Final answer:
Lamarck proposed the idea that acquired traits can be passed on to offspring, known as the inheritance of acquired characteristics, which was an early theory of evolution.
Step-by-step explanation:
Jean-Baptiste Lamarck's idea about how organisms changed was the Inheritance of acquired traits. Lamarck believed that modifications in an individual, caused by its environment or the use or disuse of a structure during its lifetime, could be passed on to its offspring. This concept is known as the inheritance of acquired characteristics and was thought to bring about change in a species over time. Although this mechanism for evolutionary change as described by Lamarck was largely discredited, it played an important role in the development of evolutionary thought.