Seasonal changes in physiological processes. Seasonal changes in physiological functions
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Being the brainchild of the solar system (and the Earth in particular), the human body naturally experiences the effects of the change of seasons in its life. Moreover, the main reason for changes in the human body is associated with the flow of solar energy to the Earth. In addition to changing the solar flux received by the Earth's surface, other parameters that depend on it also change: humidity, air ionization, oxygen partial density, ozone layer thickness. It was found that the maximum of air ions is observed from August to October, the minimum - from February to March. Therefore, the time of activity for the lungs is the autumn period. The highest partial density of oxygen significantly affects the functioning of the kidneys, they are most active in winter.
Consider the influence of the seasons of the year on the general condition of the human body.
Winter. With a decrease in external temperature, water crystallizes, everything dries up from the wind and cold, all plant life stops. The human body is in the most unfavorable external conditions: the strongest compression from solar gravity (the Earth is close to the Sun at this time) and external cold leads to various spasms in the body - strokes, heart attacks, joint stiffness. Some diseases are accompanied by acute attacks, high fever.
Summer. An increase in temperature leads to a significant evaporation of water. All this leads to the intensification of natural processes. Strong absorption of solar energy by condensed water leads to an energy explosion. In the human body, this manifests itself in the form of chills, accompanied by sunstroke, intestinal infections and food poisoning. The gravity of the Sun is the least, which leads to a weakening of a person's own gravity.
Spring and autumn combined into one “physiological season” due to a sharp change in temperature, dampness, coolness. At this time, there is an increase in colds. The gravity of the Sun is favorable for all life manifestations.
To prevent the harmful effects of the seasons of the year on the human body, folk wisdom prescribes to follow a system of preventive measures:
- cleansing the body (for example, fasting);
- maintaining a certain lifestyle in each season. For example, in autumn and spring, when it is damp and cool around, live in a warm and dry room, encourage yourself to an active lifestyle, wear clothes made of silk and cotton. In winter, when it is dry and cold, it is necessary to bask by an open fire, visit a humid steam room, rub the body with oils so that the body does not dehydrate and keep warm, and wear woolen clothes. In summer, in the heat, you should, if possible, be in a cool, ventilated room, spray aromatic substances, do not physically bother yourself; wear clothes made of linen, thin cotton;
- Eating certain foods. For example, in spring and autumn - dry, warm food, flavored with warming spices. In summer, cool, watery food with a sour taste is desirable, which helps to retain moisture and prevents overheating of the body. In winter, hot, fatty foods are needed, flavored with warming spices. An example is rich borscht, meat with mustard. However, it should be noted that abundant food should be alternated with fasting.
Based on materials from http://homosapiens.ru.
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Seasonal changes include profound shifts in the body under the influence of changes in nutrition, environmental temperature, radiant solar regime and under the influence of periodic changes in the endocrine glands, mainly associated with animal reproduction. The very question of environmental factors that determine seasonal periodicals is extremely complex and has not yet been fully resolved; in the formation of seasonal cycles, shifts in the functions of the sex glands, the thyroid gland, etc., which are very stable in nature, are of great importance. These changes, well established morphologically, are very stable in their successive development for different species and greatly complicate the analysis of the influence of physical factors causing seasonal periodicity.
Seasonal changes in the body include behavioral responses. They consist either in the phenomena of migration and nomadism (see below), or in the phenomena of winter and summer hibernation, or, finally, in a variety of activities for the construction of burrows and shelters. There is a direct relationship between the depth of the holes of some rodents and the winter temperature drop.
Of great importance for the total daily activity of the animal is the lighting regime. Therefore, seasonal periodicals cannot be considered outside the latitudinal distribution of organisms. Figure 22 shows the breeding seasons for birds in different latitudes of the northern and southern hemispheres. One can clearly see the timing of reproduction shifted to earlier months when moving from north to south in the Northern Hemisphere and an almost mirror image of these relationships in the Southern Hemisphere. Similar dependences are also known for mammals, for example, for sheep. Here we mainly consider
physiological changes in the body occurring in the temperate climate of the middle latitudes of the Northern Hemisphere. The greatest changes in the body during the seasons of the year relate to the blood system, general metabolism, thermoregulation, and partly digestion. Of exceptional importance for boreal organisms is the accumulation of fat as an energy potential spent on maintaining body temperature and muscle activity.
The most noticeable changes in motor activity in different seasons can be observed in diurnal animals, which is undoubtedly related to the lighting regime. These relationships have been best studied in monkeys (Shcherbakova, 1949). When monkeys were kept throughout the year at a constant ambient temperature, the total daily activity depended on the length of daylight hours: an increase in activity took place in May
and June. An increase in total daily activity was observed in December and January. The latter cannot be attributed in any way to the influence of daylight hours and is probably associated with spring manifestations in nature in Sukhumi conditions (Fig. 23).
These studies also found a significant seasonal variation in body temperature in monkeys. The highest temperature in the rectum was observed in June, the lowest - in January. These shifts cannot be explained by changes in temperature in the external environment, since the room temperature remained constant. It is very likely that the effect of radiative cooling took place here, due to the reduced temperature of the walls of the room.
Under natural conditions (Khrustselevsky and Kopylova, 1957), Brandt's voles in Southeastern Transbaikalia show a striking seasonal dynamics of locomotor activity. They have a sharp decrease in activity - exit from holes in January, March, November and December. The reasons for this pattern of behavior are quite complex. They are associated with the nature of the pregnancy of usually very active females, with the timing of sunrise and sunset, high temperatures in summer and low in winter. The daily activity studied under natural conditions is much more complicated and does not always reflect the picture obtained by the researcher using the actographic technique.
Similar complex relationships were discovered (Leontiev, 1957) for Brandt's vole and Mongolian gerbil in the Amur region.
In minks (Ternovsky, 1958), significant changes in motor activity are observed depending on the seasons of the year. The greatest activity takes place in spring and summer, which, apparently, is associated with the length of daylight hours. However, as the temperature drops, activity decreases, as does precipitation. In all gregarious ungulates, without exception, seasonal changes in gregariousness are observed, which is pronounced in moose. In the reindeer, herd relations (grouping, following each other) are more noticeable in autumn than in summer or spring (Salgansky, 1952).
Seasonal changes in metabolism (basal metabolism) are best studied. Back in 1930, the Japanese researcher Ishida (Ishida, 1930) found a significant increase in basal metabolism in rats in the spring. These facts have since been confirmed by numerous studies (Kayser, 1939; Sellers, Scott a. Thomas, 1954; Kocarev, 1957; Gelineo a. Heroux, 1962). It has also been established that in winter the basal metabolism in rats is much lower than in summer.
