Abiotic Factors: Temperature and Water
Apart from the equatorial region where there are constantly high temperatures throughout the year, plants and animals are often exposed to daily rhythms and temperature variations to which they need to adapt.
Among animals, metabolically controlled heat regulation exists only in those species which are warm-blooded (homoiothermic). in other words, species that are able to maintain a largely constant body temperature. Therefore, throughout their evolution, these animals were able to penetrate into permanently cold biotopes.
In cold-blooded (poikilothermic) animals, such as insects, amphibians, or reptiles, body temperature is determined by the ambient temperature, which necessitates strong dependence on temperature stability. When temperature falls below a critical value there is initially a reversible torpor; neverthless, cold-induced death can occur if temperature continues to fall.
Conversely, if temperature exceeds a critical value, this will lead to an irreversible heat rigor, leading to heat-induced death due to the protein coagulation. If animals have a broad temperature range they are eurythermic; if the temperature range is rather narrow, they are stenothermal species. Certain conformities (climatic rules) can be observed in the relationship between temperature and the appearance of an animal.
According to Bergmann’s Rule, homeo-thermic animals of a species and of related species grow larger in cold climates than they do in warmer regions (relative to volume, larger animals have a smaller surface area, which is advantageous for heat balance). Allen’s Rule (proportional rule) stipulates that individuals of a species (and related species) in colder climatic zones have smaller body appendages (e.g., ears) than those in warmer regions, in order to conserve heat.
Water as an ecological factor
Animals in regions with few open water areas usually attempt to keep their water loss as low as possible, for example by means of a nocturnal or subterranean mode of life. Plants in regions with low precipitation also have special adaptations to restrict water loss.
Many xerophytes (dry plants) have protective layers and hidden stomata to defend them against drying out.
HIBERNATION
For many warm-blooded animals, the cold season is associated with increased heat requirements, but be- cause of reduced food availability, the needed energy is often insufficient. Therefore, insect-eating bats, for example, go into hibernation.
During this dormancy period, the body temperature can drop be- low 41 °F (5°C), which then leads to a drastic slowdown of the animals metabolism, heart rate, and respiration.
BASICS
RGT RULE How strongly temperature can affect an organ- ism’s life can be estimated by the RGT (reaction speed-temperature) rule. which states that a temperature increase of 50°F (10°C) doubles the reaction speeds of metabolic processes.