Transcript ARTHROPODS
ARTHROPODS
SUBPHYLA: TRILOBITA,
CRUSTACEA, CHELICERATA, AND
UNIRAMIA
Phylum Arthropoda
“jointed feet”
Characteristics:
– segmentation
– Jointed, paire appendages
– Exoskeleton – chitin
– Cephalization
– Compound eyes
– Coelom
– Open circulatory system
– Ventral nerve cord
The Exoskelton
The exoskelton is composted of the
polysaccharide chitin. An arthropod can
not grow without periodically shedding the
exoskeleton. This process is called
molting or edcysis. During the few days
following the replacement of the
exoskeleton, the animal is extremely
vulnerable and must hide from predators.
There is also the problem of desiccation.
Advantages & Disadvantages of the
Exoskelton
Advantages
– Protection
– Support
– Site for muscle
attachment
– Flexible at the joints
Disadvantages
– Heavy
– Must be molted
Subphylum Trilobita
All members of this phylum are extinct
Subphylum Crustacea
Only arthopods with 2 pair of appendages
on their head that serve as feelers
Most have 16-20 segments which are
fused into several tagmata
Most have gills for respiration
Most have a free-swimming larva called a
nauplius
Crustacean Diversity
Subphylum Chelicerata
Have piercing and sucking mouth parts
called chelicerae
Class Arachnida
Include: spiders, scorpions, mites and
ticks
Cephalothorax and abdomen
– Cephalothorax – 6 pairs of jointed appendages
1 pair of chelicerae (used to inject venom into prey)
1 pair of pedipalps (holding food, chewing, &
reproduction
4 pairs of walking legs
8 simple eyes at anterior end
Abdomen
– Spinnerets
– Respiration
Book lung
Tracheae and spiracles
– Excretory organs
Malpighian tubules
Coxal glands
Mites and Ticks
Most abundant and specialized archnids
Completely fused head and cephalothorax
Subphylum Uniramia
Classes
– Insecta
– Diplopoda
Millipedes
2 pair of legs on each body segment
Rounded bodies
Poor vision with a good sense of smell
Feed on plants or decaying plant matter
Secrete a noxious fluid that contains cyanide
when threatened
Chilopoda
– Flattened bodies with one pair of legs per
segment ( except first and last 2 segments)
– May have 15 – 175 pairs of legs
– The appendages on the first segment are
modified into a pair of poison claws
– Long antennae and two clusters of simple
eyes
– Move quickly and feed mostly on earthworms
and other insects