The instructions for each stage were written into the DNA long before reproduction. Everything in the universe has energy, which is defined as a capacity to do work. There are many different types of energy, and absolutely nothing can happen in the universe without a complete or partial transfer of energy. Without energy organisms cannot stay alive, grow and reproduce. Life forms sense and make changes in the environment.
Organisms have receptors, which are molecules that detect specific stimuli.
A stimulus is an energy change in the environment such heat, light, or sound. Organisms respond to energy changes and their internal operating conditions remain within a narrow limit. We call this narrow limit of change homeostasis, that is a defining feature of life. Generally this is done through a process called photosynthesis. Animals that consume plants or other animals.