Even warm animal
As a warm-blooded or homoiothermes animal (from ancient Greek ὁμοῖος homoios , German , similar ' ; ancient Greek θερμός Thermos , German , warm' ; also homöotherm ) or endothermic animals are in the zoology animals ( birds , mammals ) indicates that their core body temperature of whatever Can regulate the ambient temperature to a constant temperature value. The transition from homoiothermia to poikilothermia is sometimes fluid. The heat production enables greater independence from the weather, but increases energy consumption. Furthermore, due to the need to allow heat losses only to the extent necessary, the variation in the anatomical construction plan is limited ( Bergmann's rule ).
Regulation of body temperature
In birds as well as in mammals, the same warm body temperature is generated by the metabolic activity of the animals. This affects the basal metabolic rate of the metabolism, which is significantly higher than that of cold-blooded ( poikilothermic or ectothermic ) animals.
Thermoreceptors in the skin and temperature-sensitive neurons in the central nervous system act on a temperature processing center in the hypothalamus , which increases or decreases body temperature in the event of deviations from the normal temperature.
Lowering the core body temperature
If the core body temperature is too high, heat can be dissipated in various ways. This often happens through the evaporation of water, for example in humans through sweating , in dogs through panting or by licking fur in cats. A large body surface that is well supplied with blood if necessary can also be used to dissipate heat, as in the ears of African elephants .
Increase in core body temperature
If the core body temperature is too low, the metabolic rate is increased, the increase in the metabolism of the muscles known as tremors is widespread, and micro-vibration is often sufficient for low amounts of heat . In addition, newborn mammals and all winter sleepers have large amounts of brown adipose tissue for direct thermogenesis from stored fat .
Thermal insulation
Animals of the same temperature usually have thermal insulation, which ranges from the reduction of blood circulation in the skin to insulating subcutaneous fatty tissue to the inclusion of insulating layers of air in feathers or hair .
- In birds, air pockets in the plumage, especially in the down , cause heat insulation
- In land-living mammals , air trapped in the fur has an insulating effect , especially the strongly spiraled woolen hair can trap large volumes of air.
- Aquatic mammals and birds have an insulating layer of fat (" bubbler ") under their skin, as hair and feathers in water largely lose their insulating layer of air.
- In addition to feathers, bone histological evidence of homoiothermia was found in some extinct dinosaur species .
Seasonal adjustments
Mammals that hibernate can lower their core body temperature by more than 10 ° C during the cold season in order to save energy during this inactive phase. In the event of disturbances or when they are awake, they interrupt hibernation by releasing norepinephrine and quickly reach their normal temperature again with considerable energy consumption.
Hummingbirds and platypus are a specialty , the body core temperature of which is subject to relatively strong fluctuations.
Delimitations
In contrast, honey bees , which as a state keep the temperature of the breeding area of their beehive constant at 35 ° C, are not animals of the same temperature. The individual insect is not able to do this, only the entire state. A single bee freezes at a temperature of 10 ° C and dies. (See also thermoregulation in honey bees )
Large flying insects , reptiles , amphibians and fish are all poikilothermic because their body temperature is not constant, but corresponds to the ambient temperature. During the cold season of the year they become frozen in the winter , while their metabolism is not regulated by the hypothalamus . Your ability to control your core body temperature is limited to behaviors such as intense physical exercise or staying in the sun, which causes you to warm up to a certain extent. However, in tuna , some sharks ( alopias ) and rays there are blood vessel adaptations ( countercurrent principle ) in the trunk muscles, which enable the core body temperature to be as high as possible; in swordfish and glossy fish , the brain is supplied with blood that has been warmed by the muscles. In deep-sea fish, on the other hand, the body temperature is permanently 4 ° C. However, this is solely due to the constant outside temperature, which is why they are not homoiothermic , but poikilothermic.
It is relatively unknown that there are plants, e.g. B. the "stink cabbage" ( Symplocarpus foetidus ) and other arum plants, which regulate the intensity of cellular respiration at low outside temperatures and thereby increase their internal temperature. The flower buds of early bloomers can reach temperatures that are 15 to 35 ° C above the ambient temperature.
literature
- Classification of animals according to the regulation of their body temperature. In: David J. Randall, Warren Burggren, Kathleen French: Animal Physiology . Georg Thieme Verlag, 2002, ISBN 978-3-13-664004-3 , p. 789-794 ( google.com ).
- Influence of form, function and behavior on homeostatic processes In: Neil A. Campbell, Jane B. Reece: Biologie - Gymnasiale Oberstufe . 8th edition. Pearson School, Munich 2009, ISBN 978-3-8273-7287-1 , p. 527-529 .
Web links
Individual evidence
- ^ Neil A. Campbell, Jane B. Reece: Biologie, Munich 2009, p. 1.167
- ↑ Herder: Lexicon of Biology, keyword Homoiothermie , Spektrum Akademischer Verlag 1994.
- ↑ Herder: Lexicon of Biology, keyword Homoiothermie , Spektrum Akademischer Verlag 1994.
- ↑ Herder: Lexicon of Biology, keyword Homoiothermie , Spektrum Akademischer Verlag 1994.