Very striking seasonal changes in basal metabolism are found in fur-bearing animals. Thus, the basal metabolism in arctic foxes in summer compared with winter is increased by 34%, and in silver-black foxes - by 50% (Firstov, 1952). These phenomena are undoubtedly connected not only with the seasonal Cycle, but also with the overheating that takes place in the summer (see Chap. V) and have been noted by various researchers in arctic foxes, raccoon dogs (Slonim, 1961). In the gray rats under the conditions of the Arctic, an increase in metabolism in the spring and a decrease in the autumn were also found.
Study of chemical thermoregulation in polar species (arctic foxes, foxes, hares) wintering in the conditions of the Leningrad Zoological Garden (Isaakyan and Akchurin,
1953) showed, under the same conditions of keeping, sharp seasonal changes in chemical thermoregulation in foxes and raccoon dogs and the absence of seasonal changes in arctic foxes. This is especially pronounced in the autumn months, when the animals are in summer fur. The authors explain these differences by the responses to changes in lighting that are specific to Arctic foxes. It is Arctic foxes who practically lack chemical thermoregulation in the autumn period, although the insulating layer of wool by this time had not yet become winter. Obviously, these reactions, specific for polar animals, cannot be explained only by the physical properties of the skin: they are the result of complex specific features of the nervous and hormonal mechanisms of thermoregulation. These reactions in polar forms are combined with thermal insulation (Scholander and co-workers, see p. 208).
A large amount of material on seasonal changes in gas exchange in various rodent species (Kalabukhov, Ladygina, Maizelis and Shilova, 1951; Kalabukhov, 1956, 1957; Mikhailov, 1956; Skvortsov, 1956; Chugunov, Kudryashov and Chugunova, 1956, etc.) showed that non-sleeping rodents can observe an increase in metabolism in autumn and a decrease in winter. The spring months are characterized by an increase in metabolism, and the summer months by a relative decrease. The same data on a very large material were obtained for the common vole and bank vole in the Moscow region.
Schematically, the seasonal curve of metabolic changes in non-hibernating mammals can be represented as follows. The highest level of metabolism is observed in spring during the period of sexual activity, when animals, after a winter food restriction, begin active food-procuring activities. In summer, the level of metabolism again decreases somewhat due to high temperatures, and in autumn it rises slightly or remains at the summer level, gradually decreasing towards winter. In winter, there is a slight decrease in basal metabolism, and by spring it again rises sharply. This general scheme of changes in the level of gas exchange throughout the year for individual species and under individual conditions can vary significantly. This is especially true for farm animals. So, the main metabolism in non-lactating cows (Ritzman a. Benedict, 1938) in the summer months, even on the 4-5th day of fasting, was higher than in winter and autumn. In addition, it is very important to note that the spring increase in metabolism in cows is not associated with pregnancy and lactation, with the conditions in the stall or on the pasture. With stall keeping, gas exchange in spring is higher than with pasture in autumn, although grazing itself increases gas exchange at rest throughout the pasture season (Kalitaev, 1941).
In summer, gas exchange in horses (at rest) increases by almost 40% compared to winter. At the same time, the content of erythrocytes in the blood also increases (Magidov, 1959).
Very large differences (30-50%) in energy metabolism in winter and summer are observed in reindeer (Segal, 1959). In Karakul sheep, despite the course of pregnancy in winter, there is a significant decrease in gas exchange. Cases of a decrease in metabolism in winter in reindeer and Karakul sheep are undoubtedly associated with food restrictions in winter.
Changes in basal metabolism are also accompanied by shifts in chemical and physical thermoregulation. The latter is associated with an increase in thermal insulation (insulation) wool and feather covers in winter. The decrease in thermal insulation in summer affects both at the level of the critical point (see Chap. V), and on the intensity of chemical thermoregulation. So, for example, the values of heat transfer in summer and winter in different animals are: for squirrels, as 1: 1; in a dog 1: 1.5; in a hare 1: 1.7. Depending on the seasons of the year, heat transfer from the surface of the body changes significantly due to the processes of molting and overgrowing with winter wool. In birds, the electrical activity of the skeletal muscles (due to the absence of non-shivering thermogenesis) does not change in winter and summer; in mammals, such as the gray rat, these differences are very significant (Fig. 25).
Seasonal changes in the critical point of metabolism have recently been found in polar animals in Alaska (Irving, Krogh a. Monson, 1955) - in the red fox they are + 8 ° in summer, -13 ° in winter; for squirrels - in summer and winter + 20 ° С; at the porcupine (Erethizoon dorsatum) +7°C in summer and -12°C in winter. The authors also associate these changes with seasonal changes in the thermal insulation of the fur.
The metabolism of polar animals in winter, even at a temperature of -40 ° C, increases relatively slightly: in the fox and the polar porcupine - no more than 200% of the metabolic level at the critical point, in the squirrel - about 450-500%. Similar data were obtained in the conditions of the Leningrad Zoo on arctic foxes and foxes (Olnyanskaya and Slonim, 1947). A shift in the critical point of metabolism from +30°C to +20°C was observed in the gray rat in winter (Sinichkina, 1959).
Study of seasonal changes in gas exchange in steppe lemmings ( Lagurus lagurus) showed (Bashenina, 1957) that in winter their critical point, unlike other species of voles, is unusually low - about 23 ° C. The critical point of metabolism in midday gerbils shifts in different seasons, while in Grebenshchikov it remains constant (Mokrievich, 1957 ).
The highest values of oxygen consumption at environmental temperatures from 0 to 20°C were observed in yellow-throated mice caught in the summer, and the lowest in winter (Kalabukhov, 1953). The data for mice caught in autumn were in the middle position. The same work made it possible to discover very interesting changes in the thermal conductivity of wool (taken from animals and dried skins), which strongly increases in summer and decreases in winter. Some researchers are inclined to attribute to this circumstance a leading role in changes in metabolism and chemical thermoregulation during different seasons of the year. Of course, such dependences cannot be denied, but laboratory animals (white rats) also have a pronounced seasonal dynamics even at constant environmental temperatures (Isaakyan and Izbinsky, 1951).
In experiments on monkeys and wild carnivores, it was found (Slonim and Bezuevskaya, 1940) that chemical thermoregulation in spring (April) is more intense than in autumn (October), despite the fact that the ambient temperature was the same in both cases (Fig. 26) . Obviously, this is the result of the previous influence of winter and summer and the corresponding changes.
in the endocrine systems of the body. In summer, there is a decrease in the intensity of chemical thermoregulation, in winter - an increase.
Peculiar seasonal changes in chemical thermoregulation were found in the yellow ground squirrel, which enters winter and summer hibernation, and the non-hibernating thin-clawed ground squirrel (Kalabukhov, Nurgel'dyev and Skvortsov, 1958). In the thin-toed ground squirrel, seasonal changes in thermoregulation are more pronounced than in the yellow ground squirrel (of course, in the waking state). In winter, the exchange of fine-clawed ground squirrel is sharply increased. In summer, the yellow ground squirrel's chemical thermoregulation is disturbed already at + 15-5 ° C. Seasonal changes in thermoregulation are almost absent in it and are replaced by long winter and summer hibernation (see below). Seasonal changes in thermoregulation are equally poorly expressed in the tarbagan, which falls into summer and winter hibernation.
