I believe the answer you are looking for has to do with cells, they are the basic building block of life and are the smallest life that can support itself.
Internal fertilization is the process when the syngamy (union of male and female gamete) occurs inside the female body after insemination using copulation. In contrast, External fertilization is the syngamy outside the female body, that is in the outer environment especially in water bodies.
Answer:
Homologous structures provide evidence for common ancestry
<span>First, chemical energy from organic molecules is used to make ATP (Adenosine triphosphate) in cellular respiration, after which ATP provides energy for biological processes.</span>
