~Hello There!~
To get this concept you need to understand natural selection. This is where nature favors those with better adaptations for survival. Certain species help others get things for survival e.g food. As natural selection goes on, these organisms depend more on the symbiosis for survival because natural selection favored those traits over others.
Hope This Helps You!
Good Luck :)
Have A Great Day ^_^
- Hannah ❤
