a representation of a phylogeny where evolutionary relatedness is shown by both branching order and a distance measure
-segmented bodies with paired, jointed appendages
-exoskeleton composed of chitin
-complete digestive tract
-closed circulatory system
-ventral nervous system
- like earthworm, leeches, tubifex worms
o Most numerous group of arthropods
o Jaws are mandibles
o Three tagmata (head, thorax, and abdomen)
o One pair of antenna
3 pairs of legs
o May have wings (only flying arthropods)
o Breath using trachea that open to spiracles
in the mesothorax.
large fan-like indentations important for flying insects
include areas for muscle attachment.
A type of metamorphosis in which the animal increases in size from one stage to the next, but does not dramatically change its body form. Also called incomplete metamorphosis.
prevents loss of water. also important in resistance of invasion by pathogens.
protects wax layer from being scratched or lost by absorption onto foreign objects.
fusion of sternal and pleural apophyses
secretory appendages on the end of the abdomen
lined by thin cuticular intima that is continous with cuticle of exoskeleton
intima is shed with exuvieae after moulting
thin wire of cuticle called taenidia goes spirally through the intima and gives tracheal tubes the abilitiy to flex and stretch without restricting air flow
diffusion. relies on high partial pressure and concentration of oxygen in atmosphere. passageway carries air from environment and delivers oxygen to cells
-aquatic insects modify this system for water. water scorpion has a snorkel and water beetles use air bubbles. hold air bubble underwater and oxygen diffuses into bubble from surrounding water.
- spiracles absent,
- tracheae form an internal network,
- gas exchange via cutaneous diffusion,
- some aquatic species and many endoparasitic larvae utilize this method.