Gas exchange, oxygen transport and metabolism in high-altitude waterfowl
Bibliographic record
Abstract
High-altitude life poses physiological challenges to all animals due to decreased environmental oxygen (O 2 ) availability (hypoxia) and cold. Supporting high metabolic rates and body temperatures with limited O 2 is challenging. Many birds, however, thrive at high altitudes. The O 2 -transport cascade describes the pathway involved in moving O 2 from the environment to the tissues encompassing: (i) ventilation, (ii) pulmonary O 2 diffusion, (iii) circulation, (iv) tissue O 2 diffusion, and (v) mitochondrial O 2 use for ATP production. Shared avian traits such as rigid lungs with cross-current gas exchange and unidirectional airflow aid in O 2 acquisition and transport in all birds. Many high-altitude birds, however, have evolved enhancements to some or all steps in the cascade. In this review, we summarize the current literature on gas exchange and O 2 transport in high-altitude birds, providing an overview of the O 2 -transport cascade that principally draws on the literature from high-altitude waterfowl, the most well-studied group of high-altitude birds. We close by discussing two important avenues for future research: distinguishing between the influences of plasticity and evolution and investigating whether the morphological and physiological differences discussed contribute to enhanced locomotor or thermogenic performance, a potential critical link to fitness. This article is part of the theme issue ‘The biology of the avian respiratory system’.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".