Why did Lamarck think environmental changes created new needs in animals?

According to the theory of Lamarckism, Jean-Baptiste Lamarck proposed that environmental changes act as a catalyst for biological transformation by creating new needs, or besoins, in animals.1

Lamarck argued that when an animal's environment changes, it is forced to adapt to survive. These new environmental circumstances necessitate new types of behavior, which in turn require the animal to use its existing organs in different ways. This shift in behavior and the resulting increased use—or conversely, the disuse—of specific body parts leads to material alterations in the organism, such as the strengthening or weakening of organs.12

Lamarck believed that these acquired physical changes, driven by the animal's effort to satisfy its new needs, were then passed on to the next generation. While these ideas were influential in the 19th century, they were later discredited by modern genetics, which has shown that such acquired characteristics are not inherited in the manner Lamarck described.123