A stroke can result in a number of visual problems, including visual neglect, decreased visual acuity, diplopia (double-vision), squint, and homonymous hemianopsia (visual field defects).
Natural Selection. Natural selection is the process by which individuals with characteristics that are advantageous for reproduction in a specific environment leave more offspring in the next generation, thereby increasing the proportion of their genes in the population gene pool over time.
In a changing environment, natural selection will favor variations Variation: The differences among individuals in a population. that result in a better fitness in the new environment, resulting in adaptation and evolution. Directional selection Directional selection Directional Selection: A type of selection that removes individuals from one end of a phenotypic distribution and thus causes a shift in the distribution. occurs when natural selection favors one extreme of continuous variation. Over time, the favored extreme will become more common and the other extreme will be less common or lost.