Pedicellaria
contain their own muscles and nerves, and they snap at anything
that touches them. This action prevents small organisms from
attaching themselves to the surface of the sea star.
Teaching Tip
Figure 6 Sea star. This sea
star is using its tube feet to pry
open the shell of a clam. Then
it will feed on the clam’s soft
tissues.
TAKS 2 Bio 4B
Demonstration
Sea Lilies and Feather Stars
GENERAL
Invite a marine zoologist or aquarium store employee to discuss
echinoderms. If possible, have your
guest bring in live specimens or
videotapes to show how echinoderms move and feed. LS Auditory
Brittle Stars
The sea star’s relatives, the brittle stars and sea baskets, make up
the largest class of echinoderms. Brittle stars have slender
branched arms that they move in pairs to row along the ocean floor.
Their arms break off easily, a fact that gives brittle stars their name.
Brittle stars and sea baskets live primarily on the ocean bottom,
and they usually hide under rocks or within crevices in coral reefs.
Although a few species are predators, most brittle stars are filter
feeders or feed on food in the ocean sediment.
Moving Materials Into and Out
of Cells Tell students that the
exchange of gases occurs on the
surface of the sea star because particles tend to move from an area
of greater concentration to an area
of lower concentration. The uptake
of oxygen molecules by skin gills
occurs because ocean water contains
a greater concentration of oxygen
molecules than the skin gills contain. Therefore, oxygen enters the
skin gills by diffusion.
TAKS 2 Bio 8C
READING
SKILL
BUILDER
Figure 7 Feather star. The
feathery arms of these feather
stars are adapted for filter
feeding.
The sea lilies and feather stars are the
most ancient and primitive living echinoderms. They differ from all other living
echinoderms because their mouth is
located on their upper, rather than lower,
surface. Sea lilies are sessile and are
attached to the ocean floor by a stalk that
is about 60 cm (23 in.) long. Feather stars,
shown in Figure 7, use hooklike projections to attach themselves directly to the
ocean bottom or a coral reef. They sometimes crawl or swim for short distances.
Paired Summarizing Encourage
students to pause after each paragraph they read to summarize the
main points to a partner. You might
model the technique by having a
student read a paragraph out loud
and summarize it. Then have another
student read the next paragraph and
summarize it. You may want to pair
ELL students wth native English
speakers.
English Language
LS Verbal
Learners
697
INCLUSION
Strategies
• Attention Deficit Disorder • Learning Disability
Have the students download pictures of sea
stars, brittle stars, sea lilies, sea urchins,
sand dollars, and sea cucumbers. Ask the
students to create a class poster, echinoderm
notebook, or bulletin board with these pictures. On index cards, have the students
identify each of the echinoderms with their
scientific name and a brief description as to
what characteristics they have that determines they are echinoderms.
REAL WORLD
CONNECTION
Clam farmers see sea stars as a nuisance
because sea stars devour clams. In the past, the
farmers cut the sea stars into several pieces and
flung them back into the sea. They did not
know that sea stars could regenerate from a
severed arm, as long as one piece of the central
disc was present. The clam farmers were actually making the problem worse! Today, clam
farmers spread lime on the clam beds. Lime
kills sea stars but leaves clams unharmed.
TAKS 3 Bio 12B
TAKS 2 Bio 8C; Bio 8A
Chapter 31 • Echinoderms and Invertebrate Chordates
697
Teach, continued
continued
Group Activity
Tide Pool Diorama Have students
work in small groups to conduct
library and/or Internet research on
organisms found in tide pools.
They can choose whichever ocean
coast they prefer for their tide pool
study. Instruct them to find out
about the most common kinds of
animals as well as plants that are
found in the type of tide pool they
choose. Ask them to search for pictures of these organisms in books
or on the Internet. Then have each
group construct a diorama depicting
the organisms found in the type of
tide pool they have selected.
(Students should find at least several
kinds of echinoderms, such as sea
urchins, sea stars, and starfish; several
kinds of mollusks, such as chitins,
mussels, whelks, and nudibranchs;
several kinds of arthropods, including
crabs and barnacles; cnidarians, such
as sea anemones; tunicates, such as sea
squirts; annelids, such as tube worms;
sponges; fish; water plants; and plankton.) Display the tide pool dioramas
for the whole class to observe.
LS Kinesthetic Co-op Learning
Sand dollar
Figure 8 Sea urchin and
sand dollar. Sea urchins
usually live on rocky ocean
bottoms, while sand dollars
live on sandy ocean bottoms.
