- Related Topics:
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- estivation
Acclimatization
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What is acclimatization in biology?
Acclimatization in biology refers to the gradual, long-term responses of an organism to changes in its environment. These responses are generally habitual and reversible if environmental conditions revert to their original state.
Acclimatization is an adaptive change that doesn't leave a lasting impression on the organism's genetic mechanisms. It differs from adaptation, which affects evolution through the selection of genetic capability. Adjustments to temperature, humidity, salinity, light, and pressure are all examples of acclimatization. The ability to acclimatize varies among species, with some being more versatile than others.
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Why do living things need to acclimatize to their environment?
Living things need to acclimatize to their environment to adjust to gradual, long-term changes, such as seasonal shifts in temperature, humidity, and light. Acclimatization allows organisms to maintain internal balance and sustain themselves when facing substantial environmental variations.
For example, humans ascending to high altitudes acclimatize through increased ventilation, greater diffusion of oxygen, and higher production of red blood cells, which heightens the partial pressure of oxygen. This adaptive change is reversible if the organism returns to its original environment. Only individuals that acclimatize can survive and reproduce, potentially leading to the establishment of new populations.
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How does acclimatization help organisms survive in new or changing conditions?
Acclimatization is how an organism adjusts to gradual, long-term environmental changes, like seasons. It's habitual and reversible, unlike the rapid, short-term responses managed by the nervous and hormonal systems.
This adaptation allows organisms to live in areas with changing conditions and sometimes move to new environments. Those that acclimatize can survive and reproduce, establishing new populations. The ability to acclimatize varies among species.
Acclimatization can even prepare organisms for conditions beyond their normal experience, and it can start before the actual change occurs, possibly guided by internal rhythms and external signals like day length.
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What are some examples of animals or plants acclimatizing to different temperatures?
Acclimatization refers to the gradual, long-term responses of an organism to changes in its environment.
Many organisms' distributions are limited by their ability to tolerate local environmental conditions, such as temperature. Most cannot survive long periods below 0 °C or above 45 °C, though adaptations have allowed some species to survive outside this range. For example, thermophilic bacteria can live in hot springs approaching the boiling point, while certain polar mosses and lichens can tolerate temperatures as low as -70 °C.
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How is acclimatization different from adaptation in evolution?
Acclimatization and adaptation are both ways organisms adjust to their environments, but they operate on different timescales and levels. Acclimatization involves gradual, long-term, reversible responses of an individual to environmental changes, such as adjusting to temperature, humidity, or pressure. These changes don't alter the organism's genetic makeup.
Adaptation, in the evolutionary sense, is a process driven by natural selection acting upon heritable variations over generations. It leads to changes in a population's genetic makeup, making them better suited to their environment. Unlike acclimatization, adaptation is a long-term evolutionary process that affects the genetic characteristics of a species.
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What are some physical changes that might occur in humans during acclimatization to high altitudes?
During acclimatization to high altitudes, the human body undergoes several physical changes to adjust to lower oxygen levels. The body increases ventilation, taking deeper breaths to offset the decline in the ambient partial pressure of oxygen.
To improve oxygen transport, the production of hemoglobin and red blood cells increases. Over a prolonged stay at high altitude, more blood vessels develop in the tissues, increasing capillary density and reducing the diffusion path for gases. Additionally, the size of muscle fibres decreases, further shortening the diffusion path of oxygen.
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Acclimatization, any of the numerous gradual, long-term responses of an organism to changes in its environment. Such responses are more or less habitual and reversible should environmental conditions revert to an earlier state.
The numerous sudden changes that evoke rapid and short-term responses via the nervous and hormonal systems are not examples of acclimatization. An individual organism can regulate its internal processes rapidly to sustain itself within the usual range of environmental changes that it encounters hourly or daily. But this rapid regulation, or homeostasis, is limited in its operation to a small range of environmental variations. Homeostatic regulation usually cannot meet effectively large environmental changes such as those that would allow a plant or animal living in the warmth of summer to function in the cold of winter. As summer wanes, organisms change their substance and their habits in seeming anticipation of the coming winter. This gradual adjustment to conditions is acclimatization.
In contrast to changes that occur during growth and development, acclimatization, as defined above, refers to an adaptive change that is reversible when conditions return to their former condition. Acclimatization does not leave a lasting impression upon the genetic mechanisms of the acclimatized organism. The adaptation of populations to change that effects evolution by the selection of genetic capability is a different process from the acclimatization of an individual.
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In dealing with acclimatization, the influence of climate upon life can be treated under headings of adjustments to temperature, humidity, salinity, light, pressure, and certain chemical substances in the environment. Because organisms do not have unlimited combinations of adaptations, they may use a similar process to adapt to changes of different origins. For example, in acclimatization to the low pressure of oxygen (hypoxia) in high mountains, animals, including man, improve the capacity of blood to transport oxygen by increasing the number of red blood cells (polycythemia); in the chronic disease emphysema, the inadequate supply of oxygen to the lungs is to some degree compensated for by a similar polycythemia.
Because animals and plants can be successfully introduced to new regions, it can be said that species do not necessarily thrive at their best potential in their native regions. Thus acclimatization does not invariably mean that a plant or animal is adapted to function at its maximum rate. In the hot summer, acclimatized birds and mammals often rest in the shade, and in winter cold some animals and all plants become dormant. At extreme limits an organism may suffer some impairment of vigour, but it survives; if the impairment is overt, acclimatization is considered inadequate.
Although acclimatization commonly requires modification of activity, the adaptive changes permit an organism to exploit regions of great seasonal variation and, on occasion, to move in wholly new environments. Only the individuals that acclimatize can survive to produce progeny from which a new population may become established. Ability to become acclimatized differs greatly among species of plants and animals. Some breeds of domesticated animals and cultivated plants are quite versatile in this ability, whereas others are narrowly restricted.
An interesting characteristic of seasonal acclimatization appears in animals and plants that become adjusted to cold beyond that which they are likely to encounter. Not only does acclimatization prepare them with a margin of safety but some microorganisms, insects, and plants tolerate experimental exposure at temperatures far colder or warmer than ever occur in nature. It seems strange that adaptability enables these organisms to be prepared to encounter conditions beyond their natural experience.
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Another surprising characteristic of acclimatization is its anticipatory nature—it can develop before the change occurs. It would seem that anticipation of the need for change would be required in order to make the slow physiological preparations for climatic changes that often set in very suddenly. Anticipation of acclimatization seems to require a sense of time by which the coming environmental conditions can be predicted. Length of day is one external signal, but it seems to impinge upon intrinsic rhythms that provide clues from within as to the passage of time.
Although acclimatization refers basically to adaptation to climate, the term can also be used to describe the adjustments that a person makes to urban, social, or political conditions or the adaptation of a population of plants to conditions of cultivation or of an animal to the unnatural conditions of captivity. Adaptations to strange or artificial conditions, however, are often difficult to describe, and only in a few cases can such adaptations be compared with acclimatization.