Download Features of Arthropods

Section 1
Features of Arthropods
Section 1
Focus
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. Section 1 describes the
common characteristics of arthropods. The arthropod family tree
shows that this phylum of organisms is divided into two groups:
those with jaws and those with
fangs or pincers.
Bellringer
Tell students that one of the
characteristics of arthropods is
an exoskeleton, or “outer skeleton,” constructed of the strong,
chemically-resistant material called
chitin. Ask students to brainstorm
a list of advantages and disadvantages of an exoskeleton.
(Advantages: protection, muscle
attachment, and reduction of water
loss. Disadvantages: Does not
“stretch” for growth, can be heavy,
and can be vulnerable to breaking or
cracking.) LS Visual TAKS 3 Bio 7B
Jointed Appendages
Objectives
● Summarize the evolutionary
relationship of arthropods
and annelids.
7B TAKS 3
● Identify the three subphyla
of arthropods.
8B
● Describe the characteristics
of arthropods.
8CTAKS 2
● Describe how growth
occurs in arthropods.
5A
Key Terms
appendage
thorax
cephalothorax
compound eye
molting
trachea
spiracle
Malpighian tubule
Whether you are looking at a scorpion or a leaf-footed bug, as
shown in Figure 1, when you see an arthropod, you will probably
notice its appendages. An appendage is a structure that extends
from the arthropod’s body wall. Unlike the parapodia and setae of
annelids, arthropod appendages have joints that bend. The phylum
name, Arthropoda, literally means “joint foot.” A variety of jointed
appendages are found in arthropods, including legs for walking,
antennae for sensing the environment, and mouthparts for sucking,
ripping, and chewing food.
Arthropods almost certainly share a distant common ancestor
with the annelid worms. Like annelids, arthropods have a coelom
and a segmented body. Arthropod fossils, some as much as
600 million years old, are among the oldest, best-preserved fossils
of multicellular animals. Among the most numerous of the early
arthropods were the now-extinct trilobites, which lived in the
sea. Like modern arthropods, trilobites had segmented bodies
and jointed appendages, and they were the first animals to have
eyes capable of forming images. Trilobites became extinct about
250 million years ago. The first terrestrial arthropods were probably
scorpions similar to the modern scorpion shown in Figure 1.
Figure 1 Arthropods
This leaf-footed bug and hairy desert scorpion belong to phylum Arthropoda.
Motivate
Demonstration
Bring in the exoskeleton of a lobster, crab, tarantula, or other
arthropod. Allow students to examine it with a hand lens and try to
find the areas where muscles were
attached to the
English Language
Learners
interior surface.
Leaf-footed bug
Scorpion
Evolutionary Milestone
7 Jointed appendages
Arthropods were the first animals to have jointed appendages. Joints permit
powerful movement, aiding locomotion. Jointed appendages became
specialized in many different ways, helping to create the vast diversity
seen among the arthropods.
TAKS 2 Bio 10A; Bio 5A
664
Transparencies
Chapter Resource File
pp. 664–665
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B
TEKS Bio 5A, 7B, 8B, 8C
Teacher Edition
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 7A, 7B
TAKS Obj 5 IPC 4A
TEKS Bio 5A, 7A, 7B, 8B, 8C, 10A
TEKS IPC 4A
664
Chapter 30 • Arthropods
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
• Data Sheet for Quick Lab
GENERAL
Planner CD-ROM
• Reading Organizers
• Reading Strategies
• Occupational Application
Biology Teacher GENERAL
TT
TT
TT
TT
Bellringer
Phylogenetic Tree of Arthropods
Characteristics of Arthropods
Exploration of an Arthropod
Arthropod Diversity
If a prize were given for sheer numbers, it would go to the arthropods. The total number of arthropod species exceeds that of all
other kinds of animals combined. About 900,000 species of arthropods have been recorded, and probably at least as many remain to
be classified. There are more species of beetles alone than there are
of vertebrates. Scientists estimate that 1018 arthropods are alive at
any one moment! The great majority of arthropods are small, about
1 mm (0.04 in.) in length. The very smallest are parasitic mites only
80 µm (0.003 in.) long. The largest arthropods are gigantic crabs
3.6 m (12 ft) across, found in the sea near Japan.
Living arthropods are traditionally divided into two groups,
arthropods with jaws and arthropods with fangs or pincers. As
shown in Figure 2, arthropods with jaws belong to either subphylum Uniramia (yoo nuh RAY mee uh) or to subphylum Crustacea
(kruhs TAY shuh). Arthropods with fangs or pincers belong to subphylum Chelicerata (chuh LIS uh rahd uh). Each of these three
subphyla represents a distinct evolutionary line.
Teach
www.scilinks.org
Topic: Arthropods
Keyword: HX4014
READING
SKILL
BUILDER
Reading Organizer As students
read this section, have them put the
various classes of arthropods and
their descriptions on index cards.
The class name should be placed on
one side and the description on the
other. In addition, students could
make cards with the class name on
one side and examples on the other.
Have students use the cards as flash
cards to review the section.
Figure 2 Phylogenetic tree
LS Verbal TAKS 2 Bio 8C
This phylogenetic tree shows the relationships among the three arthropod subphyla which form two groups: those with jaws and those with fangs or pincers.
READING
SKILL
BUILDER
Millipedes
Centipedes
Class
Diplopoda
Class
Chilopoda
Ladybugs Shrimps
Class
Order
Insecta Decapoda
Pill bugs
Scorpions Mites
Spiders
Order
Isopoda
Order
Order
Scorpions Acari
Order
Order
Araneae Pycnogonida
Class
Malacostraca
Subphylum
Uniramia
Sea spiders
Horseshoe crabs
Class
Merostomata
Class
Arachnida
Subphylum
Crustacea Trilobites
(extinct)
GENERAL
Interpreting Visuals Explain to
students that the phylogenetic tree
in Figure 2 “reads” like a graph up
the Y axis, but not from left to
right across the X axis. Explain
further: Time progresses up the
Y axis. That is, points on the tree
closer to the bottom of the page
denote time longer ago, and points
on the tree closer to the top of the
figure denote more recent time.
However, organismal change does
not progress from left to right
along the X axis. Organismal
change is shown whether moving
to the left or right.
TAKS 2 Bio 8C; TAKS 2 Bio 7B
Arthropods with jaws
Subphylum
Chelicerata
Teaching Tip
Arthropods with fangs
or pincers
Common ancestor
665
IPC Benchmark Review
To prepare students for the TAKS and accompany
the discussion of motion, work and power, have
students review Work and Power, TAKS 5 IPC 4A
on p. 1056 of the IPC Refresher in the Texas
Assessment Appendix of this book.
did you know?
“Jointed Foot” The prefix “arthro” comes
from a Greek word meaning “joint,” and the
prefix “pod” comes from another Greek word
meaning “foot.” The word arthritis refers to an
inflammation of the joints. A podiatrist is a
doctor who treats conditions of the feet and a
pseudopod is also known as a “false foot.”
GENERAL
Jointed Appendages Have
students read the Evolutionary
Milestone on page 664. Remind
them that jointed appendages were
a major evolutionary development.
Have students point out the joints
in the appendages shown in
Figure 1. LS Visual
TAKS 3 Bio 7A (grade 11 only); TAKS 3 Bio 7B
Chapter 30 • Arthropods
665
Arthropod Body Plan
While arthropods may be quite different in appearance, they share
a number of internal and external features, which are summarized
in Figure 3. There is great variation in appearance among arthropod
species, and not every species has every feature listed. However,
these features are characteristic of the phylum as a whole.
Teach, continued
continued
READING
SKILL
BUILDER
GENERAL
Segmentation
Interactive Reading Assign
Chapter 30 of the Holt Biology
Guided Audio CD Program to help
students achieve greater success in
reading the chapter. LS Auditory
Teaching Tip
In arthropods, individual body segments often exist only during the
larval stage. For example, when you look at a butterfly larva (a
caterpillar), you can easily see that it has many segments. However,
if you look closely at an adult butterfly, you will see only three body
regions. In most arthropods the many body segments fuse during
development to form three distinct regions—the head, the thorax
(midbody region), and the abdomen. In some arthropods, such as
the crab shown at the top in Figure 3, the head is fused with the
thorax to form a body region called the cephalothorax.
GENERAL
Arthropod Segmentation Have
students look through this chapter
and find examples of trends in
arthropod body plans. Ask: Which
are more segmented, larvae or
adults? (larvae) Which types of
arthropods show more segmentation? (Answers will vary. Millipedes
and centipedes are highly segmented.)
Figure 3 Arthropod
characteristics. These eight
characteristics are typical of
arthropods, although not
all arthropods show each
characteristic.
TAKS 3 Bio 7B; Bio 5B
Using the Figure
Have students discuss which characteristics from the list can be seen
in the two arthropods pictured in
Figure 3. (Students can see the external structures on the list, but not the
internal structures.) LS Visual
Figure 4 Compound eyes.
The compound eye of this
house fly is made of thousands of individual units.
Characteristics of Arthropods
• Jointed appendages
• Segmentation
• Distinct head, often with
compound eyes
• Exoskeleton
• Respiration by gills, tracheae,
or book lungs
• Open circulatory system
• Excretion through
Malpighian tubules
• Wings on many
arthropods
Magnification: 22ⴛ
TAKS 1 Bio/IPC 2D; Bio 3E
Compound Eyes
Many arthropods have compound eyes, shown in Figure 4.
A compound eye is an eye composed of thousands of individual visual units, each with its own lens and retina. The
brain receives input from each of the units, and then composes an image of an object. While the image formed is not
as clear as what you see, arthropods see motion much more
quickly. This is why it is so difficult to sneak up on a fly.
Some arthropods also have simple, single-lens eyes that do
not form images, but simply distinguish light from dark.
Most insects have both compound and simple eyes.
In dragonflies and locusts, these simple eyes function as
horizon detectors. The ability to see the horizon helps the
insect stabilize its position during flight.
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pp. 666–667
Student Edition
TAKS Obj 1 Bio/IPC 2B, 2C, 2D
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7A
TAKS Obj 3 Bio 7B
TEKS Bio 7A, 7B, 8C
TEKS Bio/IPC 2B, 2C, 2D
Teacher Edition
TAKS Obj 1 Bio/IPC 2B, 2C, 2D
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TAKS Obj 5 IPC 4A, 4B, 5B
TEKS Bio 3E, 5B, 7B, 10A
TEKS Bio/IPC 2B, 2C, 2D, 3C
TEKS IPC 4A, 4B, 5B
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Chapter 30 • Arthropods
MISCONCEPTION
ALERT
Compound Eyes The individual units in
a compound eye do not all see the same
image. To study the imaging capabilities
of ommatidia, the segments that make up
compound eyes, photographers isolated
eyes from insects and shot photos through
them. These pictures did not show thousands of identical images as one might
expect and as is often portrayed in science
fiction movies. Instead, the photographers
found the visual effect to be similar to that
of a mosaic. TAKS 1 Bio/IPC 2D; TAKS 2 Bio 10A
IPC Benchmark Mini-Lesson
Biology/IPC Skills TAKS 5 IPC 5B (grade 11 only)
Demonstrate wave interactions, including reflection
and refraction.