Sea urchin
Sea Urchins and Sand Dollars
The sea urchins and sand dollars, shown in Figure 8, lack distinct
arms but have the basic five-part body plan seen in other echinoderms. Both sea urchins and sand dollars have a hard, somewhat
flattened endoskeleton of fused plates covered with spines protruding from it. The spines provide protection and, in some species of sea
urchins, contain a venom that causes a severe burning sensation. In
some other species of sea urchin, a specialized type of pedicellarium contains a toxin used to paralyze prey. Sea urchins are found
on the ocean bottoms while sand dollars live in sandy areas along
the sea coast.
Sea Cucumbers
Figure 9 Sea cucumber.
When threatened, a sea
cucumber releases sticky
threads that entrap its attacker.
Sea cucumbers are soft-bodied, sluglike animals without arms.
They differ from other echinoderms in that their ossicles are small
and are not fused together. Because of this, the sea cucumber’s long,
cylindrical body is soft. Often the body has a tough, leathery exterior. The sexes of most sea cucumbers are separate, but some
species are hermaphrodites.
Sea cucumbers feed by trapping tiny organisms present in the
sea water. Their mouth, located at one end of the body, is surrounded by several dozen tube feet
modified into tentacles. The tentacles
are covered with a sticky mucus that
entraps plankton. Periodically, the sea
cucumber draws its tentacles into its
mouth and cleans off the plankton and
mucus. The tentacles are then coated
with a fresh supply of mucus. When
threatened, a sea cumber has an
unusual means of defending itself. As
shown in Figure 9, the sea cucumber
can release a number of sticky threads
from its anus to entrap its attacker.
698
pp. 698–699
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7A
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 12B
TEKS Bio 7A, 7B, 8B, 8C, 10A, 12B
Teacher Edition
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 7B
TAKS Obj 4 IPC 9B
TEKS Bio 5B, 5C, 7B, 8A, 8B, 8C, 10A
TEKS Bio/IPC 3C
TEKS IPC 9B
698
Cultural
Awareness
California’s Sea Urchin Fishery A growing demand for traditional Japanese cuisine
in the United States has created a growing
market for California sea urchins. Although
the sea urchins were once considered pests
by kelp harvesters and sports divers, they
are now commercially harvested. Most of
California’s sea urchin catch is exported
to Japan.
Chapter 31 • Echinoderms and Invertebrate Chordates
IPC Benchmark Mini-Lesson
IPC Skill TAKS 4 IPC 9B (grade 11 only) Relate the
concentration of ions in a solution to physical and
chemical properties such as pH. Activity Bring in
samples of sea water and pond or river water. Have
students test for pH level, electrolytic behavior, dissolved oxygen, etc. Then have them compare the
results of the both samples and research what substances are present in seawater that are not present
in freshwater.
Sea Daisies
In 1986, a new class of echinoderm was discovered: strange diskshaped little animals called sea daisies. Less than 1 cm (0.39 in.) in
diameter, these creatures were first found in deep waters off the
coast of New Zealand. Only a few species are known. Sea daisies
have five-part radial symmetry but no arms. Their tube feet are
located around the edges of the disk rather than along the radial
lines, like they are in other echinoderms.
Monitoring Water
Quality Bio 3C
Teaching Strategies
Use articles from newspapers
and magazines to point out
recent problems and solutions
concerning water quality. If
possible, visit a water treatment
plant or have someone from
such a facility come to school
to answer students’ questions.
Monitoring Water Quality
I
f you were swimming or fishing
in coastal waters, you likely
would not be able to detect the
presence of toxic chemicals in
the water, the sediments, or the
sea life. To help protect humans
and marine organisms, scientists
have developed several tests to
monitor marine environments for
potential health hazards. Since
sea urchin sperm and eggs are
very sensitive to many pollutants,
they are used in one of these
tests, known as the sea urchin
fertilization bioassay. (A bioassay
is the use of a living organism or
cell culture to test for the presence of a substance.)
Using Sea Urchins
Samples of ocean water, sediment, and industrial wastes that
are discharged into the ocean are
collected regularly from different
sites. Then they are tested under
controlled conditions in a lab. In
this bioassay, sea urchin sperm
and eggs are mixed together with
the collected samples. After a
short waiting period, scientists
compare the fertilization success
rate in the collected water samples with the fertilization success
rate found in control water samples. If the test samples show a
lower fertilization rate, scientists
conclude that toxic contaminants
are present.
Taking Action
What happens when the test
indicates the presence of contaminants? More specific tests
may be run to determine exactly
what contaminants are present.
