Biological Cycles

Biological Cycles


rhythmic repetition of biological phenomena in associations of organisms (populations, biocenoses), which serves as an adaptation to cyclic changes in their conditions of existence. Biological cycles are included in the more general concept of biological rhythms, which includes all rhythmically repeated biological phenomena. Biological cycles may be daily, seasonal (annual), or at intervals of many years.

Twenty-four-hour biological cycles are expressed in regular fluctuations in the physiological phenomena and behavior of animals during the course of a 24-hour day. At their base lie automatic mechanisms which are corrected by the effects of external factors: 24-hour variations in illumination, temperature, moisture, and so on.

At the base of seasonal biological cycles lie those metabolic changes which in animals are regulated by hormones. In various seasons the condition and behavior of organisms within a population or a biocenosis change: accumulation or consumption of reserve substances may occur; shedding of outer layers (molting), reproduction, animal migration, hibernation, and other seasonal phenomena begin or end. Being to a considerable degree automatized, these phenomena are corrected by external influences (weather conditions, food reserves, and so on).

Biological cycles lasting many years are conditioned by cyclic variations of climate and other conditions of existence (in connection with changes in solar activity and other cosmic and planetary factors). Such biological cycles occur in populations and biocenoses and are expressed in fluctuations in reproduction and the numbers of certain species, in resettlement of populations in new places, or in the extinction of parts of populations. These phenomena are the end result of cyclic changes in populations and biocenoses and of fluctuations in their conditions of existence, mainly climate.


Shcherbinovskii, N. S. Pustynnaia sarancha shistotserka. Moscow, 1952.
Naumov, N. P. Ekologiia zhivotnykh, 2nd ed. Moscow, 1963.
Biologicheskie chasy: Sb. statei. Moscow, 1964. (Translated from English.)
Marteka, V. Bionika. Moscow, 1967. (Translated from English.)
Emme, A. M. Biologicheskie chasy. Novosibirsk, 1967.


References in periodicals archive ?
This process has impacts on the stream biodiversity, decreasing biota process and biological cycles, erosion on the river embankment and increasing sedimentation on Klang River system [6].
It also affects the range, abundance, behaviour, biological cycles, and life history traits of the microbes or related host species, changing balances between pathogens, vectors, and reservoirs.
That is already too much, because replacing the complex natural ecology with our monocrop agriculture removes vital elements from the chemical and biological cycles that keep our climate stable.
The sub-cycles can be grouped into biological cycles (i.
This system might be a modification of an ancient circadian control system that first developed in other organisms, including cold-blooded animals, whose daily biological cycles are affected by external temperature changes.
Researchers have long believed that the sleep disturbances common among the elderly often result from a disruption of the body's circadian rhythms - biological cycles that repeat approximately every 24 hours.
But it leads one to ask whether the traditional societies noted by Clark were really not entities caught in natural biological cycles but rather class societies in which the upper class appropriated and wasted most of the surplus and the mass of producers were left at subsistence levels.
The formal study of the innate 24-hour biological cycles characteristic of most living organisms is briefly introduced as chronobiology.
Circadian rhythms are biological cycles that occur with a period of about 24 hours in the absence of environmental cues.
Circadian rhythms regulate our biological cycles for sleep, activity level, metabolism, and many other processes through our body's exposure to sunlight and darkness," said Boris I.
Insects pollinate plants, are a food source for other animals and of course they break down dead organisms allowing various biological cycles to continue.
The National Organic Standards Board (NOSB) has defined organics by describing it positively as "an ecological production management system that promotes and enhances biodiversity, biological cycles, and soil biological activity.