Editing Altitude (section)

===Other organisms===
{{main|Organisms at high altitude}}
Decreased oxygen availability and decreased temperature make life at high altitude challenging. Despite these environmental conditions, many species have been successfully [[high-altitude adaptation|adapted at high altitudes]]. Animals have developed physiological adaptations to enhance oxygen uptake and delivery to tissues which can be used to sustain metabolism. The strategies used by animals to adapt to high altitude depend on their [[Morphology (biology)|morphology]] and [[phylogeny]]. For example, small mammals face the challenge of maintaining body heat in cold temperatures, due to their small volume to surface area ratio. As oxygen is used as a source of metabolic heat production, the hypobaric hypoxia at high altitudes is problematic.

There is also a general trend of smaller body sizes and lower [[species richness]] at high altitudes, likely due to lower oxygen partial pressures.<ref name=macroinvertrichness>{{cite journal|last=Jacobsen|first=Dean|title=Low oxygen pressure as a driving factor for the altitudinal decline in taxon richness of stream macroinvertebrates|journal=Oecologia|volume=154|pages=795–807|doi=10.1007/s00442-007-0877-x|issue=4|pmid=17960424|date=24 September 2007|bibcode=2008Oecol.154..795J|s2cid=484645}}</ref> These factors may decrease [[Productivity (ecology)|productivity]] in high altitude habitats, meaning there will be less energy available for consumption, growth, and activity.<ref name="trout">{{cite journal|last1=Rasmussen|first1=Joseph B.|first2=Michael D.|last2=Robinson|first3=Alice|last3=Hontela|first4=Daniel D.|last4=Heath|title=Metabolic traits of westslope cutthroat trout, introduced rainbow trout and their hybrids in an ecotonal hybrid zone along an elevation gradient|journal=Biological Journal of the Linnean Society|volume=105|pages=56–72|doi=10.1111/j.1095-8312.2011.01768.x|date=8 July 2011|doi-access=free}}</ref>

However, some species, such as birds, thrive at high altitude.<ref>{{cite journal|last1=McCracken|first1=K. G.|last2=Barger|first2=CP|last3=Bulgarella|first3=M|last4=Johnson|first4=KP|last5=Sonsthagen|first5=SA|last6=Trucco|first6=J|last7=Valqui|first7=TH|last8=Wilson|first8=RE|last9=Winker|first9=K|display-authors=4|title=Parallel evolution in the major haemoglobin genes of eight species of Andean waterfowl|journal=Molecular Evolution|date=October 2009|volume=18|issue=19|pages=3992–4005|doi=10.1111/j.1365-294X.2009.04352.x|pmid=19754505|last10=Sorenson|first10=M. D.|bibcode=2009MolEc..18.3992M |s2cid=16820157}}</ref> Birds thrive because of physiological features that are advantageous for high-altitude flight.