Darwin and Lamarck both suggest the development of different species on the basis of evolution, with changes taking place over time. Some of the mechanisms suggested by Lamarck are also involved in the theory offered by Darwin, but there are also differences between the two.
Lamarck suggests that the reason why species change is a "felt need," and such needs make organisms respond creatively. For Lamarck, evolution takes place in an upward fashion and does so because organisms want this to be the case. Gould says that Lamarckianism is a theory of directed variation, meaning that a felt need is actually a perception on the part of the organism so that the need is then fulfilled and the organism changes, at least for subsequent generations. The Lamarckian approach has often been mistaken for the Darwinian approach, and people ask how organisms can progress deliberately, as if they were able to choose what they were and as if evolution had a direction, a purpose, and a conscious control.
Darwin's approach is not so simple and involves a two-part process. Both Lamarck and Darwin base their view on the conception of adaptation, or the idea that organisms respond to changing environments by evolving a new form, function, or behavior. Information is transmitted to the organism from the environment in both cases. For Lamarck, the organism perceives the environmental change and adapts. In the Darwinian version, the first step is random and is known as genetic variation. The process is random because it occurs with no preferred orientation in adaptive directions. Selection is the next step, and this works with unoriented variation and changes a population by giving members greater reproductive success for certain advantages.
Specialization is the adaptation of a body part to a particular function or of a whole organism to a particular environment, and much of the diversity of life is expressed through specialization. Organ...