Chapter 36 Arthropods Table of Contents - Amazon S3s3.amazonaws.com/scschoolfiles/136/mb_36_win.pdf · Chapter 36 and Myriapoda Subphylum Chelicerata, continued Life of a Spider •

Copyright © by Holt, Rinehart and Winston. All rights reserved.

Resources Chapter menu

Arthropods Chapter 36

Table of Contents

Section 1 Phylum Arthropoda

Section 2 Subphylum Crustacea

Section 3 Subphylum Chelicerata and Myriapoda




Chapter 36

Objectives

• Describe the distinguishing characteristics of

arthropods.

• Explain the process of molting in an arthropod.

• List the five major subphyla of the phylum

Arthropoda.




Chapter 36

Characteristics of Arthropods

• The members of the phylum Arthropoda are called

arthropods.

• Arthropods are segmented animals with body

segments that bear appendages.

• Arthropods have an exoskeleton that provides

protection and support and contains chitin.

• Arthropods show a high degree of cephalization.

Most have segmented antennae and compound

eyes.



Chapter 36

Segmentation




Chapter 36

Compound Eye




Chapter 36

Function of the Compound Eye





Chapter 36

Characteristics of Arthropods, continued

Molting

• The rigid exoskeleton limits the size to which an

arthropod can grow.

• So, each arthropod periodically sheds its exoskeleton

and makes a new one in the process of molting.

• An anthropod goes through many cycles of molting

during its life.



Chapter 36





Chapter 36





Chapter 36

Arthropod Exoskeleton





Chapter 36

Evolution and Classification

• Arthropods likely evolved from a common ancestor

that lived about 545 million years ago.

• However, biologists are still uncertain about much of

arthropod phylogeny.

• The similar characteristics of many modern

subgroups of arthropods may be the result of

convergent evolution.




Chapter 36

Evolution and Classification, continued

• Many ancient and extinct arthropods, such as

trilobites, had many body segments and one pair of

appendages on each segment.

• Most living arthropod species have some segments

that lack appendages and some segments that are

fused into a larger structure called a tagma (plural,

tagmata).




Chapter 36

Evolution and Classification, continued

• Arthropods are usually divided into five subphyla on the basis of

differences in development and in the structure of appendages,

such as mouthparts.

• The two major types of mouthparts are:

– mandibles, which are jawlike

– chelicerae (singular, chelicera), which are pincerlike

• The five main subphyla are:

– Trilobita

– Crustacea

– Chelicerata

– Myriapoda

– Hexapoda



Chapter 36

Phylogenetic

Diagram of

Arthropods




Chapter 36

Types of Arthropods





Chapter 36

Objectives

• Describe the characteristics of crustaceans.

• Compare aquatic crustaceans with terrestrial

crustaceans.

• Explain the functions of the appendages on a

crayfish.

• Summarize digestion, respiration, circulation,

excretion, and neural control in crayfish.




Chapter 36

Characteristics

• The subphylum Crustacea contains about 38,000

known species.

• Crustaceans are so diverse that their single defining

characteristic is having two pairs of antennae.

• Most crustaceans also have:

– a pair of mandibles

– a pair of appendages on each body segment

– some branched appendages

– 16 to 20 segments and several tagmata




Chapter 36

Characteristics, continued

Some crustaceans respire through their exoskeleton, others respire through gills.

• Many have a free-swimming larval stage called a nauplius.



Chapter 36

Anatomy of a Nauplius





Chapter 36

Diversity of Crustaceans

Aquatic Crustaceans

• Copepods are abundant in marine environments and

an important part of the ocean’s plankton.

• In freshwater environments, much of the plankton is

composed of water fleas such as Daphnia species.

• Barnacles are sessile as adults.

– Free-swimming barnacle larvae attach themselves to marine

surfaces and develop a shell that encloses the body.

– Barnacles use their cirri (singular, cirrus) to sweep food

from the water into their mouths.




Chapter 36

Diversity of Crustaceans, continued

Terrestrial Crustaceans

• Sow bugs and pill bugs are terrestrial isopods.

• They lack adaptations for conserving water and live

only in moist environments.

• They generally feed on decaying vegetation.

• Pill bugs roll into a ball when disturbed or threatened.




Chapter 36

The Crayfish

• The crayfish is an abundant freshwater crustacean

that is structurally similar to lobsters, which are

marine crustaceans.

