* Organisms can change during their lifetime in response to their environment. For example, a giraffe stretching its neck to reach higher leaves would develop a longer neck.
* These acquired characteristics can be passed on to their offspring. The giraffe's offspring would inherit the longer neck.
This theory was later disproven, as it was shown that acquired characteristics are not encoded in an organism's genes and therefore cannot be inherited. However, Lamarck's work was important in advancing the study of evolution, and his ideas paved the way for later theories such as Darwin's theory of natural selection.