Activity Each lens of a compound eye focuses light
onto its own retina. Focusing light involves bending
light rays toward a central point. Light waves can be
bent when light changes speed by passing through a
substance that is thicker or thinner than air. Have the
students think of situations in which they have noticed
light bending. (Answers may include looking in a fish
tank, using a magnifying glass, or seeing a mirage.)
Exoskeleton
The outer layer of the arthropod body is a rigid exoskeleton (often called a shell) composed primarily of chitin.
The exoskeleton is thin and flexible where the joints of the
appendages are located. Muscles attached to the interior
surfaces of the exoskeleton can pull against it, causing the
animal’s joints to bend. As shown in Figure 5, many
arthropods can use their jointed appendages to perform
complex movements. While chitin is tough, it is brittle and
breaks easily. As arthropods increase in size, their
exoskeletons must become thicker to withstand the pull of
larger muscles without breaking. However, an increase in
thickness of the exoskeleton adds weight, restricting the size arthropods can reach.
The exoskeleton of the different arthropod groups varies greatly
in thickness. If you have ever attempted to swat a large insect, you
know that its exoskeleton can be difficult to crush. Crustaceans, for
example, have a thick, relatively inflexible exoskeleton. In comparison, the exoskeleton of other insects and some arachnids is fairly
soft and flexible. Regardless of the nature of an arthropod’s
exoskeleton, it provides protection from injury and helps to prevent
water loss.
Teaching Tip
Figure 5 Jointed
appendages. The joints in
the legs of this praying mantis
permit it to perform many
complex movements, such
as manipulating prey.
TAKS 1 Bio/IPC 2B, 2C, 2D
Skills Acquired
Measuring, predicting,
drawing conclusions
Teacher’s Notes
Bring in a crab exoskeleton
to demonstrate the range of
motion in one jointed appendage.
To understand the importance of jointed appendages,
test your range of movement without and with bending
your joints.
Answers to Analysis
Materials
meterstick, paper, and pencil
Analysis
1. Work in pairs, and assign one
person to be the test subject
and one person to record the
data.
2. The test subject extends one
arm straight out in front of
the body. The subject then
places a meterstick along the
inside of the arm, as shown
in the illustration. The elbow
should not be bent.
3. The recorder measures and
records the distance along
the meterstick that the test
subject can reach with
extended (not bent) fingers.
4. The test subject now tries to
increase the range of movement by bending the fingers
only. The recorder measures
and records the closest and
farthest distance along the
meterstick that can be
reached.
5. The test subject now tries to
increase the range of motion
by bending the elbow. The
recorder measures and
records the closest and farthest distance along the
meterstick that can be
reached.
TAKS 1 Bio/IPC 2C
Evaluating Jointed
Appendages
Evaluating Jointed
Appendages 2B 2C 2D TAKS 1
Procedure
GENERAL
Armor Relate the weight of an
exoskeleton to that of the body
armor worn by the knights of the
Middle Ages. The knights had to be
assisted onto their horses, and the
weight of the armor was very tiring. Even today, law enforcement
officers sometimes dislike wearing
bulletproof vests because they are
too heavy and hot to wear.
1. Describe how eating breakfast might be different if you
did not have joints on your
fingers and at your elbows.
2. Predict the advantages an
animal with jointed
appendages has over an animal without jointed
appendages when capturing
and consuming food.
3. Predict the advantages for
an arthropod that has sense
organs (eyes and odor detectors) on the ends of jointed
appendages.
1. A person’s arms would be useless for bringing food to one’s
own mouth.
2. An animal with jointed
appendages would have a
much greater range of motion,
which would be better for
manipulating food.
3. Answers will vary. One advantage is that the animal could
move its sense organs by moving particular appendages
instead of its whole body.
667
IPC Benchmark Fact
In order to distinguish mass and weight, point out to
students that when the thickness of an exoskeleton
increases, more mass (i.e., matter) is added. The
increased mass then results in a proportional increase
in the pull of gravity on the arthropod which thereby
increases its weight, which is a measure of the force
of gravity. Finally, ask students how an exoskeleton
limits the size and movement of arthropods.
TAKS 5 IPC 4A, 4B
Cultural
Awareness
Crickets To the Japanese, crickets are
considered pets and a delightful source of
musical and artistic pleasure. Favorite pet
crickets are often given elaborate cages and
beautiful porcelain water dishes. Japanese
cricket owners even “tickle” their crickets
with delicate hand-carved brushes to encourage them to sing. To the British, a cricket on
the hearth is a sign of good luck. Bio/IPC 3C
Chapter 30 • Arthropods
667
Molting
Teach, continued
continued
Teaching Tip
Molting Ask students to brainstorm some of the problems inherent
in molting. (Emerging from an
exoskeleton can be hazardous to an
arthropod. For about two hours
after emerging from an outgrown
exoskeleton, an arthropod is vulnerable to predators and the environment
because its new exoskeleton has not
yet hardened.) Ask students how
arthropods can protect themselves
during molting. (Arthropods usually
hide until their new exoskeletons
have hardened.) TAKS 3 Bio 7B
Teaching Tip
Respiration
The majority of terrestrial arthropods respire through a network of
fine tubes called tracheae (TRAY kee ee), as shown in Figure 7. Air
enters the arthropod’s body through structures called spiracles and
passes into the tracheae, delivering oxygen throughout the body.
Valves that control the flow of air through the spiracles and prevent
water loss were a key adaptation for the first arthropods that
invaded land more than 400 million years ago.
GENERAL
Arthropod Respiratory Organs
Insects have hollow branching tubes
called tracheae that carry air into the
body’s tissues. Spiders have leaflike
plates called book lungs that have a
large surface area to exchange oxygen and carbon dioxide. Lobsters
have gills that also have a large surface area for gas exchange.
TAKS 2 Bio 10A
Real Life
Answer Bio 3B
Topical products for head lice
contain the insecticide permethrin.
Most products are shampoos or
creams used to treat the scalp.
After such treatments, health care
practitioners suggest combing the
hair with a fine-toothed comb to
remove the eggs. Creams are also
available to treat the skin all over
the body. The spread of lice can
usually be prevented if people
avoid sharing combs, brushes,
hats, towels, and other items that
may transfer lice or eggs from one
person to another.
pp. 668–669
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TEKS Bio 3B, 5A, 7B, 8B, 8C, 10A
Teacher Edition
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 7B
TEKS Bio 3B, 5A, 7B, 8B, 8C, 10A
668
Figure 6 Molting. This
green cicada is emerging from
its old exoskeleton, which it
leaves behind as a colorless
ghost of itself.
Chapter 30 • Arthropods
A tough exoskeleton protects an arthropod from predators and
helps prevent water loss. But an exoskeleton cannot grow larger, so
an arthropod cannot simply grow bigger, as many other animals do.
Imagine blowing up a balloon inside a soft drink can—after a certain point, the balloon cannot get any bigger. Arthropods have the
same problem. In a process called molting , or ecdysis (EHK duh
sihs), they shed and discard their exoskeletons periodically. Molting
is triggered by the release of certain hormones. Just before molting,
a new exoskeleton forms beneath the old one. When the new
exoskeleton is fully formed, the old one breaks open. The arthropod
emerges in its new, still-soft exoskeleton, as shown in Figure 6.
The new exoskeleton hardens within a few hours or a few days,
depending on the species.
Real Life
Head lice often infect
entire schools.
Head lice are notoriously
difficult to control. Having
clean hair will not prevent
a head lice infection, and
anti-lice shampoos often
fail to kill immature
head lice.
Figure 7 Tracheal system of a beetle
A complex series of hollow tubes called tracheae run through the bodies
of most terrestrial arthropods.
Finding Information
Research the latest remedies for treating head lice,
and find out how to avoid
infection.
3B
668
MISCONCEPTION
ALERT
Albino Roaches? People often see what
they think are “albino” insects, such as
roaches. These white insects are not really
albinos. They have just shed their exoskeletons recently and full coloration has not
yet returned.
Trachea
Muscle cell
Spiracle
Excretion
Terrestrial arthropods have a unique excretory system that efficiently
conserves water and eliminates metabolic wastes. This system is composed of excretory units called Malpighian (mal PIHG ee uhn)
tubules. Malpighian tubules are slender, fingerlike extensions from
the arthropod’s gut that are bathed by blood. Water and small
dissolved particles in the blood move through the tubules and into the
arthropod’s gut. As this fluid moves through the gut, most of the
water, valuable ions, and metabolites from the fluid are reabsorbed
into the arthropod’s body tissues by osmosis. Metabolic wastes
remain in the gut and eventually leave the body through the anus. You
can see the Malpighian tubules on the grasshopper in Up Close:
Grasshopper, in Section 2 of this chapter.
An Arthropod
on the Move
Teaching Strategies
Ask students if they have seen
migrating monarch butterflies.
The largest numbers of monarchs can be observed during
the second and third weeks of
October in west central Texas.
Good places to observe include
Seminole Caynon State Historic
Park and most locations along
the Devil’s River and Frio River.
An Arthropod on the Move
TAKS 3
T
he monarch butterfly, Danaus
plexippus, is a long-distance
traveler. Each year, millions of
these insects migrate from sites
across the United States and
Canada to their wintering grounds
in central Mexico. Some monarchs
fly up to 4,000 km on their journey.
Generations of Migrants
Four to five generations of monarchs are born each year. In
spring, most monarchs are found
in the southern United States.
The offspring of each successive
generation move farther north to
breed. Monarchs born in early fall
postpone breeding until the next
year. They respond to the shorter
days and lower temperatures by
beginning their long migration to
Mexico, where they remain until
the following March.
Monarchs funnel through Texas
during both the spring and
the fall migrations. In the fall, they
use two main flyways. One, which
passes through the center of the
state, is about 300 km wide and is
used by most monarchs. The
other flyway follows the coastline.
Finding Their Way
Scientists at the University of
Texas at El Paso have shown
that monarchs use at least two
methods to chart their course.
Under clear skies, the butterflies
Discussion
• For monarchs born in the fall,
what are the advantages of
waiting until the following
spring to breed? (Larvae born
in the spring will be more likely
to survive due to warmer climate and greater availability of
food/vegetation.)
note the direction of the sun with
respect to north. On cloudy
days, they find their way by
detecting Earth’s magnetic field.
