Transcript 1-Arthropods

Phylum Arthropoda
• What is the world’s STRONGEST
ANIMAL?
• The RHINOCEROS beetle: is able to
carry up to 100 times its own weight.
This animal can carry over 200 grams
on its 2-gram frame.
CHARACTERISTICS of
ARTHROPODS:
• 1. Arthropods have jointed appendages.
– Appendages are extensions of the
body and include legs, and antennae.
• 2. The arthropod body is segmented.
– A pair of appendages is attached to
each segment.
• 3. Arthropods have a hard exoskeleton
that provides protection and support.
• 4. Arthropods have specialized organ
systems. They consist of
– ventral nervous system,
– open circulatory system,
– a digestive system, and
– specialized receptors.
What
characteristics of
arthropods
can you
observe in
this slide?
Jointed Legs:
• The phylum of Arthropods is the
largest and most diverse animal
phylum .
• About 84 percent of known
animals species are arthropods.
• Arthropods inhabit every region of
the Earth- ocean bottoms to
mountain tops.
• This group includes :
• Spiders, crabs, scorpions, and
lobsters.
– Unlike annelids, arthropods
have jointed appendages.
Recognized by the eight legs attached to the
cephalothorax, spiders are very useful and
should not be killed. They eat only insects and
other small pests.
Scorpions catch prey with their enlarged
pedipalps and tear their prey apart. The
stinger on the tail is used mostly in defense.
The word Arthropod means:
JOINTED FEET”.
These jointed appendages of
arthropods are specialized for
SENSING, EATING,
REPRODUCTION, MOVING
and PROTECTION.
An isopod Cyclops
Exoskeleton:
• The outer covering is called an
EXOSKELETON which is a hard
covering on the outside of the body
that provides both support and
protection.
The exoskeleton is made
of CHITIN. Some
exoskeletons
are leathery like caterpillars,
and some are tough and
hard like ticks and crabs.
The water flea,
Daphnia
Centipedes are fast moving predators
with one pair of legs per body
segment. They have fangs to inject
poison and will attack animals larger
than themselves. (Class Chilopoda)
Millipedes are slow moving with two pairs
of small legs per body segment. They eat
plant material & do not have poison glands.
Their bodies are more rounded than
centipedes. When threatened, many of
them will coil up to protect their softer
underbelly (Class Diplopoda)
• The bodies of arthropods are
divided into segments.
• Some arthropods have dozens of
segments like centipedes and
millipedes
• other arthropods have THREE
segments. (ants for example)
• Muscles are attached to the
exoskeleton that enable the
arthropod to move.
• This hard outer covering provides
greater protection than the
endoskeleton of humans.
The downside:
There is a drawback to this protection.
– The arthropod must shed its covering
to grow. When an arthropod sheds
its outer exoskeleton it is called
MOLTING. When the arthropod
molts it grows a new layer of
CHITIN .
FEEDING AND
RESPIRATION:
• Arthropods include individuals with
diverse feeding habits.
– There are both herbivores and
carnivores along with filter feeders,
detritus feeders, blood-suckers, and a
host of specialized parasites.
Respiration:
• Arthropods also demonstrate
different means of respiration.
• Aquatic species of arthropods
breathe through gills, which
are feather like organs located
in a chamber beneath the
exoskeleton.
• Some arthropods breath through
layers of respiratory tissue that
resemble pages in a book.
Horseshoe
crabs
breathe
through
book gills,
and spiders
breathe
through
book lungs.
– Most terrestrial arthropods
breathe through a branching
air-filled network of structures
called TRACHEAL TUBES.
– These tubes connect the
arthropod’s tissues with
atmosphere and oxygen passes
through the tracheal tubes by
diffusion.
Circulation:
• The arthropods have an OPEN
CIRCULATORY system.
• Arthropods have welldeveloped heart that pumps
blood through arteries into
smaller vessels from which it
flows into spaces called
SINUSES.
• The muscles slosh the blood
to bathe body tissues.
• The blood collects in a large
sinus surrounding the heart.
EXCRETION:
Arthropods excrete nitrogen
wastes in several ways.
In most terrestrial species
wastes are excreted by dead
end sacs called MALPIGHIAN
TUBULES. These malpighian
tubules concentrate wastes and
add them to feces moving
through the gut.
Aquatic arthropods
•
excrete nitrogenous wastes by
allowing ammonia to diffuse
through the gill
surface.
• (add this)
Classification:
• Scientists classify arthropods
based on developmental patterns.
– There are four subphyla of
arthropods.
– Trilobita (Trie-luh-BITE-uh)
includes extinct organisms
called trilobites
– Crustacea (Kruss-TAY-shuh)
includes shrimp, lobsters, crabs,
– Chelicerata (kul-LISS-uh-RAHTuh) includes spiders, scorpions,
ticks, mites, and sea spiders
– Uniramia (YOO-nuh-RAY-mee-uh)
The only group that seems to
have evolved on land and includes
centipedes, millipedes, and all
insects.
Embyro differences:
• The four subphyla are
distinguished primarily by
differences in their
embryological development and
differences in the morphology
of structures such as
appendages and mouthparts.