Besides these symptoms of altitude sickness, others such as headache and fatigue may also occur.

除了这些症状外，高原反应还可能出现头痛和疲劳等其他症状。

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It may also occur among totally unrelated forms that compete for the same resource, such as seed-eating rodents and ants.

它也可能发生在完全不相关的、争夺相同资源的组织中，比如以种子为食的啮齿动物和蚂蚁。

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Additional social stresses may also occur because of the population explosion or problems arising from mass migration movements—themselves made relatively easy nowadays by modern means of transport.

由于人口的猛增或大量人口流动（现代交通工具使这种流动相对容易）造成的种种问题也会对社会造成新的压力。

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However, similar symptoms may also occur if there's an injury, swelling or infection of various parts of the male anatomy, so it is important that a physician make the diagnosis if something abnormal is found on a self-exam.

CNN: Should teen boys check testicles regularly?

Vomiting, chills, headache and muscle pains also may occur, according to the Mayo Clinic.

CNN: STORY HIGHLIGHTS

Apple also plans to expand distribution, which most likely refers to iPhone carriers and may occur concurrently with a new product launch.

FORBES: Apple Analysts Expect New iPhone In The Fall, Larger-Screen iPhone, SmartWatch in 2014