The Environment (11)
Albinism : A group of inherited disorders characterised by little or no melanin production.
Animals that are completely white as a result of albinism or leucism are extremely rare in the wild, since their lack of camouflage colors makes them easy targets for predators.
Albinism in humans is a congenital disorder characterized by the complete or partial absence of pigment in the skin, hair and eyes. Albinism is associated with a number of vision defects, such as photophobia, nystagmus, and amblyopia. Lack of skin pigmentation makes for more susceptibility to sunburn and skin cancers. In rare cases such as Chédiak–Higashi syndrome, albinism may be associated with deficiencies in the transportation of melanin granules. This also affects essential granules present in immune cells leading to increased susceptibility to infection.
Albinism results from inheritance of recessive gene alleles and is known to affect all vertebrates, including humans. It is due to absence or defect of tyrosinase, a copper-containing enzyme involved in the production of melanin. It is the opposite of melanism. Unlike humans, other animals have multiple pigments and for these, albinism is considered to be a hereditary condition characterised by the absence of melanin in particular, in the eyes, skin, hair, scales, feathers or cuticle. While an organism with complete absence of melanin is called an albino an organism with only a diminished amount of melanin is described as leucistic or albinoid. The term is from the Latin albus, "white".
Persecution of people with albinism (sometimes abbreviated PWA is based on the belief that certain body parts of albinistic people can transmit magical powers. Such superstition is present especially in some parts of the African Great Lakes region, it has been promulgated and exploited by witch doctors and others who use such body parts as ingredients in rituals, concoctions and potions with the claim that their magic will bring prosperity to the user (muti or medicine murder).
As a result, people with albinism have been persecuted, killed and dismembered, and graves of albinos dug up and desecrated. At the same time, people with albinism have also been ostracised and even killed for exactly the opposite reason, because they are presumed to be cursed and bring bad luck. The persecutions of people with albinism take place mostly in Sub-Saharan African communities, especially among East Africans.
Albinism is a genetically inherited condition which is very rare and, worldwide, affects approximately one in twenty thousand people. Although rare in the western world, albinism is quite common in sub-Saharan Africa, likely as a result of consanguinity. Both parents, who may or may not be albinos themselves, must carry the gene if it is to be passed on to the child. Albinism occurs in both males and females and is not specific to any race or ethnic group. Statistics prove that fifty percent of albinistic people in Tanzania have a known albinistic relative, although very few understand or are educated about the medical and genetic causes of this condition. Many believe it is a punishment from God or bad luck, and that their "disease" could be contagious, which is often the view of even members of the medical and professional community. These misconceptions, coupled with the lack of education, are some of the key reasons that albinism is so heavily persecuted. This lack of knowledge about people with albinism means that folktales and superstition in the name of witchcraft take the place of medical and scientific facts in the minds of many native Africans, with and without albinism, which in turn has major effects on the social integration of albinistic people into African society. Ninety-eight percent of albinos die by the age of forty for reasons which could easily be prevented.
Human activities have tipped the scales against the survival of these ancient mariners. Nearly all species of sea turtle are classified as Endangered. Slaughtered for their eggs, meat, skin and shells, sea turtles suffer from poaching and over-exploitation. They also face habitat destruction and accidental capture in fishing gear. Climate change has an impact on turtle nesting sites. It alters sand temperatures, which then affects the sex of hatchlings.
Turtles are reptiles of the order Testudines characterised by a special bony or cartilaginous shell developed from their ribs and acting as a shield. Sea turtles are a fundamental link in marine ecosystems. They help maintain the health of sea grass beds and coral reefs that benefit commercially valuable species such as shrimp, lobster and tuna. Sea turtles are the live representatives of a group of reptiles that have existed on Earth and traveled our seas for the last 100 million years. Turtles have major cultural significance and tourism value.
The Exocoetidae are a family of marine fish in the order Beloniformes class Actinopterygii. Fish of this family are known as flying fish. About 64 species are grouped in seven to nine genera. Flying fish can make powerful, self-propelled leaps out of water into air, where their long, wing-like fins enable gliding flight for considerable distances above the water's surface. This uncommon ability is a natural defence mechanism to evade predators.
The oldest known fossil of a flying or gliding fish, Potanichthys xingyiensis, dates back to the Middle Triassic, 235–242 million years ago. However, this fossil is not related to modern flying fish, which evolved independently about 66 million years ago.
Volans constellation lies in the southern sky. It is one of the smallest constellations. It represents the flying fish.
Volans is not associated with any myths. It was one of the constellations created by the Dutch astronomer and cartographer Petrus Plancius in the late 16th century, that first appeared depicted in a star atlas in 1603, in Johann Bayer’s Uranometria. The constellation was originally named Piscis Volans, the flying fish, by Plancius, but the name was eventually shortened to Volans.
Ocean levels are getting higher. Why is this happening, and what can we do to stem the tide?
There are two main mechanisms that contribute to observed sea level rise:
(1) thermal expansion: because of the increase in ocean heat content (ocean water expands as it warms); and
(2) the melting of major stores of land ice like ice sheets and glaciers
Core samples, tide gauge readings, and, most recently, satellite measurements tell us that over the past century, the Global Mean Sea Level (GMSL) has risen by 4 to 8 inches (10 to 20 centimeters). However, the annual rate of rise over the past 20 years has been 0.13 inches (3.2 millimeters) a year, roughly twice the average speed of the preceding 80 years.
Over the past century, the burning of fossil fuels and other human and natural activities has released enormous amounts of heat-trapping gases into the atmosphere. These emissions have caused the Earth's surface temperature to rise, and the oceans absorb about 80 percent of this additional heat.
The rise in sea levels is linked to three primary factors, all induced by this ongoing global climate change
- Thermal Expansion: When water heats up, it expands. About half of the past century's rise in sea level is attributable to warmer oceans simply occupying more space.
- Melting Glaciers and Polar Ice Caps: Large ice formations, like glaciers and the polar ice caps, naturally melt back a bit each summer. In the winter, snows, primarily from evaporated seawater, are generally sufficient to balance out the melting. Recently, though, persistently higher temperatures caused by global warming have led to greater-than-average summer melting as well as diminished snowfall due to later winters and earlier springs. This imbalance results in a significant net gain in the ratio of runoff to ocean evaporation, causing sea levels to rise.
- Ice Loss from Greenland and West Antarctica: As with the glaciers and ice caps, increased heat is causing the massive ice sheets that cover Greenland and Antarctica to melt at an accelerated pace. Scientists also believe meltwater from above and seawater from below is seeping beneath Greenland's and West Antarctica's ice sheets, effectively lubricating ice streams and causing them to move more quickly into the sea. Higher sea temperatures are causing the massive ice shelves that extend out from Antarctica to melt from below, weaken, and break off.
When sea levels rise rapidly, as they have been doing, even a small increase can have devastating effects on coastal habitats. As seawater reaches farther inland, it can cause destructive erosion, wetland flooding, aquifer and agricultural soil contamination, and lost habitat for fish, birds, and plants. (source : http://www.nationalgeographic.com/environment/global-warming/sea-level-rise/)