Natural selection is the process by which species adapt to their environment. Natural selection leads to evolutionary change when individuals with certain characteristics have a greater survival or reproductive rate than other individuals in a population and pass on these inheritable genetic characteristics to their offspring. Simply put, natural selection is a consistent difference in survival and reproduction between different genotypes, or even different genes, in what we could call reproductive success. [A genotype is a group of organisms sharing a specific genetic makeup.]
<em>Ossification is a process in which the mesenchymal cells and cartilages convert to bone during development. it is has two types: Membranous and endochondral ossifications. It occurs in mesenchyme which has formed a membranous sheath (figure 4) .</em>
