Question

List and describe synapomorphies for Arthropods. Contrast the subclades: Chelicerata, Crustacea, Myriapods, and the Hexapoda(insects).

Answer 1

Synapomorphy is define as the character shared by and ancestor and it passed down to the future generation in the course of evolution to specific species.

Similar inter-segmental tendon systems.	synapomorphic characters
Dorsal and ventral longitudinal muscle metamerically arranged.	synapomorphic characters
All muscle striated.	synapomorphic characters
Muscle tonofibrillae penetrate cuticle.	synapomorphic characters
Brain with )at least) ocular protocerebrum and usually an antennal deuterocerebrum; paired ventral nerve cords.	synapomorphic characters
Compound eyes (the compound eyes of trilobites seem to be unique and different from those of the other arthropods).	synapomorphic characters

Contrasts characters:

	Chelicerata	Crustacea	Myriapods	Hexapoda
Habitat	mostly terrestrial and rarely aquatic	They are mostly aquatic, few are terrestrial and very few are parasitic	Mostly terrestrial.	Mostly terrestrial and rarely aquatic
Respiration	by tracheae or book lungs or gills	through the gills or general body surface	by trachea	by tracheae, gills etc
Excretion	by malpighian tubules or coxal gland or both	Excretory organs are modified coelomoducts which may either maxillary glands or antennary gland	by malpighian tubules	usually by malpighian tubules
Appendages	Body is usually divided into cephalothorax and abdomen	Head is often fused with thoracic segments to form cephalothorax	body is long with numerous segments each having one or two pairs of legs	body is divided into three regions: head, thorax and abdomen.
Examples	Spider	Prawn	Millipede	House fly