Scotobiology
Encyclopedia
The term scotobiology describes the study of biology
as directly and specifically affected by darkness
, as opposed to photobiology
, which describes the biological effects of light
.
of animals, plants, and microbe
s. Some of this work has been going on for over a century, and lays the foundation for understanding the importance of dark night skies
, not only for humans but for all biological species.
The great majority of biological systems have evolved in a world of alternating day and night and have become irrevocably adapted to and dependent on the seasonally changing patterns of light and darkness. Light is essential for many biological activities such as sight
and photosynthesis
. These are the focus of the science of photobiology. But the presence of uninterrupted periods of darkness, as well as their alternation with light, is just as important to biological behaviour. Scotobiology studies the positive responses of biological systems
to the presence of darkness, and not merely the negative effects caused by the absence of light.
s, animal
s (including bird
s and amphibian
s), insect
s, and microorganism
s are either adversely affected by light pollution
at night or can only function effectively either during or as the consequence of nightly darkness. Such activities include foraging
, breeding
and social behavior
in higher animals, amphibians, and insects, which are all affected in various ways if light pollution occurs in their environment. These are not merely photobiological phenomena; light pollution acts by interrupting critical dark-requiring processes.
But perhaps the most important scotobiological phenomena relate to the regular periodic alternation of light and darkness. These include breeding behavior in a range of animals, the control of flower
ing and the induction of winter dormancy
in many plants, and the operational control of the human immune system
. In many of these biological processes the critical point is the length of the dark period rather than that of the light. For example, "short-day" and "long-day" plants are, in fact, "long-night" and "short-night" respectively. That is to say, plants do not measure the length of the light period, but of the dark period. One consequence of artificial light pollution is that even brief periods of relatively bright light during the night may prevent plants or animals (including humans) from measuring the length of the dark period, and therefore from behaving in a normal or required manner. This is a critical aspect of scotobiology, and one of the major areas in the study of the responses of biological systems to darkness.
In discussing scotobiology, it is important to remember that darkness (the absence of light) is seldom absolute. An important aspect of any scotobiological phenomenon is the level and quality (wavelength
) of light that is below the threshold of detection for that phenomenon and in any specific organism. This important variable in scotobiological studies is not always properly noted or examined. There are substantial levels of natural light pollution at night, of which moonlight
is usually the strongest. For example, plants that rely on night length to program their behaviour have the capacity to ignore full moonlight during an otherwise dark night. If this ability had not evolved, plants would not be able to respond to changing night-length for such behavioural programs as the initiation of flowering and the onset of dormancy. On the other hand, some animal behavioural patterns are strongly responsive to moonlight. It is thus most important in any scotobiological study to determine the threshold level of light that may be required to interfere with or negate the normal pattern of dark-night activity.
of the Night held in Muskoka
, Canada
, discussion centered around the many effects of night-time light pollution
on the biology
of a wide range of organisms, but it went far beyond this in describing darkness as a biological imperative for the functioning of biological systems. Presentations focused on the absolute requirement of darkness for many aspects of normal behaviour and metabolism of many organisms and for the normal progression of their life cycle
s. Because there was no suitable term to describe the Symposium's main focus, the term scotobiology was introduced. The word is derived from the Greek
scotos (dark), and relates to photobiology
, which describes the biological effects of light (photos). This term appears not to have been used previously, although related terms such as skototropism
and scotophyle have appeared in the literature.
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
as directly and specifically affected by darkness
Darkness
Darkness, in contrast with brightness, is a relative absence of visible light. It is the appearance of black in a color space. When light is not present, rod and cone cells within the eye are not stimulated. This lack of stimulation means photoreceptor cells are unable to distinguish color...
, as opposed to photobiology
Photobiology
Photobiology is the scientific study of the interactions of light and living organisms. The field includes the study of photosynthesis, photomorphogenesis, visual processing, circadian rhythms, bioluminescence, and ultraviolet radiation effects...
, which describes the biological effects of light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
.
Overview
The science of scotobiology gathers together under a single descriptive heading a wide range of approaches to the study of the biology of darkness. This includes work on the effects of darkness on the behavior and metabolismMetabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
of animals, plants, and microbe
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s. Some of this work has been going on for over a century, and lays the foundation for understanding the importance of dark night skies
Night Skies
Night Skies was a sci-fi horror film that was in development in the late 1970s, but never actually made. Steven Spielberg conceived the idea after Close Encounters of the Third Kind. Instead, material developed at the time was used in Poltergeist and E.T...
, not only for humans but for all biological species.
The great majority of biological systems have evolved in a world of alternating day and night and have become irrevocably adapted to and dependent on the seasonally changing patterns of light and darkness. Light is essential for many biological activities such as sight
Visual perception
Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...
and photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. These are the focus of the science of photobiology. But the presence of uninterrupted periods of darkness, as well as their alternation with light, is just as important to biological behaviour. Scotobiology studies the positive responses of biological systems
Systems biology
Systems biology is a term used to describe a number of trends in bioscience research, and a movement which draws on those trends. Proponents describe systems biology as a biology-based inter-disciplinary study field that focuses on complex interactions in biological systems, claiming that it uses...
to the presence of darkness, and not merely the negative effects caused by the absence of light.
