Scientists believe that land plants, such as the examples seen here, evolved from single-celled green algae. single-celled algae first evolved a colonial form, as noted in volvox, and eventually developed organs for reproduction as well as food and water conduction. one key process in this evolution was

Cell differentiation

Explanation:

Cell differentiation is the process by which an organism's cells undergo changes in their form, function, and composition to become specialized cells.

These differentiated cells can act in isolation - like gametes and sex cells from smaller organisms like bacteria. Or they can be grouped into differentiated tissues such as bone and muscle tissue. Although differentiated, cells keep the same genetic code as the first cell (zygote). The difference is in the activation and inhibition of specific groups of genes that will determine the function of each cell.

Differentiation was essential for the evolution of living organisms, an example of this can be seen in the text shown in the above question, where the whole process was only accomplished thanks to cellular differentiation.