The researchers demonstrated
the latter method by collecting
monarchs in the fall and placing
them in a chamber where the
magnetic field could be blocked
or reversed. In the absence of a
magnetic field, the butterflies flew
in random directions. When the
magnetic field was reversed, they
flew to the northeast, the opposite
of their normal migratory direction.
Close
Reteaching
Have students write the characteristics of arthopods on index cards
and quiz one another with them.
Section 1 Review
LS Interpersonal TAKS 2 Bio 8C
State the evolutionary relationship of the arthro7B
pods and the annelids.
Describe the three externally visible character-
istics common to all arthropods.
8C
Summarize how compound eyes function.
Describe how arthropods grow.
TAKS 3 Bio 7B
10A
5A
Critical Thinking Relating Concepts Draw
a concept map of the three subphyla of arthropods,
8B
with two examples of each subphylum.
TAKS Test Prep Oxygen is delivered throughout an arthropod’s body by the
10A
A Malpighian tubules. C exoskeleton.
B blood.
D tracheae.
669
Answers to Section review
1. Annelids and arthropods almost certainly share
a common ancestor. TAKS 3 Bio 7B
2. Jointed legs, an exoskeleton, and segmentation.
TAKS 2 Bio 8C
3. Compound eyes receive images from each lens
and send them to the brain, where one image is
formed. TAKS 2 Bio 10A
4. Arthropods cannot grow without shedding their
exoskeleton. A new exoskeleton forms, and the
old one splits and is molted. The new exoskeleton hardens, and the cycle begins again. Bio 5A
5. Concept maps will vary but should include the
subphyla Uniramia, Crustacea, and Chelicerata,
and two examples in each subphylum. Bio 8B
6.
A. Incorrect. Malphighian
tubules function in excretion. B. Incorrect. In
an open circulatory system, the blood moves
too sluggishly to efficiently deliver oxygen to
tissues. C. Incorrect. The exoskeleton covers
the body, protecting the arthropod. D. Correct.
The tracheae are a network of fine tubes that
deliver oxygen throughout the arthropod
body. TAKS 2 Bio 10A
Quiz
GENERAL
True or False:
1. One characteristic of arthropods
is a closed circulatory system.
(False. Arthropods have open circulatory systems.) TAKS 2 Bio 8C
2. When an arthropod molts, it
sheds its exoskeleton. (True)
TAKS 2 Bio 8C
Alternative
Assessment
GENERAL
Have students write review questions and answers for a trivia-type
game. Pair each student with a
partner, and have the students in
each pair take turns asking their
partner the questions.
LS Interpersonal
Chapter 30 • Arthropods
669
Section 2
Spiders and Other
Arachnids
Section 2
Focus
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. Section 2 describes the
characteristics of arachnids: spiders,
scorpions, ticks, mites, and daddy
longlegs.
Bellringer
Ask students to list what comes to
mind when they hear the word
“spider.” For homework, have
students determine whether their
preconceptions are accurate. For
example, if students list “poisonous” have them research which
spiders are poisonous. Are there
poisonous spiders in your state? If
students list words like “scary,”
have them clarify what characteristics of spiders make them scary and
have them determine the accuracy
of these characteristics.
Arachnid Modifications
Objectives
● Summarize the characteristics of arachnids.
8C TAKS 2
Perhaps no other group of animals is more disliked and feared by
humans than the arachnids—spiders, scorpions, ticks, mites, and
daddy longlegs. While it is true that some spiders and scorpions are
● Identify the internal and
external characteristics of TAKS 2 highly venomous, in general these creatures do more good than
harm. For example, many spiders are major predators of insect pests,
brown recluse spiders.
8C
and gardeners usually welcome them. Arachnids (uh RAK nihdz)
● Compare spiders, ticks, and
form the largest class in subphylum Chelicerata. Two minor classes,
mites.
8C TAKS 2
marine horseshoe crabs and sea spiders, also belong to this subphy● Identify the health threats
lum. The members of subphylum Chelicerata have mouthparts called
posed by some arachnids.
4D 11D chelicerae (kuh LIS uh ree) that are modified into pincers or fangs,
as shown in Figure 8.
TAKS 3
Key Terms
The arachnid body is made up of a cephalothorax and an
chelicera
abdomen. There are no antennae, and the first pair of appendages
pedipalp
are chelicerae. The second pair of appendages are pedipalps , which
spinneret
are modified to catch and handle prey. (The pedipalps are sometimes
specialized for sensory or even reproductive functions.) Following
the pedipalps are four pairs of appendages called walking legs.
All arachnids except some mites are carnivores, and most are terrestrial. Since arachnids do not have jaws, they are able to consume
only liquid food. To do so, the arachnid first injects its prey with
powerful enzymes that cause the prey’s tissues to liquefy. Then the
arachnid sucks the liquid food into its stomach.
Spiders
TAKS 1 Bio/IPC 2C, 2D
Motivate
Activity
Poisonous Spiders Have students
search the library or an on-line database for information about poisonous spiders around the world, such
as the Australian funnel-web spider,
whose bite can be lethal if left
untreated. Have students make a
pamphlet describing the spider and
its habitat, the symptoms caused by
the spider’s bite, and the measures
a person should take if bitten. LS
Verbal TAKS 1 Bio/IPC 2C, 2D
Figure 8 Chelicerae. The
baboon spider’s pointed black
chelicerae (fangs) and its two
pair of pedipalps are clearly
seen in this close-up of its
head region.
The chelicerae of spiders are modified into fangs.
Poison glands located in the spider’s anterior end
secrete a toxin through these fangs. The toxin kills or
paralyzes the prey. The spider then injects enzymes
into the prey that digest its tissues, and the spider
sucks up the liquid food. Spiders are important
predators of insects in almost every terrestrial
ecosystem. Only two species of spiders living in the
United States, the black widow and brown recluse,
are dangerous to humans. Not all spiders build
beautiful webs as the orb-builders do. Most spiders can secrete
sticky strands of silk from appendages called spinnerets located at
the end of the abdomen. Tubes located on some spinnerets do not
produce silk. Instead, they excrete a sticky substance that the spider
can use to make some silk strands adhesive.
670
Chapter Resource File
pp. 670–671
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 4D
TAKS Obj 3 Bio 7B
TEKS Bio 4D, 7B, 8C, 10A, 11D
Teacher Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 4D, 7B
TEKS Bio 4D, 7B, 8C, 10A, 11D
TEKS Bio/IPC 2C, 2D
670
Chapter 30 • Arthropods
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
Planner CD-ROM
• Reading Organizers
• Reading Strategies
Transparencies
TT Bellringer
TT Anatomy of a Spider
Up Close
Up Close
Brown Recluse Spider
TAKS 2
(Violin Spider)
Brown Recluse Spider
TAKS 2 Bio 8C, 10A; TAKS 3 Bio 7B
TAKS 3
●
Scientific name: Loxosceles reclusa
●
Size: Length of females, up to 10 mm (0.5 in.); males are smaller
●
Range: South-central United States, from central Texas to
Alabama, north to southern Ohio
●
Habitat: Dark, dry sheltered sites outdoors or indoors
●
Diet: Small insects
Teaching Strategies Have
students look up the word
recluse in a dictionary. (A
recluse is one who lives in seclusion or isolation.) Explain that
during the day, brown recluses
hide in corners or other dark
areas, such as old boxes that
are seldom opened. They are
active at night. Caution students that if they live in an area
where brown recluses live, they
should wear gloves when they
clean out an area that has been
left undisturbed for some time.
Characteristics
Cephalothorax Six eyes, in pairs, form a
semicircle around the front of the cephalothorax. Two chelicerae and two pedipalps are
located next to the mouth. Four pairs of walk-
Abdomen The abdomen
Reproduction During mating,
contains most of the spider’s
organs. Spinnerets located
here are used to spin small,
the male uses its pedipalps
modified into sperm storage
organs to insert sperm into the
ing legs attach to the cephalothorax, which is
marked on top with a distinctive violin shape.
irregular webs.
female’s body. The female lays
an average of 20–50 eggs inside
a silk cocoon that she spins and
hangs in her web.
Brain
Walking leg
Stomach
▲ Ovary
Gut
Heart
Digestive gland
Malpighian
tubule
Simple eyes
Pedipalp
Anus
Chelicera
▼ Poison gland
Genital
opening
Mouth
Silk glands
Spinnerets
Poison gland Poison
glands are connected to the
▼ Book lung
fanged chelicera. The venom
of the brown recluse is
harmful to many humans.
The severity of a person’s
reaction depends on the
individual’s sensitivity and
how much venom is injected.
Respiration Book lungs contain stacks
of thin blood-filled plates of tissue. Air enters
the book lungs through slits on the underside of the spider’s abdomen and passes
over them. Blood flowing through the plates
Air flow
picks up oxygen by diffusion.
671
did you know?
Spider Silk All spiders have silk glands and
organs called spinnerets that spin the silk. Some
spiders spin webs that are used to catch prey.
Others may use webs to protect their eggs and
young. Spiders do not discard their old webs but
eat them to recycle the protein in them. Spiders
also use silk to wrap up prey, or they spin sticky
balls to throw at prey. Burrow-dwellers line
their underground homes with silk. Bio 12C
Explain that many spiders spin
at least two varieties of silk
threads. Dry threads are used
to form the web’s radial framework; sticky threads are
arranged in a spiral around the
radial threads. Ask students
what advantage a spider gains
by spinning both dry and
sticky threads. (Spiders avoid
becoming trapped in their own
webs by walking on the dry
radial threads.)
Discussion
• Ask students what the
adaptive advantage of venom
production might be in bees,
ants, scorpions, spiders, and
centipedes. (Bees and ants use
venom for defense. Scorpions,
spiders, and centipedes use
venom to capture prey.)
• Look at the art showing the
interior of the spider. What
structures are present that
are characteristic of arthropods in general? (jointed
appendages, open circulatory
system, Malpighian tubules,
book lungs)
• What characteristics of
arachnids are present?
(pedipalps, chelicerae)
Chapter 30 • Arthropods
671
Scorpions and Mites
Teach, continued
continued
SKILL
BUILDER
www.scilinks.org
Topic: Mites and Disease
Keyword: HX4123
GENERAL
Scorpions
Scorpions have long, slender, segmented abdomens that end in a
venomous stinger used to stun their prey. The stinger-tipped
abdomen is usually folded forward over the rest of the scorpion’s
body, a trait that makes scorpions instantly recognizable. The pedipalps of scorpions are large, grasping pincers, which are used not
for defense but for seizing food and during sexual reproduction.
