Bacteria have a structure called a cell wall. Fungi and some ptotozoa also have cell walls. They are not the same as the plant cell walls made of cellulose. The other walls might be made from proteins or a substance called chiti
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.]