is insect a case of gene loss? originally same genes as humans but they lost like 30% of the genes and became more simplified creatures, then somehow copying these remaining genes further and futher evolving them and becoming very succesfull in their own niches
first there was ancestor of fish, somekind of weird worm which wasnt yet segmented
then it gave birth to octopus
after octopus (and snails) had separated from the original worm, the worm changed into a segmented type
then the segmented worm evolved into fish (pieces of fish vertebrae are the segments)
on the other hand the worm also evolved into insect ancestors some 700 million years ago, we would be talking about ocean creatures as insects themselves start on land and were never in the sea
centipedes are very segmented, each segment is kinda like a piece of human vertebrae. on the other hand insects have less segments, only the head, middle body and abdomen so you can think of them being two pieces of vertebrae
however in insects the segmentation continues in their legs as well
only centipedes, insects and spiders have so called arthropod legs, I am not entirely sure what part of human is corresponding to their legs, maybe lungs because in unsegmented worms the hairs that come out of them are the worms lungs and the hairs look like insects legs..
in terms of genes, insects are a succesfull case of "lost of genes"
they originally had all the genes a fish would have but they lost majority of it and became twisted into the form they are now, they dont contain an inner vertebrae but instead the vertebrae manifests itself as insect segmentation of the whole body
what continues to be same for fish and insect is a hollow notochord inside the creature (in fish its inside vertebrae, in insects its just stays there inside their body running from brain to anus, if a notochord is cut in half insect is paralyzed)