Vocabulary Arachnids are named
for Arachne, a weaver in Greek
mythology. Arachne boastfully
challenged the goddess Athena to a
weaving contest. Arachne produced
a beautiful tapestry. Athena was so
enraged by Arachne’s skill that she
changed Arachne into a spider.
Mites
Mites are by far the largest group of arachnids. Some mites, including chiggers and ticks, are well known to humans because of their irritating bites. They are easily recognizable because their head, thorax,
and abdomen are fused into a single, unsegmented body. Most adult
mites, such as the one shown in Figure 9, are quite small, typically less
than 1 mm (0.04 in.) long, but ticks grow larger. Many aquatic mites
are herbivores, while terrestrial mites are usually predators.
Most mites are not harmful, but some are plant and animal pests.
While feeding, plant mites may pass viral and fungal infections to
the plant. Blood-sucking ticks attach themselves to a host, often a
human. Lyme disease is spread by bites from infected deer ticks,
like the one shown in Figure 9.
LS Verbal
Close
Reteaching
Have students create crossword
puzzles using the vocabulary terms
in this section. Then have them
trade puzzles and try to solve them.
LS Verbal TAKS 1 Bio/IPC 2D
Quiz
Two other familiar groups of arachnids are scorpions and mites.
Like spiders, they have chelicerae and pedipalps, but these structures are modified differently.
GENERAL
1. Define the term “chelicerae.”
(Chelicerae are arachnid mouthparts that are modified into fangs
or pincers.) Bio 5A
2. Explain the meaning of the following statement: All arachnids
except some mites are carnivores. (The statement means that
most arachnids feed on animals,
not on plants.) TAKS 1 Bio/IPC 2C, 2D
Figure 9 Mites. The house
dust mite is a major cause of
allergies in humans. The bite
of an infected deer tick can
cause Lyme disease.
Dust mite
Deer tick
Section 2 Review
Compare the body plan of spiders, scorpions,
Alternative
Assessment
Have students write an essay on
arachnids, highlighting the organism
they think is the most fascinating
and explaining why. LS Verbal
TAKS 1 Bio/IPC 2C, 2D
and mites, including differences in appendages.
Describe the body and coloring of a brown
recluse spider.
Critical Thinking Evaluating Conclusions
8C
Is an animal that has grasping pincers, a segmented body, and two antennae correctly identified
8C
as a scorpion? Why or why not?
8C
Critical Thinking Summarizing Information
Explain why a tick bite is more a cause for concern
4D 11D
than the bite of most spiders.
672
TAKS Test Prep The relationship between a
tick and a dog is an example of
12B
A homeostasis.
C commensalism.
B parasitism.
D mutualism.
Answers to Section Review
pp. 672–673
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 4D
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 12B
TEKS Bio 4D, 7B, 8B, 8C, 11D, 12B
Teacher Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 4D, 12B
TEKS Bio 4D, 5A, 8C, 11D, 12B
TEKS Bio/IPC 2C, 2D
1. Spider—fangs modified from chelicerae; pedipalps; two segments (cephalothorax and
abdomen). Scorpion—stinger; pedipalps modified into pincers; long, slender, segmented body.
Mite—chelicerae and pedipalps; head, thorax,
and abdomen fused into one TAKS 2 Bio 8C
2. They are up to 10 mm in length, dark brown,
with a violin shape on their cephalothorax.
TAKS 2 Bio 8C
3. Only two spiders in the United States are poisonous to humans. In contrast, many ticks
transmit diseases, such as Lyme disease and
Rocky Mountain spotted fever.
TAKS 3 Bio 4D; Bio 11D
672
Chapter 30 • Arthropods
4. The identification is not correct. Scorpions
have no antennae. TAKS 2 Bio 8C
5.
A. Incorrect. Homeostasis is the
maintenance of stable internal conditions in
spite of changes in the external environment.
B. Correct. Parasitism is a relationship in
which one organism feeds on another.
C. Incorrect. Commensalism is a relationship
in which one organism benefits and the other
is neither harmed nor helped. D. Incorrect.
Mutualism is a relationship in which both
organisms benefit. TAKS 3 Bio 12B
Insects and Their
Relatives
Section 3
Section 3
Focus
Overview
Insect Diversity
Objectives
● Describe the characteristics of insects.
8C TAKS 2
Anyone who has ever been on a picnic in a wooded area does not
have to be told that insects are numerous. Ants, mosquitoes, gnats,
flies, bees, crickets—they all want to join in while the cicadas sing in
the background. These animals all belong to the arthropod subphylum Uniramia, an enormous group of mostly terrestrial arthropods
that have chewing mouthparts called mandibles (jaws). Uniramians
consist of three classes: Insecta (insects), Diplopoda (millipedes),
and Chilopoda (centipedes).
The insects are by far the largest group of organisms on Earth,
with more than 700,000 named species. Most scientists agree
that there may be several million insect species in existence, with
most of the undiscovered species living in the tropics. As shown
in Figure 10, more than 50 percent of all named animal species
are insects. More than 90 percent of these species belong to
one of the four orders shown in Table 1. To read about other orders
of insects, see “A Six-Kingdom System of Classification” in the
Appendix of this book.
● Compare complete and incomplete metamorphosis.
● Identify the external and internal structures of the Eastern
Lubber grasshopper.
8B
● Compare millipedes and
centipedes with insects.
Bellringer
mandible
metamorphosis
chrysalis
pupa
nymph
caste
Figure 10 Species of insects
Table 1 Four Orders of Insects
Fungi
Coleoptera
ra
p te
Coleoptera
“shield winged”
Beetles,
weevils
350,000
Protis
All
ts
oth
er
s
Ve
p
rte ecies
br
at
es
Diptera
“two winged”
Flies,
mosquitoes
120,000
Lepidoptera
“scale winged”
Butterflies,
moths
120,000
Hymenoptera
“membrane
winged”
Ants,
wasps,
bees
100,000
ol
lu
sk
eno
Flowering
plants
s
s
der
Spi
Hym
Number of
species
Examples
M
a
er
pt
o
d
pi
Le
Other insects
Diptera
Millipedes,
centipedes
TT
TT
TT
TT
Bellringer
Four Orders of Insects
Insect Mouthparts
Complete and Incomplete
Metamorphosis
TT Anatomy of a Grasshopper
Prepare a handout for students
with the following facts: There are
more arthropod species than all
other animal species combined.
Eighty-five percent of all animals
are arthropods. Arthropods are our
main competitors for food. If left
unchecked (by nature), they could
take over the world. There are 200
million insects for every human on
Earth. Insects destroy 10–15 percent of the world’s food supply
each year. Insects have been on
Earth for approximately 300 million years. Bush crickets have ears
on their knees. Have the students
read the facts while you take attendance, then ask students which fact
was the most interesting to them
and why. TAKS 1 Bio/IPC 2C, 2D
Motivate
Identifying
Preconceptions
673
Transparencies
TAKS 2 Bio 8C
Key Terms
The predominance of insects, especially beetles (Coleoptera), in the living world
is illustrated by the blue section of this pie chart.
Order
Before beginning this section
review with your students the
objectives listed in the Student
Edition. Section 3 describes the
general body plan and life cycles of
insects. Then, after discussing
insect flight and the social insects,
Section 3 includes the centipedes
and millipedes, members (with the
insects) of the Subphylum Uniramia.
Chapter Resource File
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
• Data Sheet for Data Lab
GENERAL
Planner CD-ROM
GENERAL
People use the terms “insects” and
“bugs” freely to refer to many
organisms, some of which are not
insects. Ask students to list 5
organisms that they think are
insects. Then have students compare the characteristics of the
organisms they listed with those of
insects. Have students determine
whether or not the organisms on
their lists are truly insects.
TAKS 1 Bio/IPC 2C, 2D; TAKS 2 Bio 8C
• Reading Organizers
• Reading Strategies
• Supplemental Reading
Journey to the Ants
Chapter 30 • Arthropods
673
Insect Body Plan
Teach
Demonstration
Bring examples of live or preserved
insects to class for display, or bring
detailed photographs of insects
from a nature magazine. Allow students to compare the animals. Ask
them to point out examples of the
arthropod characteristics. (jointed
appendages, segmentation, exoskeleton, wings, spiracles, etc.) LS Visual
Organizing Information
The numbered list on this
page lists three important
characteristics of insects.
Use this information to draw
a concept map that summarizes insect characteristics.
1. Head. Located on an insect’s head are mandibles, specialized
mouthparts, and one pair of antennae. The mandibles and mouthparts of different insect species are adapted for eating different
foods, as shown in Figure 11. In addition, an insect’s head usually
has a relatively large pair of compound eyes and a pair of antennae.
Like the mouthparts, antennae vary greatly in size and shape.
2. Thorax. The thorax is composed of three fused segments.
Attached to the thorax are three pairs of jointed walking legs.
Some insects, such as fleas, lice, and silverfish, lack wings, but
other adult insects have one or two pairs attached to the thorax.
TAKS 1 Bio/IPC 2C, 2D; TAKS 2 Bio 8C
Using the Figure
Use Figure 12 to point out how the
mouthparts of different insects are
adapted for different functions.
Grasshoppers cut and chew their
food, mosquitoes puncture skin to
draw out blood, and flies soak up
fluids with their mouthparts.
Insects are primarily a terrestrial group, and aquatic insects probably had terrestrial ancestors. Although the great majority of insects
are small (some are only a few centimeters in length), others are
much larger. The African Goliath beetle, for example, exceeds 10
cm (4 in.) in length. Generally, the larger insects live in tropical
areas. Despite great variation in their size, all insects share the
same general body plan, made up of three body sections.
3. Abdomen. The abdomen is composed of 9 to 11 segments. In
adult insects, there are no wings or legs attached to the abdomen.
Turn the facing page to learn more about one particular insect,
the grasshopper, in Up Close: Eastern Lubber Grasshopper.
Figure 11 Insect mouthparts
The mouthparts of the different insect species are adapted for different functions.
LS Visual TAKS 2 Bio 6D (grade 11 only);
TAKS 3 Bio 7B; Bio 8B
Teaching Tip
Jumping Fleas Dr. Miriam
Rothschild is a world-class entomologist and the world’s expert on
fleas. In 1977 she published a
paper giving the first description of
the flea’s jumping mechanism.
Using high-speed photography that
records 10,000 frames per second,
Dr. Rothschild concluded that a
flea’s ability to leap is equivalent to
a human jumping over a tower
30,000 times before exhaustion sets
in. She also found that a jumping
rabbit flea has 230 times more
acceleration than a spacecraft reentering the Earth’s atmosphere after
a trip to the moon.
