Transcript Phylum Arthropoda

Phylum Arthropoda
General Characteristics
General Characteristics
 Largest phylum in the animal kingdom
 Includes insects, spiders, millipedes, centipedes, crabs and
krill.
 Are bilaterally symmetrical; coelomate; protostomate.
 Exoskeleton. Major component: the polysaccharide,
chitin.
 Jointed appendages.
 Well-developed sense organs
 Open circulatory systems
 Group is important as pollinators of flowers, carries of
disease, and as food.
 About 1+ million species known at present.
Class Arachnida
 Includes ticks, mites, scorpions and spiders
Black-legged deer
tick
Acarina – Dust
mite
Striped bark
scorpion
Wolf spider
Class Arachnida
Two body regions: cephalothorax and abdomen.
Have 4 pairs legs attached to their thorax.
A pair of chelicerae (fangs).
A pair of palps. Function as sense receptors,
short arms, and pincers (in scorpions).
Class Arachnida
 All arachnids are carnivores. Most eat insects.
 No antennae.
 Many have 8 simple eyes.
 Respire through book lungs and tracheae.
 About 57,000 species, including Latrodectus mactans (black
widow spider) and Dermacentor variablis (wood tick).
Class Crustacea
Includes crabs, shrimps, water fleas, and pill
bugs.
Blue-clawed crab
Water flea
Brown shrimp
Pill bugs
Class Crustacea
 Most are marine, but some live in fresh water, and a
few live on land.
 2 main body regions in most.
 5 pairs of legs (4 pairs for walking and 1 pair for
grasping (chelipeds)).
Class Crustacea
5 pairs of head appendages, including 2 pairs
of antennae and chewing mouthparts, which
are useful in classifying them.
Class Crustacea
Respiration by gills (most are aquatic).
Many have compound eyes.
About 35,000 species, including Callinectes
sapidus (blue crab) and Homarus americanus
(American lobster).
Class Merostomata
 Horseshoe crabs. All are marine.
 2 main body regions.
 Easily recognized by horseshoe-shaped carapace and long
telson.
 5 pairs of legs (like crustaceans).
 No antennae (like arachnids).
Class Merostomata
 Respire through book gills (much like book lungs in
arachnids).
 Have both simple and compound eyes.
 Only 4 species exist
 Superbly adapted to their environment from early in
the history of life on Earth, they have changed little.
 Chesapeake Bay hosts largest population in the world.
Arachnida
(spiders)
Crustacea
(lobster)
Merostomata
(horseshoe
crab)
Yes
Yes
5 pairs of legs
Yes
Yes
True gills
Yes
2 main body regions Yes
4 pairs of legs
Yes
Book lungs/book
gills
Yes; book lungs
Yes; book gills
Yes; book gills
Antennae
No
Yes
No
Chewing
mouthparts
Yes
Yes
Yes
Dust Mites vs. Bed Bugs
Class
Arachnida
Class Insecta
Why???
Class Chilopoda
Two body regions (cephalothorax and abdomen).
Have a head with one pair of long antennae and a
pair of mandibles
Two pairs of maxilla (appendages which hold
their captured food and aid in chewing with side
to side movement).
Class Chilopoda: Centipedes
 Carnivorous.
 Head followed by 15 to 177 body segments.
 First body segment has a pair of poisonous claws.
 All other segments have 1 pair of jointed legs
 Do not have 100 legs (as their common name
suggests).
 Tracheae used for respiration.
Vietnamese
Centipede
Class Diplopoda: Millipedes
Three body regions (head, thorax, and
abdomen).
Have a head with one pair of antennae and a
pair of mandibles
One pair of maxilla
Class Diplopoda: Millipedes
Mostly herbivorous
Head followed by 20 to 200 segments
2 pairs of jointed legs on each segment.
Do no have 1,000 legs (as their common name
suggests).
Tracheae used for respiration.
Class Insecta
Single largest class of organisms; more than
750,000 known species.
Includes bees, flies, grasshoppers, lice,
butterflies, moths, and beetles (450,000
species).
Class Insecta
Three body regions
Three pairs of walking legs
Three pairs of walking legs located on thorax
One pair of antennae on head.
Class Insecta
Have complex mouth parts
with one pair of maxilla and
mandibles.
When wings are present, have
one or two pairs of wings on
thorax.
Two pairs on
Dragonfly
Mosquito
has one pair
of wings
Class Insecta
Only group of invertebrates capable of flight.
Tracheae used for respiration
Have compound eyes
Most live on land.
Many have complete metamorphosis