If the toxicity can be traced to
runoff from a factory or sewage
treatment plant, the plant may be
forced to clean its waste before
discharging it. Sediments may
Recording water temperature in a
bioassay tank
have to be removed or decontaminated. In the future, it may be
possible to clean up some pollutants by using plants that have
the ability to remove toxic chemicals from the water they are
growing in. The use of this
process, known as phytoremediation, in marine environments is
an exciting new area of research.
www.scilinks.org
Topic: Bioassay
Keyword: HX4019
Discussion
• What is a bioassay? (using
living organisms or cell cultures
to test for the presence of a
substance)
• How can scientists tell if water
samples are contaminated?
(Fewer fertilizations occur.)
• What should happen to companies found polluting our
waterways? (Answers will vary
but might include fining the
companies and making them
clean the waterways.)
Close
Reteaching
Section 1 Review
Summarize why echinoderms are considered to
TAKS Test Prep
In an echinoderm, the
functions of a circulatory system are carried out
10A
by the
A ossicles.
B pedicellariae.
C coelom.
D madreporite.
be more closely related to tunicates, lancelets,
8B 8C
and vertebrates than to other animals.
Summarize the four major echinoderm
characteristics.
8C
Describe how the sea stars use their water-
vascular system to move along the sea floor.
7B
699
Answers to Section Review
1. Echinoderms and chordates share a common
pattern of embryonic development (both are
deuterostomes), and both have an internal
skeleton. These similarities suggest that the
groups share a common ancestor.
TAKS 2 Bio 8C; Bio 8B
2. All echinoderms have an endoskeleton composed
of ossicles, five-part radial symmetry, a waterfilled vascular system, and coelomic circulation
and respiration. TAKS 2 Bio 8C
3. Water enters the madreporite and travels into
the ring canal and radial canals to the ampulla
of the tube feet. When water enters the tube
feet, they expand, and suckers attach to the
surface. When water reenters the ampulla, the
tube feet shorten and pull the sea star forward.
TAKS 3 Bio 7B
4.
A. Incorrect. The ossicles are
part of the echinoderm’s skeleton and are
not involved in circulation. B. Incorrect.
Pedicellariae are part of the skeletal system
and are not involved in circulation. C. Correct.
The coelom acts as a circulatory system.
D. Incorrect. The madreporites function in the
water vascular system but are not involved in
gas exchange. TAKS 2 Bio 10A
Make an illustrated chart of echinoderm classes and the characteristics
of each class. Leave some of the
characteristics blank and have
students fill them in. Bio 8A
Quiz
GENERAL
1. The part of the digestive tract
that develops at the ________
of an animal is determined by
whether it is a protostome or a
deuterostome. (blastopore)
2. Is the skeleton of an echinoderm
more like that of an arthropod
or a vertebrate? Explain your
answer. (a vertebrate because it is
an endoskeleton) Bio 5B, 5C
Alternative
Assessment
GENERAL
Have students write review questions for a trivia-type game about
the groups of echinoderms.
Chapter 31 • Echinoderms and Invertebrate Chordates
699
Section 2
Invertebrate Chordates
Section 2
Focus
The Chordate Skeleton
Objectives
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. This lesson introduces the
four structural and functional characteristics of the chordate phylum.
It concludes with the characteristics
of two invertebrate chordate phyla,
the tunicates and the lancelets.
Bellringer
● Describe the characteristics
of chordates.
8C TAKS 2
The second major group of deuterostomes are the chordates .
Chordates have a very different kind of endoskeleton from that of
echinoderms. The chordate endoskeleton is completely internal.
During the development of the chordate embryo, a stiff rod called the
notochord develops along the back of the embryo. Using muscles
attached to this rod, early chordates could swing their backs from
side to side, enabling them to swim through the water. The development of an internal skeleton was an important step that led to the
evolution of vertebrates. The endoskeleton, which muscles attach to,
made it possible for animals to grow large and to move quickly.
● Define the term invertebrate
chordate.
● Compare tunicates and
lancelets.
8C TAKS 2
Key Terms
chordate
notochord
pharyngeal slit
invertebrate chordate
Other Chordate Characteristics
Chordates also share three other characteristics. They have a single,
hollow, dorsal nerve cord with nerves attached to it that travel to
different parts of the body. Chordates also have a series of
pharyngeal slits (openings) that develop in the wall of the pharynx,
the muscular tube that connects the mouth to the digestive tract and
windpipe. Another chordate characteristic is a postanal tail, which
is a tail that extends beyond the anus. All chordates have all four of
these characteristics at some time in their life, even if it is only
briefly as embryos. Figure 10 shows these chordate characteristics
as seen in the body of an adult lancelet.
Put a labeled diagram of a lancelet
on the overhead. Have students list
the characteristics not found on
other animals they have studied.