TAKS 5 IPC 4A; Bio 3F
Mandible
Mandible
Mandible
Grasshopper
(adapted for biting and chewing)
Mosquito
(adapted for piercing and sucking)
Fly
(adapted for sponging and lapping)
674
Career
pp. 674–675
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B
TEKS Bio 7B, 8C
Teacher Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 2 Bio 6D, 8C
TAKS Obj 3 Bio 7B
TAKS Obj 5 IPC 4A
TEKS Bio 3D, 3F, 6D, 7B, 8B, 8C
TEKS Bio/IPC 2C, 2D
674
Chapter 30 • Arthropods
Forensic Entomologist Maggots crawling
out of eye sockets are usually the stuff of horror films. But to forensic entomologists,
insects and cadavers are part of their work.
Forensic entomology is the science of using
insect evidence to determine information
related to a crime. By using insect evidence
gathered from and around a corpse, a forensic
entomologist can determine approximate time
and location of death and may help provide
information in investigations of sudden death,
traffic accidents with no obvious cause, and
possible criminal misuse of insects. Most
forensic entomologists hold the Ph.D. degree.
However, a student with a BS degree and a
major in entomology would be qualified for a
position as a research assistant, technician, or
staff member in a research laboratory. Bio 3D
Figure 12 Complete
metamorphosis. A complete
metamorphosis includes a
pupa stage, which is passed
inside a chrysalis.
Egg
Silk Encourage students to
research the history of the discovery of silk. The Chinese were the
first to produce silk fabrics, and for
about 3,000 years, they were the
only people who knew how to cultivate silkworms. Chinese legends
colorfully tell of the discovery of
silk by Emperor Huangdi’s wife in
about 2700 B.C. Have students
create a poster or diorama of the
history of silk. Bio 3F
Adult
Adult emerging
from chrysalis
Young
larva
Older
larva
Teaching Tip
Pupa in chrysalis
Teaching Tip
Metamorphosis Ask students to
compare complete and incomplete
metamorphosis in a Graphic
Organizer similar to the one at the
bottom of this page. Students may
use either generalizations or specific insects in their comparisons.
Insect Life Cycle
The life cycles of most insects are complex, and often several molts
are required before the adult stage is reached. During the last
molt, the young insect undergoes a dramatic physical change called
metamorphosis .
Complete Metamorphosis Almost all insect species undergo
“complete” metamorphosis, as shown in Figure 12. In complete metamorphosis, the wingless, wormlike larva encloses itself within a
protective capsule called a chrysalis (KRIHS uh lihs). Here, it passes
through a pupa stage, in which it changes into an adult.
A complete metamorphosis is a complex life cycle. The larvae
can, however, exploit different habitats and food sources than
adults. For example, the larvae of
nectar-drinking butterflies are caterpillars that eat leaves! This ecological
separation of young from adults elimiAdult
nates competition. This increases the
chance of survival for each phase of
the life cycle.
LS Visual TAKS 1 Bio/IPC 2C, 2D
Figure 13 Incomplete
metamorphosis. The nymph
passes through several molts
before it becomes an adult.
Eggs
Incomplete Metamorphosis A smaller
number of species develop into adults
in a much less dramatic incomplete
metamorphosis, as shown in Figure 13.
In these species, the egg hatches into a
juvenile, or nymph (NIHMF), that
looks like a small, wingless adult. After
several molts, the nymph develops into
an adult.
SKILL
BUILDER
GENERAL
Interpreting Visuals Tell students
that each visual in Figures 12 and
13 depicts a cycle. Since there is no
beginning or end in a cycle, the student may choose any point to begin
analyzing the cycle. However, when
comparing two cycles, tell students
to choose an equivalent point in
each to begin, such as the adult, to
make the comparison easier.
TAKS 1 Bio/IPC 2C, 2D
Nymph
Nymph
Nymph
675
Graphic Organizer
Use this graphic organizer with Teaching
Tip: Metamorphosis on this page.
Complete metamorphosis
Egg
Incomplete metamorphosis
Egg
Larva
Pupa
Nymph
Adult
Adult
Chapter 30 • Arthropods
675
Up Close
Up Close
Eastern Lubber
Grasshopper TAKS 1; TAKS 2; TAKS 3
Eastern Lubber
Grasshopper TAKS 1 Bio/IPC 2C, 2D;
TAKS 2 Bio 8C, 10A;
TAKS 3 Bio 7B
Scientific name: Romalea microptera
●
Size: 5 cm (2 in.) to 6.5 cm (2.6 in.) in length
●
Range: Eastern United States
●
Habitat: Fields and meadows
●
Diet: Grasses and other leafy vegetation
External Structures
Antenna
Thorax The thorax is composed of
Head Two antennae contain
three fused segments, each with a pair
of legs. The front two pairs are walking
legs. The rear pair is larger jumping legs.
sense organs for touch and smell.
On each side of the head is a very
large compound eye. Located
During mating season, males “sing” to
potential mates by rubbing a row of pegs
on a jumping leg against ridges on
a forewing.
high on the forehead are three
light-detecting ocelli.
Compound
eye
▼
▼
Teaching Strategies Have
students look up grasshoppers
in field guides that are used for
insect identification. Ask them
to compare the external structures of the eastern lubber
grasshopper with those of
other grasshoppers. (The eastern lubber grasshopper is a
short-horned grasshopper. Longhorned grasshoppers, such as
katydids and Mormon crickets,
have long, threadlike antennae.)
Ask students to list the parts of
the digestive system that help
to physically break down food
as well as the parts that chemically break down food.
(Physical digestion is performed
by the labrum, labium,
mandible, maxilla, and gizzard.
Chemical digestion is performed
by the midgut and coelom.)
●
Ocellus
Head
Thorax
Labrum
Mandible
Maxilla
Wings Grasshoppers
have a pair of leathery
forewings that protect the
more delicate flying wings.
Labium
▲ Forewing
▼ Mouthparts
Mouthparts The stiff
upper labrum and lower
▲ Flying wing
Walking
leg
Jumping leg
Abdomen
Ovipositor
labium (lips) hold a leaf or
blade of grass in place while
the mandibles (jaws), assisted
by maxillas (graspers), tear
off pieces of the plant.
▼ Spiracles
Spiracles Spiracles admit air to the
extensively branching system of tracheae
that deliver oxygen throughout the body.
676
pp. 676–677
Student Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 7B
TEKS Bio 7B, 8C, 10A
TEKS Bio/IPC 2C, 2D
Teacher Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 7B
TEKS Bio 3F, 5A, 7B, 8C, 10A, 11B
TEKS Bio/IPC 2C, 2D
TEKS IPC 8E
676
Chapter 30 • Arthropods
Romance and the Grasshopper Almost
everyone knows that grasshoppers produce
sounds that resemble chirping “songs.” But
most people don’t know that it is generally
male grasshoppers that play these songs as part
of their courtship behaviors. They generally
have a repertoire of three. The male grasshopper’s initial song attracts the female, and
when a female comes close, the male plays a
more “intimate” melody. However, when
another male is close by and competing for
the female, the male plays the rivalry song.
Some females play no songs in response, while
the females of some species respond with short
bursts of song. Bio 11B
Internal Structures
Up Close
Reproductive system The
female collects the male’s sperm in
a storage pouch called a seminal
receptacle. Later, the female digs a
Eastern Lubber
Grasshopper
Circulatory system A long blood
vessel with a series of muscular “hearts”
runs along the grasshopper’s back. Blood
is pumped out of the open system and
hole using two pairs of pointed
ovipositors. As she releases the
eggs into the hole, they are
fertilized by the stored sperm.
bathes the body tissues directly before
returning to the heart.
▲ Dorsal blood vessel
Brain
Hearts
▲ Seminal receptacle
Flying wing
Mouth
Salivary
gland
Midgut
Gizzard
Anus
▼ Crop
Ganglia
Malpighian
tubules
▼ Nerve cord
Nervous system The nervous system is
composed of a major ventral nerve cord with
ganglia located in each body segment. Three
fused ganglia in the head serve as the brain.
Digestive system Chewed
food enters a storage pouch
called a crop and passes to the
gizzard, where it is shredded
and crushed. Food is digested in
the midgut, and food molecules
pass through the midgut wall
into the fluid of the coelom.
This fluid eventually enters the
circulatory system.
677
did you know?
Silk is an agricultural product. Today, silk
is made with cultivated silkworms, usually
caterpillars of the species Bombyx mori. The
silk-making process begins as the female lays
300 to 500 eggs on special paper provided by
silk farmers. The eggs develop into larvae.
When the silkworm larvae are ready to begin
metamorphosis, they spin a cocoon made of one
continuous silk thread, in which they will
Discussion
• How do grasshopper eyes
make it almost impossible to
sneak up on this insect?
(Grasshoppers have compound
eyes on each side of their head
and three light-detecting ocelli
on their forehead.)
• How can you tell that this
grasshopper is a female from
its external structures? (This
grasshopper has ovipositors,
which are used to deposit fertilized eggs.)
• What structures do grasshoppers use to move slowly?
How do they make quick
escapes? (Grasshoppers use
their walking legs to move
slowly. When they need to
escape quickly, they use their
jumping legs or wings.)
• What are the three main
sections of a grasshopper’s
body, and what is a major
body function that occurs in
each section?
(The grasshopper has a head,
a thorax, and an abdomen.
Touching, smelling, seeing,
and chewing occur in the head;
walking and jumping occur in
the thorax; and respiration,
reproduction, and excretion
occur in the abdomen.)
• What would happen if every
grasshopper were to freeze
during a cold winter? (The
species would continue to survive because grasshopper eggs
stay dormant in winter and
hatch in the spring.)
develop into a pupa and from which they will
emerge as a moth. Silk farmers do not allow
most pupas to become moths, because a moth
will shatter the silk cocoon as it leaves. Instead,
farmers kill most pupae and process the silk
cocoons. First the cocoon is unwound. Then
several processes strengthen the threads. Finally,
the thread is dyed and woven into fabric.
Bio 3F, 5A; IPC 8E
Chapter 30 • Arthropods
677
Flight
Teach, continued
continued
TAKS 1 Bio/IPC 2C, 2D; TAKS 3 Bio 12B
Skills Acquired
Reading graphs, interpreting information
Teacher’s Notes
Ask students to name all the
pesticides they can. Discuss
the problems associated with
their use.
Figure 14 Insect flight.
This stop-action series shows
how this insect’s wings move
during flight.
Answers to Analysis
1. Populations were stable during
the first 4 years. Both populations cycled between the same
high and low values each year.
2. As the population of the beneficial species increases, pest
numbers decrease, and vice
versa.
3. The number of beneficial species
and insect pests decreased. The
pest population eventually
recovered and further increased.
The beneficial species population did not recover.
4. Before the application of pesticide, the pest population
reached an annual maximum
of about 6,000 per hectare.
