Why must the bonds of these molecules be broken before anything else happens?

Synthesis releases energy because the molecules bond to form a stable configuration and therefore give up energy. The bonded molecules have a lower energy level than free molecules and are held in the new bond.

Explanation:

Chemical reactions make and break the chemical bonds between molecules, resulting in new materials as the products of the chemical reaction. Chemical reactions can occur spontaneously or require an outside trigger such as an input of energy. Breaking chemical bonds absorbs energy, while making new bonds releases energy, with the overall chemical reaction being endothermic or exothermic.

pregnancy happens more and more

phylogenetic tree is the tree of life or evolution tree. it shows the different branches of evolution. the sequence goes like tissues - coelom - backbone - endoskeleton - segmentation