(Labeled structure should include
those in Figure 10. Student lists should
include notochord, dorsal nerve cord,
postanal tail, and pharyngeal slits.)
Motivate
Demonstration
Show students pictures of the
embryonic stages of several vertebrates, such as humans, sheep, fish,
and chickens. Have them compare
the animals and point out which
structures they have in common.
(pharyngeal slits, notochord, dorsal
nerve cord, tail) Tell students that it
is possible for an animal to be a
chordate but not a vertebrate.
Figure 10 Lancelet
interior. Adult lancelets
possess all of the characteristics of chordates.
Mouth
Notochord
Dorsal nerve cord
Tentacles
Anus
Pharynx with slits
Intestine
Segmented muscles
Evolutionary Milestone
LS Visual
9 Notochord
Tunicates, lancelets, and all the vertebrates belong to phylum Chordata (chordates). Chordates are coelomate animals that have a flexible, dorsal rod called
a notochord. In vertebrate chordates, the notochord is replaced during
embryonic development by a vertebral column (backbone).
TAKS 2 Bio 8C; Bio 5A, 5B, 5C, 8B
700
Chapter Resource File
pp. 700–701
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TEKS Bio 5A, 7B, 8C, 10A
Teacher Edition
TAKS Obj 2 Bio 8C, 10A
TEKS Bio 3D, 5A, 5B, 5C, 8A, 8B,
8C, 10A
700
Tail
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
• Data Sheet for Quick Lab
Transparencies
TT Bellringer
TT Lancet Interior
TT Adult Tunicate
GENERAL
Planner CD-ROM
• Reading Organizers
• Reading Strategies
• Supplemental Reading Guide
Journey to the Ants
Chapter 31 • Echinoderms and Invertebrate Chordates
Invertebrate Chordates
Phylum Chordata is divided into three subphyla. The vast majority
of chordate species belong to subphylum Vertebrata, which
you will study in the next unit. Two other subphyla, Urochordata
(the tunicates) and Cephalochordata (the lancelets), contain a
small number of species. Because members of these two subphyla
are chordates that do not have backbones, they are called
invertebrate chordates.
Tunicates
Only the free-swimming tunicate larvae have a nerve cord, notochord, and postanal tail. These features are lost during the larvae’s
transformation into adulthood. However, adult tunicates, shown in
Figure 11, retain their pharyngeal slits. Most adult tunicates are sessile, filter-feeding marine animals. A tough sac, called a tunic,
develops around the adult’s body and gives tunicates their name.
Cilia beating within the tunicate cause water to enter the incurrent
siphon. The water circulates through the tunicate’s body, passes
though its pharyngeal slits, and leaves the body through the excurrent siphon. As water passes through the slits in the pharynx, food
is filtered from it and passed into the stomach. Undigested food
passes to the anus, which empties into the excurrent siphon.
All tunicates are hermaphrodites, and some are also able to
reproduce asexually by budding. While some tunicates are solitary,
budding can result in colonies of identical tunicates.
Organizing Information
Make a table to organize
information about invertebrate chordates. Across the
top, write the headings
Adult characteristics and
Larval characteristics. Along
the sides, write Lancelet
and Tunicate. Add information to the table as you read
Section 2.
www.scilinks.org
Topic: Invertebrate Chordates
Keyword: HX4105
Figure 11 Adult tunicate
Incurrent
siphon
Excurrent
siphon
Tunic
Intestine
Reproductive
organs
Heart
GENERAL
Point out the segmented muscles
in the lancelet shown in Figure 10.
Tell students that these muscle
blocks are called myomeres and that
they are actually modified body segments present in chordate muscle
tissues. The “flaky” texture of many
fish filets is an example of these
stacked muscle layers. Then, draw
student’s attention to Figure 11.
Point out the arrows that indicate
the direction of water flow in the
tunicate interior. Have students
trace the water’s path with their
finger. LS Visual
did you know?
Anus
Stomach
Tunicate interior
701
Marine Biologist Have interested students
research the career of a marine biologist and
write a report that includes the type of degree
needed, classes to take in high school and
college, summer experiences, helpful volunteer
experiences, working environment, starting
salary, and growth potential. Bio 3D
Lancelets Have Transparent Skin
Tell students that, unlike the skin of
other vertebrates, the skin of a
lancelet is transparent. This feature
allows us to see the rows
of ossicles along the side of the
notochord.
TAKS 2 Bio 10A; Bio 5A
Pharyngeal
slits
Career
Teaching Tip
Using the Figure
Pharyngeal slits are the only chordate characteristic retained by adult tunicates.
