What is the difference between insects and mammals?

Answer 1

First off, mammals are vertebrates (have a backbone and internal skeleton, phylum Chordata) and insects are invertebrates (no backbone, exoskeleton, phylum Arthropoda, though all phyla except Chordata are invertebrate). Where vertebrates have their largest blood vessels on the belly side and their nerve chord on the back side, it's the other way around in insects. Mammals are warmblooded, insects are coldblooded. Mammals breathe through lungs, insects through trachea (tubes all the way through the body). Insects have compound eyes, smell with their antennae and sometimes have ears on their legs... well, all in all, they're pretty much different in any way you can think of, because even similar structures (say, eyes) have evolved independently and work very differently. ^^

Answer 2

All insects lay eggs.