Homeostasis, aka your body maintaining life and the right amounts of stuff.
The correct answer is absence of jaws.
Lampreys and hagfish are in the class Agnatha, they are jaw-less fish. The members of the agantha class are probably the earliest vertebrates. Scientists have found fossils of agnathan species from the late Cambrian period that occurred 500 million years ago.
I believe the answer is chromosomes.
Chromosomes are basically coiled up pieces of DNA with proteins.
I hope this helps! If it doesn't, please reply.
