Hello. You did not enter the text to which this question refers, which makes it impossible for this question to be answered accurately. However, I will try to help you in the best possible way.
The author may have presented that the development of personality is complex, showing how there are many elements acting in this development and countless elements that can modify this development at any time. To illustrate this, the author can make a comparison between personality development and a complex system, such as the development of a plant or an embryo for example.
It has decreased because over time because water creates caverns and also polution can kill alge in the water witch can cause the water flow to decrease in folucules.
