lamarck in his book 'Philosophie Zoologique' 1809 gave his theory of evolution, arguing that animals modify themselves to adapt to the environment.
Postulates, Evidence and Criticism.
Internal forces of life control the growth of an organism. Eg. seed becomes a tree due to internal forces of life.
it was a vague statement and evolution of dinosaurs in two birds refutes this argument.
Ecological change creates needs/wants in an organism which lead to new organs or modifications. Eg. ducks evolved webbed toes due to needs in aquatic ecosystem.
but today we know, modifications and organs come from genetic change.
theory of use and disuse. an organ develops if it is used and goes extinct if not used. Eg. ostriches lost their wings due to disuse.
Inheritance. all acquired changes of an organism are transmitted to next generation.
But, Weissman showed that only changes in germinal cells are transferred.
recently some scientists like EJ Steele have tried to support lamarckism but these studies remain disputed.