Topic: Biomasses and vital forms of living organisms
Plan:
1. Ecological time factor
2. Daily, monthly and annual rituals of plants and animals
3. Seasonal changes in plants and animals
1 Ecological time factor: All living organisms in nature live in certain environmental conditions. There is a constant exchange of substances between the external environment and living organisms, which is important for maintaining the vital activity of organisms. One of the fundamental characteristics of living nature is characterized by the periodicity of life processes in it. All life processes on earth, from the cell to the biosphere, obey a certain rhythm. Biological rhythms in nature are divided into internal (related to their vital activities) and external characteristics for all living organisms. Biological rhythms occurring in organisms are caused by certain factors. Therefore, we will briefly touch on these factors.
Internal periodicity. These are changes that occur in organisms. All physiological processes in living organisms do not continue continuously.
External (exogenous) rhythms. Such important changes that are constantly repeated in nature include, first of all, the seasonal and diurnal cycles caused by the rotation of the Earth around the Sun, and the Moon around the Earth and its core.
As a result of the rotation of the Earth around the core, environmental factors on our planet - temperature, pressure, humidity, light regime, air, electromagnetic field in the atmosphere, overflow and return of the oceans legally change. periodic changes in solar activity are also affected
2 Daily, monthly and annual rituals of plants and animals:
Diurnal rhythms are specific adaptations of organisms in response to the complex of microclimate conditions formed as a result of movement around the earth's core. The characteristic of daily periodicity is the alternating period of rest and active activity. In some living organisms, active activity coincides with the light time of the day, while other living . in individuals it corresponds to the evening.
The circadian rhythm in the body consists of adapting to environmental factors that change periodically overnight, namely air temperature and humidity, wind, light, and many other complex factors. Also, the daily rhythm may depend on the conditions of finding food. However, just as in the seasonal rhythm, in the diurnal rhythm, light acts as the main signal (warning) factor. At the same time, the alternation of light and dark times plays a special role. This can be proven by artificially changing the light pattern.
The study of daily cycles in the plant and animal kingdoms has proven that organisms also have the ability to determine time. Most plants flower at a specific time of day, for example, the daily movement of the leaves of a bean plant can be seen with chronological precision. will give. The property of determining the time of all living organisms is called the biological clock.
Animals with fully formed nervous systems have biological clock mechanisms in particular. Studying the daily rhythms of insects shows that their biological clock is "corrected" to local time, that is, each organism measures its time based on the light factors of the place where it lives. The results of observations made in bees fully confirm the above-mentioned opinion.
In Paris, bees were given sugary juice in separate chambers for several days from 20.10-15 minutes to 22.10-15 minutes local time. The bees were then flown to New York in the evening. The next day, at about 15.00:24 p.m. New York time, exactly XNUMX hours after their last feeding in Paris, the bees began to fly into the hive.
From 20.15:22.15 to XNUMX:XNUMX New York time, not a single bee flew to the manger. A similar result was obtained when bees were moved from New York to Paris.
The results of the tests conducted on the American marsupial indicate that the regulator of daily activity in insects is based on a neurohormonal mechanism. The results of the preliminary observations on the American marsupial showed that the rhythm of movement activity depends on the presence of a special secretion in the body: special neuro-secretory cells located at the level of the belly and partially on the side of the hypolaryngeal ganglia serve as such a source of secretion. If the sublaryngeal ganglion of an active rhythmic wasp is cut and transplanted into the abdomen of an "arrhythmic" psit with its head removed, after a few days the same activity as in the previous donor insect without the ganglion being transplanted was noted. will be done. At the same time, the beginning of the period of activity depends mainly on the excitation resulting from the transition from light to dark. This stimulus is received by the normal eye.
As a result of the observations, it became clear that although the neuro-secretory cells of the sublaryngeal ganglion have the ability to independently secrete the secretion that regulates the rhythm of the insect's daily activity, the secretory of special glands, called accessory bodies, come to the sublaryngeal ganglion in order for the process to go well. should stand. This secretion to the sublaryngeal ganglia! comes through the nerves that connect with the adjacent bodies. If these nerves are cut, the rhythm of motor activity gradually fades within a week.
This condition is observed even when the insect is exposed to light and darkness. Diurnal variation affects only locomotor activity in most animals and has little effect on physiological characteristics. For example, the same situation is observed in rodents, changes in physiological activities are felt (more clearly) in the ground layers. During the daytime in summer, most of them behave like poikilothermic animals. Their body temperature will be equal to their critical temperature, breathing, blood pressure, sensory organs will be very low.
The active activity of some species corresponds to certain times of the day, in others it can change depending on the conditions. For example, the opening of the flower of the saffron plant depends on the temperature. And the basket of the sunflower plant does not open on cloudy days. The active activities of animals distributed in the desert zone correspond to different times of the day, which is mainly related to the temperature and humidity here.
The difference between the internal (endogenous) circadian rhythm and the external (exogenous) rhythm can be proven experimentally. Most species have long developmental cycles close to diurnal when light, moisture, temperature, food, etc. are constant. For example, in a fruit fly, such an internal (endogenous) rhythm continues for several tens of generations. Thus, the daily periodicity of vital activity is innately transmitted from generation to generation as a genetic characteristic of the species. Such internal (endogenous) rhythms are called circadian (Latin vinegar - around and di - day). Animals with some complex structures innately target both time and place.
