How did the motet develop from the medieval clausula?

In Western music, the motet emerged in the early 13th century as a direct evolution from the clausula, a polyphonic genre developed by the Notre-Dame school in Paris.12

The transition occurred through the following process:

• Text Application: The clausula was originally a short, textless section of organum featuring a plainchant melody in the tenor and one or more upper voices set in strictly measured rhythmic patterns known as rhythmic modes. The motet was created by adding new texts—often secular—to these previously wordless upper-voice parts.1342
• Structural Shift: While the clausula functioned as a "substitute" composition within a larger organum, the addition of text transformed it into an independent genre. As the motet developed, composers began to move beyond the original plainchant-based structure, sometimes choosing tenors from popular songs and allowing rhythmic patterns to become more varied and free.31
• Evolution of Complexity: Over time, the motet expanded from these texted clausulae into a sophisticated form that eventually incorporated techniques like isorhythm and, by the 15th century, evolved into a contrapuntal style where all voice parts shared the same text.14