A comparison of seasonal changes in chemical thermoregulation and the biological cycle of animals (N.I. Kalabukhov et al.) showed that seasonal changes are weakly expressed both in hibernating species and in species that spend the winter in deep burrows and are little exposed to low outdoor temperatures ( e.g. a large gerbil).
Thus, seasonal changes in thermoregulation are reduced mainly to an increase in thermal insulation in winter, a decrease in the intensity of the metabolic reaction (chemical thermoregulation) and a shift in the critical point to a zone of lower environmental temperatures.
The thermal sensitivity of the body also changes somewhat, which is apparently associated with a change in coat. Such data were established by N. I. Kalabukhov for arctic foxes (1950) and yellow-throated mice (1953).
In gray rats living in the middle lane, the preferred temperature in winter is from 21 to 24 ° C, in summer - 25.9-28.5 ° C, in autumn - 23.1-26.2 ° C and in spring - 24.2 ° C (Sinichkina , 1956).
Under natural conditions in wild animals, seasonal changes in oxygen consumption and heat production can largely depend on feeding conditions. However, there is no experimental confirmation yet.
The hematopoietic function changes significantly according to the seasons of the year. The most striking shifts in this regard are observed in humans in the Arctic. In spring, one can observe a large increase in the number of erythrocytes and hemoglobin (Hb) blood, which is associated with the transition from the polar night to the polar day, i.e., with changes in insolation. However, even in conditions of sufficient insolation in the Tien Shan mountains, a person has a somewhat reduced amount of hemoglobin in the blood in winter. A sharp increase in Hbobserved in spring. The number of erythrocytes decreases in spring and increases in summer (Avazbakieva, 1959). In many rodents, for example, in gerbils, the content of erythrocytes decreases in summer, and increases in spring and autumn (Kalabukhov et al., 1958). The mechanism of these phenomena is still unclear. There are also changes in nutrition, vitamin metabolism, ultraviolet radiation, etc. The influence of endocrine factors is also not excluded, and the thyroid gland, which stimulates erythropoiesis, plays a particularly important role.
The most important in maintaining the seasonal rhythm are hormonal shifts, representing both independent cycles of endogenous origin, and associated with the influence of the most important environmental factor - the lighting regime. At the same time, a scheme of relationships between the hypothalamus - the pituitary gland - the adrenal cortex is already being outlined.
Seasonal changes in hormonal relations have been revealed in wild animals under natural conditions, using the example of changes in the weight of the adrenal glands (which, as is known, play an important role in the body's adaptation to specific and non-specific conditions of "tension" - stress).
The seasonal dynamics of the weight and activity of the adrenal glands has a very complex origin and depends both on the actual “stress” in connection with living conditions (nutrition, environmental temperature) and on reproduction (Schwartz et al., 1968). In this regard, data on changes in the relative weight of the adrenal glands in non-breeding field mice are of interest (Fig. 27). During the period of enhanced nutrition and optimal temperature conditions, the weight of the adrenal glands increases dramatically. In autumn, with cooling, this weight begins to decrease, but with the establishment of snow cover it stabilizes. In the spring (April), an increase in the weight of the adrenal glands begins in connection with the growth of the organism and puberty (Shvarts, Smirnov, Dobrinsky, 1968).
The morphological picture of the thyroid gland in many species of mammals and birds is subject to significant seasonal changes. In the summer, there is a disappearance of the follicle colloid, a decrease in the epithelium, and a decrease in the weight of the thyroid gland. In winter, the reverse relationship takes place (Riddle, Smith a. Benedict, 1934; Watzka, 1934; Miller, 1939; Hoehn, 1949).
The seasonal variability in the function of the thyroid gland in the reindeer is just as clearly expressed. In May and June, its hyperfunction is observed with increased secretory activity of epithelial cells. In winter, especially in March, the secretory activity of these cells ceases. Hyperfunction is accompanied by a decrease in the volume of the gland. Similar data were obtained in sheep, but the pattern was much less pronounced.
At present, there are numerous data indicating the presence of stable seasonal fluctuations in the content of thyroxine in the blood. The highest level of thyroxin (determined by the content of iodine in the blood) is observed in May and June, the lowest - in November, December and January. Studies have shown (Sturm a. Buchholz, 1928; Curtis, Davis a. Philips, 1933; Stern, 1933) there is a direct parallelism between the intensity of thyroxine production and the level of gas exchange in humans during the seasons of the year.
There are indications of a close relationship between body cooling and the production of thyroid hormone and pituitary thyroid-stimulating hormone (Uotila, 1939; Voitkevich, 1951). These relationships are also very important in the formation of seasonal periodicals.
Apparently, a significant role in seasonal periodicals belongs to such a non-specific hormone as adrenaline. A large body of evidence suggests that adrenaline promotes better acclimatization to both heat and cold. Combinations of thyroxine and cortisone preparations are especially effective (Hermanson a. Hartmann, 1945). Animals well acclimatized to cold have a high content of ascorbic acid in the adrenal cortex (Dougal a. Fortier, 1952; Dugal, 1953).
Adaptation to low ambient temperature is accompanied by an increase in the content of ascorbic acid in tissues, an increase in the content of hemoglobin in the blood (Gelineo and Raiewskaya, 1953; Raiewskaya, 1953).
Recently, a large amount of material has been accumulated that characterizes seasonal fluctuations in the content of corticosteroids in the blood and the intensity of their release during incubation of the adrenal cortex. in vitro.
The role of the lighting regime in the formation of the seasonal rhythm is recognized by the vast majority of researchers. Lighting, as was established in the middle of the last century (Moleschott, 1855), has a significant effect on the intensity of oxidative processes in the body. Gas exchange in humans and animals under the influence of lighting increases (Moleschott u. Fubini, 1881; Arnautov and Weller, 1931).
However, until recently, the question of the effect of illumination and darkening on gas exchange in animals with different lifestyles remained completely unexplored, and only when studying the effect of illumination intensity on gas exchange in monkeys (Ivanov, Makarova and Fufachev, 1953) did it become clear that it is always higher in the light. than in the dark. However, these changes were not the same for all species. In hamadryas, they were most pronounced, followed by rhesus monkeys, and the effect of illumination had the least effect on green monkeys. The differences could only be understood in connection with the ecological features of the existence of the listed species of monkeys in nature. So, the hamadryas monkeys are the inhabitants of the treeless highlands of Ethiopia; rhesus macaques are inhabitants of the forest and agricultural cultural areas, and green monkeys are dense tropical forests.