Birds constantly make corrections to the direction of flight and the polarization of light in the sky during long-distance flight. In this, they take into account the time of the day, living organisms are not only based on the daily period (cycle), but also based on the complex geophysical period (cycle) that occurs in nature.
Annual rhythms. Annual rhythms are the most universal rhythms in living organisms. Changes in physical conditions legally over the years have produced a series of adaptations in the evolution of species. For example, the reproduction and growth of the species is related to adaptation and migration during the most unfavorable times of the year. In species with short life cycles, annual rhythms are observed in several generations (for example, Daphnia cyclomorphosis).
Seasonal variation causes profound changes in the physiological state and behavior of organisms, as well as large shifts in their life cycles and morphological structures. All living organisms have features to adapt to such changes. Due to such adaptations, the most important periods of the life of the species - the most favorable time of the year for reproduction, and the most unfavorable time of the year correspond to the very energetic period of these species.
The faster the external environment changes, the stronger the annual cycle of life activity of living organisms. For example, shedding of leaves of plants in autumn, formation of reserve oils, migration (migration), etc. Such periodicity is characteristic only for countries with temperate and cold climates. The annual cycle is very well reflected in the vital activities of plants and animals living in tropical zones.
Most species have internal annual rhythms. This is especially true of reproductive cycles. Thus, animals living in the southern hemisphere breed mainly in autumn or winter when they are kept in zoos in the north. This time corresponds to spring or summer in their homeland. Ostriches brought from Australia lay their eggs in the snow in the Askania Nova Reserve. A dog named Dingo brought from this country was born in December, which is the end of spring in his country. That is why it is necessary to take into account the annual forms of organisms in acclimatization and adaptation (acclimatization) of species
3 Seasonal changes in plants and animals
The role of photoperiod in the growth and development of plants and animals. As a result of periodic changes in environmental conditions, great changes occur in the physiological state of plants and animals during the year. If living organisms do not adapt to the seasons, they may die. For example, if the dormant stages are formed before winter, the individuals will die.
Biological processes in preparation for kish begin in summer - when the temperature in the air and soil is still high.
The change of day length is also important in the management of seasonal cycles in living organisms. The effect of day length on living organisms is called photoperiod. Its formation depends not on the provision of strong light, but on the rhythm of alternating day and night.
Photoperiodic exposure of living organisms is of great importance for their adaptation to adverse conditions. Seedlings of the birch plant, which are artificially lit during the day or where the day length exceeds 15 hours, grow continuously and do not shed their leaves. But when it is illuminated for 10-12 hours a day, the growth of these seedlings stops even in summer, and soon they lose their leaves. Under the influence of the short day of autumn, it gradually passes into the period of winter hibernation. Most deciduous trees: willow, white acacia, oak and spruce are evergreen in the long days.
The length of the day also affects animals. During the long days, ticks and insects go into hibernation. For example, if the caterpillars of the cabbage butterfly are kept under long day conditions (when the light day is 14-16 hours), butterflies emerge from their cones and several generations develop continuously. But if the worms are kept in a day shorter than 14 hours, despite the high enough temperature in the spring and summer, the wintering mushrooms will not develop for several months.
As the days lengthen in the spring, gonads develop in birds, and the instinct to build a nest is formed in them. In autumn, as the day shortens, birds begin to prepare for the winter by jumping, that is, they accumulate fat and rush to fly away (mitration).
Winter hibernation in plants. Menstruation and other seasonal events also depend on the length of the day. For example, many wild plants are long-day plants. Among cultivated plants, wheat and barley varieties, rye, oats, and flax are long-day plants. But some plants that grow in the south, such as chrysanthemum, potato flower, cotton, etc., flower in the period when the days are short. That's why they bloom only at the end of summer - in autumn (when the day shortens). These types of plants are called short day plants.
Photoperiodicity is a general adaptation that governs seasonal events in various organisms. The photoperiodic phenomenon occurs in all major periodic groups, but not all of them. There are species that are neutral to the effect of the photoperiodic phenomenon, in which the change in physiological life in developmental cycles does not depend on the length of the day. Other ways of managing life cycles may have evolved in such species. For example, the phenomenon of photoperiodism is not observed in species distributed in places where there is no strong difference in seasons. Germination of seeds, flowering, fruiting, shedding of leaves, etc. take a long time in plants growing in tropical forests. The plants that grow here produce flowers and fruits at the same time. Species growing in temperate climates, species that can complete all their life cycles in favorable times, and species that do not have active reproductive activities in unfavorable seasons of the year, will not be affected by photoperiodism. For example, the growth and development of many ephemeral and ephemeroid plants takes place during the period of the year when there is a lot of precipitation. With the onset of hot weather, their seeds are shed, and the body freezes. For seven to eight months, their seeds endure the scorching heat and go through a dormant period.
Examples of ephemeral plants are marigold, shotara, chitir, white chitir and jag-jag. About 400 of them grow in Central Asia
As for ephemeroids, plant species such as saffron, saffron, sedum, tulip, and sedum can be cited as examples.
It is known that the length of daylight depends not only on the season, but also on the geographical location of the place. Short-day species grow and live mainly in low latitudes, while long-day species grow and thrive in temperate and high latitudes. Northern individuals with wide areas and photoperiodic type differ from southern individuals. Thus, photoperiodic type is not a systematic feature of these species, but an ecological feature.
