Homologous structures refers to organs or bones that have similar anatomical features found in different animals that are suggested to have the same common ancestor and serves as an evidence of evolution.
Whakes, humans and cats have similar bones in the same order but different in function.
The fact that whales, humans, and cats all have the same bones in the same order, but they matured differently in later embryological development, is an example of homologous characters or homologous structures.
Homologous characters have the same fundamental structures. They also share the same relations with adjacent structures, and they have the same embryological development.
These structures might show variations between organisms exhibiting them, according to their function and to the environment in which the organism lives.
These homologous characters are common in organisms related and that share a common ancestor.
Internal means its on the inside external means its on the outside
so an internal regulator is when the proteins respond to events on the inside of a cell and an external regulator is when the proteins respond to events outside the cell
