Ecdysozoans

Phylum Nematoda

Found in most aquatic habitats, soil, moist tissues of plants, and body fluids and tissues of animals

Sexual reproduction usually by internal fertilization

C. elegans and T. spiralis

Commonly parasites

Phylum Arthropoda

Body completely covered by cuticle

When it grows, it molts its exoskeleton

Segmented body, hard exoskeleton, and jointed appendages

Some appendages modified for walking, feeding, sensory reception, reproduction, and defense

Have eyes, olfactory receptors, and antennae for touch and smell

Have open circulatory system with hemolymph

Cuticle

Exoskeleton made of layers of protein and chitin

Subphylum Chelicerata

Part of phylum Arthropoda

Mostly arachnids (spiders, scorpions, ticks, mites, and horseshoe crabs)

Have abdomen and cephalothorax with 6 pairs of appendages: chelicerae, pedipalps, and 4 walking leg pairs

Spider’s gas exchange happens in book lungs

Subphylum Myriapoda

Part of phylum Arthropoda

Terrestrial with jaw-like mandibles

Class Diplopoda

Part of phylum Arthropoda and subphylum Myriapoda

Millipedes

Eat decaying leaves and plant matter and small insects

Have many legs with 2 pairs per trunk segment

Class Chilopoda

Part of phylum Arthropoda and subphylum Myriapoda

Centipedes

1 pair of legs per trunk segment

Carnivorous

Have venomous claws that paralyze prey and aid in defense

Subphylum Hexapoda

Part of phylum Arthropoda

In almost every terrestrial habitat and freshwater

More species than all other life forms combined

Almost all have flight

Most have separate males and females and reproduce sexually

Find and recognize their own species by bright colors, sounds, or odors

Some are beneficial pollinators and some are pests

Order Archaeognatha

Part of phylum Arthropoda and subphylum Hexapoda

Bristletails

350 species

Order Thysanura

Part of phylum Arthropoda and subphylum Hexapoda

Silverfish

450 species

Order Coleoptera

Part of phylum Arthropoda and subphylum Hexapoda

Beetles

All winged

Complete metamorphosis

Order Diptera

Part of phylum Arthropoda and subphylum Hexapoda

Flies and mosquitoes

All winged

Complete metamorphosis

Order Hymenoptera

Part of phylum Arthropoda and subphylum Hexapoda

Bees, wasps, and ants

All winged

Complete metamorphosis

Order Lepidoptera

Part of phylum Arthropoda and subphylum Hexapoda

Butterflies and moths

All winged

Complete metamorphosis

Have proboscis

Order Hemiptera

Part of phylum Arthropoda and subphylum Hexapoda

True bugs: cicadas, aphids, bed bugs

All winged

Incomplete metamorphosis

Have piercing and sucking mouthparts

Order Orthoptera

Part of phylum Arthropoda and subphylum Hexapoda

Grasshoppers, locusts, and crickets

All winged

Incomplete metamorphosis

Subphylum Crustacea

Part of phylum Arthropoda

Typically marine and freshwater habitats

Many have branched appendages extensively specialized for feeding and movement

Small ones exchange gas through cuticle and large ones have gills

Isopods

Crustaceans that include terrestrial, marine, and freshwater species

Decapods

Crustaceans that are all relatively large and include lobsters, crabs, crayfish, and shrimp

Copepods

Planktonic crustaceans that are among the most numerous of animals

Barnacles

Mostly sessile crustaceans that are often filter feeders but sometimes parasitic

Phylum Loricifera

Inhabit deep-sea bottom

Can telescope its head, neck, and thorax in and out of lorica (pocket formed by 6 plates surrounding abdomen)

Phylum Priapula

Worms with large, rounded proboscis at anterior end

Most burrow into seafloor sediment

Phylum Onychophora

Velvet worms

Originally thrived in ocean but colonized land at some point

Now only live in tropical or temperate humid forests

Phylum Tardigrada

Water bears

Live in oceans, freshwater, and on plants or animals

Can enter dormant tun state under extreme conditions