Phylum Arthropoda (The Arthropods) By far and away, the most successful animal group ever to live Consists of over 1 million named species, 2 of every 3 animals are arthropods. Inhabit all ecosystems

General characteristics All have a hard exoskeleton Composed of protein and chitin Allows for great variation in function - biological "swiss army knives" Must molt as they grow Limits their size Have well developed body segments and appendages Have well developed sensory organs including true eyes and antennae Have open circulatory systems & special gas exchange organs

Subphylum Chilicerata (arachnids, horseshoe crabs & sea spiders) Divided into 3 classes; Arachnida, Merostomata & Pycnogonida Body divided into 2 regions Abdomen Cephalothorax (fused head & thorax) Lack jaws Have 6 appendages & no antennae First appendages form chilicerae (frequently fangs)

Class Arachnida (Spiders, Scorpions, Ticks & Mites) Very diverse class Most species parasitic or predatory Many possess book lungs for gas exchange Spiders are able to produce a strong polymer - silk Chilicera in form of fangs

Spiders

More Spiders… Tarantula Black Widow

For the true arachnophobe… The brown recluse and its bite wounds

The Camel Spider

Ticks & Mites

Ticks & Lyme Disease…

Common Mites Dust Mite Common Mite

Scorpions

Class Picogonida (Sea Spiders)

Class Merostomata Ancient group of species Changed little over 350 million years Aquatic, mostly found on Atlantic & gulf coasts of United States

Subphylum Uniramai (3 Classes) Class Insecta (insects) Class Chilopoda (Centipedes) Class Diplopoda (Millipedes)

Class Insecta (the insects) Far & away the most diverse of animal groups More types of insects alone than all other animal groups combined Inhabit all terrestrial & freshwater ecosystems. Success largely attributed to coevolution with flowering plants.

Insect Body Plan Insects have 6 legs 3 body parts Head Thorax Abdomen Most insects have wings, however in many species these are vestigial Have advanced excretory system composed of malphygian tubules Exchange gasses through a complex tracheal system

Vision Have complex compound eye which is usually extremely sensitive to motion and allows 3600 vision Most insects see well into the UV spectrum

Feeding / Mouthparts Insects usually have specialized jaws/mouthparts suited to their ecological niche

Metamorphosis Most insects undergo a process of metamorphosis - 2 types Incomplete metamorphosis Larva similar to adult, with differing body proportions Undergoes a series of molts resulting in adult phenotype

Complete Metamorphosis Larva is very unlike adult phenotype Envelopes self in a coccoon or chrysalis where body breaks-down and reforms into adult form.

Classes Chiopoda & Diplopoda Millipedes (diplopoda) are segmented worm-like animals Have 2 pairs of legs per segment Primarily herbivores & decomposers Centipedes (Chilopoda) Usually terrestrial carnivores Have 1 pair of antennae Are often poisonous, using modified front claws to immobilize prey

Centipedes vs. Millipedes

Subphylum Crustacea Includes crabs, lobsters, crayfish, shrimp, krill & barnacles Over 40,000 species Appendages are often highly specialized Gas exchange is usually through gills Many species taste delicious in butter

Some Crustaceans Crayfish Marine Maine Lobster

Crabs

Barnacles