They came over on an <span>umbilical cord.</span>
There are many internal factors which living organisms respond to, two of them are temperature and hormone levels. Organisms respond to internal factors in order to stay healthy and survive. The internal environment of living organisms has to be kept relatively constant, this is constancy is achieved through the process of homeostasis.
Cell, the smallest unit that can exist independently
Depending on the organism, the cell can get its energy from the sun (Plant; Photosynthesis) or through ATP energy (Animal).