After the pesticide application,
the pest population rose to
10,000 per hectare.
5. Answers will vary.
Analyzing the Effects of Pesticide Use
2C 2D 12B
TAKS 1, TAKS 3
Background
0100010110
011101010
0010010001001
1100100100010
0000101001001
1101010100100
0101010010010
In nature, insect pests are usually kept in balance by the presence of predators, including
other insects. The use of some pesticides can upset this balance, as shown in the graph
below. Examine the graph, and answer the analysis questions.
Analysis
1. Identify the years during which the
two insect populations appear to
maintain stability in relation to each
other. Justify your answer with data
from the graph.
2. Describe the relationship between
the two insect species before year 4.
3. Describe the changes in the two
populations after the use of a pesticide.
4. Compare the annual changes
in population size of the pest
species before and after the use
of a pesticide.
5. Critical Thinking Developing
Hypotheses Propose a hypothesis
that might explain the dramatic
changes that occur in the insect populations after the use of pesticides.
Changes in Two Insect Populations
Insect pest
Population size (1,000s per acre)
0100010110
011101010
0010010001001
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0000101001001
1101010100100
0101010010010
Analyzing the
Effects of
Pesticide Use
Insects were the first animals to have wings. For more than 100 million years, until flying reptiles appeared, insects were the only flying
organisms. Flight, illustrated in Figure 14, was a great evolutionary
innovation. Flying insects were able to reach previously inaccessible
food sources and to escape quickly from danger.
An insect’s wings develop from saclike outgrowths of the body
wall of the thorax. The wings of adult insects are composed entirely
of chitin, strengthened by a network of tubes called veins (which
carry air, not blood). In most insects, the power stroke of the wing
during flight is downward, and it is produced by strong flight
muscles. When at rest, most insects fold their wings over their
abdomen, but a few insects are unable to do this. Dragonflies, for
example, keep their wings outstretched when they rest beside a
pond. Most insects have two pairs of wings. A few groups of insects,
such as fleas and lice, are wingless.
In most insects only one pair of wings is functional for flight. In
some species, the second pair of wings serves another purpose. For
example, in grasshoppers and beetles, the forewings act as protective wing covers. In flies, the hindwings are modified into knoblike
structures that help control stability during flight.
Beneficial species
10
Pesticide
application
8
6
4
2
0
1
2
3
4
5
6
Time (years)
678
pp. 678–679
Student Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 12B
TEKS Bio 7B, 8B, 8C, 11B, 12B
TEKS Bio/IPC 2C, 2D
Teacher Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 7B, 12B
TAKS Obj 5 IPC 4A
TEKS Bio 7B, 8B, 8C, 10A, 11B, 12B
TEKS Bio/IPC 2C, 2D, 3C
TEKS IPC 4A
678
Chapter 30 • Arthropods
REAL WORLD
CONNECTION
IPC Benchmark Fact
GENERAL
Pest control Invite a pest-control authority
to class to discuss the problems and risks
associated with termites and other common
household pests, such as ants and cockroaches.
Ask the visitor to explain when such insects
are considered a hazard. Have students ask
questions about new methods used to control
pests and about how to avoid infestations.
Bio/IPC 3C
Review the concepts of work (work ⫽ force ⫻
distance) and power (power ⫽ power/time) by having
students calculate and compare the work and power
done in flight by two imaginary lacewings. For example, assume that during its flight lacewing A exerted a
force of 2 N over a distance of 10 m in 4 s while
lacewing B exerted a force of 3 N over a distance of
15 m in 10 s. Remind students that the joule (N-m) is
the work unit and watt (J/s) is the power unit. Ask students which lacewing did the most work and which
one had the highest power output. TAKS 5 IPC 4A
Social Insects
Two orders of insects, Hymenoptera (ants, bees, and
wasps) and Isoptera (termites), have elaborate social
systems. These insects often live in highly organized
societies of genetically related individuals. Within
these insect societies, there is a marked division of
labor, with different kinds of individuals performing
specific functions. The role played by an individual in
a colony is called its caste . Caste is determined by a
combination of heredity; diet, especially as a larva;
hormones; and pheromones, chemical substances
used for communication. In the termite colony shown
in Figure 15, for example, small, active members called workers
gather the food, raise the young, and excavate tunnels. Other, larger
termites, called soldiers, defend the colony with their immense jaws.
Both workers and soldiers are sterile. Reproduction is a function of
only the queen and king.
Teaching Tip
Figure 15 Termite colony.
Most of the members of this
termite colony are unable to
reproduce. The queen, with
her enormous abdomen, is
the egg-laying machine of
the colony.
Insect Relatives
Close
Centipedes and millipedes, shown in Figure 16, have similar bodies.
Each has a head region followed by numerous similar segments.
Each segment bears one or two pairs of legs. Centipedes have one
pair of legs per segment and can have up to 173 segments. Modern
millipedes have from 11 to 100 or more body segments, and most
millipede segments have two pairs of legs. While centipedes are
carnivores, most millipedes are herbivores.
Centipede
Millipede
GENERAL
Bees in Agriculture Tell students
that the widespread use of pesticide
sprays has resulted in the loss of
beehives. Have students discuss the
effects the loss of these hives might
have on consumers. (Because bees
are needed to pollinate many crops,
reduced agricultural production and
higher prices would result.) Tell students that some farmers have to rent
mobile beehives to pollinate their
crops. TAKS 1 Bio/IPC 2D; Bio/IPC 3C
Reteaching
Figure 16 Centipedes and
millipedes. Centipedes are
carnivorous predators, while
millipedes are herbivores that
feed on decayed vegetation.
Divide the class into four groups.
Write the name of each of the four
insect orders listed in Table 1 on
slips of paper. Have a representative from each group pick one of
the folded slips out of a bowl or
beaker, making sure they cannot
see the writing on the slips. Then
have each group ask questions of
the other groups about insects in
their order. The questions should
be phrased so that they can be
answered “yes” or “no.”
LS Interpersonal TAKS 1 Bio/IPC 2C, 2D;
TAKS 3 Bio 7B; Bio 8B
Quiz
Section 3 Review
GENERAL
1. List the structures usually found
Relate the Eastern Lubber grasshopper’s body
8B 8C
plan to that of a typical insect.
Compare the life cycles of grasshoppers and
butterflies.
Critical Thinking Forming Hypotheses
Based on the information given in Table 1, what
characteristic is key to determining an insect’s
8C
classification? Support your answer.
8B
Identify the distinguishing characteristics of
insects, millipedes, and centipedes.
8C
TAKS Test Prep A grasshopper’s antennae
10A 11B
contain sense organs for
A touch and smell.
C hearing and vision.
B smell and hearing.
D vision and touch.
679
Answers to Section review
1. The Eastern Lubber grasshopper has a body
plan like that of a typical insect. It has a head,
a thorax, and an abdomen; three pairs of
jointed legs; antennae; and an exoskeleton.
TAKS 2 Bio 8C; Bio 8B
2. Grasshoppers go through several nymph stages
during incomplete metamorphosis. Butterflies
go through complete metamorphosis, with egg,
larva, pupa, and adult stages. Bio 8B
3. Insects have three body sections, three pairs of
legs, and antennae; millipedes have many body
segments with two pairs of legs per segment,
and are herbivores; centipedes have many body
segments with one pair of legs per segment,
and are carnivores. TAKS 2 Bio 8C
4. Wings are the key characteristic in classification.
They are described for each class. TAKS 2 Bio 8C
5.
A. Correct. Two antennae
contain sense organs for touch and smell.
B. Incorrect. Grasshop-pers’ antennae contain
sense organs for touch but not hearing.
C. Incorrect. Grasshoppers see with compound
eyes, not their antennae. D. Incorrect.
Grasshoppers’ antennae contain sense organs
for touch, but they see with their compound
eyes. TAKS 2 Bio 10A; Bio 11B
on the insect head. (mandibles,
specialized mouth parts, and
antennae) TAKS 2 Bio 10A
2. What is the relationship between
insects and centipedes? (Insects
and centipedes are both arthropods in the Subphylum Uniramia.
However, they belong to different
Classes.) TAKS 2 Bio 8C
Alternative
Assessment
GENERAL
Collect a variety of images of
insects, centipedes, and millipedes
from nature magazines, the Web, or
other resources you may have. Have
students work in groups of three
and distribute the images equally
among the groups. Have students
develop twenty questions (and
answers) about their images. Using
their images and the questions they
developed, have groups quiz each
other. TAKS 1 Bio/IPC 2C, 2D;
TAKS 2 Bio 8C; TAKS 3 Bio 7B
Chapter 30 • Arthropods
679
Section 4
Section 4
Crustaceans
Focus
Crustacean Habitats
Objectives
Overview
Before beginning this section
review with your students the
objectives listed in the Student
Edition. Section 4 focuses on crustaceans. This section first describes
terrestrial crustaceans, such as pill
bugs, sow bugs, sand fleas, and
land crabs. Next, Section 4 discusses aquatic crustaceans, such as
crabs, lobsters, shrimps, and crayfish. The section ends with the story
of sessile crustaceans, the barnacles.
Bellringer
● Summarize how
crustaceans and insects are
similar and dissimilar.
8C
Just as insect species dominate on land, crustaceans abound in the
world’s oceans. Their great numbers have earned them the nickname “the insects of the sea.” Many are microscopic creatures that
TAKS 2 drift as plankton in the ocean currents. While primarily marine,
● Describe the body plan of
members of subphylum Crustacea are also found in fresh water and
decapods.
8C TAKS 2
in a few terrestrial habitats. Crustaceans include crabs, lobsters,
crayfish, shrimps, barnacles, water fleas (Daphnia), and pill bugs.
Key Terms
Almost all crustaceans have a distinctive larval form called a
nauplius
nauplius (NAW plee uhs). The nauplius, shown in Figure 17, has
krill
three pairs of branched appendages. Like insects, the nauplius
undergoes a series of molts before it takes on its adult form.
Adult crustaceans also have mandibles, as insects do. But crustaceans differ from insects in a number of important respects, as
summarized in Table 2.
Eye
Appendages
Terrestrial Crustaceans
Invite students to name as many
crustaceans as they can. If they
have difficulty, suggest that they
think about crustaceans they may
have seen in seafood restaurants
and aquaria. TAKS 1 Bio/IPC 2C, 2D
Motivate
Demonstration
GENERAL
Figure 17 Nauplius.
A microscopic, freeswimming nauplius larva is
a developmental stage of
almost all crustaceans.
