Biology To Life

SPECIATION AND EVOLUTIONARY CHANGE A.     Species : A Working Definintion A species is commonly defined as a population of organisms whose members have the potential to interbreed naturally to produce fertile offspring but do not interbreed with other groups. This is a working definition; it applies in most cases but must be interpreted to encompass some exceptions. There are two key ideas within this definition. First, a species is a population of organisms. Second, the definition involves the ability of individuals within the group to produce fertile offspring. Obviously, we cannot check every individual to see if it is capable of mating with any other individual that is similar to it, so we must make some judgment calls. B.      How New Species Originate Geographic Isolation The geographic area over which a species can be found is known as its range. The range of the human species is the entire world. As a species expands...

NATURAL SELECTION AND EVOLUTION A.     The Role Of Natural Selection Evolution is the continuous genetic adaptation of a population of organisms to its environment over time. Evolution results when there are changes in genes present in a population . There are three factors that interact to determine how a species changes over time: environmental factors that affect organisms, sexual reproduction among the individuals in the gene pool, and the generation of genetic variety within the gene pool. The idea that some individuals whose gene combinations favor life in their surroundings will be most likely to survive, reproduce, and pass their genes on to the next generation is known as the theory of natural selection. The theory of natural selection was first proposed by Charles Darwin and Alfred Wallace and was clearly set forth in 1859 by Darwin in his book On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Strugg...