Adult tunicate, dorsal view
Teach
INCLUSION
Other Deuterostome Phyla
In addition to echinoderms and
chordates, there are two other
deuterostome phyla. Both groups
live in the sea. Arrow worms
belong to the phylum Chaetognatha.
Their size ranges from 2.5 to 10 cm
in length, and they have straight
bodies that resemble darts or
torpedoes. Acorn worms, phylum
Hemichordata, are characterized by
their long proboscis. These bottomdwellers grow much longer than
arrow worms, ranging from 20 mm
to 2.5 m in length. Bio 8A, 8B
Strategies
• Attention Deficit Disorder • Learning Disability
• Developmental Delay
Using an index card or construction paper,
have the students write a postcard to the
teacher describing the lancelets seen on a
recent imaginary vacation. The students’
description should include the characteristics that make the lancelet an invertebrate
chordate and where the lancelet was found.
Student may also draw a picture of the
lancelet for the front of the postcard.
Chapter 31 • Echinoderms and Invertebrate Chordates
701
Lancelets
Comparing the
Structures of the
Notochord and
Nerve Cord
TAKS 2 Bio 8C; Bio 5A
Skills Acquired
Describing and
identifying structures
Figure 12 Lancelet.
Lancelets bury their tails in
sediment.
Teacher’s Notes
Ask students why they should
use a cross section, not longitudinal sections, for this lab.
Comparing the Structures of the
Notochord and Nerve Cord 5A 8C
TAKS 2
Answers to Analysis
1. The nerve cord is located
dorsally and has a small diameter. The wider notochord is
just below the nerve cord.
2. bilateral symmetry
3. Lancelets: bilateral symmetry;
Adult echinoderms: pentaradial symmetry
4. protection for the nerve cord,
points for muscle attachment,
and flexibility
Close
The notochord and hollow nerve cord are two important
characteristics of all chordates. While both are located on an
animal’s dorsal side, they differ in size, structure, and location. You can compare the two when viewing a cross section
of an adult lancelet.
Materials
compound microscope, prepared slide of the cross section
of an adult lancelet
Procedure
1. Place a prepared slide of a
cross section of an adult
lancelet under the microscope.
4. Sketch the specimen, and
label the dorsal and ventral
sides, the notochord, the
nerve cord, and the intestines.
2. Locate the dorsal side of the
specimen, and turn the slide
so the dorsal side is on top.
Analysis
3. Locate the notochord and
hollow nerve cord. If visible,
locate the intestine.
Reteaching
Have students compare lancelets
and tunicates. Bio 8B
Quiz
GENERAL
1. Which chordate characteristic
do adult tunicates retain?
(pharyngeal slits)
2. How do lancelets obtain food?
(by filtering water over their pharyngeal slits) TAKS 2 Bio 8C; Bio 8B
Alternative
Assessment
Lancelets, shown in Figure 12, receive their name from their bladelike
shape. Although lancelets may resemble fish, they are not fish.
Lancelet fossils have been found in rocks over 550 million years—
lancelets are much older than any fish species is. Lancelets are
scaleless chordates only a few centimeters long. The lancelets
V-shaped bundles of muscles are arranged in a series of repeating segments. Lancelets are found worldwide in shallow ocean water. They
spend most of their time with their mouths protruding from mud or
sand. The beating of cilia that line the front end of their digestive tract
draws water through the mouth and pharynx and out the pharyngeal
slits. Lancelets feed on microscopic protists that they filter out of the
water. Unlike tunicates, the sexes are separate in lancelets.
1. Describe the structure,
location, and size of the nerve
cord and the notochord.
2. Identify the kind of symmetry observed in the adult
lancelet.
4. Critical Thinking
Forming Hypotheses
In vertebrate chordates, the
notochord becomes a backbone that encases the nerve
cord. Why might this arrangement be an advantage to
an animal?
Section 2 Review
Describe the characteristics common to
Compare the chordate characteristics found in
all chordates.
adult tunicates with those found in adult lancelets.
8C
TAKS Test Prep The pharyngeal slits of a
10A
tunicate play a role in what system?
A skeletal
C nervous
B reproductive
D digestive
Summarize why tunicates and lancelets are
8C
classified as invertebrate chordates.
702
GENERAL
Have students build a chordate
Answers to Section Review
model that includes the four chordate
1. At some point during their development, all
characteristics. TAKS 2 Bio 8C; Bio 8A, 8B
chordates have a notochord; a hollow, dorsal
nerve cord; pharyngeal slits; and a postanal tail.
