Explanation:
Beginning in 1837, Darwin proceeded to work on the now well-understood concept that evolution is essentially brought about by the interplay of three principles: (1) variation—a liberalizing factor, which Darwin did not attempt to explain, present in all forms of life; (2) heredity—the conservative force that transmits
Answer:
Darwin's main contribution to the theory of evolution was his theory of natural selection.
Explanation:
Natural selection is the phenomenon that some organisms from a particular population fit better into their environment, that is, are more likely to provide surviving offspring than less well-adapted organisms. The best adapted organisms will increasingly gain the upper hand within the population (survival of the fittest). It is thus one of the mechanisms of evolution. Mutations in, and recombinations of, the genetic material of the organisms cause the genetic variation in the population, allowing this selection.
Answer:
1. The United States is in the Western Hemisphere (because it is west of the prime meridian) and also in the Northern Hemisphere (because it is north of the equator).
Answer: In 1959, a young senator wrote an article for a young magazine called "TV Guide" trumpeting the potential for the new medium of television to permanently change the way politics worked. In a little more than a year, that same senator, John F. Kennedy, would be elected president of the United States, thanks in no small part to his charismatic performance in a series of televised debates with opponent Richard Nixon and a TV ad campaign that featured some catchy jingles. Three years later, news coverage of Kennedy's assassination would captivate the country, becoming one of the first major tragedies covered by network news [source: Kaid]. By that time, television's place in shaping the political landscape was undeniable.
Explanation:
