Arthropoda

Core Concept

• Exoskeleton= chitin• Jointed appendage• Segmented body• brain- dorsal part of the head• Ventral nerve cord• Open circuatory system, single heart

• Body plan- adaptation for low water loss• Found in all types of habitat

• Four major subphyla– Trilobita (fossilized trilobites)– Chelicerata (spiders, ticks, mites, scorpions,

horseshoe crabs)– Crustacea (crabs, craysfish, shrimps, barnacles, pill

bugs, water fleas)– Uniramia (centipedes, millipedes,, all insects)• Class Chilopoda (centipede)• Class Diplopoda (millipedes)• Insecta

Keywords• ArthropodaTrilobita Chelicerata• Crustacea Uniramia Chilopoda• Diplopoda Insecta Molting• Metamorphosis:complete/incomplete• Hemolymph hemocoel ventral nerve cord• Head thorax abdomen cephalotorax• Carapace chelicerae malpighian tubules• Green gland book gills book lungs• Spiracles tracheal tubes

Characteristics

• 2 out of 3 organisms are arthropods• Segments: head, thorax, abdomen• Fused segments: cephalotorax• Extensive cephalization• Open circulatory system: use of hemolymph

and hemocoels• Exoskeleton: prevents water loss, attachment

of muscle

• Exoskeleton- limits growth– Molting- allows growth (energy expensive)

Bases for subdivision of phylum- number of antenna, presence or absence of jawlike mandibles, type of appendages

*Crustaceans and insects may be more closely related

Digestive system

• Complete gut• Every mode of feeding

Respiratory system

• Gills- aquatic• Book gills-

horseshoe crab• Book lungs• Tracheal tubes w/

spiracles

Circulatory System

• Well-developed heart• Open circulatory system• Hemolymph –blood + interstitial fluid• Sinus- space that surrounds organs • Hemocoel collective term

Excretory system

• Malpighian tubule- remove nitrogenous waste from blood

• Gills• Green glands- found beneath the antenna,

remove nitrogenous waste

Nervous system

• Brain- made up of pair of ganglia• Ventral nerve cord- presence of ganglia per

segment• Simple and complex sense organs– Statocysts- balance– Compound eye- ommatidium of fly

Reproductive system

• Internal fertilization• Some have queens

Subphylum Trilobita

• Oldest subphylum• Extinct• Three lengthwise lobes from

head to tail• One pair of unspecialized

appendages per body segment• Appendage divided into two

branches– Gill– Walking leg

Subphylum Chelicerata

• Cheilos- lips; cheir- arm• Chelicerae- clawlike feeding

appendage• Arachnids- chelicerae are

called pedipalps• 4 pairs of walking legs• 2 fused segments-

cephalothorax, abdomen• Lack antenna

Subphylum Crustacea

• Mostly aquatic and marine• 2 pairs of antenna• Mouth parts are called

mandibles• 2 branches of appendages• Many have carapace

Subphylum Uniramia

• Almost all are terrestrial• 1 pair of antenna• Have mandibles• Unbranched appendages

Class Chilopoda

• Centipedes• Long, worm-like body• Many segments• One pair/ segment• Poison claw for feeding• carnivorous

Class Diplopoda

• Wormlike bodies with many segments

• 2 pairs of legs per segment• Mostly herbivorous

Class Insecta

• Insects• Body parts- head, thorax,

abdomen• Three pairs of legs• Usually two pairs of

wings attach to thorax• Metamorphosis:

complete/incomplete