The fossil record shows the existence of trilobites and dinosaurs in the past. Building malls has decreased the available habitats for some organisms. Some organisms have not changed in their characteristics for millions of years. Species of antibiotic-resistant bacteria have developed in some hospital environments. True-False Section 1.
Evolution necessitates long-term progress in any set direction.
An increased variation of organisms within a species decreases the possibility that some members of the species will survive changed environmental conditions. Many organism behaviors have evolved through natural selection. Meiosis and fertilization make possible a great variety of gene combinations which drive natural selection. Evolutionary changes appear to be like the growth of a bush. Some branches survive from the beginning with little or no change, many die out all together, and others branch repeatedly, sometimes giving rise to more complex organisms.