The reaction to illumination appears relatively late in ontogeny. So, for example, in newborn kids, the increase in gas exchange in the light compared to the dark is very small. This reaction increases significantly by the 20-30th day and even more by the 60th (Fig. 28). It can be assumed that in animals with daytime activity the reaction to the intensity of illumination has the character of a natural conditioned reflex.
In the nocturnal loris lemurs, an inverse relationship has been observed. Their gas exchange was increased
in the dark and reduced when illuminated during the determination of gas exchange in the chamber. The decrease in gas exchange in the light reached 28% in lorises.
The facts of the influence of prolonged illumination or darkening on the organism of mammals were established by an experimental study of the light regime (daylight hours) in connection with the seasonal effects of illumination. A large number of studies have been devoted to the experimental study of the effect of daylight hours on seasonal periodicals. Most of the data collected for birds, where the increase in daylight hours is a factor stimulating sexual function (Svetozarov and Shtreich, 1940; Lobashov and Savvateev, 1953),
The facts obtained indicate both the value of the total length of daylight hours and the value of the change in the phases of illumination and dimming.
A good criterion for the influence of the lighting regime and the length of daylight hours for mammals is the course of ovulation. However, it is precisely in mammals that such a direct effect of light on ovulation in all species without exception cannot be established. Numerous data obtained on rabbits (Smelser, Walton a. Whethem, 1934), guinea pigs (Dempsey, Meyers, Young a. Jennison, 1934), mice (Kirchhof, 1937) and ground squirrels (Welsh, 1938) show that keeping animals in complete darkness has no effect on ovulation.
In special studies, “winter conditions” were simulated by cooling (from -5 to +7 ° C) and keeping in complete darkness. These conditions did not affect the intensity of reproduction in the common vole. ( Microtus arvalis) and developmental speed of the young. Consequently, the combination of these main environmental factors, which determine the physical side of seasonal influences, cannot explain the winter suppression of the intensity of reproduction, at least for rodents of this species.
In carnivores, a significant effect of light on the function of reproduction was found (Belyaev, 1950). A decrease in daylight hours leads to an earlier maturation of fur in minks. Changing the temperature regime does not have any effect on this process. In martens, additional lighting causes the onset of the mating period and the birth of cubs 4 months earlier than usual. Changing the lighting regime does not affect the basal metabolism (Belyaev, 1958).
However, seasonal periodicals cannot be imagined only as a result of the influence of environmental factors, as indicated by a large number of experiments. In this regard, the question arises whether there is a seasonal periodicals in animals isolated from the influence of natural factors. In dogs that were kept in a heated room under artificial lighting throughout the year, it was possible to observe the seasonal periodicity characteristic of dogs (Magnonet Guilhon, 1931). Similar facts were found in experiments on laboratory white rats (Izbinsky and Isahakyan, 1954).
Another example of the extreme durability of seasonal periodicals concerns animals brought from the southern hemisphere. So, for example, the Australian ostrich in the Askania Nova reserve lays eggs in our winter, despite the severe frost, right in the snow in the season corresponding to summer in Australia (M. M. Zavadovsky, 1930). The Australian dingo breeds at the end of December. Although these animals, like ostriches, have been bred in the northern hemisphere for many decades, no change in their natural seasonal rhythm is observed.
In humans, the change in metabolism proceeds according to the same pattern as in non-sleeping animals. There are observations obtained in a natural setting with an attempt to pervert the natural seasonal cycle. The simplest way of such a perversion and the most reliable facts are obtained in the study of transfers from one locality to another. So, for example, moving in December - January from the middle zone of the USSR to the southern one (Sochi, Sukhumi) causes the effect of increasing the reduced "winter" exchange during the first month of stay there due to the new conditions of the south. Upon returning to the north in spring, a secondary spring increase in exchange occurs. Thus, during a winter trip to the south, one can observe two spring rises in the metabolic rate in the same person during the year. Consequently, a perversion of the seasonal rhythm also takes place in humans, but only under conditions of changes in the entire complex of natural environmental factors (Ivanova, 1954).
Of particular interest is the formation of seasonal rhythms in humans in the Far North. Under these conditions, especially during life at small stations, the seasonal periodicals are sharply disturbed. Insufficient muscular activity due to the restriction of walks, often impossible in the conditions of the Arctic, creates an almost complete loss of the seasonal rhythm (Slonim, Ol'nyanskaya, Ruttenburg, 1949). Experience shows that the creation of comfortable settlements and cities in the Arctic restores it. The seasonal rhythm in humans is to some extent a reflection not only of seasonal factors common to the entire living population of our planet, but, like the daily rhythm, is a reflection of the social environment that affects humans. Large cities and towns in the Far North with artificial lighting, with theaters, cinemas, with all the rhythm of life characteristic of modern man,
create such conditions under which the seasonal rhythm manifests itself normally beyond the Arctic Circle and is revealed in the same way as in our latitudes (Kandror and Rappoport, 1954; Danishevsky, 1955; Kandror, 1968).
In the conditions of the North, where there is a large lack of ultraviolet radiation in winter, there are significant metabolic disorders, mainly phosphorus metabolism, and a lack of vitamin D (Galanin, 1952). These phenomena are especially hard on children. According to German researchers, in winter there is a so-called "dead zone", when the growth of children completely stops (Fig. 29). Interestingly, in the Southern Hemisphere (Australia), this phenomenon occurs during the months corresponding to summer in the Northern Hemisphere. Now additional ultraviolet irradiation is considered as one of the most important methods of correcting the normal seasonal rhythm in northern latitudes. Under these conditions, we have to talk not so much about the seasonal rhythm, but about the specific lack of this natural necessary factor.
Seasonal periodicals are also of great interest to animal husbandry. Scientists are now inclined to believe that a significant part of the seasonal periods should be changed by the conscious influence of man. It is primarily about the seasonal diet. If for wild animals the lack of nutrition sometimes leads to the death of a significant number of individuals, to a decrease in the number of their representatives in a given area, then in relation to cultivated agricultural animals this is completely unacceptable. The nutrition of farm animals cannot be based on seasonal resources, but must be supplemented on the basis of human economic activity.
Seasonal changes in the body of birds are closely related to their characteristic flight instinct and are based on changes in the energy balance. However, despite the flights, birds show both seasonal changes in chemical thermoregulation and changes in the thermal insulation properties of the feather cover (insulation).
Metabolic changes in the house sparrow are well expressed ( Passer domesticus), the energy balance of which at low temperatures is maintained by greater heat production in winter than in summer. The results obtained from the measurement of food intake and metabolism show a flattened type of chemical thermoregulation curve, usually found when heat production is estimated from food intake over several days, and not from oxygen consumption in a short-term experiment.
