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Why Do Some Butterflies Migrate Across Entire Continents?
为什么一些蝴蝶能跨越整个大陆迁徙？
精读先不看文字，完整听一遍。
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Monarch butterflies travel up to 4,000 kilometers from Canada to central Mexican forests each autumn.每年秋季，帝王蝶从加拿大飞往墨西哥中部森林，行程可达4000公里。
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They use Earth’s magnetic field, the sun’s position, and circadian clocks to navigate without prior experience.它们依靠地球磁场、太阳位置和生物钟导航，无需过往经验。
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No single butterfly completes the full round-trip; it takes three or four generations to return north.没有一只帝王蝶能完成全程往返；需三至四代才能返回北方。
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Their wings contain specialized photoreceptors that detect polarized light invisible to humans.其翅膀含有特殊光感受器，可探测人类不可见的偏振光。
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Fat reserves built during summer feeding fuel long flights when nectar sources are scarce.夏季取食积累的脂肪储备，支撑花蜜稀缺时的长途飞行。
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Cold temperatures trigger hormonal changes that halt reproduction and prepare bodies for migration.低温触发激素变化，暂停繁殖并为迁徙做好生理准备。
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Scientists track them with tiny radio tags and citizen science apps to map shifting routes yearly.科学家借助微型无线电标签和公民科学应用程序，逐年追踪并绘制其迁徙路线变化。
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Climate shifts now cause earlier spring arrivals and mismatched timing with milkweed plant growth.气候变化导致春季抵达时间提前，与马利筋植物生长期错配。
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Unlike birds, monarchs lack navigational learning, relying entirely on inherited genetic programming.与鸟类不同，帝王蝶不具备导航学习能力，完全依赖遗传编程。
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This fragile migration is threatened by habitat loss, pesticides, and extreme weather events worldwide.这一脆弱的迁徙现象正面临全球栖息地丧失、农药和极端天气事件的威胁。
精读 · 大约 10 分钟
听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。
③ 学 · 重点表达
- Their wings contain specialized photoreceptors that detect polarized light invisible to humans. 其翅膀含有特殊光感受器，可探测人类不可见的偏振光。
- Unlike birds, monarchs lack navigational learning, relying entirely on inherited genetic programming. 与鸟类不同，帝王蝶不具备导航学习能力，完全依赖遗传编程。
- Cold temperatures trigger hormonal changes that halt reproduction and prepare bodies for migration. 低温触发激素变化，暂停繁殖并为迁徙做好生理准备。
④ 懂 · 选一选
⑤ 今天会说这一句
Their wings contain specialized photoreceptors that detect polarized light invisible to humans.
⑥ 跟读并录音
Their wings contain specialized photoreceptors that detect polarized light invisible to humans.
第一版：录下来、回听、再听标准音。系统打分以后再加。
⑦ 说 · 自己来一句
用今天的表达，自己说一句。
例子：Their wings contain specialized photoreceptors that detect polarized light invisible to humans.
已记下。连续天数以后会显示在课表里。
陈老师指导
课程开发中，敬请期待。成人和孩子都可以先自学听读、精读。
这边的讲解音轨还在做。想先跟着老师走完固定 30 课，可以去陈老师带读社（和自学通行不是同一份会员）。
课程开发中，敬请期待。