Habitat destruction is the key one out of all of these. Animals being kept at the zoo for research are usually endangered or vulnerable species which is doing more good than harm to them. Legal hunting of animals is most likely for rabbits, deer, and a stabilized population in the wild. Habitat destruction can destroy many populations and cause loads of damage. An example of that would be the Australian wildfires at the start of 2020.
Many kinds of prokaryotes and eukaryotes contain a structure outside the cell membrane called the cell wall. With only a few exceptions, all prokaryotes have thick, rigid cell walls that give them their shape. Among the eukaryotes, some protists, and all fungi and plants, have cell walls.
Generally, epithelial cells serve the function of protection of the inner layers of the structure they are on. The fact that these columbar epithelium and transitional epithelium cells have smooth walls and are dome shaped allows them to stretch. This stretching helps the bladder retain more urine than it would be able to if the epithelial cells were rigid.