Recently, it has been found that the maximum heat production in passerines is higher in winter than in summer. In grosbeaks, pigeons columba livia and starlings Sturnus vulgaris the survival time during cold periods in winter was longer mainly as a result of the increased ability to maintain higher heat production. The duration of the period before death is also affected by the state of plumage - molting and the duration of captivity, but the seasonal effect is always pronounced. Those who are IB bird cage food intake in winter increased by 20-50%. But winter food intake in caged finches ( Fringilla montefringilla) and in wild house sparrows did not increase (Rautenberg, 1957).
Significant nocturnal hypothermia, observed in winter in freshly caught birds, is absent in the grosbeak and black-headed tit. Irving (Irving, 1960) concluded that on cold nights, northern birds cool below their daytime body temperature about the same as birds in temperate regions.
The increase in plumage weight observed in some birds during winter suggests a thermal insulating adaptation that could partially offset changes in cold metabolism. However, Irving's research on several species of wild birds in winter and summer, as well as Davis (Davis, 1955) and Hart (Hart, 1962) provide little evidence for the assumption that the increase in metabolism with a 1° drop in temperature was different in these seasons. It was found that the heat production in pigeons, measured at 15°C, was lower in winter than in summer. However, the magnitude of these seasonal changes was small and no shifts were observed in the range of critical temperatures. Data on shifts in the critical temperature level were obtained for the cardinal ( Richmonda cardinalis) ( lawson, 1958).
Walgren (Wallgren, 1954) studied energy metabolism in yellow bunting ( Emberiza citrinella) at 32.5°C and at -11°C at different times of the year. Exchange at rest showed no seasonal changes; at -11 0 C in June and July, the exchange was significantly higher than in February and March. This insulative adaptation is partly explained by the greater thickness and "fluffiness" of the plumage and the greater vasoconstriction in winter (since the plumage was most dense in September - after the molt, and the maximum metabolic changes - in February).
Theoretically, changes in plumage can explain the decrease in lethal temperature by about 40 ° C.
Studies conducted on the black-headed tit ( Parus atricapillus), also indicate the presence of low heat production as a result of thermal insulation adaptation in winter. The pulse rate and respiration rate had seasonal shifts, and the decrease was greater in winter at 6°C than in summer. The critical temperature at which respiration sharply increased also shifted to a lower level in winter.
The increase in basal metabolism at thermoneutral temperatures, which is pronounced in mammals and birds exposed to cold for several weeks, does not play a significant role during winter adaptation. The only evidence of a significant seasonal variation in basal metabolism has been obtained in house sparrows, but there is no evidence to suggest that it plays any significant role in birds living in the wild. Most of the studied species do not show any changes at all. King and Farner (King a. Farrier, 1961) indicate that a high intensity of basal metabolism in winter would be unfavorable, since the bird would need to increase the consumption of its energy reserves at night.
The most characteristic seasonal shifts in birds are their ability to change their thermal insulation and the amazing ability to maintain a higher level of heat production in cold conditions. Based on the measurement of food intake and excretion at different temperatures and photoperiods, estimates of energy requirements for existence and productive processes were made at different times of the year. For this purpose, the birds were housed in individual cages where their metabolized energy (maximum energy influx minus excretion energy at different temperatures and photoperiods) was measured. The smallest metabolized energy required for existence at certain temperatures and photoperiods of the test is called "existence energy". Its correlation with temperature is shown on the left side of Figure 30. Potential energy is the maximum metabolized energy measured at a temperature corresponding to the lethal limit, which is the lowest temperature at which a bird can support its body weight. Productivity energy is the difference between potential energy and existence energy.
The right side of Figure 30 shows different energy categories calculated for different seasons from average outdoor temperatures and photoperiods. For these calculations, it is assumed that the maximum metabolized energy is found in cold conditions, as well as for productive processes at higher temperatures. In the house sparrow, potential energy is subject to seasonal changes due to seasonal changes in survival limits. The energy of existence also changes according to the average outdoor temperature. Due to seasonal changes in potential energy and energy of existence, the energy of productivity remains constant throughout the year. Some authors point out that the ability of the house sparrow to live in the far northern latitudes is due to its ability to stretch its maximum energy balance throughout the winter and metabolize as much energy during a short daytime photoperiod in winter as during long photoperiods in summer.
At the white-throated sparrow (Z. albicallis) and the junkoJ. hue- malls) with a 10-hour photoperiod, the amount of metabolized energy is less than with a 15-hour photoperiod, which is a serious disadvantage of winter time (Seibert, 1949). These observations were compared with the fact that both species migrate south in winter.
Unlike the house sparrow, the tropical blue-black finch ( Votatinia jacarina) could maintain energy balance down to about 0°C for a 15-hour photoperiod and up to 4°C for a 10-hour photoperiod. The photoperiod limited the energy to a greater extent with a decrease in temperature, which is the difference between these birds and the house sparrow. Due to the influence of the photoperiod, the potential energy was lowest in winter, when the energy of existence is highest. Consequently, the productivity energy was also the lowest at that time of the year. These physiological characteristics do not allow this species to exist in winter in northern latitudes.
Although the energy requirements for thermoregulation in the cold season turn out to be maximum, various types of bird activity are apparently distributed evenly throughout the year, and therefore the cumulative effects are negligible. The distribution of established energy demands for various activities throughout the year is best described for three sparrows. S. arborea ( West, 1960). In this species, the highest amount of productivity energy was potentially in the summer. Therefore, activities that require energy expenditure, such as migration, nesting and molting, are evenly distributed between April and October. The additional cost of free existence is an unknown that may or may not increase the theoretical potential. However, it is quite possible that potential energy can be used at any time of the year, at least for short periods - for the duration of the flight.
Light. Solar energy is practically the only source of light and heat on our planet. The amount of sunlight naturally changes throughout the year and day. Its biological effect is due to the intensity, spectral composition, seasonal and daily periodicity. In this regard, in living organisms, adaptations also have a seasonal and zonal character.
Ultra-violet rays destructive to all living things. The main part of this radiation is delayed by the ozone screen of the atmosphere. Therefore, living organisms are distributed to the ozone layer. But a small amount of ultraviolet rays is useful for animals and humans, as they contribute to the production of vitamin D.
visible spectrum light essential for plants and animals. Green plants in the light, mainly in the red spectrum, photosynthesize organic substances. Many unicellular organisms react to light. Highly organized animals have light-sensitive cells or special organs - the eyes. They are able to perceive objects, find food, lead an active lifestyle during the day.
The human eye and most animals do not perceive infrared rays, as a source of thermal energy.
These rays are especially important for cold-blooded animals (insects, reptiles), which use them to increase body temperature.
Light mode varies depending on the geographical latitude, relief, time of year and day. In connection with the rotation of the Earth, the light regime has a distinct daily and seasonal periodicity.