TAKS 2 Bio 8C
pp. 702–703
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7A
TAKS Obj 3 Bio 7B
TEKS Bio 5A, 7A, 7B, 8C, 10A
Teacher Edition
TAKS Obj 2 Bio 8C, 10A
TEKS Bio 5A, 8A, 8B, 8C, 10A
702
3. Compare the lancelet’s
symmetry with the symmetry
of adult echinoderms.
2. Tunicates and lancelets possess all four basic
chordate characteristics, but they lack a
backbone. TAKS 2 Bio 8C
3. Adult tunicates retain their pharyngeal slits.
The nerve cord, notochord, and tail are lost
after the larval stage. Adult lancelets have a
notochord, a dorsal nerve cord, a postanal tail,
and pharyngeal slits. TAKS 2 Bio 8C
Chapter 31 • Echinoderms and Invertebrate Chordates
4.
A. Incorrect. The tunic provides
support and protection. B. Incorrect.
Reproductive organs are located next to the
pharynx. Tunicates are hermaphroditic, and
some reproduce by budding. C. Incorrect. The
nerve cord is lost in adult tunicates. D. Correct.
The pharygeal slits work with the digestive
system. TAKS 2 Bio 10A
8C
Study
CHAPTER HIGHLIGHTS
ZONE
Key Concepts
Alternative
Assessment
Key Terms
1 Echinoderms
Section 1
●
blastopore (692)
protostome (692)
deuterostome (692)
ossicle (694)
water-vascular system (695)
skin gill (695)
●
●
●
●
●
During embryonic development, a protostome’s mouth
develops from the blastopore. In a deuterostome, the anus
forms from the blastopore and the mouth forms later from
a different opening.
Because echinoderms and chordates are both deuterostomes, scientists believe that both groups were derived
from a common ancestor.
Echinoderms lack a head or brain. Their nervous system
consists of a central ring of nerves with branches extending
into each of the five parts of its body plan.
Echinoderms share four characteristics: an endoskeleton
composed of ossicles; five-part radial symmetry; a watervascular system; and coelomic circulation and respiration.
In many echinoderm species, respiration and waste removal
are performed by skin gills.
Echinoderms are a diverse group consisting of seven
classes: sea stars, brittle stars, sea lilies, feather stars, sea
urchins and sand dollars, sea cucumbers, and sea daisies.
• Science Skills Worksheet GENERAL
• Critical Thinking Worksheet
• Test Prep Pretest GENERAL
• Chapter Test GENERAL
Section 2
●
chordate (700)
notochord (700)
pharyngeal slit (700)
invertebrate chordate (701)
●
●
●
Have students write questions to be
used in the exam for this chapter.
They should write several types of
questions: multiple choice, true/false,
fill-in-the-blank, essay. Be sure
students provide the correct answers
as well. Use the best questions in
the test for this chapter.
Chapter Resource File
2 Invertebrate Chordates
●
GENERAL
At some point in their lives, all chordates have a notochord,
a dorsal nerve chord, pharyngeal slits, and a postanal tail.
Phylum Chordata includes invertebrate and vertebrate
chordates.
Invertebrate chordates do not have a backbone (vertebral
column). Two invertebrate subphyla are Urochordata
(tunicates) and Cephalochordata (lancelets).
Tunicate larvae have a nerve cord, notochord, pharyngeal
slits, and a postanal tail. As adults, they lose all of these
characteristics except the pharyngeal slits.
Lancelets retain their notochord, dorsal nerve cord, pharyngeal slits, and postanal tail into adulthood.
703
Answer to Concept Map
The following is one of several possible answers to Performance Zone item 15.
Animals
that are
Protostomes
Deuterostomes
have a
have an
mouth
anus
such as
echinoderms
chordates
have
must have
that develops from the
blastopore
postanal tail
nerve cord
water
vascular
system
skin
gills
notochord
pharyngeal
slits
Chapter 31 • Echinoderms and Invertebrate Chordates
703
Performance
CHAPTER REVIEW
ZONE
CHAPTER 31
ANSWERS
Using Key Terms
match between an adult echinoderm and
one of its characteristics?
8B
a. sea cucumber: leathery epidermis
b. sand dollar: five arms
c. sea lily: free-swimming
d. sea star: sessile
1. Which of the following patterns of develop-
1. b TAKS 2 Bio 8C
2. d Bio 5A, 5B
3. d TAKS 2 Bio 10A
4. c Bio 11B
5. a. Protostomes are animals
with a mouth that develops
from or near the blastopore.
Deuterostomes are animals
with an anus that develops
from or near the blastopore.
b. Ossicles are hard, calciumrich plates that make up the
endoskeleton of echinoderms.
Skin gills are soft, fingerlike
projections that grow between
an echinoderm’s spines. Skin
gills aid with respiration and
waste removal.
c. The nerve cord is dorsal and
has a very small diameter. The
notochord is dorsal, ventral to
the nerve cord, and larger in
diameter than the nerve cord.
