Bacteria, protozoa, etc. simply split into two. Organisms develop as result of blueprint of instructions encoded in their genes. Genes are made of long molecules of DNA that specify how the organism is ordered. Adaptations are modifications that make an organism suited to its way of life. Natural selection is process by which species becomes modified over time.
Species is a group of interbreeding individuals.
In natural selection, members may inherit a genetic change that makes them better suited to a particular environment. Consequently, these members are more likely to produce more surviving offspring. Adaptations to different ways of life explain diversity of life forms. Populations within a community interact among themselves and with the physical and chemical environment, forming an ecosystem. All ecosystems together make up the biosphere, the thin layer of life that encircles the earth.