The reaction of the body to a daily change in lighting mode (day and night) is called photoperiodism.
In connection with photoperiodism in the body, the processes of metabolism, growth and development change. Photoperiodicity is one of the main factors affecting the body's biological clock, which determines its physiological rhythms in accordance with changes in the environment.
In plants, daily photoperiodism affects the processes of photosynthesis, budding, flowering, and leaf fall. Some plants open their flowers at night and are pollinated by pollinating insects active at that time of day.
Animals also have adaptations for diurnal and nocturnal lifestyles. For example, most ungulates, bears, wolves, eagles, and larks are active during the day, while tigers, mice, ground squirrels, hedgehogs, and owls are most active at night. The length of daylight hours affects the onset of the mating season, migrations and flights (in birds), hibernation, etc.
It is also of great importance degree of illumination. Depending on the ability to grow in conditions of shading or lighting, there are shade-tolerant And light-loving plants. Steppe and meadow grasses, most woody plants (birch, oak, pine) are photophilous. Shade-tolerant plants often live in the forest, in its lower tier. These are oxalis, mosses, ferns, lilies of the valley, etc. Of the woody plants, this is spruce, so its crown is most magnificent in the lower part. Spruce forests are always gloomier and darker than pine and broadleaf forests. The ability to exist in different light conditions determines the layering of plant communities.
The degree of illumination at different times of the year depends on the geographical latitude. The length of the day at the equator is always the same and is 12 hours. As we get closer to the poles, the length of the day increases in summer and decreases in winter. And only on the days of the spring (March 23) and autumn (September 23) equinox, the length of the day is everywhere equal to 12 hours. In winter, polar night dominates beyond the Arctic Circle, when the sun does not rise above the horizon, and in summer - polar day, when it does not set around the clock. In the Southern Hemisphere, the opposite is true. In connection with seasonal changes in illumination, the activity of living organisms also changes.
Seasonal Rhythms It is the body's response to changing seasons.
So, with the onset of a short autumn day, plants shed their leaves and prepare for winter dormancy.
winter calm- these are the adaptive properties of perennial plants: cessation of growth, death of above-ground shoots (in grasses) or leaf fall (in trees and shrubs), slowing down or stopping many life processes.
In animals, a significant decrease in activity is also observed in winter. A signal for the mass departure of birds is a change in the length of daylight hours. Many animals fall into hibernation- adaptation to endure the unfavorable winter season.
In connection with the constant daily and seasonal changes in nature, certain mechanisms of an adaptive nature have been developed in living organisms.
Warm. All life processes take place at a certain temperature - mainly from 10 to 40 ° C. Only a few organisms are adapted to life at higher temperatures. For example, some mollusks live in thermal springs at temperatures up to 53 ° C, blue-green (cyanobacteria) and bacteria can live at 70-85 ° C. The optimum temperature for the life of most organisms ranges from 10 to 30 °C. However, the range of temperature fluctuations on land is much wider (from -50 to 40 °C) than in water (from 0 to 40 °C), so the temperature tolerance limit for aquatic organisms is narrower than for terrestrial ones.
Depending on the mechanisms of maintaining a constant body temperature, organisms are divided into poikilothermic and homeothermic.
Poikilothermic, or cold-blooded, organisms have unstable body temperature. An increase in ambient temperature causes them a strong acceleration of all physiological processes, changes the activity of behavior. So, lizards prefer a temperature zone of about 37 ° C. As the temperature rises, the development of some animals accelerates. So, for example, at 26 ° C in a caterpillar of a cabbage butterfly, the period from leaving the egg to pupation lasts 10-11 days, and at 10 ° C it increases to 100 days, i.e. 10 times.
Many cold-blooded animals have anabiosis- a temporary state of the body, in which vital processes slow down significantly, and there are no visible signs of life. Anabiosis can occur in animals both with a decrease in the temperature of the environment, and with its increase. For example, in snakes, lizards, when the air temperature rises above 45 ° C, torpor occurs, in amphibians, when the water temperature drops below 4 ° C, vital activity is practically absent.
In insects (bumblebees, locusts, butterflies) during the flight, the body temperature reaches 35-40 ° C, but with the termination of the flight it quickly drops to air temperature.
homeothermic, or warm-blooded, animals with a constant body temperature have more perfect thermoregulation and are less dependent on the temperature of the environment. The ability to maintain a constant body temperature is an important feature of animals such as birds and mammals. Most birds have a body temperature of 41-43°C, while mammals have a body temperature of 35-38°C. It remains at a constant level, regardless of fluctuations in air temperature. For example, in a frost of -40 ° C, the body temperature of the arctic fox is 38 ° C, and that of the ptarmigan is 43 ° C. In more primitive groups of mammals (oviparous, small rodents), thermoregulation is imperfect (Fig. 93).
Rice. 93. Dependence of body temperature of various animals on air temperature
The temperature regime is of great importance for plants. The process of photosynthesis is most intensive in the range of 15-25 °C. At high temperatures, severe dehydration of plants occurs and their inhibition begins. The processes of respiration and water evaporation (transpiration) begin to prevail over photosynthesis. At lower temperatures (less than 10 °C), cold damage to cellular structures and inhibition of photosynthesis can occur.
The main adaptations of plants to cold habitats are a decrease in size and the appearance of specific growth forms. In the North, beyond the Arctic Circle, dwarf birches, willows, creeping forms of juniper, and mountain ash grow. Even during the long polar summer, when the illumination is very high, the lack of heat affects the processes of photosynthesis.
Plants have special mechanisms to prevent freezing of water in cells at low temperatures (below 0 °C). So, in winter, plant tissues contain concentrated solutions of sugars, glycerin and other substances that prevent water from freezing.
The temperature, as well as the light regime on which it depends, also naturally changes during the day, year and at different latitudes. At the equator, it is relatively constant (about 25-30 ° C). As we approach the poles, the amplitude increases, and in summer it is much less than in winter. Therefore, the presence in animals and plants of adaptations to endure low temperatures is of particular importance.
Water. The presence of water is a necessary condition for the existence of all organisms on Earth. All living organisms are at least 30% water. Maintaining water balance is the main physiological function of the body. Water is distributed unevenly across the globe. Since most terrestrial plants and animals are moisture-loving, its lack is often the reason that limits the distribution of organisms.
The presence of water is one of the main environmental factors limiting the growth and development of plants. In the absence of water, the plant withers and may die, so many plants have special adaptations that allow them to endure the lack of moisture.