The notochord gives rise to the
vertebral column in vertebrates.
Understanding Key Ideas
6. c TAKS 2 Bio 8C
7. d TAKS 2 Bio 8C
8. a Bio 8B
9. c TAKS 3 Bio 12B
10. b TAKS 2 Bio 8C
11. b TAKS 2 Bio 8C
12. The notochord represented the
beginnings of an internal skeleton.
An internal skeleton provided
points for muscle attachment and
allowed vertebrates to grow large
and move quickly. TAKS 3 Bio 7A
ment is characteristic of echinoderms and
8C
lancelets?
a. protostome
c. acoelomate
b. deuterostome
d. pseudocoelomate
2. In protostomes, the area labeled A in the
pp. 702–703
Review and Assess
TAKS Obj 2 Bio 4B, 8C, 10A, 10B
TAKS Obj 3 Bio 4B, 7A, 7B, 12B
TEKS Bio 3D, 3E, 5A, 5B, 7A, 7B,
8B, 8C, 10A, 10B, 11B, 11C, 12B, 12C
9. Which echinoderm group includes species
diagram below becomes the
5A 5B
a. anus.
c. coelom.
b. gastrula.
d. mouth.
that specialize in hunting bivalves?
a. sea cucumbers
c. sea stars
b. sand dollars
d. sea lilies
12B
10. Animals with a notochord, a dorsal nerve
cord, and pharyngeal slits are members of
the phylum
8C
a. Echinodermata.
b. Chordata.
c. Annelida.
d. Cnidaria.
A
11. Which of the following do adult chor-
dates and adult echinoderms have
in common?
8C
a. a nonsegmented body
b. an internal skeleton
c. a water-vascular system
d. bilateral symmetry
3. The ossicles of Asterias produce pincerlike
structures called
a. madreporites.
b. tube feet.
10A
c. ampullae.
d. pedicellaria.
4. Sea star movements are coordinated
by the
11B
a. radula.
b. mantle.
12. In what way was the notochord an impor-
c. nerve ring.
d. tube foot.
5. For each pair of terms, explain the differ-
ences in their meanings.
a. protostome, deuterostome
b. ossicle, skin gills
c. notochord, nerve cord
tant development in the evolution of
7A
vertebrates?
13.
how gas exchange occurs in most crustaceans, insects, and echinoderms.
(Hint: See Chapter 30, Sections 1 and 4.)
6. The phylum characterized by radial sym-
metry and a water-vascular system is
a. Chordata.
c. Echinodermata.
b. Arthropoda.
d. Cnidaria.
7. The presence of which of the following
characteristics is typical among
echinoderms?
8C
a. nauplius larvae
b. a notochord
c. an exoskeleton
d. a water-vascular system
Once preliminary tests
determine that coastal waters are polluted,
what kinds of actions might be taken to
reduce the pollution?
11C 12C
14. Gas exchange is essential to life. Compare
Understanding Key Ideas
8C
15.
Concept Mapping Construct a
concept map that outlines the development and body plan of echinoderms and
invertebrate chordates. Try to include the
following terms in your map: blastopore,
protostome, deuterostome, water-vascular
system, skin gills, notochord, nerve cord, and
3E
pharyngeal slits.
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13. Scientists can run specific tests to determine
what contaminants are present. If the toxicity
can be traced to a specific source, waste can be
treated before it is discharged. Contaminated
sediments can be removed or decontaminated.
In the future, plants may be used to remove
toxic chemicals from contaminated water.
Bio 11C, 12C
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8. Which of the following pairs is a correct
Using Key Terms
14. In most crustaceans, gas exchange occurs
across gills. Insects have a system of tracheae
and spiracles for gas exchange. In echinoderms, gas exchange occurs as dissolved oxygen moves through the water-filled coelomic
cavity. Many echinoderms also have skin gills
Chapter 31 • Echinoderms and Invertebrate Chordates
that provide extra surface area for gas
exchange. TAKS 2 Bio 4B
15. One possible answer to the concept map is
found at the bottom of the Study Zone page.
Bio 3E
Assignment Guide
Section
1
2
Questions
1-3, 5a-b, 6-9, 11, 13-16, 18-21
4, 5c, 10, 12, 15, 17, 19
4B
Critical Thinking
Alternative Assessment
Critical Thinking
16. Evaluating Conclusions Sea cucumbers
20. Finding and Communicating Information
16. Answers will vary. Swimming
enables these echinoderm larvae
to find underexploited living
spaces and food sources.
and sea lilies are relatively sessile. Their
larvae, however, are capable of swimming.
