Jean-Baptiste Lamarck had the most influence over Darwin’s development of his theory of Natural selection. After serving time in the Army, Lamarck studied medicine and botany and becoming a expert on the subjects. He wrote a book in 1778 on the plants of France.
Lamarck began his career as a botanist working in the gardens of the Jardin des Plantes which was also a center for medical education and biological research. Lamarck moved away from the garden when the Jardin des Plantes was reorganized as the Musée National d'Histoire Naturelle and offered to be a professor of the natural history of insects and worms. This field studied invertebrates, which he was not a subject matter expert. Lamarck actually came up with the word invertebrates and challenged himself to learn everything about these species, in return he created a new field of biology. After ten years of research, he began to lecture students at the Musée. Lamarck would again write a book, but this time a series of books on invertebrate zoology and paleontology. The book, Philosophie zoologique clearly states Lamarck's theories of evolution. In Introduction to Physical Anthropology, “Lamarck suggested a dynamic relationship between species and the environment such that if the external environment changed, an animal’s activity patterns would also change to accommodate the new circumstances”(29). Lamark never gained respect that some of his colleagues had and one even used some of Lamark’s work to discredit him, since he had no use for Lamark’s work. Lamarck’s scientific thought was:
Lamarck began his career as a botanist working in the gardens of the Jardin des Plantes which was also a center for medical education and biological research. Lamarck moved away from the garden when the Jardin des Plantes was reorganized as the Musée National d'Histoire Naturelle and offered to be a professor of the natural history of insects and worms. This field studied invertebrates, which he was not a subject matter expert. Lamarck actually came up with the word invertebrates and challenged himself to learn everything about these species, in return he created a new field of biology. After ten years of research, he began to lecture students at the Musée. Lamarck would again write a book, but this time a series of books on invertebrate zoology and paleontology. The book, Philosophie zoologique clearly states Lamarck's theories of evolution. In Introduction to Physical Anthropology, “Lamarck suggested a dynamic relationship between species and the environment such that if the external environment changed, an animal’s activity patterns would also change to accommodate the new circumstances”(29). Lamark never gained respect that some of his colleagues had and one even used some of Lamark’s work to discredit him, since he had no use for Lamark’s work. Lamarck’s scientific thought was:
organisms are not passively altered by their environment, …. Instead, a change in the environment causes changes in the needs of organisms living in that environment, which in turn causes changes in their behavior. Altered behavior leads to greater or lesser use of a given structure or organ; use would cause the structure to increase in size over several generations, whereas disuse would cause it to shrink or even disappear. This rule -- that use or disuse causes structures to enlarge or shrink -- Lamarck called the "First Law" in his book Philosophie zoologique. Lamarck's "Second Law" stated that all such changes were heritable. The result of these laws was the continuous, gradual change of all organisms, as they became adapted to their environments; the physiological needs of organisms, created by their interactions with the environment, drive Lamarckian evolution.
http://www.ucmp.berkeley.edu/history/lamarck.html
The point “In order for traits to evolve and change, they MUST be heritable” is the one that directly affected his work. This influenced his work because he believed the environment change organisms and their behavior was altered by his rule of use or disuse of organs causes structures to enlarge or shrink.
Darwin could not have developed his theory of natural selection without the influence and ideas of Lamarck. One idea was the use and disuse that Darwin said might be an important in evolution.