So, in deserts and semi-deserts are widespread xerophytes, plants in arid habitats. They can tolerate temporary wilt with up to 50% water loss. They have a well-developed root system, ten times larger than the aerial part in mass. The roots can go as deep as 15-20 m (for black saxaul - up to 30 m), which allows them to extract water at great depths. The economical use of water is also ensured by the development of special adaptations of above-ground organs. To reduce the evaporation of water, the leaves of steppe and desert plants are usually small, narrow, often they are turned into spines or scales (cacti, camel thorn, feather grass). The cuticle of the leaf is thickened, waxy or densely pubescent. Sometimes there is a complete loss of leaves (saxaul, juzgun). Photosynthesis in such plants is carried out by green stems. In some desert dwellers (agave, spurge, cactus), a large amount of moisture is stored in the tissues of strongly thickened, fleshy stems.
Mesophytes- These are plants that develop in conditions where there is enough water. These include deciduous trees, shrubs, and many herbs of the forest and forest-steppe zones.
Hygrophytes- plants of humid habitats, have large succulent leaves and stems and a much worse developed root system. Intercellular spaces in leaves and green stems are well developed. These plants include rice, marsh marigold, arrowhead, mosses, etc.
At hydrophytes- aquatic inhabitants are often poorly developed or absent mechanical tissue, root system (duckweed, elodea).
Animals also need water. Most of the inhabitants of the desert - camels, antelopes, kulans, saigas - are able to do without water for a long time. Great mobility and endurance allow them to migrate over considerable distances in search of water. Their ways of regulating the water balance are more diverse. So, for example, fat deposits in a camel (in the humps), rodents (under the skin), insects (adipose tissue) serve as a source of metabolic water, which is released as a result of fat oxidation. Most inhabitants of arid places are nocturnal, thereby avoiding overheating and excessive evaporation of water.
Organisms living in conditions of periodic dryness are characterized by a decrease in vital activity, a state of physiological rest in the absence of moisture. In hot, dry summers, plants can shed their leaves, sometimes above-ground shoots die off completely. This is especially true for bulbous and rhizomatous plants (tulips, sedges), which grow rapidly and bloom in spring, and spend the rest of the year in the form of dormant underground shoots.
Animals with the onset of a hot and dry period can hibernate (marmots), move less and feed. Some species fall into a state of suspended animation.
The soil serves as a habitat for many microorganisms, animals, and plant roots and fungal hyphae are fixed in it. The primary factors important for soil inhabitants are its structure, chemical composition, humidity, and the presence of nutrients.
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§ 66. Ecology as a science. Environmental factors§ 68. Interaction of factors. limiting factor
During severe frosts and winds, 200-300, and sometimes 500 penguins gather in a crowd and, straightening up to their full height, tightly press against each other, forming the so-called "turtle" - a tight circle. This circle rotates slowly but continuously around the center, the huddled birds warm each other. After the storm, the penguins disperse. French scientists were struck by such a "public" thermoregulation. By measuring the temperature inside the "turtle" and along its edges, they made sure that at -19°C the temperature of the birds in the center reaches 36°C, and by the time the temperature was measured, the birds had been starving for about 2 months. Alone, the penguin daily loses over 200 g in weight, and in the "turtle" - about 100 g, that is, it "burns fuel" half as much.
We see that the features of adaptation are of great importance for the survival of the species. In May - June, when it is winter in Antarctica, emperor penguins lay eggs weighing about 400-450 g. Until the day of laying the eggs, the female is starving. Then the female penguins leave for a 2-month campaign for food, and the males eat nothing all this time, warming the egg. As a rule, the chicks leave the egg after the mother returns. The chicks are reared by the mother from about July to December.
In the Antarctic spring, ice floes begin to melt and break apart. These ice floes carry young and adult penguins to the open sea, where the kids finally form into independent members of the amazing penguin society. This seasonality manifests itself from year to year.
Seasonal changes in physiological processes are also observed in humans. There is a lot of information about this. Observations of scientists testify that "assimilation of rhythm" (AA Ukhtomsky) occurs not only in micro-intervals of time, but also in macro-intervals. The most striking of the temporal cyclic changes in physiological processes are annual seasonal changes closely related to seasonal meteorological cycles, namely, an increase in basal metabolism in spring and a decrease in autumn and winter, an increase in the percentage of hemoglobin in spring and summer, a change in the excitability of the respiratory center in spring and summer. Scientists have found that the hemoglobin content and the number of erythrocytes in human blood are 21% higher in winter than in summer. The maximum and minimum blood pressure rises from month to month as it gets colder. The difference between summer and winter blood pressure reaches 16%. The vascular system and blood are especially sensitive to seasonal changes. The maximum and minimum blood pressure in summer is lower than in winter. The number of erythrocytes in summer in men is slightly higher, and in women is lower than in winter, and the hemoglobin index, on the contrary, is lower in men in summer, and higher in women than in other seasons. The color index of blood in summer is lower than in other seasons.
A. D. Slonim and his co-workers obtained somewhat different data while observing people living in the conditions of the North. They found that the highest percentage of blood hemoglobin is observed in the summer months, and the lowest - in winter and spring. A large amount of experimental material on the study of the seasonal dynamics of erythrocytes, hemoglobin, blood pressure, pulse, erythrocyte sedimentation reaction (ERS) has been accumulated by M. F. Avazbakieva in the conditions of Central Asia and Kazakhstan. About 3000 people (2000 men and 1000 women) were examined. It is shown that ROE in men accelerates somewhat in summer, however, upon arrival in the mountains in all seasons of the year, as a rule, it slows down. Scientists believe that the changes in the ESR observed in the mountains are due to the action of solar radiation. These changes indicate a general favorable effect of the high mountain climate on humans and a decrease in protein breakdown during acclimatization.
Under laboratory conditions, by exposing a person to ultraviolet rays, it is possible to cause changes similar to those observed in the natural conditions of high mountains. Regularly, for a long time examining 3746 people living in Kiev, V.V. Kovalsky found that the maximum content of hemoglobin in the blood of men occurs in spring (mainly in March), and in women - in winter (most often in January). The minimum content of hemoglobin is observed in men in August, in women - in July.
In lower monkeys (hamadryas baboons), seasonal fluctuations in such biochemical blood parameters as sugar, cholesterol, residual nitrogen, proteins, and adenosine triphosphoric acid have been established. He found that blood sugar levels decreased in winter and adenosine triphosphoric acid and cholesterol levels increased compared to summer. It was found that if in the middle lane the level of basal metabolism drops significantly in winter, and this is probably due to the fact that light irritations are reduced in winter (short day) and human motor activity decreases, then when a person moves in winter from the middle lane to the conditions of the subtropics of Abkhazia, it is like would transfer its body from winter conditions to spring and summer conditions. In these cases, the metabolism increases, the respiratory coefficient practically does not change in the winter months and remains the same as in summer. The author considers these changes as a peculiar case of a perversion of the seasonal rhythm in humans.
