Cecily M Costello1, Lori L Roberts1, Daniel D Bjornlie2,3

  • 1Montana Fish, Wildlife and Parks Kalispell Montana USA.

Ecology and evolution
|January 23, 2026
PubMed
概括

灰熊的出生时间平衡了母亲的能量储备和幼的生存,女性的晚产需要更多的时间,而那些能量充足的人则需要早产. 这种灵活的战略有助于气候变化抵御能力.

相关概念视频

Energetics of Solution Formation02:35

Energetics of Solution Formation

The formation of a solution is an example of a spontaneous process, which is a process that occurs under specified conditions without energy from some external source.
When the strengths of the intermolecular forces of attraction between solute and solvent species in a solution are no different than those present in the separated components, the solution is formed with no accompanying energy change. Formation of the solution requires the solute–solute and solvent–solvent...
7.4K
Bearing Stress01:22

Bearing Stress

Bearing stress refers to the contact pressure between two separate bodies. To visualize this, imagine a bolt thrust through a plate. The bolt applies a force to the plate, which exerts an equal but opposite force back onto the bolt. This force isn't just a singular entity but a compilation of numerous smaller forces distributed across the contact surface between the bolt and the plate.
Due to the intricacy of these microforces, an average value, known as bearing stress, is often used by...
2.0K
Azimuths and Bearings01:19

Azimuths and Bearings

Azimuths and bearings are essential concepts in surveying, providing methods to express the direction of a line relative to a meridian. Azimuths refer to the clockwise angle measured from the north end of a reference meridian to the given line, ranging from zero to 360 degrees. This method gives a comprehensive directional reference within a full 360-degree circle, making it a straightforward way to communicate direction in various fields, including navigation, cartography, and...
623
Collar Bearings01:23

Collar Bearings

Collar bearings are essential in various machines designed to support axial loads on rotating shafts. Depending on the specific application and requirements, they can be found with single or multiple collars.
1.6K
Pivot Bearings01:23

Pivot Bearings

In mechanical systems, bearings are crucial in facilitating relative motion between two components while minimizing friction and wear. They help distribute various loads (radial, axial or a combination of both loads) across machinery parts, ensuring smooth and efficient operation.
A pivot bearing is a specialized type of bearing designed to support axial loads on a rotating shaft. The bearing surface, or the pivot, is positioned at the end of a shaft to support the axial thrust. The pivot may...
2.2K
Journal Bearings01:23

Journal Bearings

Journal bearings are mechanical components that support and provide lateral stability to rotating shafts and axles. They are crucial in reducing friction, wear, and vibration in machinery such as engines, turbines, and pumps. The principle behind journal bearings is forming a thin lubricant film between the bearing surface and the rotating shaft, which minimizes direct contact and reduces frictional forces.
To better understand the concept of journal bearings, consider a rope winch with dry or...
1.1K