molecular instructions that guide how all living things develop and function
https://en.wikipedia.org/wiki/DNAAnimal Development & Growth
The way your body works now is not the way it has always worked. Think about it—today, your voice might be a little deeper, you might be a little taller, and you might even think differently than you did just a few years ago. This process of how an organism changes through time is called development.

Why Do Scientists Study Animals?
Scientists and others have many reasons for why it can be both good and bad to use animals for research. In the table are examples of both sides of this debate. And below we provide more details for each side.