Form and Function
Extreme Temperatures Survival Mechanisms
Animals
The most common mechanism for extreme temperature survival in animals is Thermoregulation. Thermoregulation is a mechanism that allows an organism to keep its body temperature within certain limits even under extreme temperatures. In cold conditions, birds and mammals utilize adaptations and tactics to avoid excessive heat loss:
1. Mammals and Birds use small smooth muscles which are attached to feather or hair shafts.
2. Mammals and Birds increase their body size in order to maintain their core body temperature.
3. Mammals and Bird store energy as fat.
4. The countercurrent blood flow in mammals’ and birds’ extremities aid in avoiding the tissues from freezing.
In warm conditions, birds and mammals utilize different tactics in order to maximize heat loss:
1. Animals adapt to extreme heat through behavioral adaptations such as living in burrows and being active during the nighttime.
2. Perspiration and panting
3. Animals store fat reserves in one place in order to avoid its insulating effect.
4. Elongated and vascularized extremities help animals in conducting their body heat to the air.
Other mechanisms that help animals to survive extreme temperatures are hibernation, aestivation, and daily torpor. Hibernation is a practice among certain animals where in they spend part of the cold season in a more or less dormant state as a protection from cold when normal body temperature cannot be maintained and food is scarce. Aestivation on the other hand is a mechanism that animals employ to escape from heat and drought. Daily torpor happens enables endotherms such as bats and humming birds to conserve their energy by metabolic rates reduction.
Plants
Temperature affects many processes in plants, including photosynthesis, respiration, growth, reproduction, and transportation. Plants vary enormously in their ability to tolerate either heat or cold ( 2004, ). According to (2004), there are five broad categories of cold tolerance in plants. Temperatures lower than 10°C damage chilling-sensitive plants, which are mostly tropical. Chilling-resistant plants can survive at temperatures below 10°C but are damaged when ice forms within their tissues. Frost-resistant plants make physiological changes that enable them to survive temperatures as low as about -15°C. Frost-tolerant plants survive by withdrawing water from their cells, so preventing ice forming. The withdrawal of water increases the concentration in sap and protoplasm, which acts as a kind of antifreeze, and lowers freezing point (). Excessive heat is as detrimental to plants as excessive colds. Plants have evolved resistance to heat stress, though the changes are not so marked as resistance to cold stress. Different parts of plants acquire differing degrees of heat resistance, but the pattern varies between species. In some species, the uppermost canopy leaves are often most heat resistant; in other species, it is the middle canopy leaves, or the leaves at the base of the plant ( 2004, ).
Microorganisms
According to (), thermophiles are bacteria that have the capacity to live under high temperatures. Thermophiles (heat lovers in Latin) are bacteria that can be found in water that are super heated like hot springs. There is almost no oxygen in water with high temperatures but most bacteria can adapt to this condition because they do not need oxygen. Aside from lack of oxygen, proteins and DNA collapse speedily while the fragile internal membrane that is made of fatty acids will melt ensuing outflow of internal parts. Thermophiles have special mechanisms to adapt to these risks and avoid depletion of proteins:
1. Thermophiles have the capacity to replace their proteins quickly.
2. Thermophiles’ proteins are more actively working at high temperatures.
3. To avoid the reduction of DNA, it is thought that termophiles use unique proteins to hold the DNA together.
4. In order to prevent the membrane from melting, special kinds of fats are being used by thermophiles.
Psychrophiles (cold lovers) and Psychorotrophs are bacteria that live in extreme cold conditions. These bacteria can adapt to extreme cold because:
1. Psychrophiles developed new enzymes that permit chemical reactions essential to life to take place at almost normal rates under very low temperatures.
2. Psychotrophs can stand low temperature because they have means for adjusting to the cold.
Special fats compose the psychrophiles’ fatty acid membrane that do not turn hard at low temperatures. Numerous bacterial cells contain an anti-freeze like substance that prevents them from rupturing as the temperature drops.
Bibliography
Credit:ivythesis.typepad.com
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