Answer: Only some of the organisms survive and reproduce.
Natural selection is a process of differential survival and reproduction in which organisms bearing favorable phenotypic traits survive in changing environmental conditions. Therefore, only some of the organisms survive and reproduce which have suitable phenotypic trait. For example a population of beetle bearing two colors red and green. The green colored beetles mimic the color of grass will remain undetected by birds and those with red color easily observed and detected by birds. Hence, only green beetles are favored for survival over red beetles.