According to some researchers, the seasonal variability of physiological processes observed during the year to some extent repeats their daily periodicity, and the state of organisms in summer and winter to some extent coincides with their state day and night. Studying the behavior of bats in the Adzaba cave near Sukhumi, A. D. Slonim notes that the daily periodic changes in thermoregulation in time coincide with the departure of mice from the cave - the period of their activity in the evening and at night, and this rhythm is best expressed in spring and summer.
Spring, spring... Each spring excites us anew. o It is in the spring that we all, regardless of age, have that exciting feeling when we are ready to repeat after the poets and very young people: everything this spring is special. Spring sets a person in a special way, because spring is, first of all, morning, early awakening. Everything around is renewed in nature. But man is also a part of nature, and spring takes place in each of us. Spring is not only a time of hope, but also a time of anxiety.
Ask any farmer, and he will answer you that in the spring the man who has connected his life with the earth is more concerned than ever. We must appreciate all the seasons, all twelve months. Isn't autumn wonderful! It is autumn that is rich in rich harvests in gardens, fields and orchards, bright colors, wedding songs. Since the time of Pushkin, it has been customary to consider this time of the year as that wonderful time when inspiration comes to a person, when a surge of creative forces comes ("And every autumn I bloom again ..."). Pushkin's Boldin autumn is the best proof of this. Omnipotent spell of autumn. But "how to explain it?" the poet asked himself.
A person's addiction to a particular season is usually subjective. And yet, scientists have noticed that in autumn a person’s metabolism and general tone of the body increase, vital processes intensify, an increase in vital functions is observed, and oxygen consumption increases. All this is a natural reaction of adaptation, preparation of the body for a long and difficult winter. In addition, the colors of autumn - yellow, red - have an exciting effect on a person. After the summer heat, the cool air invigorates. Pictures of fading nature, at first disposing to sadness, reflection, subsequently activate the activity of a healthy person.
But don't other seasons - winter, summer - have their charms? Between the seasons there are no pauses - life is continuous. No matter how severe the frosts were, no matter how dense the winter was in the yard, it still ends with the melting of snow. And the clarity of spring dawns is replaced by a hot summer day. The relationship between body functions and seasons, first noticed by Hippocrates and Avicenna, did not find scientific justification for a long time.
It has now been established that one of the synchronizers of seasonal rhythms, as well as daily rhythms, is the length of daylight hours. The data of experimental studies show that the height of the endogenous rhythm reaches a maximum in the spring-summer, and a minimum - in the autumn-winter period. An analysis of experimental data indicates that a characteristic feature of seasonal changes in the reactivity of an organism is the absence of unidirectional shifts in its various components. This gives reason to believe that seasonal changes depend on the biological expediency of each of its components, which ensures the constancy of the internal environment of the organism. The spring-summer functional maximum is probably associated with the reproductive stage of the organism's life. The simultaneous increase in the function of various endocrine glands observed during this period serves as a clear indicator of the phylogenetically fixed features of the organism, aimed at enhancing metabolic processes during the reproduction period.
The seasonal periodicity of the organism's vital activity is a general manifestation of the organism's adaptation to environmental conditions. Synchronization of biological rhythms with the geophysical cycles of the Earth, which favors the species differentiation of plants and animals, has not lost its significance for humans. The dependence of the frequency of cases of various diseases on the time of year was established. The study of the given data and indicators of hospitalization in different seasons of the year of patients in three large clinics in Leningrad indicates that different seasonality is noted for different diseases. The winter period is the most unfavorable for hypertensive patients. For patients with coronary disease, autumn turned out to be a particularly threatening season. It is this period that is characterized by the largest number of visits by ambulance doctors to patients with myocardial infarction and angina pectoris. In comparison with other seasons of the year, the largest number of cerebrovascular accidents was registered in the spring period, and the smallest in summer.
Spring and, to a lesser extent, autumn periods are the least threatened for the occurrence of infectious diseases. Further study of the seasonal frequency of diseases will make it possible to develop evidence-based therapeutic and preventive measures.
» Impact on organisms of some environmental factors
Seasonal Rhythms
is the body's response to the change in the seasons. Actual information buy float valve from us.
So, with the onset of a short autumn day, plants shed their leaves and prepare for winter dormancy.
winter calm
- these are the adaptive properties of perennial plants: cessation of growth, death of above-ground shoots (in grasses) or leaf fall (in trees and shrubs), slowing down or stopping many life processes.
In animals, a significant decrease in activity is also observed in winter. A signal for the mass departure of birds is a change in the length of daylight hours. Many animals fall into hibernation
- adaptation to endure the unfavorable winter season.
In connection with the constant daily and seasonal changes in nature, certain mechanisms of an adaptive nature have been developed in living organisms.
Warm.
All life processes take place at a certain temperature - mainly from 10 to 40 ° C. Only a few organisms are adapted to life at higher temperatures. For example, some mollusks live in thermal springs at temperatures up to 53 ° C, blue-green (cyanobacteria) and bacteria can live at 70–85 ° C. The optimum temperature for the life of most organisms ranges from 10 to 30 °C. However, the range of temperature fluctuations on land is much wider (from -50 to 40 °C) than in water (from 0 to 40 °C), so the temperature tolerance limit for aquatic organisms is narrower than for terrestrial ones.
Depending on the mechanisms of maintaining a constant body temperature, organisms are divided into poikilothermic and homeothermic.
Poikilothermic,
or cold-blooded,
organisms have unstable body temperature. An increase in ambient temperature causes them a strong acceleration of all physiological processes, changes the activity of behavior. So, lizards prefer a temperature zone of about 37 ° C. As the temperature rises, the development of some animals accelerates. So, for example, at 26 °C in a caterpillar of a cabbage butterfly, the period from leaving the egg to pupation lasts 10–11 days, and at 10 °C it increases to 100 days, i.e. 10 times.
Many cold-blooded animals have anabiosis
- a temporary state of the body, in which vital processes slow down significantly, and there are no visible signs of life. Anabiosis can occur in animals both with a decrease in the temperature of the environment, and with its increase. For example, in snakes, lizards, when the air temperature rises above 45 ° C, torpor occurs, in amphibians, when the water temperature drops below 4 ° C, vital activity is practically absent.
In insects (bumblebees, locusts, butterflies) during the flight, the body temperature reaches 35-40 ° C, but with the termination of the flight it quickly drops to air temperature.
homeothermic,
or warm-blooded,
animals with a constant body temperature have more perfect thermoregulation and are less dependent on the temperature of the environment. The ability to maintain a constant body temperature is an important feature of animals such as birds and mammals. Most birds have a body temperature of 41-43°C, while mammals have a body temperature of 35-38°C. It remains at a constant level, regardless of fluctuations in air temperature. For example, in a frost of -40 °C, the body temperature of the arctic fox is 38 °C, and that of the ptarmigan is 43 °C. In more primitive groups of mammals (oviparous, small rodents), thermoregulation is imperfect (Fig. 93).