Thermohaline circulation refers to the deepwater circulation of the oceans and is primarily caused by differences in density between the waters of different regions. It is mainly a convection process in which cold, dense water formed in the polar regions sinks and flows slowly toward the equator. The circulation of ocean waters is vitally important in dispersing heat energy around the globe. Two factors determine the density of ocean water; one is temperature, what is the other? Discuss
Source: The Free Dictionary
Nori is the Japanese name for an edible, dried preparation of red algae of the genus Porphyra. It is farmed in the sea, where Porphyra plants grow attached to nets suspended at the sea’s surface. Farmers operate from boats and use mechanical harvesters to collect their crops. The nori sheets are then produced in a process that is quite similar to papermaking and involves a shredding and rack-drying process. This “sea vegetable” is commonly used in the preparation of what foods? 
A virus is a minute infectious agent that, in general, cannot be seen with a light microscope. It lacks an independent metabolism and is able to replicate only within a living host cell. A free virus particle does not carry out the functions of a living cell, such as respiration and growth, and may be thought of as a packaging device by which viral genetic material can be introduced into appropriate host cells. What are the arguments for and against classifying viruses as living organisms? 
The medicinal properties of opium have been known for millennia, and by 4000 BCE, both Sumerian and European cultures were using it as a narcotic. Early in the 19th century, British merchants began smuggling opium into China, and by 1905, more than a quarter of China’s male population was addicted to the drug. The generous use of opium-derived morphine in treating wounded American Civil War soldiers also produced many addicts. How much morphine does one gram of poppy seeds contain? 
Mangroves are large tropical evergreen trees of the genus Rhizophora. They are found in the muddy swamps of tropical and subtropical coastlines and estuaries and grow most abundantly in tropical Asia, Africa, and the islands of the southwest Pacific. Mangrove trunks produce aerial roots that become embedded in the mud and rapidly form close-growing mangrove thickets. These swamps are rich breeding grounds for fish and shellfish. How many plant species can be found in a mangrove habitat? 
In the spring of 1771, an outbreak of bubonic plague swept through Moscow. Authorities instituted a number of policies in an attempt to contain the epidemic, but the severe measures were unpopular with the general public. Factories and stores were shut down, and the economy was essentially at a standstill. Fearful, and faced with acute food shortages, the people took to the streets in an uprising that would later be known as the Plague Riot. What was done to the bell that mobilized the rioters? 
The Sumerian civilization was the world’s earliest civilization, developing at the confluence of the Tigris and Euphrates rivers in lower Mesopotamia in about 3500 BCE. The Sumerians had a well-organized communal life and were adept at building canals and irrigation systems. Unfortunately, the evaporation of irrigated waters led to increased soil salinity and greatly reduced agricultural yields, weakening the predominantly agricultural civilization. What form of writing did the Sumerians invent? 
Althaea officinalis, or the Marsh Mallow, flourishes on riverbanks and in salt marshes. Its velvety leaves, pale pink flowers, and mucilaginous root all have medicinal properties. When the plant flowers, its leaves are collected and used to treat pulmonary and urinary diseases. The root, which is harvested in late autumn, is generally used to treat gastrointestinal disorders and skin conditions. What part of the Marsh Mallow is used to make marshmallow candy treats? 
An allergy is an abnormally high sensitivity to an otherwise harmless foreign substance, or allergen, that leads to an exaggerated response of the natural immune defense mechanism. Allergens can be airborne substances, infectious agents, foods, contactants, or physical agents; and reactions can range from the relatively benign runny nose to severe inflammation, anaphylactic shock, and even death. Why do some scientists believe that children with no siblings are more prone to allergies? .jpg)
Many cultures consider dragonflies sinister creatures, and a number of the common, vernacular names for the flying insects, such as “devil’s needle” and “ear cutter,” link them with evil or injury. In truth, dragonflies generally do not attack humans and are valued for their predatory control of harmful insect populations. Dragonflies lay eggs in or near water, and most of the dragonfly’s life is spent underwater in larval form. In what country are dragonflies considered a delicacy?