UGC NTA NET/JRF Exam, Environmental Sciences, September-2022

Land breeze: Blowing breeze from land towards the sea is called a land breeze. They are formed during the night when sea water and land both lose heat, specific heat capacity of land being very low as compared to that of sea water, land loses heat energy fast and cools more rapidly as compared to the sea.

Sea water being at higher temperature, the air becomes lighter and rises up. Air from land being at higher pressure. So air from land starts blowing towards the sea and gives rise to a land breeze. Sea breeze: Blowing breeze from sea towards land during the day is called sea breeze.

They are formed during the day time when land and sea both are heated equally by the sun, but land has very low specific heat capacity as compared to the sea, so it is heated up more quickly, thus air above land due to heat becomes lighter and rises up.

Thus pressure decreases and cold and humid air above the sea blowing towards land. An ocean gyre is a large system of circular ocean currents formed by global wind patterns and forces created by Earth's rotation. The movement of the world's major ocean gyres helps drive the "ocean conveyor belt."

The ocean conveyor belt circulates ocean water around the entire planet. Also known as thermohaline circulation, the ocean conveyor belt is essential for regulating temperature, salinity and nutrient flow throughout the ocean.

An isobar is an imaginary line that connects places of equal barometric pressure. They can be used to find areas of low or high pressure over a large area. Isobars make it easier to read and analyse weather maps.

The stratosphere is crucial to life on Earth because it contains small amounts of ozone, a form of oxygen that prevents harmful UV rays from reaching Earth. The region within the stratosphere where this thin shell of ozone is found is called the ozone layer.

Troposphere: The troposphere is the atmospheric layer closest to the planet and contains the largest percentage (around 80%) of the mass of the total atmosphere.

Temperature and water vapor content in the troposphere decrease rapidly with altitude. Water vapor plays a major role in regulating air temperature because it absorbs solar energy and thermal radiation from the planet's surface.

The troposphere contains 99 % of the water vapor in the atmosphere. Water vapor concentrations vary with latitude. They are greatest above the tropics, where they may be as high as 3 %, and decrease toward the polar regions.

Thermosphere: The thermosphere is located above the mesosphere. The temperature in the thermosphere generally increases with altitude reaching 600 to 3000 F (600-2000 K) depending on solar activity.

This increase in temperature is due to the absorption of intense solar radiation by the limited amount of remaining molecular oxygen. At this extreme altitude gas molecules are widely separated.

Above 60 miles (100 km) from Earth's surface the chemical composition of air becomes strongly dependent on altitude and the atmosphere becomes enriched with lighter gases (atomic oxygen, helium and hydrogen). Also at 60 miles (100 km) altitude.

Exosphere: The exosphere is the most distant atmospheric region from Earth's surface. In the exosphere, an upward travelling molecule can escape to space (if it is moving fast enough) or be pulled back to Earth by gravity (if it isn't) with little probability of colliding with another molecule.

The altitude of its lower boundary, known as the thermopause or exobase, ranges from about 150 to 300 miles (250-500 km) depending on solar activity.

The upper boundary can be defined theoretically by the altitude (about 120,000 miles, half the distance to the Moon) at which the influence of solar radiation pressure on atomic hydrogen velocities exceeds that of
the Earth's gravitational pull.

Mono-climax Theory: According to the mono-climax theory of succession (Clements, 1936), every region has one climaх community toward which all communities are developing. He believed that climate was the determining factor for vegetation and the climax of any area was solely a function of its climate.

Poly-climax Theory: This theory was proposed by Tansley (1939) and later supported by Daubenmire (1966). The polyclimax theory of succession holds that many different types of vegetation as climax communities may be recognized in a given area. These will be climaxes, controlled by soil moisture, soil nutrients, activity of animals and other factors.

Climax-pattern Theory: Whittaker (1953) emphasized that a natural community is adapted to the whole pattern of environmental factors in which it exists; the major factors are: genetic structure of each species, climate, site, soil, biotic factors (activity of animals), fire, and wind, availability of plant and animal species, and chances of dispersal.

Climax as Vegetation: According to Egler (1954) one can say that "climaxes" in a broad sense are nothing more than totality of vegetation, itself. He, thus, favours the study, of vegetation; as it is, with careful observations to explain and interpret past, present, and future conditions of particular communities.

There are 12 soil orders (the top hierarchical level) in soil taxonomy. The names of the orders end with the suffix-sol. The criteria for the different soil orders include properties that reflect major differences in the genesis of soils. Some of them are:

Andisol: Volcanic ash soils. They are young soils. They cover 1% of the world's ice-free surface.
Aridisol: Dry soils forming under desert conditions which have fewer than 90 consecutive days of moisture during the growing season and are nonleached. They include nearly 12% of soils on Earth. Soil formation is slow, and accumulated organic matter is scarce.

They may have subsurface zones of caliche or duripan. Many aridisols have well-developed Bt horizons showing clay movement from past periods of greater moisture.

Entisol: Recently formed soils that lack well-developed horizons. Commonly found on unconsolidated river and beach sediments of sand and clay or volcanic ash, some have an A horizon on top of bedrock. They are 18% of soils worldwide.

Gelisol: Permafrost soils with permafrost within two metres of the surface or gelic materials and permafrost within one metre. They constitute 9% of soils worldwide.

Histosol: Organic soils, formerly called bog soils, are 1% of soils worldwide.

Inceptisol: Young soils. They have subsurface horizon formation but show little eluviation and illuviation. They constitute 15% of soils worldwide.

Mollisol: Soft, deep, dark soil formed in grasslands and some hardwood forests with very thick A horizons. They are 7% of soils worldwide.

Ultisol: Acid soils in the humid tropics and subtropics, which are depleted in calcium, magnesium and potassium (important plant nutrients). They are highly weathered, but not as weathered as Oxisols. They make up 8% of the soil worldwide.

Vertisol: Inverted soils. They are clay-rich and tend to swell when wet and shrink upon drying, often forming deep cracks into which surface layers can fall.

They are difficult to farm or to construct roads and buildings due to their high expansion rate. They constitute 2% of soils worldwide.