How did new needs lead to new habits in Lamarck’s theory?

In Jean-Baptiste Lamarck’s theory of evolution, the emergence of new habits is a direct response to environmental change. According to Lamarck, shifts in an environment create new needs (besoins) for an animal.12

To satisfy these needs, the animal makes a conscious or instinctive effort, which leads to the adoption of new behaviors or habits. These new habits necessitate the increased use of certain organs—or the disuse of others—resulting in physical modifications such as the strengthening or enlargement of frequently used parts and the decline of those left idle. Lamarck proposed that these material alterations, acquired during an individual's lifetime, were then inherited by the next generation, eventually leading to species-wide changes over long periods.12

While these ideas were historically significant as an early comprehensive theory of organic transformation, they have been discredited by modern genetics, as there is no evidence that such acquired physical traits are passed to offspring through biological inheritance.132