Transcript 28-1 Introduction to the Arthropods

Biology
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28-1 Introduction to the
Arthropods
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28-1 Introduction to the Arthropods
What Is an Arthropod?
What are the main features of
arthropods?
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28-1 Introduction to the Arthropods
What Is an Arthropod?
What Is an Arthropod?
Arthropods have a segmented body, a
tough exoskeleton, and jointed
appendages.
Arthropods include insects, crabs, centipedes,
and spiders.
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28-1 Introduction to the Arthropods
What Is an Arthropod?
Arthropods are surrounded by a tough external
covering, or exoskeleton.
The exoskeleton is made from protein and chitin.
Chitin is a carbohydrate.
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28-1 Introduction to the Arthropods
What Is an Arthropod?
All arthropods have jointed appendages.
Appendages are structures that extend from the
body wall.
Legs and antennae are appendages.
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28-1 Introduction to the Arthropods
Evolution of Arthropods
What are the important trends in
arthropod evolution?
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28-1 Introduction to the Arthropods
Evolution of
Arthropods
Evolution of Arthropods
Fossilized Trilobites
A typical primitive
arthropod was
composed of many
identical segments,
each carrying a pair of
appendages.
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28-1 Introduction to the Arthropods
Evolution of Arthropods
This early body plan was modified gradually.
Body segments were lost or fused over time.
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28-1 Introduction to the Arthropods
Evolution of Arthropods
The evolution of arthropods has led to
fewer body segments and highly
specialized appendages for feeding,
movement, and other functions.
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
Form and Function in Arthropods
Arthropods use complex organ systems to carry
out different essential functions.
Organ systems are interrelated; the functioning of
one system depends on that of other systems.
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
Feeding
Arthropods include herbivores, carnivores, and
omnivores. There are filter feeders, detritivores,
and parasites.
The mouthparts of arthropods are adapted to the
type of food the arthropod eats.
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
Respiration
Most terrestrial
arthropods breathe
through a network of
branching tracheal
tubes that extend
throughout the body.
Tracheal tubes
Tracheal tubes
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28-1 Introduction to the Arthropods
Air enters and leaves the
tracheal tubes through
spiracles, which are
small openings located
along the side of the
body.
Form and Function in
Arthropods
Spiracles
Spiracles
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
Other terrestrial
arthropods, such as
spiders, respire using
book lungs.
Spiracles
Book lungs are organs
that have layers of
respiratory tissue stacked
like pages of a book.
Book lung
Airflow
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Form and Function in
Arthropods
Most aquatic arthropods, such as lobsters and crabs,
respire through featherlike gills.
Horseshoe crabs respire through book gills.
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
Circulation
Arthropods have an
open circulatory
system.
The heart pumps blood
through arteries that
branch and enter the
tissues.
Heart
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
Blood leaves the blood
vessels and moves
through sinuses, or
cavities.
Blood collects in a large
sinus surrounding the
heart and re-enters the
heart.
Heart
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
Excretion
Most terrestrial arthropods dispose of nitrogenous
wastes using Malpighian tubules.
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28-1 Introduction to the Arthropods
Malpighian tubules
are saclike organs that
extract wastes from the
blood and then add
them to digestive
wastes.
Form and Function in
Arthropods
Malpighian tubules
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
In aquatic arthropods, diffusion moves wastes from
the body into the surrounding water.
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
Brain
Response
Most arthropods have a
well-developed nervous
system.
All arthropods have a
brain.
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
Two nerves connect
the brain to a ventral
nerve cord.
Nerve
cord
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
Along this nerve cord are
several groups of nerve cells
called ganglia.
These ganglia coordinate the
movements of individual legs
and wings.
Ganglia
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28-1 Introduction to the Arthropods
Most arthropods have
sophisticated sense
organs such as
compound eyes.
Form and Function in
Arthropods
Compound eyes
Compound eyes may
have more than 2000
separate lenses and can
detect color and motion
very well.
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28-1 Introduction to the Arthropods
Form and Function in
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Movement
Arthropods move using well-developed groups of
muscles that are coordinated and controlled by the
nervous system.
Muscles generate force by contracting and then
pulling on the exoskeleton.
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
At each body joint, different muscles either flex
(bend) or extend (straighten) the joint.
Flexed
Extended
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28-1 Introduction to the Arthropods
Form and Function in
Arthropods
Reproduction
Terrestrial arthropods have internal fertilization.
In some species, males deposit sperm inside
females.
In other species, the males deposit a sperm packet
that is picked up by the females.
Aquatic arthropods may have internal or external
fertilization.
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28-1 Introduction to the Arthropods
Growth and Development
in Arthropods
What happens when an arthropod
outgrows its exoskeleton?
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28-1 Introduction to the Arthropods
Growth and Development
in Arthropods
Growth and Development in Arthropods
When they outgrow their exoskeletons,
arthropods undergo periods of molting.
During molting, an arthropod sheds its entire
exoskeleton and manufactures a larger one
to take its place.
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28-1 Introduction to the Arthropods
Growth and Development
in Arthropods
Molting is controlled by the arthropod's endocrine
system.
Most arthropods molt several times.
The arthropod is vulnerable to predators while its
shell is soft.
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28-1 Introduction to the Arthropods
Growth and Development
in Arthropods
Skin glands digest the inner part of the exoskeleton,
and other glands secrete a new skeleton.
When the new exoskeleton is ready, the animal pulls
itself out of what remains of the original skeleton.
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The mouthparts of arthropods are
a. similar in all species.
b. adapted to enable different species to eat
different foods.
c. adapted to enable different species to
respire in different ways.
d. useful for locomotion as well as feeding.
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Arthropods have open circulatory systems,
which means that blood
a. leaves the blood vessels, flows through
sinuses, and then returns to the heart.
b. flows from the heart directly into sinuses and
then returns to the heart.
c. never leaves the circulatory system.
d. vessels open to the external environment.
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Characteristics which define the arthropods
include
a. an endoskeleton made of chitin and jointed
appendages.
b. an endoskeleton made of chitin and six pairs
of appendages.
c. an exoskeleton made of chitin and jointed
appendages.
d. an exoskeleton made of chitin and
Malpighian tubules.
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What type(s) of fertilization do terrestrial
arthropods have?
a. internal
b. external
c. both internal and external
d. hermaphroditic
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What happens to the exoskeleton of an
arthropod as the animal grows?
a. It remains soft until the animal reaches
adulthood.
b. It develops additional body segments.
c. It softens and stretches to a larger size.
d. It is discarded and replaced by a new, larger
exoskeleton.
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