Remember that prokaryotic cells are simple and do not contain membrane-bound organelles and that eukaryotic cells are more complex and do contain membrane-bound organelles, as well as a nucleus. The endosymbiosis theory explains how eukaryotic cells may have evolved from prokaryotic cells. Symbiosis is a close relationship between two different organisms. We saw that, over time, one ancient cell became the host for other ancient cells that were capable of specific activities.
aviary, An aviary is a large enclosure for confining birds. Unlike cages, aviaries allow birds a larger living space where they can fly; hence, aviaries are also sometimes known as flight cages. Aviaries often contain plants and shrubbery to simulate a natural environment.
A zoo (short for zoological garden or zoological park, and also called an animal park or menagerie) is a facility in which animals are confined within enclosures, displayed to the public, and in which they may also be bred.