His heart was broken also because of how alienated he felt from his family and did not want to burden them. Gregor feels terrible about the trouble and pain he's causes his family. ... They used him for money and he was no longer useful to them when he could not work and take care of the family.
Over time animals and plants of all sorts have evolved into several different things. there is no limit to the differences that can exist, as life is ever changing.
