磁线索触发了大量的加油
T Fransson1, S Jakobsson, P Johansson
1Department of Zoology, Stockholm University, SE-106 91 Stockholm, Sweden. thord.fransson@nrm.se
Nature
|November 2, 2001
概括
磁线可以帮助年轻的歌鸟为长途迁徙旅行做好准备. 暴露于模拟的磁场促使夜增加脂肪储备,有助于跨越沙漠等生态障碍的生存.
科学领域:
- 鸟类学 鸟类学是一门学科.
- 动物迁徙 动物迁徙
- 行为生态学 行为生态学
背景情况:
- 迁徙鸟类依靠脂肪储备来穿越不补充燃料的生态障碍,如沙漠和海洋.
- 没有经验的鸟类可能很难确定关键的停留地点来补充能量储备.
研究的目的:
- 为了确定磁线是否可以向鸟类发出信号,在面临重大迁徙挑战之前储存脂肪.
- 研究磁场在航空航行和资源管理中的作用.
主要方法:
- 夜 (Luscinia luscinia) 在瑞典第一次迁徙之前被捕获.
- 鸟类被暴露在一个磁场中,模拟了在埃及北部,撒哈拉沙漠之前的停留地点.
- 在对模拟磁场的反应中监测脂肪沉积的持续时间.
主要成果:
- 暴露于模拟的磁场显著延长了夜的脂肪沉积期.
- 这表明磁性线索可以触发对迁移的生理准备.
结论:
- 磁线索可能在引导没有经验的候鸟到必要的加油点方面发挥着至关重要的作用.
- 这种机制可以帮助小歌鸟在迁徙期间成功地导航和生存在大型生态障碍.
相关概念视频
01:19Magnetic Field Lines
The representation of magnetic fields by magnetic field lines is very useful in visualizing the strength and direction of the magnetic field. Each of the magnetic field lines forms a closed loop. The field lines emerge from the north pole (N), loop around to the south pole (S), and continue through the bar magnet back to the north pole.
Magnetic field lines follow several hard-and-fast rules:
Magnetic field lines follow several hard-and-fast rules:
01:22Magnetic Force On Current-Carrying Wires: Example
In a magnetic field, moving charges encounter a force. If a wire contains these moving charges, i.e., if the wire is carrying a current, then a force acts on the wire as well. Consider a pair of flexible leads holding a wire that is 40 cm long and 10 g in weight in a horizontal position. The wire is placed in a constant magnetic field of 0.40 T, as shown in Figure 1(a). Determine the magnitude and direction of the current flowing in the wire needed to remove the tension in the supporting leads.
01:19Magnetic Flux
The magnetic flux measures the number of magnetic field lines passing through a given surface area. The SI unit for magnetic flux is the weber (Wb). Magnetic flux is a scalar quantity. It depends on three factors: the strength of the magnetic field B, the area through which the field lines pass, and the relative orientation of the field with the surface area.
Suppose a surface is divided into elements of area dA. For each element, the component of the magnetic field that is normal to the...
Suppose a surface is divided into elements of area dA. For each element, the component of the magnetic field that is normal to the...
01:18Magnetic Force
In addition to the electric forces between electric charges, moving electric charges exert magnetic forces on each other. A magnetic field is created by a moving charge or a group of moving charges known as the electric current. A magnetic force is experienced by a second current or moving charge in response to this magnetic field. Fundamentally, interactions between moving electrons in the atoms of two bodies produce magnetic forces between them.
The magnetic force acting on a moving charge...
The magnetic force acting on a moving charge...
01:24Potential Due to a Magnetized Object
Magnetic dipoles in magnetic materials are aligned when placed under an external magnetic field. For paramagnets and ferromagnets, dipole alignment occurs in the direction of the magnetic field. However, the dipoles align opposite to the field in the case of diamagnets. This state of magnetic polarization due to the external field is called magnetization. Magnetization is defined as the dipole moment per unit volume. It plays a similar role to polarization in electrostatics.
The vector...
The vector...
01:17Magnetic Damping
Eddy currents can produce significant drag on motion, called magnetic damping. For instance, when a metallic pendulum bob swings between the poles of a strong magnet, significant drag acts on the bob as it enters and leaves the field, quickly damping the motion.
If, however, the bob is a slotted metal plate, the magnet produces a much smaller effect. When a slotted metal plate enters the field, an emf is induced by the change in flux; however, it is less effective because the slots limit the...
If, however, the bob is a slotted metal plate, the magnet produces a much smaller effect. When a slotted metal plate enters the field, an emf is induced by the change in flux; however, it is less effective because the slots limit the...