Fontes das imagens: http://2.bp.blogspot.com/-Z0nJMhy1K3Q/TcRpuyIGT7I/AAAAAAAAAs0/8jLZo_zUVcU/s1600/evolucao.jpg http://portaldoprofessor.mec.gov.br/storage/discovirtual/aulas/588/imagens/patterns_intro.gif