5.2: Temperature, Water, and other Factors

Temperature

Temperature affects the physiology of living things as well as the density and state of water. It exerts an important influence on living organisms because few can survive at temperatures below 0 °C (32 °F) due to metabolic constraints. It is also rare for them to survive at temperatures exceeding 45 °C (113 °F). This is a reflection of evolutionary response to typical temperatures.

Temperature can limit the distribution of living things. Enzymes are most efficient within a narrow and specific range of temperatures; enzyme degradation can occur at higher temperatures. Therefore, organisms must either maintain an internal temperature or inhabit an environment that will keep the body within a temperature range that supports metabolism. Some animals have adapted to enable their bodies to survive significant temperature fluctuations, as seen in hibernation or reptilian torpor. Similarly, some bacteria have adapted to survive in extremely-hot temperatures found in places such as geysers. Such bacteria are examples of extremophiles: organisms that thrive in extreme environments.

For instance, organisms that live in cold climates, such as the polar bear (Figure \(\PageIndex{1}\)), have adaptations that help them withstand low temperatures and conserve body heat. Structures that aid in this type of insulation include fur, feathers, blubber, and fat. In hot climates, organisms have adaptations (such as perspiration in humans or panting in dogs) that help them to shed excess body heat.

Figure \(\PageIndex{1}\): Polar bears (Ursus maritimus) and other mammals living in ice-covered regions maintain their body temperature by generating heat and reducing heat loss through thick fur and a dense layer of fat under their skin. (credit: “longhorndave”/Flickr)

Animals faced with temperature fluctuations may respond with adaptations, such as migration, in order to survive. Migration, the movement from one place to another, is common in animals, including many that inhabit seasonally-cold climates. Migration solves problems related to temperature, locating food, and finding a mate. In migration, for instance, the arctic tern (Sterna paradisaea) makes a 40,000 km (24,000 mi) round trip flight each year between its feeding grounds in the southern hemisphere and its breeding grounds in the Arctic Ocean (Figure \(\PageIndex{2}\)). Monarch butterflies (Danaus plexippus) live in the eastern United States in the warmer months, but migrate to Mexico and the southern United States in the wintertime. Some species of mammals also make migratory forays: reindeer (Rangifer tarandus) travel about 5,000 km (3,100 mi) each year to find food. Amphibians and reptiles are more limited in their distribution because they lack migratory ability. Not all animals that can migrate do so, as migration carries risk and comes at a high energy cost.

Figure \(\PageIndex{2}\): Arctic tern: The arctic tern is an example of a species that must migrate yearly to deal with temperature fluctuations that exist in the regions where it is found. (CC BY; OpenStax)

Some animals hibernate or estivate to survive hostile temperatures. Hibernation enables animals to survive cold conditions, while estivation allows animals to survive the hostile conditions of a hot, dry climate. Animals that hibernate or estivate enter a state known as torpor, a condition in which their metabolic rate is significantly lowered. This enables the animal to wait until its environment better supports its survival. Some amphibians, such as the wood frog (Rana sylvatica), have an antifreeze-like chemical in their cells, which retains the cells’ integrity and prevents them from bursting.

Figure \(\PageIndex{3}\): Wood frog: The wood frog, like all other amphibians and reptiles, cannot migrate; as a result, the species survives extreme temperature changes through the antifreeze-like chemical found in their cells. (CC BY; OpenStax)

Water

Water is required by all living things because it is critical for cellular processes. Plants require water for photosynthesis. Most of the water molecules taken up by a plant’s roots move up the stem into the leaves, out the stomata in the leaves, and then evaporate into the atmosphere. Evapotranspiration (often just called transpiration) refers to the movement of water in the plant from root to stem to leaf and out through the stomata to the atmosphere. This isn’t just a dribble of water. An acre of corn will transpire about 3,000–4,000 gallons of water each day, and a large oak tree can transpire 40,000 gallons each year.

Similarly animals lose water through their skin and lungs (evaporation), and in the feces and urine. These losses must be made up by water in food and drink and from the water that is a by-product of chemical reactions. If the animal does not manage to compensate for water loss the dissolved substances in the blood may become so concentrated they become lethal.

The rate of water loss by a plant or animal is influenced by temperature, humidity and wind. As temperatures rise, water evaporates out of the living organisms more readily. On hot summer days, the leaves of plants thus have a tendency to wilt due to lack of water in the soil and to the increased rate of transpiration. When the air around an organism is dryer there is greater evaporation losses than if the air around the organisms is saturated with water. Finally, aA breeze will clear water vapor away from the surface of an organism, leaving the humidity on the surface low and increasing the rate of evaporation and/or transpiration.

Since terrestrial organisms lose water to the environment by simple diffusion, they have evolved many adaptations to retain water. Plants have a number of interesting features on their leaves, such as leaf hairs and a waxy cuticle, that serve to decrease the rate of water loss via transpiration.

Some desert animals, like the camel, have developed a great tolerance for dehydration. Smaller animals are more able to avoid extremes of temperature or dry conditions by resting in sheltered, more humid situations during the day and being active only at night. The kangaroo rat is able to survive without access to any drinking water at all because it does not sweat and produces extremely concentrated urine. Water from its food and from chemical processes is sufficient to supply all its requirements.

Inorganic Nutrients and Soil

Inorganic nutrients, such as nitrogen and phosphorus, are important in the distribution and the abundance of living things. Plants obtain these inorganic nutrients from the soil when water moves into the plant through the roots. Therefore, soil structure (particle size of soil components), soil pH, and soil nutrient content play an important role in the distribution of plants. Animals obtain inorganic nutrients from the food they consume. Therefore, animal distributions are related to the distribution of what they eat. In some cases, animals will follow their food resource as it moves through the environment.

Attribution

This page is a modified derivative of:

• 1.2 Themes and Concepts of Biology by Open Stax Licence CC-BY
• 44.2 Biogeography by Open Stax Licence CC-BY