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The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. The ozone layer contains less than 10 parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole is about 0.3 parts per million. The ozone layer is mainly found in the lower portion of the stratosphere, from approximately 15 to 35 kilometers (9 to 22 mi) above Earth, although its thickness varies seasonally and geographically.
Rickets is a condition that results in weak or soft bones in children, and is caused by either dietary deficiency or genetic causes. Symptoms include bowed legs, stunted growth, bone pain, large forehead, and trouble sleeping. Complications may include bone deformities, bone pseudofractures and fractures, muscle spasms, or an abnormally curved spine.
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere as daylight when the Sun is above the horizon. When direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat (Atmospheric). When blocked by clouds or reflected off other objects, sunlight is diffused. Sources estimate a global average of between 164 watts to 340 watts per square meter over a 24-hour day; this figure is estimated by NASA to be about a quarter of Earth's average total solar irradiance.
Ultraviolet (UV) light is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs; Cherenkov radiation; and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights.
Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among individuals is caused by variation in pigmentation, which is the result of genetics, exposure to the sun, disorders, or some combination thereof. Differences across populations evolved through natural selection or sexual selection, because of social norms and differences in environment, as well as regulations of the biochemical effects of ultraviolet radiation penetrating the skin.
Melanin consist of oligomers or polymers arranged in a manner which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. They have been described as "among the last remaining biological frontiers with the unknown".
The polar regions, also called the frigid zones or polar zones, of Earth are Earth's polar ice caps, the regions of the planet that surround its geographical poles, lying within the polar circles. These high latitudes are dominated by floating sea ice covering much of the Arctic Ocean in the north, and by the Antarctic ice sheet on the continent of Antarctica and the Southern Ocean in the south.
The slaty bristlefront is a member of the Neotropical bird family Rhinocryptidae, the tapaculos. It is endemic to south-east Brazil.
Constantin Wilhelm Lambert Gloger was a German zoologist and ornithologist.
The checkered woodpecker is a species of bird in subfamily Picinae of the woodpecker family Picidae. It is found in Argentina, Bolivia, Brazil, Paraguay, and Uruguay.
Daytime as observed on Earth is the period of the day during which a given location experiences natural illumination from direct sunlight. Daytime occurs when the Sun appears above the local horizon, that is, anywhere on the globe's hemisphere facing the Sun. In direct sunlight the movement of the sun can be recorded and observed using a sundial that casts a shadow that slowly moves during the day. Other planets and natural satellites that rotate relative to a luminous primary body, such as a local star, also experience daytime, but this article primarily discusses daytime on Earth.
The stripe-crowned spinetail is a species of bird in the Furnariinae subfamily of the ovenbird family Furnariidae. It is found in Argentina, Bolivia, Brazil, Paraguay, and Uruguay.
The ochraceous piculet is a species of bird in subfamily Picumninae of the woodpecker family Picidae. It is endemic to eastern Brazil.
Light skin is a human skin color that has a low level of eumelanin pigmentation as an adaptation to environments of low UV radiation. Light skin is most commonly found amongst the native populations of Europe, West Asia, Central Asia, and Northeast Asia as measured through skin reflectance. People with light skin pigmentation are often referred to as "white" although these usages can be ambiguous in some countries where they are used to refer specifically to certain ethnic groups or populations.
Sunburn is a form of radiation burn that affects living tissue, such as skin, that results from an overexposure to ultraviolet (UV) radiation, usually from the Sun. Common symptoms in humans and other animals include red or reddish skin that is hot to the touch or painful, general fatigue, and mild dizziness. Other symptoms include blistering, peeling skin, swelling, itching, and nausea. Excessive UV radiation is the leading cause of (primarily) non-malignant skin tumors, which in extreme cases can be life-threatening. Sunburn is an inflammatory response in the tissue triggered by direct DNA damage by UV radiation. When the cells' DNA is overly damaged by UV radiation, type I cell-death is triggered and the tissue is replaced.
Exposing skin to the ultraviolet radiation in sunlight has both positive and negative health effects. On the positive side, exposure allows for the synthesis of vitamin D3. Vitamin D has been suggested as having a wide range of positive health effects, which include strengthening bones and possibly inhibiting the growth of some cancers. A dietary supplement can also supply vitamin D, but there are also benefits to exposure not obtainable through Vitamin D supplementation. Long-term sun exposure is associated with reduced all-cause mortality and reduced mortality risk from cardiovascular disease (CVD), some forms of cancer, and non-CVD/noncancer related disease, with indications in these studies that Vitamin D is not the mediator. Supplementation offers limited bioavailability and no synthesis of subdermal nitric oxide. UV exposure also has positive effects for endorphin levels, and possibly for protection against multiple sclerosis. Abundant visible light to the eyes gives health benefits through its association with the timing of melatonin synthesis, maintenance of normal and robust circadian rhythms, and reduced risk of seasonal affective disorder.
Dark skin is a type of human skin color that is rich in melanin pigments. People with dark skin are often referred to as "black people", although this usage can be ambiguous in some countries where it is also used to specifically refer to different ethnic groups or populations.
Edward "Jed" Howland Burtt Jr. was an American ornithologist, writer, and educator, and was responsible for many discoveries in ornithology.
A biological rule or biological law is a generalized law, principle, or rule of thumb formulated to describe patterns observed in living organisms. Biological rules and laws are often developed as succinct, broadly applicable ways to explain complex phenomena or salient observations about the ecology and biogeographical distributions of plant and animal species around the world, though they have been proposed for or extended to all types of organisms. Many of these regularities of ecology and biogeography are named after the biologists who first described them.
Sunning or basking, sometimes also known as sunbathing, is a thermoregulatory or comfort behaviour used by humans, animals, especially birds, reptiles, and insects, to help raise their body temperature, reduce the energy needed for temperature maintenance or to provide comfort. They may also have additional functions of ridding animals of ectoparasites, bacteria, or excess moisture.
