Answer AND Explanation:
The variations that Darwin regarded as raw materials for the process of evolution have been traced to changes that occur at the gene level or the chromosome and these changes are called mutations. Organisms with beneficial mutations are able to pass them on to their offspring during reproduction. Transmission of such mutations through many generations could lead to the emergence of new species. The emergence of new species requires a long time and is also affected by the rate of mutations that a particular species undergoes. This leads to evolution.
The type of joint that allows bones to move backward and forward in only one direction is the hinge joints. Ball and socket are the joints that allows movement in all directions. Gilding joints are type of joints that are the vertebral disks that allow twisting, turning, and sliding. Hinge joints are formed between two or more bones where the bones can only move along one axis to flex or extend. They include the ankle, elbow and knee joints.