Only a few crustacean groups have successfully invaded terrestrial
habitats. The most widespread group of terrestrial crustaceans is
composed of the pill bugs and sow bugs. They live among leafy
ground litter found in gardens and woods. Pill bugs and sow bugs
belong to a group called isopods and are the only crustaceans that
are truly terrestrial. Another group, the sand fleas, includes several
thousand species typically found along beaches. In addition, a few
species of land crabs live in damp areas. Land crabs are only partly
adapted to terrestrial living. They are active primarily at night,
when the air is more moist. Their life cycle is tied to the ocean,
where the larvae live until maturity.
Bring in a few crayfish in a bucket
for students to observe. Have students predict how the crayfish will
move if a stick is suddenly placed
in front of them. Students may be
surprised when the crayfish shoot
off backwards. Have students
observe the crayfish’s movements
for several minutes. LS Visual
TAKS 1 Bio/IPC 2C, 2D
Table 2 Comparison of Crustaceans and Insects
Characteristic
www.scilinks.org
Topic: Crustaceans
Keyword: HX4054
Crustaceans
Insects
Nature of
appendages
Most are branched
at the end
Unbranched
at the end
Antennae
Two pairs
One pair
Chewing
appendages
Usually three pairs
One pair
Location of
appendages
Cephalothorax
and abdomen
Head and abdomen
Respiration
Gills
Tracheal system
680
Chapter Resource File
pp. 680–681
Student Edition
TAKS Obj 2 Bio 8C
TAKS Obj 2 Bio 10A
TAKS Obj 3 Bio 7B
TEKS Bio 7B, 8C, 10A
Teacher Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 1 IPC 3A
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 7B, 12B
TEKS Bio 3A, 3F, 5B, 7B, 8C, 10A, 11D
TEKS Bio/IPC 2C, 2D
TEKS Bio/IPC 3A
680
Chapter 30 • Arthropods
• Lesson Plan GENERAL
• Directed Reading
• Active Reading GENERAL
• Data Sheet for Data Lab
• Data Sheet for Data Lab
Transparencies
TT Bellringer
TT Comparing Crustaceans and Insects
GENERAL
GENERAL
Planner CD-ROM
• Reading Organizers
• Reading Strategies
Aquatic Crustaceans
Crustaceans are a major food source for humans and
some animals. The members of some orders of crustaceans are quite small. Common are fairy shrimps,
water fleas, ostracods, and tiny copepods (KOH puh
pahds). Copepods are among the most abundant multicellular organisms on Earth and are a key food source in
the marine food chain. Another small marine crustacean,
Euphausia superba, swarms in huge groups and is known
by its common name, krill. Krill, shown in Figure 18, are
the chief food for many marine species.
Teach
Teaching Tip
Decapods
Large marine crustaceans such as shrimps, lobsters, and crabs,
along with the freshwater crayfish shown in Figure 19, have five
pairs of legs and are often referred to as decapods. Almost one
quarter of all crustaceans are decapods. The head and thorax of
decapods are fused into a single cephalothorax, which is covered on
top by a protective shield called a carapace.
In crayfish and lobsters, the anterior pair of legs are modified
into large pincers called chelipeds (KEE luh pehdz). Appendages
called swimmerets are attached to the underside of the abdomen
and are used in swimming and in reproduction. Flattened, paddlelike appendages called uropods are at the end of the abdomen.
Many decapods have a telson, or tail spine. Decapods can propel
themselves through the water by forcefully flexing their abdomen.
Figure 18 Krill. Found in
icy Antarctic waters, krill are
the favorite food of many
marine animals.
www.scilinks.org
Topic: Texas Crustaceans
Keyword: HXX4012
GENERAL
Health Some crabs have been
found to carry human parasites. In
Asia, freshwater crabs can carry
lung flukes, which can then be
transmitted to humans who eat the
crabs. In Africa, onchocerciasis, an
eye disease that is transmitted by
flies, is also carried on the backs of
river crabs, where the fly larvae
live. However, most decapods are
not harmful to people when they
are cooked properly. Students in
the United States are often unaware
of diseases that afflict people in
countries that do not have effective
public health systems. Encourage
students to find out more about
these parasitic diseases.
TAKS 1 Bio/IPC 2D; IPC 3A; Bio 3A, 11D
Figure 19 Crayfish
Like all decapods, the crayfish has five pairs of legs.
Relating Molting
to Mortality Rates
Antenna
Antennules
TAKS 1 BioIPC 2C, 2D; TAKS 3 Bio 7B, 12B
Cephalothorax
0100010110
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Cheliped
Abdomen
Teacher’s Notes
Have students infer what softshelled crabs are and when they
are most readily available in
restaurants.
Telson
Answers to Analysis
Swimmerets
Walking legs
Uropod
681
did you know?
How the fiddler crab got its name. The
male fiddler crab has one large cheliped
(pincer) and one small one. The male waves
its large cheliped back and forth, much like
playing a fiddle, when it is in the presence
of a female. Bio 3F
Skills Acquired
Reading graphs, applying information
MISCONCEPTION
ALERT
Pill Bugs Although their name implies
otherwise, pill bugs or potato bugs are
actually terrestrial crustaceans, not insects.
Pill bugs belong to the Order Isopoda (the
isopods). Whereas insects have three pairs
of legs and breathe with a system of tracheae, pill bugs have seven pairs of legs and
breathe with gills.
1. Most crabs die in April, May,
and June.
2. Most crabs molt in April, May,
and June.
3. During their molting season,
many crabs fall prey to predators and disease.
4. When the crabs molt, more
will die due to disease and
predation.
5. Answers will vary. Crabs are
fragile after molting and are
more susceptible to disease.
TAKS 1 Bio/IPC 2D; TAKS 2 Bio 8C
Chapter 30 • Arthropods
681
Sessile Crustaceans
Barnacles are a group of crustaceans that are sessile as adults.
Free-swimming larvae attach themselves to a rock, post, or some
other submerged object, where they remain. Hard plates that can
open and close protect the barnacle’s body. When feeding, barnacles
extend their jointed feeding appendages (legs) through the open
plates. Their feathery legs stir food from the water into the barnacles’
mouth. Unlike most crustaceans, barnacles are hermaphrodites.
However, they do not usually fertilize their own eggs.
Close
Reteaching
Show photographs of a lobster
and a water flea, and ask students
to identify the similarities and
differences. LS Visual
TAKS 2 Bio 8C; TAKS 3 Bio 7B
TAKS 1,
TAKS 3
During the soft-shell stage that follows molting, many crustaceans die of disease
or are eaten by predators. The bar graph below shows the percent mortality for
crabs over a 9-month period. Study the data, and answer the analysis questions.
Analysis
Molting and Mortality Data
20
15
10
5
molting crabs to the water.
How might the length of
time a molting crab is
exposed to air or how
Sept
Aug
July
0
May
4. Critical Thinking
Developing Hypotheses
Propose a hypothesis that
explains the relationship
between the percent of crabs
molting and mortality rates.
30
25
June
3. Describe the relationship
between the mortality rates
and molting periods of crabs.
In molt
Predation
April
2. Summarize what the
graph shows about molting
in crabs.
5. Critical Thinking
Making Predictions
Most states have laws that
require crab fishers to return
Disease
35
March
1. Summarize what the data
in the graph tell you about
crab mortality.
Feb
0100010110
011101010
0010010001001
1100100100010
0000101001001
1101010100100
0101010010010
Jan
True or False:
1. Pill bugs and sow bugs are terrestrial crustaceans, not insects.
(True) TAKS 2 Bio 8C
2. Lobsters and crabs are called
decapods because they have five
pairs of legs. (True) TAKS 2 Bio 8C
2C 2D 12B
Background
GENERAL
Molt and mortality data
(in percentage of population)
Quiz
Relating Molting to Mortality Rates
roughly a crab is handled
affect whether the crab
survives being caught
and released?
Section 4 Review
Compare the body plan of a crustacean with that
of an insect.
8C
Describe the external body plan of a decapod.
8C
Critical Thinking Making Predictions Pill
TAKS Test Prep Which structures are
adaptations of crustaceans to life in aquatic
biomes?
7B 12C
A antennae.
C walking legs.
B gills.
D mandibles.
bugs respire with gills. How might this affect the
11B
distribution of pill bugs in an ecosystem?
682
Answers to Section Review
pp. 682–683
Student Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B
TAKS Obj 3 Bio 12B
TEKS Bio 7B, 8B, 8C, 11B, 12B, 12C
TEKS Bio/IPC 2C, 2D
Teacher Edition
TAKS Obj 1 Bio/IPC 2C, 2D
TAKS Obj 2 Bio 8C
TAKS Obj 3 Bio 7B, 12B
TEKS Bio 7B, 8C, 11B, 12B, 12C
TEKS Bio/IPC 2C, 2D
682
Chapter 30 • Arthropods
1. Answers should summarize the information
given in Table 2 of this section. TAKS 2 Bio 8C
2. Decapods have antennae, pincers, a
cephalothorax with walking legs, and a
segmented abdomen. TAKS 2 Bio 8C
3. You would most likely find pill bugs only in
moist environments. Bio 11B
4.
A. Incorrect. Antennae work
well in terrestrial environments, sensing touch
and smell. B. Correct. Gills allow organisms to
breathe in water. C. Incorrect. Walking legs
work well in terrestrial environments and are
not very useful in aquatic environments.
D. Incorrect. Mandibles work equally well
in terrestrial and aquatic environments.
TAKS 3 Bio 7B; Bio 12C
Study
CHAPTER HIGHLIGHTS
ZONE
Key Concepts
Alternative
Assessment
Key Terms
1 Features of Arthropods
Section 1
●
appendage (664)
thorax (666)
cephalothorax (666)
compound eye (666)
molting (668)
trachea (668)
spiracle (668)
Malpighian tubule (669)
●
●
All arthropods have a coelom, a segmented body, and
jointed appendages that are modified to perform different
functions.
Arthropods have an exoskeleton made of chitin, which they
discard periodically in a process called molting.
Arthropods are grouped into three subphyla: Chelicerata,
Uniramia, and Crustacea.
2 Spiders and Other Arachnids
Section 2
●
chelicera (670)
pedipalp (670)
spinneret (670)
●
●
●
Members of subphylum Chelicerata have mouthparts, called
chelicerae, that are modified into fangs or pincers.
Spiders have a head and a cephalothorax, no antennae, six
or eight pairs of simple eyes, a pair of fangs and pedipalps,
and four pairs of walking legs.
Scorpions have pedipalps modified into large, grasping
pincers. A stinger is located at the end of their abdomen.
Mites have body parts that are fused to form an unsegmented body. Many mites transmit diseases.
• Science Skills Worksheet GENERAL
• Critical Thinking Worksheet
• Test Prep Pretest GENERAL
• Chapter Test GENERAL
Section 3
●
mandible (673)
metamorphosis (675)
chrysalis (675)
pupa (675)
nymph (675)
caste (679)
●
●
4 Crustaceans
Section 4
●
nauplius (680)
krill (681)
●
●
Crustaceans have a distinctive larval form called a nauplius.