Effects of darkness
Many of the biological and behavioural activities of plantPlant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s, animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s (including bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s and amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
s), insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s, and microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s are either adversely affected by light pollution
Light pollution
Light pollution, also known as photopollution or luminous pollution, is excessive or obtrusive artificial light.The International Dark-Sky Association defines light pollution as:...
at night or can only function effectively either during or as the consequence of nightly darkness. Such activities include foraging
Foraging
- Definitions and significance of foraging behavior :Foraging is the act of searching for and exploiting food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce...
, breeding
Breeding
Breeding is the reproduction, that is, producing of offspring, usually animals or plants:* Breeding in the wild, the natural process of reproduction in the animal kingdom* Animal husbandry, through selected specimens such as dogs, horses, and rabbits...
and social behavior
Social behavior
In physics, physiology and sociology, social behavior is behavior directed towards society, or taking place between, members of the same species. Behavior such as predation which involves members of different species is not social...
in higher animals, amphibians, and insects, which are all affected in various ways if light pollution occurs in their environment. These are not merely photobiological phenomena; light pollution acts by interrupting critical dark-requiring processes.
But perhaps the most important scotobiological phenomena relate to the regular periodic alternation of light and darkness. These include breeding behavior in a range of animals, the control of flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
ing and the induction of winter dormancy
Dormancy
Dormancy is a period in an organism's life cycle when growth, development, and physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be closely associated with environmental conditions...
in many plants, and the operational control of the human immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
. In many of these biological processes the critical point is the length of the dark period rather than that of the light. For example, "short-day" and "long-day" plants are, in fact, "long-night" and "short-night" respectively. That is to say, plants do not measure the length of the light period, but of the dark period. One consequence of artificial light pollution is that even brief periods of relatively bright light during the night may prevent plants or animals (including humans) from measuring the length of the dark period, and therefore from behaving in a normal or required manner. This is a critical aspect of scotobiology, and one of the major areas in the study of the responses of biological systems to darkness.
In discussing scotobiology, it is important to remember that darkness (the absence of light) is seldom absolute. An important aspect of any scotobiological phenomenon is the level and quality (wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
) of light that is below the threshold of detection for that phenomenon and in any specific organism. This important variable in scotobiological studies is not always properly noted or examined. There are substantial levels of natural light pollution at night, of which moonlight
Moonlight
Moonlight is the light that reaches Earth from the Moon. This light does not originate from the Moon, but from sunlight. The Moon does not, however, reflect sunlight like a mirror, but it reflects light from those portions of its surface which the Sun's light strikes. See diffuse reflection.In...
is usually the strongest. For example, plants that rely on night length to program their behaviour have the capacity to ignore full moonlight during an otherwise dark night. If this ability had not evolved, plants would not be able to respond to changing night-length for such behavioural programs as the initiation of flowering and the onset of dormancy. On the other hand, some animal behavioural patterns are strongly responsive to moonlight. It is thus most important in any scotobiological study to determine the threshold level of light that may be required to interfere with or negate the normal pattern of dark-night activity.
Etymology
In 2003, at a symposium on the EcologyEcology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
of the Night held in Muskoka
Muskoka District Municipality, Ontario
The District Municipality of Muskoka, more generally referred to as the District of Muskoka, or simply Muskoka, is a Regional Municipality located in Central Ontario, Canada. Muskoka extends from Georgian Bay in the west, to the northern tip of Lake Couchiching in the south, to the western border...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, discussion centered around the many effects of night-time light pollution
Light pollution
Light pollution, also known as photopollution or luminous pollution, is excessive or obtrusive artificial light.The International Dark-Sky Association defines light pollution as:...
on the biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
of a wide range of organisms, but it went far beyond this in describing darkness as a biological imperative for the functioning of biological systems. Presentations focused on the absolute requirement of darkness for many aspects of normal behaviour and metabolism of many organisms and for the normal progression of their life cycle
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
s. Because there was no suitable term to describe the Symposium's main focus, the term scotobiology was introduced. The word is derived from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
scotos (dark), and relates to photobiology
Photobiology
Photobiology is the scientific study of the interactions of light and living organisms. The field includes the study of photosynthesis, photomorphogenesis, visual processing, circadian rhythms, bioluminescence, and ultraviolet radiation effects...
, which describes the biological effects of light (photos). This term appears not to have been used previously, although related terms such as skototropism
Phototropism
Phototropism is directional growth in which the direction of growth is determined by the direction of the light source. In other words, it is the growth and response to a light stimulus. Phototropism is most often observed in plants, but can also occur in other organisms such as fungi...
and scotophyle have appeared in the literature.
See also
- Dark-sky movementDark-sky movementThe dark-sky movement is a campaign by people who want to reduce light pollution so people can see the stars, to reduce the effects of unnatural lighting on the environment, and to cut down on energy usage....
- Dark-sky preserve
- Light effects on circadian rhythmLight effects on circadian rhythmNumerous organisms maintain inherent individual daily rhythms to biological processes, known as circadian rhythms, that assist the organism in maintaining functional periodicity relative to the 24-hour day/night cycle of the earth...
- Light pollutionLight pollutionLight pollution, also known as photopollution or luminous pollution, is excessive or obtrusive artificial light.The International Dark-Sky Association defines light pollution as:...
- PhotoperiodismPhotoperiodismPhotoperiodism is the physiological reaction of organisms to the length of day or night. It occurs in plants and animals.Photoperiodism can also be defined as the developmental responses of plants to the relative lengths of the light and dark periods...
- Sky brightnessSky brightnessThe fact that the sky is not completely dark at night can be easily observed. Were the sky absolutely dark, one would not be able to see the silhouette of an object against the sky....