• Crayfish, lobsters, crabs, and shrimp are decapods,

or members of the order Decapoda. Decapoda

means “10 feet.”

• Decapods have five pairs of legs that are used for

locomotion.




Chapter 36

The Crayfish, continued

External Structure

• The crayfish’s body is divided into

– the cephalothorax, which is covered by the

carapace and is divided into

• the head, which has five segments

• the thorax, which has eight segments

– the abdomen, which is is divided into six

segments




Chapter 36


External Structure, continued

• A pair of appendages is attached to each segment of the crayfish.

Several pairs have specialized functions.

• These appendages include:

– Antennae

– Antennules

– Mandibles

– Maxillae

– Maxillipeds

– Chelipeds

– Walking legs

– Swimmerets



Chapter 36

External Anatomy of a Crayfish





Chapter 36


Digestion

• Crayfish have a digestive gland that is near the

stomach and that secretes enzymes for digestion.

Respiration

• Walking circulates water across the gills.

Circulation

• The circulatory system is open.




Chapter 36


Excretion

• Green glands assist in excretion of excess water that enters the

body by osmosis.

Neural Control

• The nervous system of the crayfish is typical of arthropods and

is similar to that of annelids.

Sensory Organs

• Crayfish sense vibrations and chemicals in the water with

thousands of small sensory hairs.

• Their compound eyes are set on two stalks.



Chapter 36

Internal Anatomy

of a Crayfish




Chapter 36

Anatomy of a Crayfish




Chapter 36

Characteristics of Crustaceans




Section 3 Subphyla Chelicerata

and Myriapoda Chapter 36

Objectives

• List the characteristics of arachnids, as represented

by a spider.

• Explain the adaptations that spiders have for a

predatory life on land.

• Identify the unique characteristics of scorpions,

mites, and ticks.

• Compare the characteristics of millipedes and

centipedes.





Subphylum Chelicerata

• The subphylum Chelicerata, the chelicerates,

includes spiders, scorpions, mites, sea spiders, and

horseshoe crabs.

• Chelicerates lack antennae and typically have six

pairs of appendages.

• The first pair of appendages, the chelicerae, are

modified into pincers or fangs.





Subphylum Chelicerata, continued

Class Arachnida

• Class Arachnida, the arachnids, includes spiders,

scorpions, mites, and ticks.

• The arachnid’s body is divided into:

– a cephalothorax that usually bears six pairs of jointed

appendages:

• one pair of chelicerae

• one pair of pedipalps

• four pairs of walking legs

– an abdomen






Anatomy of a Spider

• Spiders have eight simple eyes and chelicerae that

are modified as fangs.

• Spiders produce silk threads using spinnerets.

• Spiders respire through spiracles that connect to

book lungs or tracheae.

• Malpighian tubules function to excrete wastes while

conserving water.



Chapter 36

Anatomy of a Brown Recluse Spider


and Myriapoda



Chapter 36

Spinneret


and Myriapoda






Life of a Spider

• Spiders feed on insects and other small animals.

Many species are adapted to capture certain prey.

• Spiders rarely harm humans, but two species in the

United States are dangerous:

– the black widow

– the brown recluse

• A male spider is usually smaller than the female.

• Females lay eggs in a silken case.



Chapter 36

Feeding Habits of Spiders


and Myriapoda






Scorpions

• Scorpions have large, pincerlike pedipalps and a

stinger on the last segment of the abdomen.

Mites and Ticks

• Mites and ticks have a completely fused

cephalothorax and abdomen.

• Many species are parasitic, and some spread

diseases that affect humans.





Subphylum Myriapoda

• Members of the subphylum Myriapoda have antennae,

mandibles, and unbranched appendages.

Class Diplopoda

• Millipedes have rounded bodies and two pairs of

jointed legs on each body segment except the last two

segments.

Class Chilopoda

• Centipedes have flattened bodies and one pair of

jointed legs on each body segment except the first

segment and the last two segments.



Chapter 36

Characteristics of Arachnids


and Myriapoda



Chapter 36

Types of Arachnids


and Myriapoda



Multiple Choice

1. What do all arthropods have in common?

A. spiracles

B. antennae

C. a cephalothorax

D. jointed appendages

Standardized Test Prep Chapter 36



Multiple Choice, continued

1. What do all arthropods have in common?

A. spiracles

B. antennae

C. a cephalothorax

D. jointed appendages





2. What is the chitin-containing structure that protects

and supports the body of an arthropod?

