What is thermoregulation? Control systems operate in organisms to cope with environmental stresses including temperature extremes. Let’s discuss in detail thermoregulation in plants and animals are as under;
THERMOREGULATION IN PLANTS
Adaptations to high temperature
Damages of high temperature: High temperature denatures the enzymes and damages the metabolism therefore harms or kills the plants.
i) Evaporative cooling: Plants use evaporative cooling to manage with high temperature. Hot and dry weather, however, causes water deficiency resulting in the closing of stomata, thus plants suffer in such conditions.
ii) Heat-shock proteins: Most plants have adapted to survive in heat stress as the plants of temperate regions face the stress of 400C and above temperature. The cells of these plants synthesize large quantities of special proteins called heat-shock proteins. These proteins embrace enzymes and other proteins thus help prevent denaturation.
Adaptations to Low Temperature
Damages of low temperatures: In low temperature, the fluidity of the cell membrane is altered, because lipids of the membrane become locked into crystalline structures, which affects the transport of the solutes. The structure of the membrane proteins is also affected,
Adaptations: Plants respond to cold stress by increasing proportion of unsaturated fatty acids, which help membrane to maintain structure at low temperature by preventing crystal formation. This adaptation requires time because of this reason rapid chilling to plants is more stressful than a gradual drop in air temperature.
Adaptations to Freezing temperature
Damages of freezing temperatures: Freezing temperature causes ice crystal formation. The confinement of ice formation around cell wall does not affect as badly and plants survive, however, a formation of ice crystals within protoplasm perforates membranes and organelle hence killing the cells.
Adaptations: The plants native to cold regions such as oaks, maples, roses and other plants have adapted to bring changes in solutes composition of the cells, which causes cytosol to super cool without ice formation, although ice crystals may form in the cell walls.
THERMOREGULATION IN ANIMALS
Body Heat, Heat Gain and Loss
Temperature of an animal depends upon the rate of change of body heat and that further depends on the rate of heat production through metabolic processes and the rate of external heat gain and rate of heat loss. This transfer of heat between an animal and its environment is done in numerous ways. Principally, infrared thermal radiation and direct and reflected sunlight transfer heat into the animal; whereas radiation and evaporation transfer heat out to the environment.
Temperature Classification of Animals
1. Classification scheme based on temperature fluctuation in the environment
Animals deal with variation in the thermal characteristics of their environment, So animals can be divided into two categories:
Poikilotherms (cold-blooded): These are animals in which body temperature tends to fluctuate more or less as the air or water temperature change. All invertebrates, amphibians and reptiles are considered in this category.
Homeotherms (warm-blooded): These animals, when e posed to changing air or water temperature, maintain their body temperature. These include birds and mammals.
Several difficulties arise with this terminology. It is observed that deep-sea fishes maintain their body temperature due to the constant natural surroundings and lizards regulate their body temperature: and in contrast, numerous birds and mammals vary their body temperature.
2. Classification scheme based on the source of heat production
It is more widely applicable temperature classification scheme. So animals are divided into three categories:
Endotherms: The animals that generate their own body heat through heat production as a by-product of metabolism are called Endotherms, such as mammals, birds, some fishes and flying insects.
Ectotherms: These are the animals which produce metabolic heat at a low level and that is also exchanged quickly with the environment, however, absorb heat from their surroundings. Most invertebrates, fish, amphibians and reptiles are in this category.
Heterotherms: Those animals who are capable of varying degrees of endothermic heat production but generally do not regulate their body temperature within a narrow range e.g. bats, humming bird etc., are called heterotherms.
Regulation of Heat Exchange between Animals and Environment
Animals use a different mechanism for such regulation and these are of structural, physiological and behavioural nature.
Structural adaptations: These may be long-term changes in subdermal fatty layer insulation or pelage (the fur, hair, wool, etc. of a mammal). The presence of sweat glands and lungs modified for panting (to take short fast shallow breaths,. especially when excited, hot, or after physical exertion).
Physiological adaptations: These regulate blood flow to the skin specifically greater blood flow in warmth to dissipate heat and lower in colds to economize heat loss, also the activation of certain muscles cause plumage (collectively feathers) fluffing (to shake, pat, or brush something in order to get air into it). Similarly, activation of sweat glands is done for evaporative cooling.
Behavioural adaptations: These include moving of the animal to an environment where heat exchange between these is minimal e.g., ground squirrels move to burrows in midday heat and lizards bask (lie around or relax) in sun to gain heat, Animals also control the amount of surface area available for heat exchange by adjusting their postures.