定向进化

Also known as orthogenetic evolution, evolutionary progress, progressive evolution, progressionism

thumb|Evolutionary progress as a tree of life (biology)|tree of life. [[Ernst Haeckel, 1866]] thumb|upright=1.4|Lamarck's two-factor theory involves 1) a complexifying force that drives animal body plans towards higher levels (orthogenesis) creating a ladder of phyla, and 2) an adaptive force that causes animals with a given body plan to adapt to circumstances (use and disuse, [[inheritance of acquired characteristics), creating a diversity of species and genera. Popular views of Lamarckism only consider an aspect of the adaptive force.]] Orthogenesis is an obsolete biological hypothesis that