Download Chapter 28: Arthropods

Chapter 28: Arthropods
Section 1: Introduction to Arthropods
Introduction to Arthropods

________________________________ – animal having a segmented body, an
exoskeleton containing chitin, and a series of jointed appendages; belong to the
phylum Arthropoda
o More than ________________________ species have been described
o Vary enormously in size, shape, and habits
Diversity and Evolution in Arthropods

Arthropods are divided into _____________ subphyla:
o _________________________

Oldest subphylum of arthropods

____________________________ were dwellers in ancient seas

______________________
o __________________________

____________________________________ include spiders, ticks,
mites, scorpions, and horseshoe crabs
o __________________________

_________________________________ include such familiar
(and edible) organisms as crab and shrimp
o __________________________

__________________________________ include most
arthropods: centipedes, millipedes, and all insects—including bees,
moths, grasshoppers, flies, and beetles
Form and Function in Arthropods

All arthropods exhibit several key features
o 3 most important features

Tough _______________________________

Series of ______________________________________________

__________________________________________
o Other characteristics

Brain located in dorsal part of head

Ventral nerve cord

Open circulatory system powered by a single heart
The Arthropod Body Plan

The _________________________________ is a system of external supporting
structures that are made primarily of the carbohydrate ____________________

Provide excellent protection from physical damage

________________________________
o Prevents water loss

Helps arthropods move efficiently and adapt to their environment

Disadvantages
o Cannot ________________ as the animal grows
o Movement can occur only at the joints of the “armor”

All arthropods have jointed appendages that enable them to move

Over millions of years, appendages have evolved into marvelously versatile
adaptations to different environments
o _____________________________
o ______________
o ____________________________________
o ________________
o __________________________

All arthropods have segmented bodies
Feeding

Appendages enable these animals to eat almost any food you can imagine

Exhibit every mode of feeding
o ___________________________

Some eat any plant, others are more selective
o ___________________________

Some catch and eat other animals, others feed on animals that are
primarily already dead
o ___________________________

External parasites drink blood or body fluids from animals, internal
parasites passively absorb nutrients through body walls
o ___________________________________

Use comb like bristles on mouthparts or legs to filter plants and
animals from water
o ___________________________________
Respiration

Have evolved three basic types of respiratory structures—______________,
_____________________________________________________, and
_______________________________________
o Most have only one of these respiratory structures

Aquatic arthropods have gills just under the cover of their
exoskeleton

Are formed from part of the same appendages that form
mouthparts and legs

Book gills (horseshoe crabs) and book lungs (spiders and their
relatives) are unique to these arthropods

______________________________________________
are layered like the pages of a book


Increase the surface area for gas exchange
Tracheal tubes (terrestrial arthropods)

From spiracles, long branching tracheal tubes reach deep
into the animals’ tissues

Supplies oxygen by _________________________ to all
body tissues

Work well in only small animals
Internal Transport

A well-developed heart pumps blood through an _______________ circulatory
system

When the heart contracts, it pumps blood through arteries that branch into smaller
vessels and enter the tissues

There the blood leaves the vessels and moves through spaces in the tissues called
_________________________

Eventually, the blood collects in a large cavity surrounding the heart, from which
it re-enters the heart through small openings and is pumped around again
Excretion

Undigested food becomes solid waste that leaves through the anus

Most terrestrial arthropods dispose of nitrogen-containing wastes by using a set of
____________________________________________
o Bathed in blood inside the body sinuses
o Remove wastes from the blood, concentrate them, and then add them to
undigested food before it leaves via the anus

Terrestrial arthropods may have small excretory glands by their legs instead of
Malpighian tubules

Aquatic arthropods dispose of cellular wastes by diffusing them from the body
into the surrounding water
o Also eliminate nitrogen-containing wastes through a pair of
____________________________________ located near the base of the
antennae

Are emptied to the outside through a pair of openings in the head
Response

Have well-developed nervous systems

All have a ________________________ that consists of a pair of ganglia in the
head

Have a nerve cord with several other pairs of ganglia
o Serve as local command centers to coordinate the movement of
____________________________________

Why insects can move after their heads are cut off

Have simple sense organs such as statocysts and chemical receptors

Have compound eyes that contain more than 2000 separate lenses that can detect
color and motion

Have well-developed sense of ___________________
o Receptors located on mouthparts, antennae, and legs

Insect ears are found in strange places
o Eardrums are normally located __________________________________

Sense organs help it detect and escape predators

Some also have venomous stings and bites

Some arthropods trick predators by _____________________________________
o Drop a claw or a leg

Body part keeps moving to distract the predator while the rest of
the animal scurries away

Use visual trickery to fool predators

Hide through _____________________________

Others imitate the warning coloration of poisonous or dangerous species—
_________________________
Movement

Have well-developed ___________________________________ that are
coordinated by the nervous system

Muscle generate force by _____________________________, then transfer that
force to the _________________________________

At each joint, some muscles are positioned to flex the joint and other muscles
extend to it
o Allows arthropods to beat their wings against the air to fly, push their legs
against the ground to walk, or beat their flippers against the water to swim
Reproduction

Reproduction is ______________________

Males and females produce sperm and eggs

Fertilization takes place ______________________________________________
____________________________

The male uses a special reproductive organ to deposit sperm inside the female

EXCEPTION: In spiders and some crustaceans, the male deposits a small packet
of sperm that the female picks up
Growth and Development in Arthropods

Exoskeletons present a problem in terms of ________________________

Arthropods must replace their exoskeletons with larger ones in order to allow
their bodies to increase in size as they mature

In order to grow, all arthropods must ________________, or shed, their
exoskeletons
o Controlled by ___________________________

When molting time is near, the epidermis digests the inner part of the exoskeleton
and absorbs much of the chitin

After it secretes a new exoskeleton inside the old one, an arthropod pulls
completely out of its old skeleton
o Often _______________ what is left of the old exoskeleton
o Must then wait for the new exoskeleton to __________________

Can take a few hours to a few days

Molt several times between hatching and adulthood

In most cases, the process of growth and development involves
__________________________________, or a dramatic change in form

As the young grow, they keep molting and getting larger until they reach adult
size

Along the way, they gradually acquire the characteristics of adults

Many insects undergo _____________________________________________
—a four stage process where the eggs of insects hatch into larvae that look
nothing like their parents

As they grow, they molt repeatedly

When it reaches a certain age, it sheds its larval skin one last time and becomes a
________________
o During this stage the insects body is completely rearranged
o After metamorphosis, the animal emerges as a fully grown adult with both
internal and external body parts that are completely different from what it
had before