Copepods and krill, which are tiny marine crustaceans, are
the chief food of many marine species.
Most crustaceans have branched appendages, two pairs of
antennae, three chewing appendages, walking legs attached
to the thorax, and gills. Like insects, crustaceans have jaws
called mandibles.
Have students construct concept
maps that show the similarities and
differences among the following
arthropods: arachnids, insects,
millipedes and centipedes, and
crustaceans. TAKS 2 Bio 8C; Bio 8B
Chapter Resource File
3 Insects and Their Relatives
Insects make up more than half of all named animal
species.
All insects have a body plan with three body sections (head,
thorax, and abdomen), three pairs of legs (all attached to
the thorax), and one pair of antennae.
The life cycles of insects are complex and involve a process
of change called metamorphosis, during which larvae
change into the adult insects.
GENERAL
683
Answer to Concept Map
The following is one possible answer to
Performance Zone item 15.
Arthropods
develop through
egg
tracheae
incomplete
metamorphosis
complete
metamorphosis
with
with
nymph
adult
egg
larva
is a
nauplius
in
crustaceans
body regions fuse
forming a
breathe
using
spiracles
cephalothorax
with modified
pupa
adult
develops
within a
appendages
such as
pedipalps
chelicerae
chrysalis
Chapter 30 • Arthropods
683
Performance
CHAPTER REVIEW
ZONE
CHAPTER 30
ANSWERS
Using Key Terms
Using Key Terms
9. In
a.
b.
c.
d.
1. The chief organ of excretion in insects
1. a TAKS 2 Bio 10A
2. b TAKS 3 Bio 7B
3. c TAKS 2 Bio 8C
4. b TAKS 2 Bio 10A
5. a. The cephalothorax is the headchest region of an arthropod;
the exoskeleton is the hard
outer covering of an arthropod.
b. Tracheae are breathing tubes;
spiracles are breathing holes in
the exoskeleton.
c. Pedipalps catch and handle
prey; spinnerets make silk.
d. Chelicerae are mouthparts of
arachnids; mandibles are
mouthparts of uniramians and
crustaceans.
Understanding Key Ideas
6. c Bio 8B
7. c TAKS 2 Bio 8C
8. d TAKS 3 Bio 7B
9. c TAKS 2 Bio 8C
10. a TAKS 2 Bio 8C
11. d TAKS 2 Bio 8C; Bio 8B
12. b TAKS 2 Bio 8C
13. a TAKS 3 Bio 12B, 12E; Bio 12D
14. Monarch butterflies use either the
direction of the sun or the Earth’s
magnetic field to navigate during
migration. Bio 11B
15. The answer to the concept map is
at the bottom of page 701.
is the
10A
a. Malpighian tubule.
b. pedipalp.
c. nephridium.
d. spiracle.
10. Which of the following sequences shows a
2. In spiders, chelicerae are modified into
a. spinnerets.
c. legs.
b. fangs.
d. antennae.
3. Spinnerets are located on the spider’s
a. thorax.
c. abdomen.
b. cephalothorax. d. pedipalps.
complete metamorphosis?
8C
a. egg → larva → pupa → adult
b. egg → larva → adult
c. egg → young juvenile → older juvenile
d. egg → pupa → winged juvenile → adult
7B
8C
11. Millipedes and centipedes differ in that
millipedes
8B 8C
a. are terrestrial and segmented.
b. have one pair of legs on each segment.
c. have poisonous fangs.
d. are herbivores.
4. Insects respire through structures
called
10A
a. book lungs.
b. spiracles.
adult insects
8C
the abdomen has wings.
there are two pairs of antennae.
the legs are attached to the thorax.
the first appendages are chelicerae.
c. gills.
d. ganglia.
12. Which of the following is not a
5. For each pair of terms, explain the differ-
ences in their meanings.
a. cephalothorax, exoskeleton
b. tracheae, spiracles
c. pedipalps, spinnerets
d. chelicera, mandible
crustacean?
a. lobster
b. scorpion
animals on Earth because they are
12B 12D 12E
a. a critical link in the marine food chain.
b. found in both the ocean and fresh water.
c. accomplished predators.
d. easier to collect and study than other
arthropods.
6. What evidence suggests that arthropods
14.
Why is Earth’s magnetic
field important to Monarch
butterflies?
11B
15.
Concept Mapping Construct a
concept map that outlines the three major
groups of arthropods and that gives the
characteristics for each group. Try to
include the following terms in your
concept map: appendages, cephalothorax,
tracheae, spiracles, chelicerae, pedipalps,
complete metamorphosis, chrysalis, pupa,
and nauplius.
2C 3E
7. Which is a feature of the arthropod
body plan?
8C
a. a hydrostatic support system
b. pharyngeal slits
c. an exoskeleton
d. a nonsegmented body
8. Arthropods molt because
7B
a. their body grows faster than their shell.
b. of damage to their exoskeleton.
c. their exoskeleton cracks and lets in
c. copepod
d. water flea
13. Copepods are said to be the most important
Understanding Key Ideas
are closely related to annelids?
8B
a. Arthropods and annelids have gills.
b. Both groups have marine species.
c. Segmentation is present in both groups.
d. Arthropods have vestigial parapodia.
8C
water.
TAKS 1 Bio/IPC 2C; Bio 3E
d. their hard exoskeleton cannot grow
larger.
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Assignment Guide
Section
1
2
3
pp. 684–685
Review and Assess
TAKS Obj 1 Bio/IPC 2C
TAKS Obj 2 Bio 8C, 10A
TAKS Obj 3 Bio 4C, 4D, 7B, 12B, 12E
TEKS Bio 3D, 3E, 7B, 8B, 8C, 11B,
11D, 12B, 12D, 12E
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Chapter 30 • Arthropods
4
Questions
5a, 6, 7, 8, 21
2, 3, 5, 7, 15, 17, 20
1, 4, 5, 9, 10, 11, 14, 15, 16, 17, 18, 19,
20, 22
12, 13, 15, 18, 21
Critical Thinking
Alternative Assessment
Critical Thinking
16. Applying Information If levels of vegeta-
20. Forming a Model Using papier mâché or
16. A species that undergoes complete metamorphosis would
probably have the advantage.
In complete metamorphosis, the
larvae have different food sources
from the adults, and this difference might help one or the other
survive. Also, during complete
metamorphosis, the pupa is
within a protective chrysalis and
would likely survive the drought.
In incomplete metamorphosis,
the nymph is similar to the adult,
and both nymphs and adults
would likely be affected.
tion were reduced, which arthropod
species would likely have a greater advantage—an arthropod species that undergoes
complete metamorphosis or one that
undergoes incomplete metamorphosis?
Explain your answer.
7B 12D
17. Recognizing Logical Inconsistencies
A neighbor commented that there was an
increased number of insects around her
house and that she was killing every spider
she saw. How might these actions affect the
number of insects around a house?
12E
18. Inferring Conclusions An unknown arthro-
pod has three body segments, one pair of
antennae, and three pairs of jointed legs.
What kind of arthropod is it? Explain how
you arrived at this conclusion.
8C
19. Recognizing Relationships The wings of the
atlas moth, Attacus atlas, look much like the
head of a snake. Why might it benefit a fly7B
ing insect to look like a snake?
some other material, make a model of a
grasshopper or a spider. Decide in advance
how many features of insects you must
show to make an adequate model. Present
your model to the class, and describe the
structures that you modeled.
3E
21. Communicating Information Use the media
center or Internet sources to learn more
about diseases transmitted by arthropods.
Develop a brochure that presents your
findings. The brochure should discuss the
species that transmit the disease, as well as
the symptoms and treatment of
4C 4D 11D 12B
the disease.
22. Career Connection Agricultural Insect
Inspector Research the field of inspecting
field crops for the presence of harmful
insects, and write a report on your findings.
Your report should include a job description, training required, kinds of employers,
growth prospects, and starting salary.
3D
TAKS Test Prep
TAKS 3 Bio 7B; Bio 12D
17. Spiders eat insects. When spiders
are removed, insects have fewer
predators. Killing the spiders
probably led to an increase in the
insect population. TAKS 3 Bio 12E
18. It is an insect because it has three
common insect characteristics.
TAKS 2 Bio 8C
Use the illustration below and your knowledge
of science to answer questions 1–3.
1. What type of environmental stimulus is
11B
structure A sensitive to?
A touch
C light
B sound
D odor
2. Structures B and C are specialized for
F inhaling and exhaling air.
G biting and chewing leaves.
H sponging and lapping liquids.
J catching and handling prey.
A
B
19. Predators might think the moth is
a snake and therefore not attack it.
TAKS 3 Bio 7B
Alternative Assessment
7B
3. This animal’s exoskeleton is adapted to
A prevent movement at the joints.
10A
B withstand pressure in deep water.
C help prevent water loss.
D grow as the animal grows.
C
Test
TAKS 3 Bio 4C, 4D, 12B; Bio 11D
If points are not deducted for guessing, answer
every question.
685
1. A. Incorrect. Touch is detected by the
grasshopper’s antennae. B. Incorrect. Sound is
not detected in the grasshopper by structure A.
C. Correct. Structure A is an ocellus, a lightdetecting organ of the grasshopper. D. Incorrect.
Smell is detected by the grasshopper’s antennae.
Bio 11B
2. F. Incorrect. Air enters and leaves the grasshopper through the spiracles. G. Correct. The
mandibles and the maxillas are used to bite
and chew leaves. H. Incorrect. The grasshopper
20. Models will vary but should
show the external structures illustrated in the drawings of the
spider or grasshopper depicted
in the Up Close features in this
chapter. Bio 3E
21. Answers will vary, but brochures
should be well organized and
present the group’s findings
accurately.
has no structures for sponging and lapping
liquids. J. Incorrect. Grasshoppers are herbivores and do not catch and handle prey.
TAKS 3 Bio 7B
22. Answers will vary. Agricultural
insect inspectors work for crop
producers to identify harmful and
helpful insects. A college degree
in entomology may be required.
Employers include agricultural
stations, universities, and government agencies. Growth prospects
are good. Starting salary will
vary by region. Bio 3D
3. A. Incorrect. The exoskeleton is hinged at the
joints for movement. B. Incorrect. Grasshoppers
do not inhabit deep water. They are terrestrial.
C. Correct. The exoskeleton is efficient in
conserving body moisture. D. Incorrect. The
exoskeleton does not grow; grasshoppers molt
to allow for growth. TAKS 2 Bio 10A
Chapter 30 • Arthropods
685