F. a tagma

G. a chelicera

H. an appendage

J. an exoskeleton





2. What is the chitin-containing structure that protects

and supports the body of an arthropod?

F. a tagma

G. a chelicera

H. an appendage

J. an exoskeleton





3. Which of the following statements about compound

eyes is true?

A. Compound eyes have a single lens.

B. Compound eyes are located on the abdomen of

scorpions.

C. Compound eyes are found in all arthropods except

crayfish.

D. Compound eyes are composed of many individual

light detectors.





3. Which of the following statements about compound

eyes is true?

A. Compound eyes have a single lens.

B. Compound eyes are located on the abdomen of

scorpions.

C. Compound eyes are found in all arthropods except

crayfish.

D. Compound eyes are composed of many individual

light detectors.





4. What are the major respiratory organs of crayfish?

F. gills

G. lungs

H. tracheae

J. book lungs





4. What are the major respiratory organs of crayfish?

F. gills

G. lungs

H. tracheae

J. book lungs





5. How do mites and ticks differ from spiders?

A. Mites and ticks have mandibles.

B. Mites and ticks have two pairs of antennae.

C. Mites and ticks have a unique respiratory system.

D. Mites and ticks have a fused cephalothorax and

abdomen.





5. How do mites and ticks differ from spiders?

A. Mites and ticks have mandibles.

B. Mites and ticks have two pairs of antennae.

C. Mites and ticks have a unique respiratory system.

D. Mites and ticks have a fused cephalothorax and

abdomen.





The illustration below shows four animals. Use the

illustration to answer the question that follows.





6. Which animal has a chitinous exoskeleton?

F. snail

G. grasshopper

H. hydra

J. squid





6. Which animal has a chitinous exoskeleton?

F. snail

G. grasshopper

H. hydra

J. squid





7. mandible : crayfish :: chelicera :

A. pill bug

B. scorpion

C. barnacle

D. millipede





7. mandible : crayfish :: chelicera :

A. pill bug

B. scorpion

C. barnacle

D. millipede





The graph below shows data about molting and two

causes of mortality in crabs. Use the graph to answer

the questions that follow.





8. During which months are you most likely to find crabs

in molt?

F. January through March

G. April through June

H. July through September

J. September through January





8. During which months are you most likely to find crabs

in molt?

F. January through March

G. April through June

H. July through September

J. September through January





9. What is the relationship between molting and

mortality?

A. Molting increases mortality.

B. Molting decreases mortality.

C. Molting has no effect on mortality.

D. Molting and mortality occur at different times of the

year.





9. What is the relationship between molting and

mortality?

A. Molting increases mortality.

B. Molting decreases mortality.

C. Molting has no effect on mortality.

D. Molting and mortality occur at different times of the

year.




Short Response

Some arthropods are terrestrial and some are aquatic.

Give examples and describe the distinguishing

characteristics of each type of arthropod.




Short Response, continued

Some arthropods are terrestrial and some are aquatic.

Give examples and describe the distinguishing

characteristics of each type of arthropod.

Answer: Spiders and millipedes are terrestrial. The

exoskeleton is lighter, respiration is by book lungs

or tracheae, and water is conserved. Crayfish and

crabs are aquatic, the exoskeleton is heavier,

respiration is by gills, and excess water is excreted

by green glands.





Extended Response

Base your answers to parts A & B on the information

below.

All arthropods undergo many cycles of molting

throughout their lifetime.

Part A Describe the process of molting in arthropods.

Part B Explain how the anatomical structure of an

arthropod relates to the function of molting.




Extended Response, continued

Answer:

Part A In between molts, the tissues swell and put

pressure on the exoskeleton. Molting is then

induced by hormones. Enzymes digest the old

exoskeleton and the epidermis synthesizes a

new one. The old exoskeleton then loosens,

breaks along specific lines, and is shed.

Part B: The exoskeleton covers the body and

therefore limits growth. Molting provides a

means for allowing growth.

Documents

Chapter 36 Arthropods Table of Contents - Amazon S3s3.amazonaws.com/scschoolfiles/136/mb_36_win.pdf · Chapter 36 and Myriapoda Subphylum Chelicerata, continued Life of a Spider •