Phylum Arthropoda The largest group of animals within this kingdom

Arthropods are the most biologically successful group 1 million known species of arthropods They are suited for life in most conditions

Division of Arthropoda The phylum arthropoda can be divided into five groups, or subphylum: –Crustaceans –Centipedes –Millipedes –Arachnids –Insects

They All Share Certain Characteristics... Bilateral Symmetry Coelomates Segmented body Organ / system level of organization Complete digestive tract

What Separates Them From Other Animals?? Jointed appendages Exoskeleton Chitin and protein Well-developed nervous system Distinct brain, nerve cords Open circulatory system Tubular heart and arteries

Jointed appendages Legs are made up of several pieces These pieces are connected at hinged joints Different arrangements of these joints along with opposing sets of muscles allow different functions Arthropoda = “jointed feet”

The Exoskeleton Composed of protein and chitin, a carbohydrate Provides protection to the soft body parts Prevents water loss Adaptation to life on land Exoskeletons do not grow along with the organism »Molting – shedding of the exoskeleton, replacement with larger one

Arthropods Are Segmented... Segments are modified and fused Form specific body regions –HEAD Six segments Contains specialized mouth Antennae Compound eyes –THORAX The middle region –ABDOMEN The posterior region

Advancements in the Nervous System Cephalization is extensive –Disinct anterior region –Most sensory organs located in anterior region Well-developed sensory organs –Eyes –Receptors for smell –Antennae to respond to touch

All Arthropods Have an Open Circulatory System Tubular heart located dorsally –Above digestive tract Transport medium called hemolymph Arteries carry hemolymph away from heart –Flow into spaces surrounding tissues and organs Hemolymph brought back to the heart through pores equipped with valves

Arthropoda : Reviewing Their Success Their success has been brought about by several evolutionary events –Exoskeleton acting as a cuticle –Segmentation and appendages –Extensive nervous system and behaviors