The fundamental difference between a human and a flower is determined by their genetic code, specifically the DNA they inherit from their parents.

Here's how it works:

* DNA: Every living organism has DNA, a complex molecule that contains the instructions for building and maintaining that organism. DNA is like a blueprint.

* Genes: DNA is made up of genes, which are segments of DNA that code for specific traits. These traits can be anything from eye color to the structure of a leaf.

* Inheritance: When organisms reproduce, they pass on their DNA to their offspring. Humans inherit their DNA from their parents, and flowers inherit theirs from their parents.

* Differences in Genes: The DNA of a human is drastically different from the DNA of a flower. This difference is due to the different genes each organism carries. The genes that determine human development are completely different from the genes that determine the development of a flower.

So, to summarize:

* A human embryo will develop into a human because it carries human DNA, with genes that dictate human development.

* A flower seed will develop into a flower because it carries flower DNA, with genes that dictate flower development.

It's important to note that the environment can also play a role in development, but the fundamental blueprint for an organism's form is laid out in its DNA.