Implications of the late palaeozoic oxygen pulse for physiology and evolution

Article Abstract:

The pulse of oxygen concentration in the late palaeozoic oxygen may have fluctuated between as high as 35% to as low as 15% and thereby influenced the evolution of major groups of organisms. Enhancement of diffusion-dependent processes such as respiration may result from an increase in atmospheric oxygen which in turn will increase body-size. Increase in oxygen concentration can also enhance metabolic rate and resource accessibility, which may result in promoting the radiation of some extra taxa.

Environmental aspects, Earth, Atmospheric chemistry, Atmospheric research

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Limits to vertebrate locomotor energetics suggested by hummingbirds hovering in heliox

Article Abstract:

The muscle mass-specific power for the hovering ruby-throated hummingbirds' wingbeats ranges from 98 watt/kg in normal air to 133 watt/kg, when aerodynamic failure results. The muscle efficiency is constant at 10% despite changes in the power consumption. By changing the wing-stroke amplitude, modulation of the power output is achieved. A study of hummingbirds showed that wingbeat was also modified by changes in density of the surrounding gas.

Measurement, Observations, Muscle strength, Oxygen consumption, Oxygen consumption (Metabolism), Physiological regulation, Hummingbirds, Locomotion

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Directed aerial descent in canopy ants

Article Abstract:

The workers of the neotropical ant, 'Cephalotes atratus', which use directed aerial descent to return to their home tree trunk with less than 80% success during the fall, are shown. It is revealed that 'Cephalotes atratus' workers descend abdomen-first through steep glide trajectories at relatively high velocities.

United States, Natural history, Insects, Ants

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