Overdose: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: unusual excitement, fast/irregular heartbeat, seizures.
Natural Variation Natural variation includes internal and external variability influences such as the solar Schwabe cycle, oceanic cycles, seasonal influences based on changes caused by the interaction of the various natural oscillations in the climate system.
Over time, the intermediate states become more common and each extreme variation will become less common or lost. Natural selection can occur with or without environmental change. 1  In a constant environment, natural selection will keep a population stable and essentially maintain the status quo. 2  In a constant environment, if a new variationVariation:The differences among individuals in a population.