1)The defining characteristic that separates invertebrates from other organisms is the absence of the spinal column and backbone.
A notochord, a dorsal hollow nerve cord, pharyngeal slits, post-ana.l tail.
2) Carbon dioxide is a waste product produced by the animal's cells during cellular respiration, as well as ammonia because it could be very toxic and is also a common by-product of animal waste due to the often inefficient conversion of feed nitrogen into animal product.