Darwin proposed that Changes in species was due to procreation or breeding. Those species that spawned changes which helped to adapt to the new conditions, survived, while those that didn’t eventually died. The theory was one of natural selection and survival of the fittest. As the environment underwent changes, the species affected by these changes underwent changes in response to changes in the environment.
Lamarck's theory held that species underwent changes in response to changes in their environment. This change was permanent for as long as the new environmental conditions continued to apply. Nature chose the best possible solution and organisms (species) responded accordingly. In short, Lamarck does not believe in survival of the fittest while Darwin’s theory is based on survival of the fittest. Lamarck believes that there is an inner vital force while Darwin does not. Lamarck does not consider struggle for existence, while in Darwin's theory, struggle for existence is very important in this theory.
