What is meant by the law of use and disuse and by the law of the transmission of acquired characteristics?
As per to the law of use and disuse the characteristics of a body vary as it is more or less used. This rule is valid for instance for features like the muscular mass and the size of the bones.
The law of the transmission of obtained characteristics in its turn established that parents could transmit to their offspring characteristics acquired by the law of use and disuse.