Explain how swimming larvae provide an
advantage for these echinoderms.
7B
Use the media center or Internet resources
to learn more about the crown-of-thorns
sea star, or Acanthaster planci, which is
abundant on the Great Barrier Reef. Find
out why this echinoderm poses such a
threat to its environment, and prepare a
report on your findings. Include steps being
taken by the Australian government to deal
with the problem.
12B
17. Forming Reasoned Opinions A scientist
collects several specimens of an unidentified animal. After conducting an in-depth
study of the mysterious species, the scientist observes that they have tube feet, an
endoskeleton, and a protostome pattern of
embryonic development. Why is the classi8B
fication of these organisms difficult?
21. Identifying Functions Use library or Inter-
net resources to investigate how tube feet
vary in the different groups of echinoderms.
Make a series of drawings illustrating
the differences.
7B 8B
18. Forming Reasoned Opinions Scientists
have found many echinoderm fossils from
the Cambrian period, but they have found
few fossils of other species that must have
lived then. What might explain the large
number of fossilized echinoderms?
7A
22. Career Connection Underwater Photographer
Research the field of underwater photography. Write a report on your findings that
includes a job description, training required,
kinds of employers, growth prospects, and
starting salary.
3D
19. Inferring Relationships Explain why the lar-
val form of an organism can be valuable in
determining relationships among species.
7A
TAKS Test Prep
The diagram below shows a vertical cross section
of an adult tunicate. Use the diagram and your
knowledge of science to answer questions 1–3.
A
organism have as an adult?
8B
F pharyngeal slits
H notochord
G dorsal nerve cord J postanal tail
Alternative Assessment
10B
between structures A and B?
A B releases undigested food into the water
that leaves the body through A.
B B releases gametes into the water that
leaves the body through A.
C B collects food from the water that
enters the body through A.
D B extracts oxygen from the water that
enters the body through A.
8B
1. A. Incorrect. Sea anemones are Cnidarians.
B. Incorrect. Sponges are not chordates.
C. Incorrect. Sea cucumbers are echinoderms.
D. Correct. Humans are also chordates.
Bio 8B
2. F. Correct. G. Incorrect. These characteristics
are present in the larval form but disappear
in adults. H. Incorrect. See answer G.
J. Incorrect. See answer G. Bio 8B
20. Acanthaster planci is dangerous
to the Great Barrier Reef because
it is a voracious eater. A. planci
often eats in large groups, secreting a chemical that attracts more
starfish to the area to feed.
Marine biologists in Australia
have tried injecting starfish with
poisons and asking amateur
divers to remove them by hand.
TAKS 3 Bio 12B
Test
1. This organism is in the same phylum as
A sea anemones. C sponges.
B sea cucumbers. D humans.
17. Answers will vary. The species
has characteristics of echinoderms, including tube feet and
an endoskeleton. However,
echinoderms are deuterostomes.
Thus, classification into an existing phylum is difficult. Bio 8B
18. Answers will vary. Students
might note that endoskeletons of
echinoderms are easily fossilized.
Echinoderms also live on the sea
floor, where sediment forms sedimentary rock, where many fossils
are found. TAKS 3 Bio 7A (grade 11 only)
19. In many animal species, the larval
form may have characteristics not
present in the adult form and that
are similar to characteristics of
other, possibly related species.
TAKS 3 Bio 7A (grade 11 only)
2. Which chordate characteristic does this
3. What is the significance of the relationship
B
TAKS 3 Bio 7B
If you’re not sure of an answer, go to the next
question, but remember to skip that number on
your answer sheet as well.
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3. A. Incorrect. Undigested food does not
leave the body through the incurrent siphon.
B. Incorrect. Gametes do not leave the body
through the incurrent siphon. C. Correct.
D. Incorrect. Both incurrent siphon and pharynx are involved in circulating materials
through the tunicate’s body.
TAKS 2 Bio 10B (grade 11 only)
21. Answers will vary. Students may
note that the tube feet of many
sea stars that live on soft surfaces
lack suckers. Many brittle stars
have worm-like feet that bring
food particles to the animal’s
mouth. TAKS 3 Bio 7B; Bio 8B
22. Answers will vary. Underwater
photographers take still or moving pictures of underwater scenes.
Underwater photographers have
hands-on training in photography and oceanography. Some
have a college degree in art with
a concentration in photography.
Underwater photographers are
often self-employed, although
some have permanent positions
with museums, aquariums, and
organizations. Starting salary will
vary by region. Bio 3D
Chapter 31 • Echinoderms and Invertebrate Chordates
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